SovietRxiv

Activity of halogens in some of the simplest halogenated hydrocarbons as a function of the position of the halogens in the molecule

B. V. Tronov and L. G. Boldyreva.
Submitted 1931 | SovietRxiv: ru-193101.07578 | Translated from Russian

Abstract Generated abstract

This study examines how the position of halogen atoms in simple saturated halogenated hydrocarbons affects carbon halogen bond reactivity. Twenty two chloro, bromo, and iodo derivatives with three to five carbon atoms were reacted at room temperature with pyridine, piperidine, and sodium methylate, taken as reagents favoring different modes of bond cleavage, and relative rates were estimated from comparable extents of reaction. The results show systematic effects of halogen identity, chain length, branching, and substitution position: branching generally lowers activity, primary halides react more readily than secondary halides with amines, while tertiary halides react especially rapidly with alcoholates. The authors interpret these trends as supporting their earlier distinction between ionic and neutral cleavage of the carbon halogen bond.

Full Text

B. V. Tronov and L. G. Boldyreva.

Activity of Halides in Some of the Simplest Halogenated Hydrocarbons as a Function of the Position of the Halide in the Molecule

In the article “Activity of Halides in Organic Compounds as a Function of the Electrochemical Character of the Radical with Which the Halide Is Bound”1, one of us expressed the idea that there are two types of rupture of the bond between carbon and halide:

\[ \mathrm{C}\ \mathrm{X} \longrightarrow \mathrm{C}^{+} + [\mathrm{X}]^{-} \]

and

\[ \mathrm{C}\ \mathrm{X} \longrightarrow \mathrm{C}^{-} + \mathrm{X} \]

i.e., the halide may depart either in the form of a negative ion, together with the pair of electrons of its bond with carbon (as in the dissociation of hydrohalic acids), or in the form of a neutral atom, taking only one of the bonding electrons (as in molecules of free halides). Which reaction will proceed in any given case depends both on the nature of the halogen compound and on the reagent acting upon it. Of the most commonly used reagents, alkalis and alcoholates readily detach halide in the form of a neutral atom, while amines and salts of alkali metals detach it in the form of an ion. As for the influence of a hydrocarbon, or generally organic, radical, if this radical is electropositive, then the corresponding halogen derivative will be similar in its chemical character to hydrohalic acid; an electronegative radical makes the substance similar to a molecule of a free halide.

A comparison of the activities of halogenated propanes and isopropanes2 showed that primary halogenated hydrocarbons are more capable of ionic cleavage than secondary ones. This is also confirmed by the study of halogen-substituted complex ethers3. Tertiary halogen compounds have been very little studied. Experiments with methyl-bromomalonic ester indicated, as might have been expected, a very high neutral activity with low ionic activity.

In the present work we aimed to extend the investigation to substances of the simplest possible composition and structure.

Polyhalogenated derivatives of saturated hydrocarbons with three, four, and five carbon atoms were taken.

In all, 22 compounds were studied:

\[ \begin{gathered} \mathrm{CH_3.CH_2.CH_2Cl,\ CH_3.CH_2.CH_2Br,\ CH_3.CH_2.CH_2J,\ CH_3.CHCl.CH_3,}\\ \mathrm{CH_3.CHBr.CH_3,\ CH_3CHJ.CH_3,\ CH_3.CH_2.CH_2.CH_2Cl,}\\ \mathrm{CH_3.CH_2.CH_2.CH_2Br,\ CH_3.CH_2.CH_2.CH_2J,\ CH_3.CHBr.CH_2.CH_3,}\\ \mathrm{(CH_3)_2CH.CH_2Cl,\ (CH_3)_2CH.CH_2Br,\ (CH_3)_2CH.CH_2J,\ (CH_3)_3CCl,}\\ \mathrm{(CH_3)_3CBr,\ (CH_3)_3CJ,\ (CH_3)_2CH.CH_2.CH_2Cl,\ (CH_3)_2CH.CH_2.CH_2Br,}\\ \mathrm{(CH_3)_2CH.CH_2.CH_2J,\ (CH_3)_2CCl.CH_2.CH_3,\ (CH_3)_2CBr.CH_2.CH_3,}\\ \mathrm{(CH_3)_2CJ.CH_2.CH_3.} \end{gathered} \]

As typical reagents for ionic and neutral cleavage of the bond we used pyridine, piperidine, and sodium methylate, the first two without solvent, \(\mathrm{CH_3ONa}\) in the form of a normal solution in methyl alcohol. The reacting components were taken in equimolecular amounts. The experiments were carried out at ordinary temperature (16–20°).

In the following tables are given the percentages of halide that reacted over definite intervals of time. The nature of the reaction product is also indicated (under the conditions of our experiments, without isolation).

Experiments with pyridine.

  1. \(\mathrm{CH_3.CH_2.CH_2Cl}\). Reaction product—oil.

Duration of experiment: 7 days, 17 days, 27 days.
% reacted halide . . . 0.42%, 1.3, 2.3.

  1. \(\mathrm{CH_3.CHCl.CH_3}\). Product—oil.

Duration of experiment: 932 days.
% . . . . . . . . . . . 0.74%.

  1. \(\mathrm{CH_3.CH_2.CH_2.CH_2Cl}\). Product—oil.

Time . . . . . 3 days, 23 days, 34 days, 40 days.
% . . . . . . 0.05, 0.85, 1.21, 2.14.

  1. \(\mathrm{(CH_3)_2CH.CH_2Cl}\). Reaction product crystalline.

Time . . . . . 240 days, 270 days.
% . . . . . . 1.24, 1.62.

  1. \(\mathrm{(CH_3)_3CCl}\). Product cryst.

Time . . . . . 308 days.
% . . . . . . 1.42.

  1. \(\mathrm{(CH_3)_2CH.CH_2.CH_2Cl}\). Product—oil.

Time . . . . . 210 days, 215 days, 270 days.
% . . . . . . 3.01, 3.05, 4.8.

  1. \(\mathrm{CH_3.CH_2.CH_2Br}\). Product—oil.

Time . . . . . 4 h, 7 h, 14 h, 24 h, 48 h, 96 h.
% . . . . . . 0.93, 2.75, 5.22, 9.32, 17.5, 34.07.

  1. \(\mathrm{CH_3.CHBr.CH_3}\). Product—oil.

Time . . . . . 168 h, 360 h, 516 h, 768 h, 1302 h.
% . . . . . . 3.25, 3.44, 7.88, 8.2, 12.23.

  1. $\mathrm{CH_3.CH_2.CH_2.CH_2Br}$. Product—oil.
Time 20 h 30 h 48 h 120 h 192 h
% 5,4 8,8 16,1 39,17 49,18
  1. $\mathrm{CH_3.CH_2.CHBr.CH_3}$. Product—oil.
Time 120 h 192 h 240 h 648 h 3600 h
% 2,09 2,36 4,37 12,68 56,42
  1. $\mathrm{(CH_3)_2CH.CH_2Br}$. Product—oil.
Time 24 h 48 h 48 h 120 h 270 h
% 1,5 3,27 3,67 7,15 13,93
  1. $\mathrm{(CH_3)_3CBr}$. Crystalline product.
Time 840 h 1776 h 5040 h
% 6,7 7,52 14,81
  1. $\mathrm{(CH_3)_2CH.CH_2.CH_2Br}$. Crystalline product.
Time 24 h 120 h 208 h 384 h 504 h
% 2,77 27,4 38,0 52,5 95,2
  1. $\mathrm{(CH_3)_2CBr.CH_2.CH_3}$. Product—oil.
Time 6 h 18 h 24 h 48 h 96 h 192 h
% 2,6 3,5 4,8 7,18 11,01 19,15
  1. $\mathrm{CH_3.CH_2.CH_2J}$. Product—oil.
Time 1 h 5 h 15 h 48 h
% 2,0 9,49 18,5 47,2
  1. $\mathrm{CH_3.CHJ.CH_3}$. Product—oil.
Time 3,4 h 8 h 23 h 44 h 96 h
% 1,16 2,15 4,65 9,41 21,57
  1. $\mathrm{CH_3.CH_2.CH_2.CH_2J}$. Product—oil.
Time 5 h 8 h 11 h 24 h 35 h 48 h
% 2,78 9,47 12,12 19,58 27,11 41,44
  1. $\mathrm{(CH_3)_2CH.CH_2J}$. Product—oil.
Time 8 h 10 h 12 h 24 h 48 h 96 h 144 h
% 1,22 2,3 3,05 4,56 8,06 12,7 16,2
  1. $\mathrm{(CH_3)_3CJ}$. Crystalline product.
Time 2 h 13,6 h 48,6 h 120 h
% 1,22 4,82 9,11 25,5
  1. $\mathrm{(CH_3)_2CH.CH_2.CH_2J}$. Product—oil.
Time 12,3 h 72 h 168 h
% 9,04 38,82 60,7
  1. $\mathrm{(CH_3)_2CJ.CH_2.CH_3}$. Crystalline product.
Time 35 min 1 h 2 h 8 h 16 h
% 3,81 6,75 13,5 24,88 33,58

Experiments with piperidine

  1. $\mathrm{CH_3.CH_2.CH_2Cl}$. Crystalline product.
Time 13 h 1 d 3 d 6 d
% 3,6 8,5 15,32 29,1
  1. \( \mathrm{CH_3.CHCl.CH_3} \). Product crystalline.
Time 4 days 8 days 16 days 30 days 42 days
% 0.2 0.48 2.62 3.5 5.45
  1. \( \mathrm{CH_3.CH_2.CH_2.CH_2Cl} \). Product crystalline.
Time 6 h 24 h 50.4 h 3 days 6 days 9 days
% 1.26 5.86 9.65 17.05 27.96 37.2
  1. \( \mathrm{(CH_3)_2CH.CH_2Cl} \). Product—oil.
Time 13.5 h 24.7 h 50.1 h 75 h
% 1.14 2.13 4.12 10.63
  1. \( \mathrm{(CH_3)_3CCl} \). Product—oil.
Time 23.9 days 24 days
% 2.22 2.39
  1. \( \mathrm{(CH_3)_2CH.CH_2.CH_2Cl} \). Product crystalline.
Time 22 h 98 h 195 h 403 h 528 h
% 0.86 4.8 5.58 16.5 17.27
  1. \( \mathrm{(CH_3)_2CCl.CH_2.CH_3} \). Product crystalline.
Time 22 days 30 days 50 days
% 1.92 1.93 2.6
  1. \( \mathrm{CH_3.CH_2.CH_2Br} \). Product crystalline.
Time 1 min 2 min 4 min 6 min 8 min
% 1.58 3.22 6.32 9.46 10.5
  1. \( \mathrm{CH_3.CHBr.CH_3} \). Product crystalline.
Time 2 h 6 h 10 h 24 h 48 h
% 3.72 7.4 8.75 16.15 22.75
  1. \( \mathrm{CH_3.CH_2.CH_2CH_2Br} \). Product crystalline.
Time 3 min 5 min 10 min 30 min
% 2.9 4.77 9.65 19.78
  1. \( \mathrm{CH_3.CH_2.CHBr.CH_3} \). Product crystalline.
Time 3 h 15 h 58 h 148 h
% 1.6 4.07 15.85 20.69
  1. \( \mathrm{(CH_3)_2CH.CH_2Br} \). Product crystalline.
Time 7 min 30 min 1 h 3 h 6 h
% 5.05 10.68 15.7 19.28 22.16
  1. \( \mathrm{(CH_3)_3CBr} \). Product crystalline.
Time 165 h 264 h 528 h
% 10.01 20.4 39.95
  1. \( \mathrm{(CH_3)_2CH.CH_2.CH_2Br} \). Product crystalline.
Time 10 min 30 min 1 h 2 h
% 3.15 5.33 6.5 8.7
  1. \( \mathrm{(CH_3)_2CBr.CH_2.CH_3} \). Product crystalline.
Time 6 h 24 h 51 h 70 h 240 h 408 h
% 6.29 10.5 15.98 25.8 32.5 42.26
  1. $\mathrm{CH_3.CH_2.CH_2.CH_2J}$. Crystalline product.
Time 0.5 min. 1 min. 3 min. 5 min. 10 min.
% 1.75 2.15 7.76 11.62 21.59
  1. $(\mathrm{CH_3})_2\mathrm{CH.CH_2J}$. Crystalline product.
Time 1 min. 5 min. 10 min. 30 min. 72 min.
% 1.86 4.33 6.75 12.63 19.24
  1. $(\mathrm{CH_3})_3\mathrm{CJ}$. Crystalline product.
Time 11 min. 75 min. 90 min. 180 min.
% 1.53 8.48 17.58 34.2
  1. $(\mathrm{CH_3})_2\mathrm{CH.CH_2.CH_2J}$. Crystalline product.
Time 10 min. 42 min.
% 14.83 24.28
  1. $(\mathrm{CH_3})_2\mathrm{CJ.CH_2.CH_3}$. Crystalline product.
Time 10 min. 15 min. 30 min. 1 h 2 h 4 h
% 4.5 5.8 11.02 17.5 32.02 59.8

Experiments with sodium methylate

  1. $\mathrm{CH_3.CH_2.CH_2Cl}$.
Time 156 h 216 h 312 h 392 h 766 h
% 4.5 7.97 9.08 11.21 17.9
  1. $\mathrm{CH_3.CHCl.CH_3}$.
Time 10 d 20 d
% 1.25 2.57
  1. $\mathrm{CH_3.CH_2.CH_2.CH_2Cl}$.
Time 31 h 72 h 192 h 408 h 600 h
% 1.8 2.33 6.14 11.18 15.07
  1. $(\mathrm{CH_3})_2\mathrm{CH.CH_2Cl}$.
Time 180 d 196 d 225 d 922 d
% 10.98 12.21 14.0 25.37
  1. $(\mathrm{CH_3})_2\mathrm{CCl}$
Time 1 h 13 h 72 h 120 h
% 3.6 8.83 18.65 25.9
  1. $(\mathrm{CH_3})_2\mathrm{CH.CH_2.CH_2Cl}$.
Time 2 d 8 d 16 d 32 d 64 d
% 0.59 2.89 4.43 8.75 15.25
  1. $(\mathrm{CH_3})_2\mathrm{CCl.CH_2.CH_3}$.
Time 16 h 2 d 6 d 12 d 24 d
% 4.58 10.98 15.33 24.9 55.1
  1. $\mathrm{CH_3.CH_2.CH_2Br}$.
Time 2 h 8 h 12 h 15 h 48 h 77 h
% 4.15 9.6 14.34 16.0 36.93 48.84
  1. $\mathrm{CH_3CHBr.CH_3}$.
Time 0.5 d 1 d 2 d 5 d 8 d 12 d
% 3.48 7.2 16.2 33.44 34.37 42.0
  1. \( \mathrm{CH_3.CH_2.CH_2.CH_2Br} \).
Time 30 min. 120 min. 260 min. 570 min.
% 1.27 4.09 7.95 15.85
  1. \( \mathrm{CH_3.CH_2.CHBr.CH_3} \).
Time 3.3 h. 16 h. 40 h. 50.8 h. 70.3 h.
% 1.72 1.97 12.08 17.09 21.78
  1. \( \mathrm{(CH_3)_2CH.CH_2Br} \).
Time 6 h. 10 h. 24 h. 48 h. 72 h.
% 3.72 5.01 7.33 15.55 20.7
  1. \( \mathrm{(CH_3)_3CBr} \).
Time 13 sec. 1 min. 5 min. 20 min.
% 24.0 32.3 36.5 42.16
  1. \( \mathrm{(CH_3)_2CH.CH_2.CH_2Br} \).
Time 3 h. 11 h. 24 h. 125 h. 264 h.
% 1.09 4.81 17.29 30.65 49.55
  1. \( \mathrm{(CH_3)_2CBr.CH_2.CH_3} \).
Time 5 sec. 10 sec. 30 sec. 60 sec. 300 sec.
% 10.87 13.11 15.[[unclear: digit]] 16.92 20.31
  1. \( \mathrm{CH_3.CH_2.CH_2J} \).
Time 67 min. 240 min. 945 min. 3180 min.
% 5.01 11.1 22.9 53.12
  1. \( \mathrm{CH_3.CHJ.CH_3} \).
Time 2 h. 8 h. 17 h. 47.0 h.
% 2.75 8.34 15.55 30.11
  1. \( \mathrm{CH_3.CH_2.CHJ.CH_3} \).
Time 0.8 h. 1 h. 2 h. 4 h. 6 h. 12 h.
% 1.91 2.58 4.72 8.04 12.53 20.29
  1. \( \mathrm{(CH_3)_2CH.CH_2J} \).
Time 1 h. 3 h. 6 h. 9 h. 12 h.
% 1.55 8.08 11.10 17.59 20.29
  1. \( \mathrm{(CH_3)_3CJ} \).
Time 8 sec. 30 sec. 1 min. 3 min. 5 min. 30 min.
% 9.08 10.9 13.64 22.16 27.05 44.75
  1. \( \mathrm{(CH_3)_2CH.CH_2.CH_2J} \).
Time 1 h. 3 h. 8 h. 17.6 h. 24 h.
% 1.96 6.07 10.84 19.07 24.93
  1. \( \mathrm{(CH_3)_2CJ.CH_2.CH_3} \).
Time 0.5 min. 1 min. 5 min. 20 min. 30 min.
% 3.12 10.80 16.24 25.52 31.42

In the summary table are given the values of the average relative reaction rates. The rate of reaction of chlorine ...

propyl bromide with pyridine. The constants were not calculated; instead, comparison was made according to the intervals of time during which the same percentage reacts. The mean values were calculated within the range up to approximately 40% where possible; moreover, as an intermediate unit of comparison for comparatively rapidly reacting compounds, the reaction rate of \(n\text{-}C_3H_7Br + C_5H_5N\) was taken. The first numbers were sometimes discarded as less reliable.

Summary table of relative reaction rates

Halide compounds Relative rate of reaction with pyridine, \(X=Cl\) Relative rate of reaction with pyridine, \(X=Br\) Relative rate of reaction with pyridine, \(X=J\) Relative rate of reaction with piperidine, \(X=Cl\) Relative rate of reaction with piperidine, \(X=Br\) Relative rate of reaction with piperidine, \(X=J\) Relative rate of reaction with \(CH_3ONa\), \(X=Cl\) Relative rate of reaction with \(CH_3ONa\), \(X=Br\) Relative rate of reaction with \(CH_3ONa\), \(X=J\)
\(CH_3.CH_2X\) 1 90 500 64 24500 — 7.5 405 645
\(CH_3.CHX.CH_3\) 0.002 4.0 5.3 1.1 370 — 1.6 75.5 313
\(CH_3.CH_2.CH_2.CH_2X\) 0.75 69 190 58 14000 41500 7.1 500 580
\(CH_3.CH_2.CHX.CH_3\) — 4.5 — — 88 — — 70 —
\((CH_3)_2CH.CH_2X\) 0.07 17 47 20 8100 9000 0.54 125 477
\((CH_3)_3CX\) 0.06 1.3 77 1.1 18.5 2400 90 \(1.2 \cdot 10^?\) 210
\((CH_3)_2CH.CH_2.CH_2X\) 0.17 41 165 8.4 3200 17500 3.3 81 470
\((CH_3)_2CX.CH_2.CH_3\) — 5.2 \(1400^?\) 0.8 70 5800 58.5 110 \(1.2 \cdot 10^5\)

Conclusions:

1. Relative activity of various halides

Halide compounds Activity according to pyridine, \(Br:Cl\) Activity according to pyridine, \(J:Cl\) Activity according to pyridine, \(J:Br\) Activity according to piperidine, \(Br:Cl\) Activity according to piperidine, \(J:Cl\) Activity according to piperidine, \(J:Br\) Activity according to \(CH_3ONa\), \(Br:Cl\) Activity according to \(CH_3ONa\), \(J:Cl\) Activity according to \(CH_3ONa\), \(J:Br\)
\(CH_3.CH_2.CH_2X\) 90 500 5.6 383 — — 78 86 1.6
\(CH_3.CHX.CH_3\) 333 4420 1.3 264 — — 47 196 4.1
\(CH_3.CH_2.CH_2.CH_2X\) 126 346 2.8 241 715 3.0 69 82 1.2
\((CH_3)CH.CH_2X\) 243 671 2.8 311 363 1.2 231 883 3.8
\((CH_3)_3CX\) 22 1280 59 17 2180 130 \(1.3 \cdot 10^?\) \(2.2 \cdot 10^?\) 0.17
\((CH_3)_2CH.CH_2.CH_2X\) 241 970 4.0 381 1820 4.8 28 142 5.2
\((CH_3)_2CX.CH_2.CH_3\) — — 282 90 7325 74 \(1.9 \cdot 10^?\) \(2.5 \cdot 10^?\) 0.13

From the previous experimental data the following regularities could be derived:

a) The activity of the halides increases from chlorine to iodine.
b) The difference between bromine and chlorine is in general greater than between iodine and bromine;
c) The difference in the activity of the halides in reaction with amines is greater than in reaction with alcoholates.

The results of the present work confirm these rules for primary and secondary halogenated hydrocarbons, but tertiary ones deviate noticeably. In them the difference between J and Br becomes, for reaction with amines, approximately the same, and sometimes even greater, than between Br and Cl; with alcoholates, however, chlorine proves to be relatively extremely little active, while bromine exceeds iodine severalfold. Such an inversion of the activity relations is observed very rarely. Hitherto it was known in certain halonitro derivatives1 and halocyanide compounds2 of the benzene series, where chlorine is sometimes split off more readily than bromine, and also in CH\(_3\)J and CH\(_3\)Br, of which the latter reacts more rapidly with alcoholates3.

2. Influence of chain length.

The following table includes, in addition to the experimental data obtained by us, also the results of certain supplementary, in part still unpublished experiments and literature data3.

Compounds compared Relative activity toward pyridine at X = Cl Relative activity toward pyridine at X = Br Relative activity toward pyridine at X = J Relative activity toward piperidine at X = Cl Relative activity toward piperidine at X = Br Relative activity toward piperidine at X = J Relative activity toward CH\(_3\)ONa at X = Cl Relative activity toward CH\(_3\)ONa at X = Br Relative activity toward CH\(_3\)ONa at X = J
CH\(_3\)X — 200 200 — — — — 25 17.9
CH\(_3\)CH\(_2\)X 9.6 3 8.4 — — — — 2.2 2.8
CH\(_3\)CH\(_2\)CH\(_2\)X 1.8 1.3 2.5 1.1 1.75 — 1.06 0.8 1.1
CH\(_3\)CH\(_2\)CH\(_2\)CH\(_2\)X 1 1 1 1 1 — 1 1 1

As was also established in other works4, the activity of the halide decreases with increasing chain length. The sole exception was observed in the reaction of propyl and butyl bromides with sodium methylate, but the difference may be due to experimental error. There is an indication in the literature that with further lengthening of the carbon chain the activity of the halide again increases somewhat. Thus \(n\)-C\(_5\)H\(_{11}\)Cl, \(n\)-C\(_6\)H\(_{13}\)Cl, \(n\)-C\(_7\)H\(_{15}\)Cl, \(n\)-C\(_8\)H\(_{17}\)Cl react with potassium iodide somewhat more rapidly than propyl and butyl chlorides5. We have not investigated halogen derivatives with a chain of five or more carbon atoms.

3. Influence of Side Chains

Compounds compared Relative activity with \(C_2H_5N\) Cl Relative activity with \(C_2H_5N\) Br Relative activity with \(C_2H_5N\) J Relative activity with \(C_5H_{11}N\) Cl Relative activity with \(C_5H_{11}N\) Br Relative activity with \(C_5H_{11}N\) J Relative activity with \(CH_3ONa\) Cl Relative activity with \(CH_3ONa\) Br Relative activity with \(CH_3ONa\) J
\(CH_3.CH_2.CH_2X\) 14 5.3 11 2.5 3.0 — 14 3.2 1.4
\((CH_3)_2CH.CH_2X\) 1 1 1 1 1 1 1 1 1
\(CH_3.CH_2.CH_2.CH_2X\) 7.9 4.1 4.5 2.2 1.7 4.3 13 4 1.2
\(CH_3.CH_2.CH_2.CH_2X\) 3.2 1.7 1.15 6.9 4.4 2.7 2.1 5.5 1.2
\((CH_3)_2CH.CH_2.CH_2X\) 1 1 1 1 1 1 1 1 1

As was also noted in all the preceding studies, branching of the chain lowers the activity, and the more so the closer the side chain is to the halogen atom.

4. Influence of the Position of the Halogen in the Molecule

Compounds compared Relative activity with \(C_2H_5N\) Cl Relative activity with \(C_2H_5N\) Br Relative activity with \(C_2H_5N\) J Relative activity with \(C_5H_{11}N\) Cl Relative activity with \(C_5H_{11}N\) Br Relative activity with \(C_5H_{11}N\) J Relative activity with \(CH_3ONa\) Cl Relative activity with \(CH_3ONa\) Br Relative activity with \(CH_3ONa\) J
\(CH_3.CH_2.CH_2X\) 83 22.5 9.4 46 66 — 4.7 5.4 2.1
\(CH_3.CHX.CH_3\) 1 1 1 1 1 1 1 1 1
\(CH_3.CH_2.CH_2.CH_2X\) — 16 — — 159 — — 7.1 —
\(CH_3.CH_2.CHX.CH_3\) — 1 — — 1 — — 1 —
\((CH_3)_2CH.CH_2X\) 1.2 13 0.61 24 438 4 1 1 1
\((CH_3)_3CX\) 1 1 1 1 1 1 167 9600 420
\((CH_3)_2CH.CH_2.CH_2X\) — — — 10 40 3 1 1 1
\((CH_3)_2CX.CH_2.CH_3\) — — — 1 1 1 18 12000 255

Primary halide compounds in all cases prove to be more active than secondary ones with the same carbon skeleton. At the same time, the difference is noticeably greater in the reaction with amines than in the reaction with \(CH_3ONa\). Tertiary haloalkanes, with respect to amines, approach the secondary ones, but in the rate of interaction with alcoholates they surpass even the primary ones many times over.

5. Influence of the nature of the reagent acting on halogen compounds.

Halogen compounds \(\mathrm{CH_3ONa:C_5H_5N}\), \(X=\mathrm{Cl}\) \(\mathrm{CH_3ONa:C_5H_5N}\), \(X=\mathrm{Br}\) \(\mathrm{CH_3ONa:C_5H_5N}\), \(X=\mathrm{J}\) \(\mathrm{CH_3ONa:C_5H_{11}N}\), \(X=\mathrm{Cl}\) \(\mathrm{CH_3ONa:C_5H_{11}N}\), \(X=\mathrm{Br}\) \(\mathrm{CH_3ONa:C_5H_{11}N}\), \(X=\mathrm{J}\) \(\mathrm{C_5H_{11}N:C_5H_5N}\), \(X=\mathrm{Cl}\) \(\mathrm{C_5H_{11}N:C_5H_5N}\), \(X=\mathrm{Br}\) \(\mathrm{C_5H_{11}N:C_5H_5N}\), \(X=\mathrm{J}\)
\(\mathrm{CH_3.CH_2.CH_2X}\) 7,5 4,5 1,3 0,12 0,017 -- 64 272 —
\(\mathrm{CH_3.CHX.CH_3}\) 133 19 5,0 1,1 0,2 -- 117 92 —
\(\mathrm{CH_3.CH_2.CH_2.CH_2X}\) 13 7,3 3,1 0,12 0,036 0,014 106 203 218
\(\mathrm{CH_3.CH_2.CHX.CH_3}\) — 16 -- — 0,8 -- — 20 —
\(\mathrm{(CH_3)_2CH.CH_2CH_2X}\) 7,7 7,4 10,1 0,021 0,015 0,05 371 476 204
\(\mathrm{(CH_3)_3CX}\) 1500 [[unclear: \(9.10^{?}\)]] 2600 82 [[unclear: \(6,5\cdot 10^{?}\)]] 83 183 14 31
\(\mathrm{(CH_3)_2CH.CH_2.CHX}\) 20 2,2 2,9 0,39 0,028 0,031 49 78 93
\(\mathrm{(CH_3)_2CX.CH_2.CH_3}\) — [[unclear: \(2.10^{?}\)]] [[unclear: \(100^{?}\)]] [[unclear: 73?]] [[unclear: \(1,2\cdot 10^{?}\)]] [[unclear: \(20^{?}\)]] — 1,5? 4,2

Comparison of the rate of interaction of alkyl halides with pyridine and piperidine gives the usual picture: piperidine reacts several tens, and even hundreds, of times faster than pyridine. Only with tertiary bromo- and iodo-derivatives does the difference noticeably decrease. Alkoxides belong to a different group of reagents, and therefore the activity ratios \(\mathrm{CH_3ONa:C_5H_5N}\) and \(\mathrm{CH_3ONa:C_5H_{11}N}\) change sharply depending on the nature of the halogen compound. Primary alkyl halides, for which all the previous experimental data and theoretical considerations led one to expect predominantly ionic cleavage, react with the comparatively weak amine—piperidine—only slightly more slowly than with \(\mathrm{CH_3ONa}\), and with pyridine sometimes several tens of times faster. Tertiary compounds give up their halogen under the action of methylate many times more readily. Both regularities are especially noticeable in the ratio of the reaction rates of bromides with \(\mathrm{CH_3ONa}\) and piperidine.

In the last tables the substances giving off the halogen at a secondary unit stand out more sharply than before. The ratio of the activities toward \(\mathrm{CH_3ONa}\) and \(\mathrm{C_5H_{11}N}\) is expressed, for \(\mathrm{R.CH_2X}\), mostly by numbers of the order \(10^{-2}\); for \(\mathrm{R_2CHX}\) it is close to unity; for \(\mathrm{R_3CX}\) we have an order of magnitude \(10^2\)–\(10^4\).

The influence of chain branching is still difficult to detect here.

In general, the experimental material obtained by us confirms the opinion expressed earlier regarding two types of cleavage of the carbon–halogen bond.

The regularities noted in earlier works have now been traced in a considerably larger number of cases, and moreover in compounds of the simplest structure, where the course of the process cannot be obscured by various substituents.

14 November 1929.

  1. See, for example, P. K. Lulofs, C. 1901. II, 1290. ↩↩

  2. H. P. Baudet. C. 1924. II, 2646. ↩↩

  3. M. Conrad, C. Brückner. Zeit. phys. Chem. 4, 631–657 (1889). ↩↩↩

  4. M. Conrad, C. Brückner, l. c.; works of N. A. Menshutkin, B. V. Tronov. Zh. R. Kh. O. 38, 1278–1301, etc. ↩

  5. J. Conant, R. E. Hussey. J. Amer. Chem. Soc. 47, 476–488 (1925). ↩

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[v1] 1931

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Activity of halogens in some of the simplest halogenated hydrocarbons as a function of the position of the halogens in the molecule