Oxalyl chloride decomposition

This photochemical reaction has been measured with the greatest care and is used as a standard in actinometry. Leighton and Forbes, J. Am. Chem. Soc., 52, 3139 (1930). Oxalyl chloride decomposition. (COCl)2 = COCl24-CO. 

Japanese workers prepared examples of 2-alkenyl-4,5-oxazolediones 40a and 40b, which are key intermediates in the synthesis of alkenoyl isocyanates 41a and 41b (Scheme 6.13). These reactive monomers are precursors to a variety of functionalized polymers including instantaneously curable compositions. Thus, reaction of oxalyl chloride with acrylamide 39a or methacrylamide 39b affords 40a and 40b isolated as hydrochloride salts in high yields. Subsequent decomposition of the 2-alkenyl-4,5-oxazolediones in the presence of a metal halide or synthetic zeolite affords 41a and 41b contaminated with varying amounts of 42a and 42b. The synthesis and reactions of other 2-substituted 4,5-oxazolediones have been described independently by Speziale and co-workers ° and Sasaki and co-workers. ... 

The decomposition of acid-sensitive substrates during Swern oxidations can also be explained by the presence of adventitious hydrogen chloride. This can be avoided by the use of freshly distilled oxalyl chloride and carefully dried DMSO.174... 

As traces of HC1 promoted the decomposition of the starting compound, adventitious HC1 had to be carefully excluded during the Swern oxidation, by using freshly distilled oxalyl chloride and carefully dried DMSO. 

If excess oxalyl chloride (and/or phosgene) is not removed, the vigorous reaction with water during decomposition of the aluminum chloride complex contributes to hydrolysis of the product acid chloride by increasing the time needed to complete this step. The more dilute solution achieved by additional solvent helps to prevent this hydrolysis as does maintenance of a low temperature during decomposition of the complex. 

Like other derivatives of oxalic acid, heating splits off carbon monoxide. By passing oxalyl chloride vapour through a tube I m. long heated to 600° C. quantitative decomposition takes place ... 

Many unsaturated chloro- and bromo-hydrocarbons and many polychloro and polybromo compounds decompose by radical-chain mechanisms, but only the chloro compounds have been studied in reasonable detail, presumably owing to the complex nature of the chain reactions in the case of the bromo compounds. Other examples of compounds which undergo radical-chain decompositions are 2,2-dichlorodiethyl ether oxalyl chloride alkyl hypochlorites alkyl peroxychloroformates and alkyl chloro-sulphites in the gas phase ... 

Scheme 177 Preparation oftetrachloroethylene carbonate and its decomposition to oxalyl chloride and phosgene.

This decomposition is today s standard process for the manufacture of oxalyl chloride. 

The likely reactive species and source of electrophilic chlorine is thought to be 7 and/or its decomposition product 8, which reacts with the enol of the ketone or P-ketoester, that is, the expected oxidised product. This side reaction can be avoided by employing one equivalent of the oxalyl chloride or by using either trifluoroacetic anhydride or acetic anhydride with DMSO. 

When anhydrous oxalic acid is treated with phosphorus pentachloride, oxalyl chloride, (COCl)2, is formed. The decomposition of the chloride with water is abnormal instead of yielding oxalic acid and hydrochloric acid, it is converted into carbon dioxide, carbon monoxide, and hydrochloric acid. 

Starting from 6-methoxynaphth-2-oic acid (64), the 1,2,3,4,5,8-hexahydro-derivative (65) was prepared by reduction with excess lithium and t-butyl alcohol in liquid ammonia. Compound (65) was converted into the keto-acid (66) by hydrolysis. Reduction of (66) with lithium tri-t-butoxyaluminium hydride gave the hydroxy-acid (67). The acetate derivative (68) was converted into the acid chloride (69) by reaction with oxalyl chloride in pyridine. Treatment of this compound with diazomethane afforded the diazoketone (70). Decomposition of the latter with copper powder in cyclohexane gave the cyclopropyl ketone (71) in yields of 70—80%. The acetate function was then hydrolysed, and the resulting hydroxy-ketone (72) was oxidized to the cyclopropyl diketone (73) with Jones reagent. Treatment of (73) with a weakly acidic acetone solution or adsorption on to basic alumina produced the enedione (74) via a retrograde... 

The gas-phase elimination kinetics of several ethyl esters of 2-oxocarboxylic acid have been found to be homogeneous, unimolecular, and follow a first-order rate law. ° Ethyl oxalyl chloride undergoes only decarboxylation, while both ethyl piperidinegly-oxilate and ethyl benzoyl formate exhibit parallel decarboxylation and decarbonylation reactions. The mechanisms of these decomposition reactions were described in terms of concerted discrete polar cyclic TS structures. 

Oxalyl chloride is a colorless liquid with a bp of 63-64 °C. It is quite stable and can be stored for several months without appreciable decomposition. Nevertheless, it is a very reactive compound and should be handled with extreme care, particularly on a large scale. It fumes in moist air and reacts violently with water with the liberation of hydrogen chloride, carbon dioxide, and carbon monoxide [100],... 

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