Chemistry

Yu. A. Ol’dekop, A. M. Kalinina, and S. A. Shklyar

A New Method for the Synthesis of Acid Chlorides and Acid Bromides of Aromatic Acids

(Presented by Academician M. I. Kabachnik, January 2, 1961)

Among the relatively large number of methods for the synthesis of acid chlorides, there is a synthetic method based on the reaction between an aldehyde and a chlorinating agent. Thus, benzoyl chloride is obtained by the reaction of benzaldehyde with chlorine \(^{(1)}\), sulfuryl chloride \(^{(2)}\), sulfuryl chloride \(^{(3)}\), and ethyl hypochlorite \(^{(4)}\). Among syntheses of preparative significance, the preparation of the acid chloride of o-chlorobenzoic acid from o-chlorobenzaldehyde and chlorine \(^{(5)}\) should be noted.

In a brief publication by Winstein and Syubold \(^{(6)}\), the reaction between isovaleric and \(\beta\)-phenylisovaleric aldehydes and carbon tetrachloride, proceeding in the presence of benzoyl peroxide, is described. As a result of the reaction, the acid chlorides of the corresponding acids were obtained in yields of 60 and 55%. Continuing investigations on the study of thermal reactions of \(\mathrm{CCl_4}\) \(^{(7,8)}\), in the present work we report that \(\mathrm{CCl_4}\) reacts with aromatic aldehydes at \(180\text{—}205^\circ\) without the addition of peroxides and in this process forms acid chlorides in high yields (see Table 1)

\[ \mathrm{ArC(=O)H + CCl_4 \rightarrow ArC(=O)Cl + CHCl_3,} \]

where \(\mathrm{Ar = C_6H_5,\ p\text{-}CH_3C_6H_4,\ p\text{-}CH_3OC_6H_4,\ m\text{-}ClC_6H_4,\ p\text{-}ClC_6H_4,\ \alpha\text{-}C_{10}H_7}\).

Analogously to the reactions of carbon tetrachloride, the reactions of bromotrichloromethane with aldehydes proceed smoothly; in this case acid bromides are also formed in high yields

\[ \mathrm{ArC(=O)H + CBrCl_3 \rightarrow ArC(=O)Br + CHCl_3,} \]

where \(\mathrm{Ar = C_6H_5,\ p\text{-}CH_3OC_6H_4}\).

The amount of chloroform (with both halides) usually corresponded to the amount of the acid halide obtained. Reactions between aromatic aldehydes and chloroform were not observed.

In the reaction of \(\mathrm{CCl_4}\) with p-methylbenzaldehyde, in addition to the main reaction, exchange of chlorine for hydrogen from the side chain occurred. The formation of hydrogen chloride and resins in the experiments was usually insignificant. On the contrary, resin formation was very great in the reaction of cinnamaldehyde and furfural with \(\mathrm{CCl_4}\); acid chlorides were absent from the reaction products. In the reaction with m- and p-nitrobenzaldehydes, formation of acid chlorides and chloroform likewise was not observed; formation of phosgene, hydrogen chloride, and resin was noted.

Carrying out the reaction of \(\mathrm{CCl_4}\) with benzaldehyde in an atmosphere of nitrogen greatly reduced the yield of benzoyl chloride; this makes it possible to conclude that traces of peroxides, usually formed in the interaction of aldehydes with oxygen, initiated the reaction. Introduction of inhibitors (hydro-

Table 1

* Molar ratio of halide to aldehyde 5 : 1.

quinone, pyrocatechol) led to a slight decrease in the yield of benzoyl chloride and chloroform. The increase in this case in the relative amounts of chloroform, as compared with the acid chloride, indicates a reaction between \( \mathrm{CCl_4} \) and the inhibitors. The introduction of an inhibitor promoted resin formation.

The addition, in some cases, of cuprous chloride caused a slight increase in the yield of the acid chloride.

Experimental procedure

The experiments were carried out in thick-walled glass tubes, which were filled with a thoroughly purified reaction mixture, sealed, and heated in a Karius furnace. The reaction mixture was distilled on an efficient rectification column. The amount of chloroform was determined analogously8. After distillation of the unreacted carbon tetrachloride (or bromotrichloromethane), the residue (the acid halide) was distilled under vacuum. The acid halide was identified by its boiling point and refractive index; in addition, the corresponding anilide was obtained.

Work in this direction is continuing.

Belorussian State University
named after V. I. Lenin

Received
26 XII 1960

References cited

1. F. Wöhler, J. Liebig, Ann., 3, 262 (1832). ↩

2. F. Loth, A. Michaelis, Ber., 27, 2548 (1894). ↩

3. T. H. Durrans, J. Chem. Soc., 121, 45 (1922). ↩

4. S. Goldschmidt, R. Endress, R. Dirch, Ber., 58, 576 (1925). ↩

5. Syntheses of Organic Preparations, collection 1, Moscow, 1949, 474. ↩

6. S. Winstein, F. M. Seubold, Jr., J. Am. Chem. Soc., 69, 2916 (1947). ↩

7. Yu. A. Oldekop, DAN, 93, 75 (1953). ↩

8. Yu. A. Oldekop, A. M. Kalinina, ZhOKh, 30, 3358 (1960). ↩