Studies in the Field of Cyclic Compounds. 1. On the Transformation of Cyclobutyldimethylcarbinol. 2. On the Hydrogenation of Tetramethylenecarboxylic Acid
Abstract Generated abstract
This paper investigates transformations of cyclobutyldimethylcarbinol and the reduction of tetramethylenecarboxylic acid, with particular attention to the stability and rearrangement of four-membered rings. Through reactions with oxalic acid, dilute sulfuric acid, hydrobromic acid, chromic mixture, and hydrogen iodide, the study isolates and characterizes a primary alcohol, an aldehyde, unsaturated hydrocarbons, and reduction products using boiling points, densities, refractive indices, and derivative analyses. The results indicate that cyclobutyldimethylcarbinol can isomerize before oxidation or dehydration, and that tetramethylenecarboxylic acid is reduced mainly by ring rupture to normal valeric acid rather than by retention or expansion of the original ring. The author argues that related cyclic products from substituted cyclobutylcarbinols likely arise through ring opening followed by formation of more stable cyclic systems.
Full Text
Proceedings of the Tomsk Technological Institute
of Emperor Nicholas II,
vol. 9. 1908, No. 1.
II.
N. M. Kizhner.
Studies in the Field of Cyclic Compounds
1. On the transformation of cyclobutyldimethylcarbinol. 2. On the hydrogenation of tetramethylenecarboxylic acid.
1–32.
Contents
| No. | Title | Page |
|---|---|---|
| 1. | On the transformations of cyclobutyldimethylcarbinol | 1 |
| 2. | On the hydrogenation of tetramethylenecarboxylic acid | 29 |
STUDIES
in the field of cyclic compounds.
1. On the transformations of cyclobutyldimethylcarbinol.
The present article comprises a continuation of studies on the transformations of cyclobutyldimethylcarbinol, part of which was published three years ago1.
Although the work in many details still remains unfinished, nevertheless I consider it necessary and timely to publish the greater part of the accumulated material.
In the preceding work2 there was described a bromide obtained by the action of hydrobromic acid on cyclobutyldimethylcarbinol, as well as an unsaturated hydrocarbon \(\mathrm{C_7H_{12}}\), isolated en route in obtaining the bromide.
Both compounds were then regarded as direct derivatives of cyclobutyldimethylcarbinol.
On further study of the transformations of cyclobutyldimethylcarbinol, it became necessary to abandon this point of view.
In continuing the work it was necessary, first of all, to characterize more closely the unsaturated hydrocarbon briefly described in the preceding article.
For its preparation, the method of Kalbaum was applied: the action of crystalline oxalic acid on cyclobutyldimethylcarbinol, since it was supposed that one and the same hydrocarbon should be obtained, despite the different method of preparation. However, no such identity was found, and upon closer study of the subject it became clear that the question of the structure of the hydrocarbon \(\mathrm{C_7H_{12}}\) was more complex than it could have seemed at the beginning of the work.
On a more detailed study of this hydrocarbon, its identity with Renard’s heptine, isolated from the products of the dry distillation of camphor, and with the same hydrocarbon obtained by Markovnikov by distilling perseitol with hydriodic acid, became clear. At the same time, doubts arose as to the correctness of the views on the structure of Markovnikov’s and Renard’s heptine as methylcyclohexene-1. This view of the structure of heptine had been expressed by Markovnikov and was shared by the late V. V. Markovnikov.
In experiments aimed at obtaining the unsaturated hydrocarbon, it was found that cyclobutyldimethylcarbinol, under the influence of oxalic acid, undergoes a completely unexpected isomerization into a primary alcohol; the same occurs under the action of dilute sulfuric acid, as a result of which cyclobutyldimethylcarbinol is oxidized directly by chromic mixture to the aldehyde corresponding to the isomeric primary alcohol.
Action of Oxalic Acid on Cyclobutyldimethylcarbinol. Isomerization into a Primary Alcohol.
A mixture of 20 g of cyclobutyldimethylcarbinol and 60 g of crystalline oxalic acid was boiled over a low flame with a reflux condenser for 2 hours. The upper oily layer, as it boils, begins to turn yellow, then the color gradually takes on a bright emerald shade; toward the end of the boiling the color begins to fade and then becomes pale yellow.
After the addition of 1 volume of water, the unsaturated hydrocarbon that had formed was distilled off by boiling the liquid without passing steam through it; 9 g of hydrocarbon distilled over, i.e., 54% of the theoretical yield.
In the flask, on the surface of the concentrated solution of oxalic acid, there remains a thick oily liquid, almost nonvolatile with water vapors; it was extracted with ether. The ethereal extract was carefully washed with soda and dried with sodium sulfate.
The substance proved to be the neutral oxalic ether of a new primary alcohol1.
After distilling off the ether on a water bath, its residues were removed in a rarefied space over sulfuric acid. Ten grams of substance were obtained.
The oxalate ester obtained in this way, without preliminary purification—which would have entailed unavoidable losses of the difficultly accessible material—was saponified with caustic potash. The accounting of the products obtained on saponification showed that the substance is an almost pure neutral ester of a primary alcohol.
The ester was saponified by boiling for half an hour with a solution of 25 g of caustic potash in 50 cc of water, after which the alcohol formed was distilled off with steam. The distillate was saturated with potash, since the alcohol is somewhat soluble in water.
7 g of undistilled alcohol were obtained. From 10 g of neutral oxalate ester, \(C_2O_4(C_7H_{13})_2\), theory requires 7.7 g of the alcohol \(C_7H_{13}OH\). The alcohol was weighed after separation from the potash solution; it, of course, contained an admixture of water.
From the alkaline liquid remaining after the alcohol had been distilled off, oxalic acid was precipitated by the usual methods in the form of the calcium salt.
4.3 g of \(C_2O_4Ca\) were obtained instead of the 4.5 g required by theory for 10 g of \(C_2O_4(C_7H_{13})_2\). In another experiment, from 30 g of cyclobutyldimethylcarbinol, after boiling for 1 hour with oxalic acid, 18 g of substance were distilled off with steam; from this 12 g of hydrocarbon were separated, and 10 g of alcohol were obtained. The unsaturated hydrocarbon will be described below.
Primary alcohol \(C_7H_{13}OH\).
The alcohol obtained by the method indicated was dried over fused potash with heating on a water bath. After this it solidifies in snow to a crystalline mass. The alcohol boils at \(157^\circ\) at 773 mm, and solidifies in the receiver to a crystalline mass.
The beginning of melting is at \(27^\circ\), the end at \(28^\circ\).
Solidification begins at \(26^\circ\), ends at \(25^\circ\).
The odor of the alcohol is faintly minty, in contrast to cyclobutyldimethylcarbinol, which has a sharp menthol odor.
Analysis.
0.1518 g of substance gave 0.1692 g of \(H_2O\) and 0.4108 g of \(CO_2\).
| Obtained | Calculated for \(C_7H_{14}O\). | |
|---|---|---|
| C | 73.80 | 73.61 |
| H | 12.47 | 12.36 |
The specific gravity was determined at \(32^\circ\).
Weight of substance at \(32^\circ\)—2.2008 g.
Weight of water at \(0^\circ\)—2.4300 g.
\[ d^{32}_{0}=0.9057 \]
refractive index \(n_{\mathrm{Na}}^{32}=1.4489^{1})\).
Molecular refraction \(R^2=33.75\).
Calculated for cyclic alcohol \( \mathrm{C_7H_{13}OH}\), \(R^2=33.74\).
Cyclobutyldimethylcarbinol boils at \(147^\circ\); \(d^{20}_{0}=0.8952\).
Phenylurethane of the primary alcohol crystallizes in long needles; m.p. \(88\text{–}89^\circ\).
0.1993 g of substance gave 10.7 cc N at \(17^\circ\) and 751 mm.
\[ \begin{array}{c c c} \text{Found} & \text{Calculated for} & \mathrm{CO}\!\begin{matrix}/\mathrm{NHC_6H_5}\\ \backslash \mathrm{OC_7H_{13}}\end{matrix} \\ \mathrm{N}\quad 6.12 & & \mathrm{N}\quad 6.00 \end{array} \]
Acetic ester was obtained by boiling the alcohol with acetic anhydride; boiling point \(171^\circ\) at 751 mm.
Specific gravity.
Weight of substance at \(15^\circ\)—0.4412 g.
Weight of water at \(0^\circ\)—0.4692 g.
\[ d^{15}_{0}=0.9403. \]
Refractive index \(n_{15}=1.4359\).
Molecular refraction \(R^2=43.35\).
Calculated for cyclic \( \mathrm{CH_3COOC_7H_{13}}\), \(R^2=43.29\).
Oxidation of the alcohol to the aldehyde \( \mathrm{C_6H_{11}CHO}\).
The primary character of the alcohol was proved by oxidizing it to the aldehyde with chromic mixture. For 2 g of crystalline alcohol there were taken 3 g of \( \mathrm{K_2Cr_2O_7}\), 2.5 g of \( \mathrm{H_2SO_4}\), and 15 cc of water.
On shaking the mixture, warming occurs; it was moderated by cooling with water. After the reaction was complete, the mixture was diluted with water, the aldehyde distilled off with steam, washed with soda, and converted into the semicarbazone in order to separate it from the admixture of unchanged alcohol. The semicarbazone, previously pressed out on a porous plate, was recrystallized from alcohol, decomposed with a 10% solution of sulfuric acid, and the separated aldehyde was distilled off with steam, washed with soda, and dried over calcium chloride.
From 2.5 g of semicarbazone there was obtained 1.5 g of perfectly pure aldehyde.
\(^{1})\) The refractive indices in all cases were determined for sodium light.
Analysis.
0.1105 g of substance gave 0.1067 g of \(H_2O\) and 0.3027 g of \(CO_2\).
| Found | Calculated for \(C_7H_{12}O\). | ||
|---|---|---|---|
| C | 74.71 | C | 74.94 |
| H | 10.70 | H | 10.79 |
Specific gravity.
Weight of the substance at \(13.5^\circ = 0.4247\) g.
” ” ” \(20^\circ = 0.4216\) ”
Weight of water at \(0^\circ = 0.4692\) ”
\[ d^{13.5}_{0}=0.9072;\qquad d^{20}_{0}=0.8985 \]
Index of refraction \(n_{13.5}=1.4359\)
Molecular refraction \(R^2=32.26\)
Calculated for \(C_6H_{11}CHO\) (cycl.) \(R^2=32.40\).
The aldehyde is a colorless, mobile liquid with the odor of higher fatty aldehydes; it is slightly soluble in water. With fuchsin–sulfurous acid it gives a pink coloration; with an ammoniacal solution of silver oxide in the presence of caustic potash it causes the formation of a silver mirror.
It was not possible to obtain a crystalline compound with acid sodium sulfite, despite the prolonged action of a concentrated solution of bisulfite alkali on the aldehyde with frequent shaking.
The aldehyde is converted very rapidly into the semicarbazone by the action of an aqueous solution of semicarbazide hydrochloride and potassium acetate. (1 part \(NH_2CONHNH_3Cl\), 1 part \(C_2H_3O_2K\), and 5 parts \(H_2O\)).
Semicarbazone \(C_6H_{11}CH{=}N—NHCONH_2\), from methyl alcohol, crystallizes in rhombic envelopes, m.p. \(188–189^\circ\).
Determination of nitrogen.
0.1115 g of substance gave 24.5 c.c. of nitrogen at \(16^\circ\) and 749 mm.
| Found | Calculated for \(C_7H_{12}NNHCONH_2\) | ||
|---|---|---|---|
| N | 25.12 | N | 24.85 |
Oxime \(C_6H_{11}CH:NOH\) was obtained by the action of hydroxylamine hydrochloride and sodium carbonate on a hydroalcoholic solution of the aldehyde. After the alcohol had been distilled off on a water bath, the oxime separated upon addition of a small amount of water; for more complete separation potash had to be added.
From methyl alcohol the oxime crystallizes in beautifully formed rhombic plates; m.p. \(65^\circ\).
\(0.1783\) g of substance gave \(17.7\) cc of nitrogen at \(20^\circ\) and 749 mm.
| Found | Calculated for \(\mathrm{C_7H_{12}NOH}\) |
|---|---|
| \(\mathrm{N}\) 11.13 | \(\mathrm{N}\) 11.02 |
Conversion of cyclobutyldimethylcarbinol into an aldehyde on oxidation. Isomerization into a primary alcohol under the action of sulfuric acid.
Cyclobutyldimethylcarbinol reacts with chromic mixture only after some warming, in contrast to a primary alcohol.
The oxidation product, with an aldehydic odor, was distilled with steam and converted into the semicarbazone; at the same time the presence of an unsaturated hydrocarbon was detected. The semicarbazone, pressed on a porous plate, was recrystallized from methyl alcohol. It crystallizes in the same rhombic envelopes as the semicarbazone described above; the melting point is likewise \(188–189^\circ\).
\(0.1017\) g of substance gave \(22.2\) cc of nitrogen at \(14^\circ\) and 746 mm.
| Found | Calculated for \(\mathrm{C_7H_{12}NNHCONH_2}\) |
|---|---|
| \(\mathrm{N}\) 25.08 | \(\mathrm{N}\) 24.85 |
On decomposition of the semicarbazone, a substance is obtained with characteristic aldehyde reactions toward fuchsine-sulfurous acid and ammoniacal silver oxide solution.
The quite unusual transformation of a tertiary alcohol into an aldehyde on oxidation with chromic mixture depends on the preliminary isomerization of the tertiary alcohol into a primary one under the influence of sulfuric acid, as shown by the experiments cited below.
The sulfuric acid was taken in the same concentration as in the oxidation with chromic mixture.
3 g of cyclobutyldimethylcarbinol were boiled for one hour with a solution of 5 g of concentrated sulfuric acid in 30 cc of water. A naphthylene odor quickly appears, indicating the formation of the hydrocarbon \(\mathrm{C_7H_{12}}\), and at the same time the sharp minty odor of cyclobutyldimethylcarbinol soon disappears. The product distilled off with steam was dried with potash.
The greater part of the reaction product distilled at \(156^\circ\) at 753 mm. The alcohol crystallized in the receiver. From the first fractions a hydrocarbon with a boiling point of \(103–105^\circ\) at 764 mm was isolated.
This experiment leaves no doubt that the formation of the aldehyde upon oxidation of cyclobutyldimethylcarbinol is preceded by its isomerization into a primary alcohol under the influence of sulfuric acid.
As the investigation of the unsaturated hydrocarbon obtained by the action of oxalic acid on cyclobutyldimethylcarbinol shows, this reaction is accompanied by isomerization of the four-membered ring into a five- or six-membered one; but this does not exclude the possibility that the four-membered ring is retained in the primary alcohol obtained. In that case the primary alcohol should have the following structure:
\[ \begin{array}{ccc} & \mathrm{CH_3} & \\ & | & \\ \mathrm{H_2C}---\mathrm{CH}---\mathrm{C}---\mathrm{H} \\ | & | & | \\ \mathrm{H_2C}---\mathrm{CH_2} & & \mathrm{CH_2OH} \end{array} \]
In the event of isomerization, the question of the structure of the primary alcohol becomes more complicated; while not denying the possibility that a five-membered ring may be present in the primary alcohol, I leave the question of its structure open for the present, hoping to answer it more definitely in the further continuation of the present investigation.
Unsaturated hydrocarbon \(\mathrm{C_7H_{12}}\) from the primary alcohol.
In studying the action of fuming hydrobromic acid on the primary alcohol, an unsaturated hydrocarbon was obtained. Two experiments were carried out.
Experiment 1.
4 g of the crystalline alcohol were heated in a sealed tube with 6 vol. of fuming hydrobromic acid for 4 hours at \(100^\circ\). After dilution of the contents of the tube with water, the bromide was separated and washed with soda. 5 g of crude bromide were obtained, i.e. 82% of theory. On distillation of the bromide with steam, almost complete decomposition of the bromide into an unsaturated hydrocarbon occurred.
The distillate obtained was lighter than water; 3 g of it were obtained. During the first distillation almost the entire product distilled over up to \(110^\circ\), and only an insignificant portion distilled within the range \(145\)—\(155^\circ\), with evolution of
hydrogen bromide. The low-boiling fraction was heated for 4 hours at \(100^\circ\) in a sealed tube with metallic sodium. The hydrocarbon thus purified boiled at \(103—103.5^\circ\) at 757 mm.
Analysis.
0.1560 g of substance gave 0.1779 g \(H_2O\) and 0.5005 g \(CO_2\)
| Found | Calculated for \(C_7H_{12}\) | ||
|---|---|---|---|
| C | 87.50 | C | 87.42 |
| H | 12.76 | H | 12.58 |
Specific gravity.
\[ \begin{aligned} &\text{Weight of substance at }13.5^\circ = 0.7338\ \text{g},\\ &\qquad\qquad\qquad\ \ 20^\circ = 0.7275\ \text{g},\\ &\text{Weight of water at }0^\circ = 0.9182\ \text{g},\\ &d^{13.5}_0 = 0.7992;\qquad d^{20}_0 = 0.7923. \end{aligned} \]
Refractive index at \(13.5^\circ\) \(n_{13.5}=1.4447\)
Molecular refraction \(R^2=31.94\)
Calculated for cycl. \(C_7H_{12}\) with 1 double bond. \(R^2=31.82\)
The odor of the hydrocarbon is light, turpentine-like.
2nd experiment.
7 g of crystalline alcohol were dissolved in 6 vol. of hydrobromic acid (saturated at \(0^\circ\)). After standing for 12 hours at room temperature, the reaction mixture was heated in a closed vessel for one hour at \(70^\circ\).
Upon dilution of the mixture with water, the bromide separates out in the form of a heavy oil; on distilling it with steam it almost completely decomposes into an unsaturated hydrocarbon, as in the first case. 5.5 g of substance were obtained, which in the first distillation passed over almost entirely up to \(105^\circ\). The residue was extremely small.
Treated with metallic sodium, as in the preceding experiment, the hydrocarbon boiled at \(103.7—104^\circ\) at 752. 4 g of pure hydrocarbon were obtained.
Specific gravity.
\[ \begin{aligned} &\text{Weight of hydrocarbon at }0^\circ = 2.5668\ \text{g},\\ &\qquad\qquad\qquad\quad\ 20^\circ = 2.5134\ \text{g},\\ &\text{Weight of water at }0^\circ = 3.1670\ \text{g},\\ &d^0_0 = 0.8105;\qquad d^{20}_0 = 0.7936. \end{aligned} \]
Refractive index \(n_{20}=1.4430\)
Molecular refraction \(R^2=32.07\)
Calculated for \(C_7H_{12}\) with 1 double bond. \(R^2=31.82\)
The physical properties of the two hydrocarbons are very close.
The behavior of the primary alcohol toward hydrobromic acid is entirely different from that of cyclobutyldimethylcarbinol; under analogous conditions the latter alcohol gives bromide1 \(C_7H_{13}Br\), distilling without decomposition at \(167^\circ\) at 757 mm.; it contains only a small admixture of bromide, which decomposes into an unsaturated hydrocarbon on distillation with steam.
The study of the hydrocarbon will be described below.
Unsaturated hydrocarbon from cyclobutyldimethylcarbinol.
In obtaining the primary alcohol from cyclobutyldimethylcarbinol by the action of oxalic acid, an unsaturated hydrocarbon is also formed; the physical properties of the hydrocarbon apparently depend on the duration of the action of the oxalic acid.
In the first experiment for obtaining the primary alcohol, boiling with oxalic acid was continued for 2 hours, until the emerald-green coloration of the oily layer had disappeared.
The hydrocarbon, purified by boiling over metallic sodium, boiled at \(103.5—105^\circ\) at 764 mm.
Specific gravity.
\[ \begin{aligned} \text{Weight of substance at }20^\circ &= 2.5071\ \text{g.}\\ \text{Weight of water at }0^\circ &= 3.1670\ \text{g.}\\ d^{20}_{0} &= 0.7916 \end{aligned} \]
Refractive index \(n_{20}=1.4417\)
Molecular refraction \(R^2=32.07\)
Calculated for unsat. hydrocarbon \(C_7H_{12}\) \(R^2=31.82\)
The odor of the hydrocarbon is turpentine-like, with an admixture of a naphthalene odor.
In the second experiment boiling with oxalic acid was continued for about an hour; the intense green color still remained; the yield of hydrocarbon was considerably greater.
The hydrocarbon, previously boiled over metallic sodium, boiled at \(102—105^\circ\) at 773 mm.
Analysis.
0.1503 g of substance gave 0.1709 g of \(H_2O\) and 0.4815 g of \(CO_2\).
| Found | Calculated for \(C_7H_{12}\) | ||
|---|---|---|---|
| C | 87.37 | C | 87.42 |
| H | 12.72 | H | 12.58 |
Specific gravity.
Weight of substance at \(20^\circ\)—2.4992 g.
Weight of water at \(0^\circ\)—3.1670 g.
\[ d^{20}_{0}=0.7892 \]
Refractive index \(n_{20}=1.4410\)
Molecular refraction \(R^2=32.12\)
Calculated for \(C_7H_{12}\) \(\quad R^2=31.82\)
The hydrocarbon has a sharper odor in comparison with the first preparation.
The physical properties of all samples of the hydrocarbon \(C_7H_{12}\), in the order of their description, are collected in the appended table.
| \(C_7H_{12}\) | Boiling point | Pressure | \(d^{20}_{0}\) | \(n_D\) | \(R^2\) |
|---|---|---|---|---|---|
| I | \(103—103.5^\circ\) | 757 mm | 0.7923 | 1.4447 at \(13.5^\circ\) | 31.94 |
| II | \(103.7—104^\circ\) | 752 mm | 0.7936 | 1.4430 at \(20^\circ\) | 32.07 |
| III | \(103.5—105^\circ\) | 764 mm | 0.7916 | 1.4417 at \(20^\circ\) | 32.07 |
| IV | \(102—105^\circ\) | 773 mm | 0.7892 | 1.4410 at \(20^\circ\) | 32.12 |
As the investigations have shown, all these samples of hydrocarbons \(C_7H_{12}\) consist, in the main mass, of one and the same individual substance. In describing transformations in those cases where the reaction was studied on any one of these preparations, the corresponding preparation will be indicated.
The hydrocarbon has a clearly pronounced unsaturated character with respect to bromine and chameleon. The molecular refraction indicates the presence of one double bond.
All four samples of the hydrocarbon give the characteristic reaction with sulfuric acid described by Maken1 for the hydrocarbon \(C_7H_{12}\) from Persian essence.
If a drop of the hydrocarbon is heated with a drop of concentrated sulfuric acid until it turns brown, and several cubic centimeters of alcohol are added, an intense green coloration is obtained. The same coloration is obtained if the hydrocarbon is shaken with sulfuric acid diluted with two volumes of water.
This reaction led us to pay closer attention to the similarity of the described hydrocarbon to the heptine of Renard and Maken. Maken2 established the identity of Renard’s heptine3 with the hydrocarbon from Persian essence.
The physical properties of the heptine of Renard and Maken are very close to those of the described preparations of the hydrocarbon \(C_7H_{12}\), especially II.
For the heptine obtained from Persian essence,4 Maken gives the following physical constants: boiling temperature \(103.5\text{--}105.5^\circ\) at 765 mm; \(d_{18}=0.780\).
I compare in the table the properties of the heptine obtained by Maken from the nitrosyl chloride of the heptine of turpentine essence5 and of preparation II.
| Maken’s heptine | Hydrocarbon \(C_7H_{12}\) II | |
|---|---|---|
| Boiling temp. | \(104.9\text{--}105.4^\circ\) at 767.5 mm | \(103.7\text{--}104^\circ\) at 752 mm |
| Specific | \(0.8142\ \left(\dfrac{0}{4}\right)\) | \(0.8105\ \left(\dfrac{0}{0}\right)\) |
| gravity | \(0.7921\ (25^\circ)\) | \(0.7936\ \left(\dfrac{20}{0}\right)\) |
| \(n_D\) | 1.44195 at \(25^\circ\) | 1.4430 at \(20^\circ\) |
Reduction of the hydrocarbon \(C_7H_{12}\) with sulfuric and hydriodic acids.
Markovnikov\(^{1}\), by the action of concentrated sulfuric acid on heptyne, obtained the hydrocarbon \(C_7H_{14}\), which he considers identical with Wreden’s hexahydrotoluene; the boiling point of the hydrocarbon is \(94—96^\circ\) at 765 mm; \(d^0_4 = 0.7723\); \(d^{20}_0 = 0.7546\); \(n_{25} = 1.41035\). On heating cyclobutyldimethylcarbinol with hydriodic acid to \(225^\circ\), I obtained the hydrocarbon \(C_7H_{14}\) with very similar properties: b.p. \(94—95^\circ\) at 755 mm; \(d^{20}_0 = 0.7563\); \(n_{20} = 1.4144\); it was of interest to determine what hydrocarbons would be obtained from the described unsaturated hydrocarbon under the action of sulfuric acid, and also of hydriodic acid.
A hydrocarbon with boiling point \(102—105^\circ\) at 773 mm (IV) was shaken at \(0^\circ\) with one volume of fuming sulfuric acid. Sulfurous acid is evolved; the sulfuric acid turns brown; the naphthene odor soon disappears. The sulfuric acid was drained off and replaced with fresh acid until it ceased to turn brown.
The remaining hydrocarbon was washed with alkali and distilled with steam to separate it from polymers. The odor of the hydrocarbon is that of a pure naphthene. The hydrocarbon boils at \(94—94.5^\circ\) at 772 mm.
Analysis.
0.1889 g of substance gave 0.2427 g \(H_2O\) and 0.5913 g \(CO_2\).
| Obtained | Calculated for \(C_7H_{14}\) | |
|---|---|---|
| C | 85.37 | 85.62 |
| H | 14.37 | 14.38 |
Specific gravity.
Weight of hydrocarbon at \(20^\circ = 0.3547\) g.
Weight of water at \(0^\circ = 0.4692\) g.
\[ d^{20}_0 = 0.7560. \]
Refractive index \(n_{10} = 1.4145\).
Molecular refraction \(R^2 = 32.46\).
Calculated for a cyclic hydrocarbon \(C_7H_{14}\), \(R^2 = 32.22\).
The hydrocarbon reacts on warming with fuming nitric acid of sp. gr. 1.52, dissolving completely in it. With bromine in the presence of aluminum bromide the reaction proceeds vigorously, but no crystalline products were obtained.
\(^{1}\) An. de chim. et phys [6], XXVIII, 279.
When hydriodic acid was allowed to act on the same unsaturated hydrocarbon \(C_7H_{12}\) (IV), a cyclic hydrocarbon \(C_7H_{14}\), very close to the preceding one, was obtained.
Two cc of the hydrocarbon were heated in a sealed tube with 20 cc of hydriodic acid, sp. gr. 1.96, at \(215^\circ\) for 7 hours.
Distillation of the hydrocarbon with steam indicated the formation of polymers.
The hydrocarbon boiled at \(94\text{--}96^\circ\) at 767 mm.
Specific gravity.
Weight of substance at \(14.5^\circ = 1.8528\) g.
" " " \(20^\circ = 1.8418\) "
Weight of water at \(0^\circ = 2.4300\) "
\[ d^{14.5}_{0}=0.7625;\quad d^{20}_{0}=0.7579. \]
Refractive index . . . . . . . . . . . \(n_{14.5}=1.4176\)
Molecular refraction . . . . . . . . . . \(R^2=32.36\)
Calculated for cyclic \(C_7H_{14}\) . . . . . \(R^2=32.22\)
The behavior toward nitric acid is the same as in the preceding hydrocarbon.
On treatment with bromine and aluminum bromide, crystalline bromide likewise was not obtained.
The latter hydrocarbon differs from the preceding one in having a lower constant boiling point; it contains an admixture of a higher-boiling hydrocarbon (methylcyclohexane).
Makène regards the hydrocarbon \(C_7H_{14}\) from heptine as hexahydrotoluene; while, when Makène’s article was published (1893), Wreden’s hexahydrotoluene had to be regarded as pure methylcyclohexane. Establishing the closeness (but not identity) of his hydrocarbon \(C_7H_{14}\) from heptine to hexahydrotoluene, and regarding heptine as tetrahydrotoluene, Makène had, of course, a basis for considering the hydrocarbon \(C_7H_{14}\) obtained by him as a cyclohexane derivative. At present, of course, there can be no doubt that Wreden’s hexahydrotoluene contains an admixture of one of the isomeric dimethylcyclopentanes. One of these isomers also constitutes the chief mass of Makène’s hydrocarbon, only with some admixture of methylcyclohexane. This is indicated by the low boiling point (\(94\text{--}96^\circ\)) of Makène’s hydrocarbon as compared with methylcyclohexane (\(103^\circ\)).
The presence of the latter is indicated by the formation of pentabromotoluene from Makène’s hydrocarbon; the latter fact was reported by Makène in
letter to V. V. Markovnikov1); in his article2 Makene reports that, on treatment with bromine and aluminum chloride, a resinous product was obtained.
Makene’s hydrocarbon and all three hydrocarbons obtained by me are extremely close in their properties, as the table shows:
Hydrocarbon \(C_7H_{14}\).
| Origin | Boiling point | \(d^{20}_{0}\) | \(n_{\mathrm{Na}}\) |
|---|---|---|---|
| From cyclobutyldimethylcarbinol | \(94—95^\circ\) at 755 mm | 0.7561 | 1.4144 at \(20^\circ\) |
| \(C_7H_{12} + H_2SO_4\) | \(94—94.5^\circ\) at 772 mm | 0.7560 | 1.4145 at \(20^\circ\) |
| \(C_7H_{12} + HJ\) | \(94—96^\circ\) at 767 mm | 0.7579 | 1.4176 at \(14.5^\circ\) |
| Heptene + \(H_2SO_4\) | \(94—96^\circ\) at 765 mm | 0.7546 | 1.41035 at \(25^\circ\) |
For hydrocarbons of composition \(C_7H_{14}\) with a five-membered ring, the existence of four isomers of the following structure is possible:
\[ \begin{array}{cccc} \begin{array}{c} CH_3\\ |\\ CH_2\\ |\\ CH\\ /\ \backslash\\ H_2C^{5}\quad {}^{2}CH_2\\ |\quad |\\ H_2C^{4}—{}^{3}CH_2 \end{array} & \begin{array}{c} CH_3\\ |\\ CH\\ /\ \backslash\\ H_2C^{5}\quad {}^{2}CHCH_3\\ |\quad |\\ H_2C^{4}—{}^{3}CH_2 \end{array} & \begin{array}{c} CH_3\\ |\\ CH\\ /\ \backslash\\ H_2C^{5}\quad {}^{2}CH_2\\ |\quad |\\ H_2C^{4}—{}^{3}CHCH_3 \end{array} & \begin{array}{c} CH_3\quad CH_3\\ \backslash\ /\ \\ C\\ /\ \backslash\\ H_2C^{5}\quad {}^{2}CH_2\\ |\quad |\\ H_2C^{4}—{}^{3}CH_2 \end{array} \end{array} \]
Ethylcyclopentane is unknown; but its boiling point should be about \(99^\circ\) (from a comparison of the boiling points of ethylcyclohexane, methylcyclohexane, and methylcyclopentane).
Of the remaining three isomers, only 1,3-dimethylcyclopentane has been obtained synthetically: the structure of this isomer has been established by its origin.
It exists in two modifications: optically active and inactive.
Both modifications were obtained by N. D. Zelinsky3. The physical properties of the one and the other modification are very close.
The inactive \(1,3\)-dimethylcyclopentane boils at \(90.5\)—\(91^\circ\) at 751 mm.; \(d^{24}_{4}=0.7410\); \(n_{24}=1.4066\), while the dextrorotatory \(1,3\)-dimethylcyclopentane boils at \(90.5\)—\(91^\circ\) at 755 mm. \(d^{18}_{4}=0.7497\); \(n_{18}=1.4110\).
The \(1,3\)-dimethylcyclopentane described earlier\(^1\) by N. D. Zelinsky was obtained by the action of hydriodic acid on \(1,3\)-dimethylcyclopentanol; its boiling point is \(93^\circ\), \(d^{20}_{4}=0.7543\).
The conditions of formation of the hydrocarbon do not exclude the possibility of partial or complete isomerization into \(1,2\)-dimethylcyclopentane; this is indicated by the higher boiling temperature and the higher specific gravity of the hydrocarbon as compared with pure \(1,3\)-dimethylcyclopentane. \(1,2\)-Dimethylcyclopentane must have a higher specific gravity and a higher boiling temperature as compared with \(1,3\)-dimethylcyclopentane, if one bears in mind their analogy with \(1,2\)- and \(1,3\)-dimethylcyclohexanes:
\[ 1,2\text{-dimethylcyclohexane, b.p. }126^\circ;\quad d^{0}_{4}=0.8008. \]
\[ 1,3\text{-dimethylcyclohexane, b.p. }120^\circ;\quad d^{0}_{4}=0.7847. \]
The hydrocarbon \(C_{7}H_{14}\), obtained from cyclobutyldimethylcarbinol by the action of hydriodic acid, I at first\(^2\) was inclined to regard as \(1,3\)-dimethylcyclopentane, but this occurred because I had not taken into consideration the physical properties of \(1,3\)-dimethylcyclopentane cited in the second work of N. D. Zelinsky. The hydrocarbon \(C_{7}H_{14}\), obtained by reduction with zinc–copper couple of the bromide\(^3\) from cyclobutyldimethylcarbinol, I regard as \(1,1\)-dimethylcyclopentane. Such a structure of the hydrocarbon is in full accord with its unusual stability toward fuming nitric acid (1.52). The boiling temperature of the hydrocarbon is \(88.3\)—\(88.5^\circ\) at 756 mm.; \(89\)—\(89.3^\circ\) at 772 mm.; \(d^{20}_{0}=0.7553\); \(n_{20}=1.4132\).
Taking all this into consideration, I arrive at the conclusion that the hydrocarbon \(C_{7}H_{14}\), obtained from cyclobutyldimethylcarbinol by the action of hydriodic acid, and also the hydrocarbons \(C_{7}H_{14}\) described in this article, consist chiefly of \(1,2\)-dimethylcyclopentane; in the hydrocarbon obtained by the action of hydriodic acid on the unsaturated hydrocarbon \(C_{7}H_{12}\), judging by its boiling point, there may be an admixture of methylcyclohexane.
\(^1\) Ber. 1896, 404.
\(^1\) Zh. 37,517.
\(^2\) Zh. 37,514.
With regard to the hydrocarbon $C_7H_{14}$ obtained by Markovnikov from heptine, Aschan1 expresses the supposition that it may possibly be identical with $1,3$-dimethylcyclopentane. On the basis of the preceding considerations, it is more probable that this is a mixture of $1,2$-dimethylcyclopentane and methylcyclohexane.
Action of hydrogen bromide on the hydrocarbon $C_7H_{12}$
4 g of the hydrocarbon, b.p. $102$–$105^\circ$ at 773 mm (IV), on standing overnight with 6 volumes of fuming hydrobromic acid, dissolved completely. On dilution of the liquid with water, a heavy bromide separated in the form of a green oil. On distillation with steam, the bromide decomposed almost completely into an unsaturated hydrocarbon.
The greater part of the substance distilled over at $103$–$106^\circ$. The hydrocarbon was then heated at $100^\circ$ with fuming hydrobromic acid in a sealed tube. The bromide that separated was washed with water and alkali and dried over calcium chloride.
Already at ordinary temperature the bromide evolves hydrogen bromide. On distillation at ordinary pressure it evolves an abundant quantity of hydrogen bromide and decomposes almost completely into an unsaturated hydrocarbon.
The evolution of hydrogen bromide proceeds continuously throughout the distillation; the thermometer rises to $145^\circ$.
The hydrocarbon obtained boils at $101$–$103^\circ$ at 759 mm: $d^{20}_{0}=0.7962$. There is an admixture of halide.
Thus the bromide obtained by addition of hydrogen bromide to the unsaturated hydrocarbon, by the ease with which it decomposes into the unsaturated hydrocarbon, is quite analogous to the bromide formed by the action of hydrobromic acid on a primary alcohol.
Nitrosyl chloride $C_7H_{12}NOCl$.
In obtaining the nitrosyl chloride, no substantial difference was found between preparations of the hydrocarbon $C_7H_{12}$ of different origin; in all cases the same characteristic phenomena were observed as those described by Markovnikov2 for the reaction by which heptine nitrosyl chloride is obtained.
The reaction was carried out according to Markovnikov, with those modifications indicated by V. V. Markovnikov3. For 2 c.c. of hydrocarbon, 5 c.c. of
water and 17 cc of fuming hydrochloric acid. Sodium nitrite was introduced in small portions while cooling with ice water, and the mixture was shaken vigorously.
After the addition of sodium nitrite, the hydrocarbon becomes bluish-green in color, and then very quickly, as the nitrous-acid salt is added, it is converted into a crystalline mass of the color of copper sulfate. Among the crystals there is also an admixture of a greenish-blue liquid. The reaction product was thoroughly washed with water and soda with vigorous shaking, then finally washed with water on a Büchner funnel and transferred to a porous plate, on which it was dried in a desiccator over sulfuric acid and caustic potash. The crystals, as Wallach also indicates for his nitrosyl chloride, have the color of copper sulfate powder.
The nitrosyl chloride has a strong camphoraceous odor, is readily soluble in all solvents, and possesses extraordinary volatility, as Wallach also indicates for the nitrosyl chloride from heptine. Owing to this volatility, it can be crystallized only from the most concentrated solutions of the most volatile solvents (ether or petroleum ether with b.p. 30–45°); but even then a large loss of substance is observed: on crystallization from dilute ethereal solutions, nothing remains in the crystallization dish.
Owing to such properties, and also to its instability, the nitrosyl chloride is difficult to purify from impurities. Various samples of nitrosyl chloride melted from 73° to 75°; on melting it sublimes. Sublimation, however, begins considerably below the melting temperature. A small quantity of nitrosyl chloride was sealed in a long glass tube. Sublimation proceeds well at 40°. The nitrosyl chloride is deposited on the walls of the tube in the form of stellate, faintly colored crystals.
A nitrogen determination was made for the preparation dried on a porous plate in a desiccator.
0.1881 g of substance gave 14.0 cc of nitrogen at 17° and 753 mm.
| found | calculated for \(C_7H_{12}NOCl\) |
|---|---|
| N 8.51 | N 8.66 |
The nitrosyl chloride of heptine melts at 92° and in doing so partly sublimes, as Wallach indicates.
The nitrosyl chloride obtained by V. V. Markovnikov1 from 1,2-methylcyclohexene had no definite melting temperature; it melted from 70° to 72°, but no sublimation was ever observed.
Nitrosyl chloride, obtained by A. Favorskii1 from pure 1,2-methylcyclohexene, is a stable compound, crystallizing in colorless plate-like crystals with a melting point of 97.5°.
Bromide of the hydrocarbon \(C_7H_{12}\)
Renard, describing2 heptine from resin essence, says that under the action of bromine in ethereal solution it is converted into the bromide \(C_7H_{12}Br_2\). The composition of the bromide was determined by taking into account the amount of bromine entering into reaction with the heptine. On evaporation of the ethereal solution of the bromide, colorless crystals are obtained, but they are extremely unstable; a few minutes after their formation they decompose, turn green, and give off hydrogen bromide. Macène3 likewise characterizes the bromide of heptine.
In the first experiments on obtaining the bromide from the hydrocarbon \(C_7H_{12}\) preparations described above, I obtained the same results as Renard and Macène, but later it proved possible, by observing special precautions, to obtain the bromide \(C_7H_{12}Br_2\) in a state sufficiently pure for analysis.
If bromine is added, with good cooling by ice water, to a dry ethereal solution of the hydrocarbon until saturation, then on evaporation of the solution colorless crystals of the bromide first appear, but then they rapidly turn green; the ethereal solution also turns green, and the result is a green mass from which it is no longer possible to isolate a crystalline substance. The cause of the rapid decomposition is hydrogen bromide, which is always formed when the hydrocarbon in ethereal solution is combined with bromine. Better results are obtained if, after adding bromine until a faint permanent coloration is produced, the ethereal solution is thoroughly washed with a weak solution of caustic alkali. On evaporation of the dried ethereal solution, an almost colorless bromide is obtained in the form of needles; pressed on a porous plate, the bromide continues to turn green, but much more slowly than in the first case; it cannot be purified by repeated crystallizations from ether.
The bromide decomposes especially rapidly upon crystallization from acetic ether.
In these experiments it was observed that a porous clay plate accelerates the decomposition of the bromide. In the end, to obtain the bromide, it was necessary to adopt the following procedure.
The hydrocarbon was dissolved in pure carbon disulfide; then, with cooling by ice water, a carbon-disulfide solution of bromine was carefully added to the solution until a permanent bromine coloration was obtained. After this the solution was washed with caustic potash and dried with calcium chloride. On evaporating the carbon disulfide there remained a crystalline, only slightly yellowish mass with a small admixture of an oily substance. The crystals were pressed between papers, since when pressed on a porous plate they quickly begin to turn green. The dry crystals melt with decomposition to a green liquid at 113°–114°.
Determination of bromine.
0.1968 g of substance gave 0.2885 g of AgBr.
| Found | Calculated for $\mathrm{C_7H_{12}Br_2}$ |
|---|---|
| Br 62.38 | Br 62.49 |
On crystallization from ether, the bromide begins to turn green already in solution. Decomposition proceeds still more rapidly on crystallization from methyl or ethyl alcohol. After these experiments the bromide was crystallized from carbon disulfide or petroleum ether (b.p. 30–50°) in a constant stream of dry hydrogen. From petroleum ether colorless elongated rhombi are obtained. The bromide melts at 115°–115.5° to a dark-green liquid. The odor is camphor-like.
Analysis.
I. 0.1816 g of substance gave 0.0776 g of $\mathrm{H_2O}$ and 0.2188 g of $\mathrm{CO_2}$.
II. 0.2101 g of substance gave 0.3078 g of AgBr.
| Found I | Found II | Calculated for $\mathrm{C_7H_{12}Br_2}$ | |
|---|---|---|---|
| C | 32.86 | — | 32.81 |
| H | 4.78 | — | 4.84 |
| Br | — | 62.35 | 62.49 |
In a stream of hydrogen at 70° the bromide sublimes without residue; the melting point of the sublimed bromide is 112–113°. On standing in air the bromide gradually turns green. Moistened with methyl alcohol on a porous plate, it begins rapidly to turn green; on paper this is not noticeable. The influence of the porous plate on the rate of decomposition of the bromide apparently has a catalytic character.
By carefully adding heptine to cooled bromine and leaving the mixture, with an excess of bromine, to stand in the dark for two or three days, Renard1 obtained a crystalline bromide with a melting point of \(134^\circ\); on the basis of the bromine determination Renard assigned this bromide the formula: \(\mathrm{C_7H_6Br_6}\).
This reaction, with some modification, was carried out with hydrocarbon III (b.p. \(103.5\text{--}105^\circ\) at 764 mm). To moderate the reaction, the hydrocarbon was diluted with three volumes of ether, and the solution was added little by little to the cooled bromine.
The reaction product was left for two days at room temperature in diffused light. A thick, brownish-red liquid was obtained, containing free bromine. The product was dissolved in ether; the ethereal solution was washed with alkali to remove the free bromine, then with water, and, after the addition of one volume of methyl alcohol, was poured into a crystallizing dish.
On evaporation, large crystals of the bromide were obtained together with an oily bromide. The crystals were pressed on a porous plate, washed with a small amount of ether, and recrystallized from a mixture of ether and methyl alcohol.
The bromide melts at \(134\text{--}135^\circ\), and at this temperature begins to evolve gas bubbles. On heating above the melting point, it first gives off bromine vapors, and then begins to evolve hydrogen bromide. In melting point the bromide is identical with Renard’s bromide, but analysis gave somewhat different results.
I. \(0.1219\) g of substance gave (by Carius) \(0.2463\) g \(\mathrm{AgBr}\).
II. \(0.1091\) g ,, ,, ,, \(0.2208\) g ,,
III. \(0.1851\) g of substance gave \(0.0143\) g \(\mathrm{H_2O}\) and \(0.0892\) g \(\mathrm{CO_2}\).
| Obtained I | Obtained II | Obtained III | Calculated for \(\mathrm{C_6H_6Br_6}\) | Calculated for \(\mathrm{C_7H_6Br_6}\) | |
|---|---|---|---|---|---|
| C | — | — | 13.14 | C 12.90 | C 14.74 |
| H | — | — | 0.86 | H 1.10 | H 1.05 |
| Br | 85.98 | 86.09 | — | Br 86.00 | Br 84.21 |
The splitting off of one carbon atom in the formation of the polybromide is, of course, quite possible, but I consider the question of the composition of the bromide to be as yet unresolved.
The complete similarity of the transformations of the hydrocarbons \(C_7H_{12}\), obtained by me from the primary and the tertiary alcohol, insofar as this could be followed experimentally, gives grounds for concluding that in both cases, at least in predominant amount, one and the same hydrocarbon is obtained. On the other hand, I believe I have adduced enough data to regard this hydrocarbon as identical with Renard and Macé’s heptine.
Macé1 regards this hydrocarbon as methylcyclohexene-1; V. V. Markovnikov likewise views the structure of Renard and Macé’s heptine in the same way. V. V. Markovnikov arrived at this conclusion on the basis of a study of methylcyclohexene-1, which he obtained from the tertiary chloride of heptanaphthene, and also from the corresponding amine of heptanaphthene (1,1-methylchlorocyclohexane and 1,1-methylaminocyclohexane). Markovnikov’s methylcyclohexene-1 gave the characteristic reaction with sulfuric acid and alcohol (green coloration), and, in the preparation of the nitrosochloride, the same phenomena were observed as those described by Macé for Renard’s heptine. But between V. V. Markovnikov’s methylcyclohexene and Macé’s heptine there is a substantial difference in boiling points. For his hydrocarbon V. V. Markovnikov gives a boiling point of \(109^\circ\) at 768 mm, whereas Macé’s hydrocarbon boiled at \(104.9—105.4^\circ\) at 767.5 mm. It is difficult to suppose that Macé, who had at his disposal 2 liters of heptine from resinous essence with boiling point \(103.5—105^\circ\) at 765 mm, and 50 g of hydrocarbon isolated from crystalline nitrosochloride with the above-mentioned boiling point, would have failed to notice in it the presence of a hydrocarbon (methylcyclohexene-1) boiling 4–5° higher. Markovnikov, however, considers Macé’s hydrocarbon pure and merely expresses the following supposition: “is the difference in the b.p. not to be explained by the fact that at that time the French chemists did not use thermometers with a shortened scale?”
I think that the explanation of the difference in the boiling points of Macé’s heptine and methylcyclohexene-1 should rather be sought in a difference in the structure of the named hydrocarbons. The belonging of heptine to the cyclohexene series has as yet not been proved by anything at all; there are still fewer data for considering this hydrocarbon identical with methylcyclohexene-1. Besides the difference in the physical properties of these hydrocarbons, one must also bear in mind the difference in the properties of the nitrosochloride of heptine from the nitrosochloride of methylcyclohexene-1, recently described by A. Favorskii.
What structure Macé’s heptine has, and consequently also the hydrocarbon obtained by me, remains as yet undetermined.
Aschan1, among other things, expresses the supposition that Maker’s hydrocarbon may prove to be one of the dimethylcyclopentenes. The facts cited in this article speak in favor of such a view of the structure of this hydrocarbon.
It is possible that Renard and Maker’s heptine, as well as the hydrocarbon \(C_7H_{12}\) described by me, has the following structure:
\[ \begin{array}{c} \begin{array}{cc} \mathrm{CH_3} & \mathrm{CH_3}\\ | & |\\ \mathrm{C}=\mathrm{C}\\ | & |\\ \mathrm{CH_2} & \mathrm{CH_2}\\ \multicolumn{2}{c}{\diagdown\ \diagup}\\[-2pt] \multicolumn{2}{c}{\mathrm{CH_2}} \end{array} \end{array} \]
The fluctuations in the physical properties of hydrocarbon preparations \(C_7H_{12}\) of different origin, described in this work and obtained by me, may depend on a different admixture of hydrocarbons with a four-membered ring of the following structure:
\[ \begin{array}{ccc} \begin{array}{ccc} \mathrm{CH_3} & - & \mathrm{CH} & - & \mathrm{C}\\ & | & & & \|\\ \mathrm{CH_2} & - & \mathrm{CH_2} & & \mathrm{CH_2}\\ & & & & |\\ & & & & \mathrm{CH_3} \end{array} & \text{or} & \begin{array}{ccc} \mathrm{CH_2} & - & \mathrm{C} = \mathrm{C}\\ | & & | & \ \ \ |\\ \mathrm{CH_2} & - & \mathrm{CH_2} & \ \ \ \mathrm{CH_3}\\ & & & \ \ \ |\\ & & & \ \ \ \mathrm{CH_3} \end{array} \end{array} \]
Clarifying the structure of the hydrocarbon obtained by me will constitute the nearest task in the continuation of the present investigation.
On the Hydrocarbons from the Bromide of Cyclobutyldimethylcarbinol.
In contrast to the primary alcohol, cyclobutyldimethylcarbinol gives a constant bromide, distilling without decomposition at \(167^\circ\) at 757 mm. The bromide was described2 three years ago and was regarded as a direct derivative of cyclobutyldimethylcarbinol.
The latter point of view, at the basis of which lay the origin of the bromide, must be abandoned. To explain the properties and transformations of the bromide, it is necessary to admit the presence in the bromide of a five-membered closed skeleton.
In preparing the bromide once again, the aim was, above all, to determine what hydrocarbons are formed from the bromide upon elimination of the hydrohalic acid, for comparison with the hydrocarbon \( \mathrm{C_7H_{12}} \) described above.
In addition, it was of interest to compare the results of reduction of the bromide by a copper–zinc couple with the results obtained at present in reducing the bromide with hydriodic acid.
12 g of cyclobutyldimethylcarbinol were heated with 4 volumes of fuming hydrobromic acid for 2 hours at \(100^\circ\).
After separation with water and washing, 17 g of crude bromide were obtained. Since, in the first experiment for obtaining the bromide, it had been observed that the bromide contains an admixture of unstable bromide decomposing on distillation with steam into an unsaturated hydrocarbon, the crude bromide was boiled for half an hour with a solution of 20 g of caustic potash in 50 g of water and was then distilled with steam. 15 g of substance were obtained.
On distillation with a dephlegmator, a fraction up to \(110^\circ\) was separated; from it, after boiling over metallic sodium, 2 g of hydrocarbon with a boiling point of \(102.5\text{--}104.5^\circ\) at 752 mm were obtained.
Yield of hydrocarbon.
Weight of hydrocarbon at \(20^\circ\)—0.7249 g.
Weight of water at \(0^\circ\)—0.9182 g.
\[ d^{20}_{0}=0.7895 \]
Refractive index \(n_{20}=1.4402\)
Molecular refraction . . . . . . . . . . . . . . \(R^2=32.06\)
Calculated for \( \mathrm{C_7H_{12}} \) with a double bond . . . . . \(R^2=31.82\)
With sulfuric acid and alcohol (according to Markov), the hydrocarbon gives an intense green coloration; it gives a crystalline nitrosochloride with the same properties as described above for the hydrocarbon \( \mathrm{C_7H_{12}} \).
The physical properties of the hydrocarbon correspond to heptine (IV), obtained by the action of oxalic acid on cyclobutyldimethylcarbinol.
11 g of bromide were obtained; its physical properties are close to those of the previously described bromide of the same origin.
Boiling point \(167^\circ\) at 764 mm; it distils without traces of decomposition.
Specific gravity
Weight of substance at \(20^\circ = 3.9659\) g.
Weight of water at \(0^\circ = 3.1670\) g.
\[ d^{20}_{0}=1.2523. \]
Refractive index \(n_{20}=1.4794\).
Molecular refraction \(R^2=40.01\).
Calculated for \(C_7H_{13}Br\), \(R^2=40.10\).
The specific gravity of the bromide obtained earlier: \(d^{20}_{0}=1.2562\).
The constancy of the bromide with respect to an aqueous solution of caustic potash on boiling suggested the possibility of obtaining an alcohol from it by prolonged saponification with potash; however, under these conditions an unsaturated hydrocarbon was obtained as the principal reaction product; it was not possible to isolate alcohol in any appreciable quantities.
7 g of the bromide and 100 c.c. of a 10% potash solution were boiled for 15 hours with a reflux condenser. In all, the bromide was in contact with the potash for 3 days.
The reaction product was distilled off with steam; the distillate was saturated with potash; the oily layer was dried with fused potash. Of undistilled product, 3.5 g were obtained.
Distillation showed the absence of any appreciable quantities of alcohol. The product, purified by heating at \(100^\circ\) with metallic sodium, boiled at \(100\text{—}102^\circ\) at 753 mm.
Specific gravity.
Weight of hydrocarbon at \(20^\circ = 0.7233\) g.
Weight of water at \(0^\circ = 0.9182\) g.
\[ d^{20}_{0}=0.7877. \]
Refractive index \(n_{20}=1.4396\).
Molecular refraction \(R^2=32.09\).
Calculated for \(C_7H_{12}\) with two double bonds, \(R^2=31.82\).
The hydrocarbon has a sharp naphthene odor; it decolorizes potassium permanganate; with sulfuric acid and alcohol it gives a faint green coloration. On the action of strong sulfuric acid on the hydrocarbon at \(0^\circ\), a saturated hydrocarbon was obtained, which boiled at \(90\text{—}92^\circ\) at 753 mm. When this latter hydrocarbon was treated at room temperature with fuming nitric acid of specific gravity 1.52, only about half of the hydrocarbon dissolved; the remaining half stubbornly
withstands the action of nitric acid, notwithstanding the prolonged contact of the hydrocarbon with nitric acid (2 days). This compels one to recognize the presence in the hydrocarbon of 1,1-dimethylcyclopentane. The limiting hydrocarbon has not yet been studied in greater detail.
Reduction of the bromide with so-called 167° hydriodic acid.
4 g of the bromide were heated with 20 c.c. of hydriodic acid, sp. gr. 1.96, for 6 hours at 205°.
On distillation of the hydrocarbon, washed and dried with calcium chloride, a small quantity of polymers was found.
The first distillation gave a product with boiling point 94–100°. In the second distillation the main fraction, 94.5–96° at 753 mm, separated.
Hydrocarbon.
Weight of substance at 20° = 0.7000 g.
Weight of water at 0° = 0.9182 g.
\[ d^{20}_{0}=0.7624 \]
Refractive index \(n_{20}=1.4151\).
Molecular refraction \(R^{2}=32.20\).
Calculated for \(C_{7}H_{14}\) (cycl.) \(R^{2}=32.20\).
The hydrocarbon reacts vigorously with bromine and aluminum bromide. A thick mass of bromide is obtained, which was washed first with caustic potassium to remove bromine, and then with petroleum ether.
The residue was dissolved in benzene. On evaporation of the benzene, in addition to oil, needle-like crystals separated; these were pressed off and recrystallized from benzene; colorless needles are obtained; their melting point, 282–283°, corresponds to pentabromotoluene.
The hydrocarbon \(C_{7}H_{14}\) obtained, judging by its boiling point, represents a mixture of dimethylcyclopentane (1,2) and methylcyclohexane; the presence of the latter is also indicated by the high specific gravity of the hydrocarbon, as well as by the formation of pentabromotoluene on bromination of the hydrocarbon.
The formation of methylcyclohexane in the reduction of the bromide \(C_{7}H_{13}Br\) represents one of the cases of isomerization of a five-membered ring into a six-membered one.
To answer definitely the question of what structure the bromo compound has that is formed by the action of hydrogen bromide on cyclobutyldimethylcarbinol is, at present, still impossible; but there is no doubt that its formation is accompanied by isomerization of the tetramethylene ring into a cyclopentane derivative. That the bromo compound cannot be an immediate derivative of cyclobutyldimethylcarbinol is already indicated by the discrepancy between the boiling point of the bromo compound and that of the alcohol, a point to which sufficient attention was not paid in the first paper. The bromo compound boils \(20^\circ\) higher than cyclobutyldimethylcarbinol. Such a considerable difference is not observed in the fatty and cyclic series for alcohols and the corresponding bromo compounds, except for the very lowest members with a small number of carbon atoms. The normal alcohols, hexyl, heptyl, octyl, have boiling points very close to those of the corresponding bromo compounds; the difference is \(1–2^\circ\). The same is also observed in the cyclic series:
| Alcohols. | B.p. | Bromo compounds. | B.p. |
|---|---|---|---|
| Cyclopentanol | 139 | Bromocyclopentane | 137–139° |
| Cyclohexanol | 160.9° | Bromocyclohexane | 162–163° |
| Methyl-1-cyclohexanol-3 | 175–176° | 1,3-bromomethylcyclohexane | 181.5–182° |
On reduction of the bromo compound with a zinc–copper couple, a hydrocarbon \(C_7H_{14}\) was obtained, the structure of which is determined by its behavior toward fuming nitric acid. The hydrocarbon is extraordinarily resistant toward nitric acid, sp. gr. 1.52, which indicates the absence in it of tertiary hydrogen; this leads to the only possible structure of the hydrocarbon in such a case:
\[ \begin{array}{c} \mathrm{CH_3}\qquad \mathrm{CH_3}\\ \diagdown\quad \diagup\\ \mathrm{C}\\ /\quad \backslash\\ \mathrm{H_2C}\qquad \mathrm{CH_2}\\ |\qquad |\\ \mathrm{H_2C}—\mathrm{CH_2} \end{array} \]
The belonging of the hydrocarbon to the cyclopentane series1 is proved by the unchanged state of the hydrocarbon under the action of fuming hydriodic acid at \(230^\circ\).
The same hydrocarbon, 1,1-dimethylcyclopentane, is also obtained by the action of sulfuric acid on the unsaturated hydrocarbon \(C_7H_{12}\), formed from the bromo derivative by the action of potash.
Thus, it must be regarded as fully established that the last-mentioned bromo derivative is a derivative of 1,1-dimethylcyclopentane. It remains only to determine the position of the bromine. If the bromine is situated in the side chain, the bromo derivative must have the following structure:
\[ \begin{array}{c} \mathrm{CH_3}\qquad \mathrm{CH_2Br}\\ \diagdown\quad\diagup\\ \mathrm{C}\\ /\quad\backslash\\ \mathrm{H_2C}\qquad \mathrm{CH_2}\\ |\qquad |\\ \mathrm{H_2C}-\mathrm{CH_2} \end{array} \]
The splitting off of hydrogen bromide from such a bromo derivative would lead to the formation of a bicyclic hydrocarbon; but under the conditions in which an unsaturated hydrocarbon can be obtained (the action of an aqueous solution of potash), with such a structure of the bromo derivative a primary alcohol should have been obtained:
\[ \begin{array}{c} \mathrm{CH_3}\qquad \mathrm{CH_2OH}\\ \diagdown\quad\diagup\\ \mathrm{C}\\ /\quad\backslash\\ \mathrm{H_2C}\qquad \mathrm{CH_2}\\ |\qquad |\\ \mathrm{H_2C}-\mathrm{CH_2} \end{array} \]
The formation of an unsaturated hydrocarbon under the action of an aqueous solution of potash indicates the position of the bromine in the ring; and therefore the bromo derivative may have one of the following structural formulae:
\[ \begin{array}{cc} \text{1)}& \begin{array}{c} \mathrm{CH_3}\qquad \mathrm{CH_3}\\ \diagdown\quad\diagup\\ \mathrm{C}\\ /\quad\backslash\\ \mathrm{H_2C}\qquad \mathrm{CH_2Br}\\ |\qquad |\\ \mathrm{H_2C}-\mathrm{CH_2} \end{array} \qquad \text{2)}& \begin{array}{c} \mathrm{CH_3}\qquad \mathrm{CH_3}\\ \diagdown\quad\diagup\\ \mathrm{C}\\ /\quad\backslash\\ \mathrm{H_2C}\qquad \mathrm{CH_2}\\ |\qquad |\\ \mathrm{H_2C}-\mathrm{CH_2Br} \end{array} \end{array} \]
This direction of isomerization of cyclobutyldimethylcarbinol into a cyclopentane derivative with bromine in the ring is entirely analogous to the conversion of cyclobutylcarbinol into bromocyclopentane:
\[ \begin{array}{ccc} \begin{array}{c} \mathrm{H_2C{-}CH{-}CH_2OH}\\ \left| \hspace{2.7em} \right|\\ \mathrm{H_2C{-}CH_2} \end{array} & \longrightarrow & \begin{array}{c} \mathrm{CHBr}\\[-0.2em] / \hspace{2.5em} \backslash\\[-0.2em] \mathrm{H_2C} \hspace{2.2em} \mathrm{CH_2}\\ \left| \hspace{2.8em} \right|\\ \mathrm{H_2C{-}CH_2} \end{array} \end{array} \]
The latter transformation was demonstrated by N. Ya. Dem’yanov1.
The very same character of isomerization is also observed in the conversion of pinene, under the influence of hydrochloric acid, into bornyl chloride:
\[ \begin{array}{ccccc} \begin{array}{c} \mathrm{CH{=}C{-}CH}\\[-0.2em] \hspace{2.2em} |\\[-0.2em] \hspace{2.0em}\mathrm{CH_3}\\[-0.2em] \left| \hspace{4.5em} \right|\\ \mathrm{\ \ \ CH_3{-}C{-}CH_3}\\[-0.2em] \hspace{2.2em} |\\[-0.2em] \mathrm{CH_2{-}CH{-}CH_2} \end{array} & +\mathrm{HCl} & \longrightarrow & \begin{array}{c} \mathrm{CH_2{-}C{-}CH}\\[-0.2em] \hspace{2.2em} | \hspace{2.4em}\\[-0.2em] \hspace{2.0em}\mathrm{CH_3}\\[-0.2em] \hspace{2.2em}\mathrm{Cl}\\[-0.2em] \left| \hspace{4.5em} \right|\\ \mathrm{CH_3{-}C{-}CH_3}\\[-0.2em] \hspace{2.2em} |\\[-0.2em] \mathrm{CH_2{-}CH{-}CH_2} \end{array} & \longrightarrow \begin{array}{c} \mathrm{CH_2{-}C{-}CHCl}\\[-0.2em] \hspace{2.2em} |\\[-0.2em] \hspace{2.0em}\mathrm{CH_3}\\[-0.2em] \left| \hspace{4.5em} \right|\\ \mathrm{CH_3{-}C{-}CH_3}\\[-0.2em] \hspace{2.2em} |\\[-0.2em] \mathrm{CH_2{-}CH{-}CH_2} \end{array} \\[1em] \text{pinene} &&& \text{intermediate stage} & \text{bornyl chloride} \end{array} \]
If for the bromide \(\mathrm{C_7H_{13}Br}\) one adopts the structure of 1,1,2-dimethylbromocyclopentane, then the analogy in the isomerization will be complete:
\[ \begin{array}{ccccc} \begin{array}{c} \hspace{2.2em}\mathrm{CH_3}\\[-0.2em] \hspace{2.2em}|\\[-0.2em] \mathrm{CH_3{-}C{-}CH}\\[-0.2em] \hspace{2.2em}| \hspace{2.2em} \left|\\[-0.2em] \hspace{2.2em}\mathrm{OH}\\[-0.2em] \hspace{1.2em}/ \hspace{2.9em}\left|\\[-0.2em] \mathrm{CH_2} \hspace{3.0em}\\[-0.2em] \left| \hspace{3.6em} \right|\\[-0.2em] \mathrm{CH_2{-}CH_2} \end{array} & +\mathrm{BrH} & \longrightarrow & \begin{array}{c} \hspace{2.2em}\mathrm{CH_3}\\[-0.2em] \hspace{2.2em}|\\[-0.2em] \mathrm{CH_3{-}C{-}CH}\\[-0.2em] \hspace{2.2em}| \hspace{2.2em} \left|\\[-0.2em] \hspace{2.2em}\mathrm{Br}\\[-0.2em] \hspace{1.2em}/ \hspace{2.9em}\left|\\[-0.2em] \mathrm{CH_2} \hspace{3.0em}\\[-0.2em] \left| \hspace{3.6em} \right|\\[-0.2em] \mathrm{CH_2{-}CH_2} \end{array} & \longrightarrow \begin{array}{c} \hspace{2.2em}\mathrm{CH_3}\\[-0.2em] \hspace{2.2em}|\\[-0.2em] \mathrm{CH_3{-}C{-}CHBr}\\[-0.2em] \hspace{2.2em}| \hspace{2.8em} \left|\\[-0.2em] \hspace{2.2em}\mathrm{CH_2}\\[-0.2em] \hspace{2.2em}| \hspace{2.8em} \left|\\[-0.2em] \hspace{2.2em}\mathrm{CH_2{-}CH_2} \end{array} \\[1em] \begin{array}{c} \text{cyclobutyldimethyl-}\\ \text{carbinol} \end{array} &&& \begin{array}{c} \text{intermediate}\\ \text{stage} \end{array} & \begin{array}{c} \text{1,1,2-dimethylbromo-}\\ \text{cyclopentane} \end{array} \end{array} \]
Further investigations must decide how far the considerations expressed here are correct.
2. On the Hydrogenation of Tetramethylenecarboxylic Acid.
N. Kizhner.
Three years ago, under the action of hydriodic acid on cyclobutyldimethylcarbinol,¹ I obtained a cyclic hydrocarbon, \(C_7H_{14}\). Since it was difficult to suppose that, under the conditions of the experiment, the tetramethylene ring could remain unchanged, in view of the difference between the hydrocarbon obtained and methylcyclohexane, the supposition was expressed that the formation of the hydrocarbon is accompanied by isomerization of the four-membered ring into a five-membered one. It was indicated at that time that, in order to determine the degree of stability of the tetramethylene ring under the conditions of the experiments described, it would be of interest to study the behavior of tetramethylenecarboxylic acid toward hydriodic acid.
The present article presents the result of experiments on the reduction of tetramethylenecarboxylic acid carried out in the indicated direction.
Completely pure tetramethylenecarboxylic acid, with boiling point \(195.5\text{–}196^\circ\) at 760 mm, was taken for the reaction.
The acid was heated in sealed tubes with hydriodic acid of specific gravity 1.96 at \(200\text{–}210^\circ\) for 9 hours. For 2.5 g of tetramethylenecarboxylic acid, 25 g of hydriodic acid was used.
The contents of the tubes were diluted with water; the iodine was decolorized by adding an excess of acid sodium sulfite; the neutral products were distilled off with steam.
From 5 g of tetramethylenecarboxylic acid taken into the reaction, a total of 0.2 g of neutral products was obtained. The substance has a hydrocarbon odor; its boiling point is about \(150^\circ\).
¹ Zh. 37, 516.
To isolate the acidic products of reduction, the residue from the steam distillation was distilled until about half of the liquid had distilled over; the distillate was neutralized with caustic soda and evaporated. After addition of sulfuric acid, the organic acid that separated was extracted with light petroleum ether (b.p. 34–50°); the petroleum solution was dried with sodium sulfate. After removal of the petroleum ether, the remaining acid was distilled. Three grams of acid were obtained, with a constant boiling point of 186.4–187° at 768 mm. On repeated distillations the boiling temperature did not change, and the specific gravity likewise remained unchanged.
Determination of the specific gravity.
Weight of substance at 20°—0.8703 g.
Weight of water at . . . . . 0°—0.9182 g.
\[ d^{20}_{0}=0.9478 \]
Refractive index . . . . . . \(n_{20}=1.4105\)
Molecular refraction . . . . \(R^{2}=26.69\)
Calculated for \(C_{4}H_{9}COOH\) . . . . \(R^{2}=26.82\)
The physical properties of the acid correspond to those of normal valeric acid:
\[ \text{b.p. } 186\text{–}186.4^\circ;\quad d_{20}=0.9415. \]
The calcium salt crystallizes in plates characteristic of normal valeric acid, with one particle of water of crystallization. On heating a saturated solution of the salt to 70°, the solution begins to become turbid and crystals of the calcium salt separate. Such a decrease in solubility is also characteristic of the calcium salt of normal valeric acid.
On drying 0.5540 g of the salt at 125°, 0.0384 g of \(H_{2}O\) was obtained.
\[ \begin{array}{cc} \text{Found} & \text{Calculated for } (C_{5}H_{9}O_{2})_{2}Ca+H_{2}O \\ H_{2}O \quad 6.93 & H_{2}O \quad 6.92 \end{array} \]
0.2528 g of the anhydrous salt gave 0.0544 g of \(CaO\).
\[ \begin{array}{cc} \text{Found} & \text{Calculated for } (C_{5}H_{9}O_{2})_{2}Ca \\ Ca \quad 16.70 & Ca \quad 16.51 \end{array} \]
The formation of normal valeric acid shows that rupture of the ring occurs at the bond nearest to the carboxyl group:
in cleavage in the other direction, methylethylacetic acid would be obtained:
\[ \begin{array}{c@{\qquad\qquad}c} \begin{array}{c} \mathrm{CH_2}\\[-2pt] /\ \ \ \backslash\\[-2pt] \mathrm{CH_2}\ \ \ \mathrm{CH{-}COOH}\\[-2pt] \backslash\ \ \ /\\[-2pt] \mathrm{CH_2} \end{array} & \mathrm{CH_3{-}CH_2{-}CH_2{-}CH_2COOH} \\[3em] & \begin{array}{c} \mathrm{H}\\[-2pt] |\\[-2pt] \mathrm{CH_3{-}CH_2{-}C{-}COOH}\\[-2pt] |\\[-2pt] \mathrm{CH_3} \end{array} \end{array} \]
The second direction of the reaction would be analogous to the conversion of bromocyclobutane, under the action of hydrogen bromide, into 1,3-dibromobutane (Perkin):
\[ \begin{array}{c@{\qquad\qquad}c} \begin{array}{c} \mathrm{CH_2}\\[-2pt] /\ \ \ \backslash\\[-2pt] \mathrm{CH_2}\ \ \ \mathrm{CHBr}\\[-2pt] \backslash\ \ \ /\\[-2pt] \mathrm{CH_2} \end{array} & \begin{array}{c} \mathrm{H}\\[-2pt] |\\[-2pt] \mathrm{CH_2Br{-}CH_2{-}C{-}Br}\\[-2pt] |\\[-2pt] \mathrm{CH_3} \end{array} \end{array} \]
It is possible that $\alpha$-bromotetramethylenecarboxylic acid, on hydrogenation, will pass into methylethylacetic acid. The clarification of this question will be the subject of the next investigation.
From the results of the present experiments I see that, under the conditions described, it is almost exclusively the nucleus of tetramethylenecarboxylic acid that undergoes hydrogenation.
Since the carboxyl group, at the moment of rupture of the ring, remains without change, this excludes any possibility of the formation of a five-membered ring, and the reduction leads to the formation of an open carbon chain. In the reduction with hydrogen iodide of cyclobutyldimethylcarbinol (Kizhner) and cyclobutyldiethylcarbinol (Kizhner and Amozov) ^1) exclusively cyclic hydrocarbons, $\mathrm{C_7H_{14}}$ and $\mathrm{C_9H_{18}}$, are formed.
Since there are no grounds whatever for thinking that the tetramethylene ring of the indicated compounds, in its degree of resistance toward hydrogen iodide, differs in any essential way from the nucleus of tetramethylenecarboxylic acid, the formation of cyclic hydrocarbons, and not paraffins, can in no way be explained by retention of the tetramethylene ring in this case.
Rupture of the tetramethylene ring also occurs in these cases, but it leads not only to the formation of open chains,
^1) Zh. 37, 517.
as in the case of tetramethylenecarboxylic acid, but lead to the formation of new, more stable cyclic systems.
In these cases, there is hardly a complete rupture of the tetramethylene ring in the sense of the formation of some actual compound with an open carbon chain; rather, one may think that at the moment of rupture of the ring, the open chain being formed, by its configuration, is closer to a closed grouping (five-membered or six-membered) than to an actual open chain, as a result of which such an opened or, more correctly, half-opened chain, bypassing the stage of real existence of an aliphatic compound, passes directly into another cyclic system.
By such an interpretation, those cases of formation of cyclic compounds are most simply explained in which, with greater probability, one should have expected the formation of compounds of the aliphatic series.