Ozonolysis of Technical Low-Percentage Phenanthrene
Abstract Generated abstract
This paper examines the hydrolysis of 3,8-dimethoxy-4,5-6,7-dibenzo-1,2-dioxacyclooctane obtained by ozonolysis of low-percentage technical phenanthrene. The authors vary alkali concentration, dimethoxy peroxide to alkali ratio, and methanol content in aqueous and alcoholic potassium hydroxide systems to direct formation of 2′-formyldiphenyl-2-carboxylic acid and its methyl ester. They report optimized conditions using 20% alkali and limited methanol that shorten reaction time, reduce alkali and alcohol consumption, proceed without external heating, and increase product yields relative to a literature procedure. The work also shows that anthracene impurities in technical phenanthrene are converted to anthraquinone, which can be isolated during hydrolysis, supporting a lower-cost route to pure aldehydo acid and ester products.
Full Text
OZONOLYSIS OF TECHNICAL LOW-PERCENTAGE PHENANTHRENE
Communication III. Study of the Hydrolysis of 3,8-Dimethoxy-4,5-6,7-dibenzo-1,2-dioxacyclooctane (Dimethoxy Peroxide)
A. K. LEBEDEV, A. N. NOVIKOV
(Presented by the scientific-methodological seminar of the Faculty of Chemical Technology)
It is known that, in the ozonization of phenanthrene in a methanol medium, the principal reaction product is 3,8-dimethoxy-4,5-6,7-dibenzo-1,2-dioxacyclooctane (dimethoxy peroxide) [1].
From dimethoxy peroxide, by means of hydrolysis and subsequent simple operations, one can readily obtain 2′-formyldiphenyl-2-carboxylic acid (aldehydo acid), the methyl ester of the aldehydo acid and, finally, 2,2′-diphenic acid [1, 2]. The conditions for converting dimethoxy peroxide into one or another product have not been widely studied.
We have investigated the dependence of the course of the hydrolysis reaction of dimethoxy peroxide on the concentration of the aqueous alkali solution, the molar ratios of dimethoxy peroxide and alkali, and the amount of alcohol added.
As a result of the investigations carried out, it was found that the best conditions for the hydrolysis of dimethoxy peroxide are the use of a 20% aqueous alkali solution in molar ratios with the addition, per 1 g of dimethoxy peroxide, of 2–4.4 ml of methanol.
Under these conditions, the hydrolysis reaction of dimethoxy peroxide proceeds mainly without external heating in 4–5 min.
Replacing the alkali with solutions of mineral acids or soda offers no advantages and, on the contrary, considerably lowers the yield and quality of the products obtained. The consumption of acids and soda, as well as the reaction time, increases considerably.
When hydrolysis was carried out under the above-described conditions, we observed for the first time that here, along with the aldehydo acid, the methyl ester of the aldehydo acid is formed.
In this case, a decrease in the amount of alkali leads, correspondingly, to an increase in the yield of the ester and a decrease in the yield of the aldehydo acid.
The use of quite insignificant amounts of alkali under the same reaction conditions (the amount of methanol added, the hydrolysis time) leads to the formation of only the ester.
In order to obtain only the aldehydo acid, it is necessary to take 1.5 moles of alkali per mole of dimethoxy peroxide.
The use of an alcoholic alkali solution for the hydrolysis of dimethoxy peroxide makes it possible to reduce the hydrolysis time by half.
Carrying out the hydrolysis of dimethoxy peroxide under the conditions developed by us, in comparison with the method described in the literature [1], reduces the consumption of alkali almost threefold and that of alcohol twentyfold; in addition, the hydrolysis time is reduced 7–8 times, the reaction proceeds without external heating, and the yield of hydrolysis products is 10–12% higher.
The melting points of the obtained 2′-formyldiphenyl-2-carboxylic acid, 134–135° (literature 134–135°), and of the methyl ester of 2′-formyldiphenyl-2-carboxylic acid, 50–51° (literature 50–51°).
It should be noted that Bailey [1] obtained these compounds by ozonizing pure phenanthrene, which to this day is a very expensive and difficult-to-obtain product.
In contrast to Bailey, we obtained the above-mentioned compounds from technical low-percentage, readily available and inexpensive phenanthrene [2, 3], which contained 9–10% anthracene. Under the ozonization conditions, anthracene was converted into anthraquinone, which is not changed during hydrolysis of the dimethoxy peroxide and is isolated in pure form.
Thus, the cost of the chemically pure compounds obtained by us is considerably lower than the cost of preparing them by the methods described in the literature.
Experimental Part
I. Hydrolysis of dimethoxy peroxide with an aqueous solution of alkali.
Preparation of the aldehyde acid and the aldehyde ester
25 g of dimethoxy peroxide obtained from technical phenanthrene was placed in a round-bottom flask equipped with a reflux condenser; 50 ml of methyl alcohol and 22 ml of 20% aqueous KOH solution (equimolecular amount) were added. The reaction mixture was heated to the boiling point of the alcohol, after which hydrolysis of the dimethoxy peroxide began and was completed in 1–2 minutes. The resulting solution was filtered. The precipitate on the filter was washed with 4 ml of methanol, then with water. The washing alcohol and water were combined with the filtrate. The precipitate on the filter was anthraquinone, which had been present in the dimethoxy peroxide as an impurity [3]. Anthraquinone was obtained as light-yellow needles, 0.35 g, m.p. 276–278°.
To the filtrate obtained after separation of anthraquinone, water was gradually added until addition of the next portion of water no longer caused turbidity (milky-white color) of the solution. The white crystals of the methyl ester of the aldehyde acid that separated out were filtered off, washed with water, and dried.
4.15 g of ester, m.p. 50–51°, was obtained.
Yield 18.8%.
To the filtrate obtained after separation of the ester, dilute hydrochloric acid solution was gradually added until an acid reaction (to Congo). On rubbing the walls of the beaker with a glass rod, very fine white crystals of the aldehyde acid precipitated.
16.20 g of aldehyde acid, m.p. 134–135°, was obtained.
Yield 78.3%.
Thus, the total yield of aldehyde acid and aldehyde ester was 97.1% of theory, based on the dimethoxy peroxide taken.
Carrying out the hydrolysis under the conditions described, changing only the molar ratios of dimethoxy peroxide and alkali, gave the corresponding amounts of aldehyde acid or aldehyde ester, or both compounds simultaneously.
The results obtained are presented in Table 1.
Results of the hydrolysis of dimethoxyperoxide with an aqueous alkali solution
\[ \text{Dimethoxyperoxide (DMP)} \ \xrightarrow[\ ]{\mathrm{KOH},\ \mathrm{CH_3OH}}\ \text{Aldehyde acid} \ +\ \text{Aldehyde acid} \ \xrightleftharpoons[-\mathrm{HCl}]{+\mathrm{HCl}}\ \text{Anhydro compound} \]
Table 1
| No. | DMP, g | 20% aq. KOH, ml | Methanol, ml | Hydrolysis time, min | Aldehyde acid: yield, % of DMP | Aldehyde acid: mp, °C | Reaction products: aldehyde ester, yield, % of DMP | Reaction products: aldehyde ester, mp, °C | Reaction products: total yield, % of DMP | Anthraquinone: g | Anthraquinone: mp, °C | Note |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 25,0 | 22,0 | 50 | 30 | 78,3 | 134–135 | 18,8 | 48–50 | 97,1 | 0,35 | 273–5 | Technical DMP |
| 2 | 25,0 | 11,0 | 50 | 30 | 33,7 | 132–133 | 60,8 | 49–50 | 94,5 | 0,35 | 273–5 | ” |
| 3 | 25,0 | 11,0 | 50 | 30 | 37,1 | 132–133 | 61,5 | 49–50 | 98,6 | 0,3 | 275–276 | ” |
| 4 | 12,5 | 11,0 | 25 | 30 | 80,9 | 134–135 | 14,5 | 49–50 | 95,4 | 0,11 | 276–278 | ” |
| 5 | 12,5 | 11,0 | 25 | 30 | 72,4 | 134–135 | 15,4 | 49–50 | 87,9 | 0,11 | 276–278 | ” |
| 6 | 12,5 | 16 | 25 | 3–5 | 91,3 | 134–135 | — | — | 91,3 | 0,11 | 276–278 | ” |
| 7 | 12,5 | 5,5 | 25 | 3–5 | 14,0 | 132–133 | 56,7 | 51–52 | 70,7 | 0,11 | 276–278 | ” |
| 8 | 12,5 | 0,5 | 25 | 1–2 | — | — | 90,3 | 50–52 | 90,3 | 0,11 | 276–278 | ” |
| 9 | 12,5 | 0,25 | 25 | 5 | — | — | 92,1 | 50–51 | 92,1 | 0,11 | 276–278 | ” |
| 10 | 12,5 | 0,1 | 50 | 120 | — | — | 88,9 | 50–51 | 88,9 | 0,15 | 278–280 | ” |
Table 2
Results of hydrolysis of DMP with an alcoholic alkali solution
| No. | DMP | 20% alcoholic KOH solution, ml | Methanol, ml | Hydrolysis time, min | Reaction products: aldehydo acid, yield as % of DMP | Reaction products: aldehydo acid, m.p., °C | Reaction products: aldehydo ester, yield as % of DMP | Reaction products: aldehydo ester, m.p., °C | Total yield as % of DMP I + II | Anthraquinone, g | Anthraquinone, m.p., °C | Note |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 12.5 | 11.0 | 10 | 2–2.5 | 64.5 | 134–135 | 23.3 | 51–52 | 87.8 | 0.11 | 276–278 | Pure DMP |
| 2 | 12.5 | 11.0 | — | 2–2.5 | 77.1 | 133–134 | 13.2 | 50–51 | 90.3 | 0.11 | 276–278 | Technical DMP |
| 3 | 12.5 | 16.5 | — | 1 min 45 sec | 95.9 | 134–135 | — | — | 95.9 | — | 276–280 | ” |
| 4 | 12.5 | 1 | 10 | 5 min | — | — | 91.2 | 49–50 | 91.2 | 0.15 | 278–280 | ” |
II. Hydrolysis of the Dimethoxy Peroxide with an Alcoholic Alkali Solution
Preparation of the Aldehydo Acid and the Aldehydo Ester
12.5 g of dimethoxy peroxide was placed in a round-bottom flask equipped with a reflux condenser, and 11 ml of a 20% solution of alkali in methyl alcohol was added (molar proportions). At 1.5 minutes after mixing of the reagents, a reaction begins, which is completed after 1 minute.
The hydrolysis reaction proceeds vigorously without heating and is complete 2–2.5 minutes after the reagents have been mixed. The dimethoxy peroxide is converted into an amorphous mass resembling nostril tissue in appearance. Water was gradually added to the reaction mixture with stirring, in small portions (2–3 ml each). The solidified mass dissolved. The solution was filtered; the precipitate on the filter was washed with 4 ml of methyl alcohol and then with water. The washing alcohol and water were combined with the filtrate.
The anthraquinone washed on the filter was dried. 0.15 g of anthraquinone was obtained. M.p. 276–278°. Yield based on the weight of dimethoxy peroxide: 1.2–1.4%.
Subsequent operations were carried out in the same way as in the hydrolysis of the dimethoxy peroxide with an aqueous alkali solution.
Yield of the aldehydo ester: 13.2%, m.p. 50–51°.
Yield of the aldehydo acid: 77.1%, m.p. 134–135°.
The total yield of aldehydo acid and aldehydo ester is 90.3%.
The results obtained are presented in Table 2.
In both the first and the second case, 90–95% of the alcohol is regenerated.
Conclusions
-
Optimal conditions have been found for obtaining very pure aldehydo acid and aldehydo ester from dimethoxy peroxide prepared from inexpensive, low-percentage technical phenanthrene.
-
Anthraquinone, present in the technical dimethoxy peroxide, was isolated as a by-product during hydrolysis.
LITERATURE
- P. S. Bailey, J. Am. Chem. Soc., 78, 3811, 1956.
- L. P. Kulev, V. A. Salskii, A. K. Lebedev, V. P. Shabrov. Journal of the All-Union Chemical Society, vol. VII, No. 5, 599, 1962.
- A. K. Lebedev. The present collection.