Zelinsky

The conversion of an aliphatic carboxylic acid into the a-bromo- (or a-chloro ) acid by treatment with bromine (or chlorine) in the presence of a catal3rtic amount of phosphorus tribromide (or trichloride) or of red phosphorus is known as the Hell-Volhard-Zelinsky reaction. The procedure probably involves the intermediate formation of the acyl halide, since it is known that halogens react more rapidly with acyl haUdes than with the acids themselves ... 

Haworth reaction Hell-Volhard-Zelinsky reaction Hoesch reaction Hofmaim reaction. ... 

This method of a bromination of carboxylic acids is called the Hell-Volhard-Zelinsky reaction This reaction is sometimes carried out by using a small amount of phosphorus instead of phosphorus trichloride Phosphorus reacts with bromine to yield phosphorus tribromide as the active catalyst under these conditions... 

Nucleophilic substitution by ammonia on a halo acids (Section 19 16) The a halo acids obtained by halogenation of car boxylic acids under conditions of the Hell-Volhard-Zelinsky reaction are reac tive substrates in nucleophilic substitu tion processes A standard method for the preparation of a ammo acids is dis placement of halide from a halo acids by nucleophilic substitution using excess aqueous ammonia... 

Bromoacetic acid can be prepared by the bromination of acetic acid in the presence of acetic anhydride and a trace of pyridine (55), by the HeU-VoUiard-Zelinsky bromination cataly2ed by phosphoms, and by direct bromination of acetic acid at high temperatures or with hydrogen chloride as catalyst. Other methods of preparation include treatment of chloroacetic acid with hydrobromic acid at elevated temperatures (56), oxidation of ethylene bromide with Aiming nitric acid, hydrolysis of dibromovinyl ether, and air oxidation of bromoacetylene in ethanol. 

P. Cagle and co-workers, in B. Zelinski and co-workers, eds., better Ceramics Through ChemistylJC, MRS Proc. 180 1990, p. 961. 

Other direct methods for the sulfonation of the higher fatty acids are by the use of sulfur trioxide vapor or by the use of chlorosulfonic acid. Indirect methods are also available for the preparation of a-sulfo fatty acids and their salts from an a-bromo fatty acid made by the Hell-Volhard-Zelinsky reaction. The bromo compound may be converted directly to the sodium salt of a sulfonic acid through the Strecker reaction or may be converted to the mercaptan and oxidized to the sulfonate. Sulfonation of the lower fatty acids has been studied by Backer and co-workers. ... 

OL HALOGENATION OF CARBOXYLIC ACIDS THE HELL-VOLHARD-ZELINSKY REACTION... 

The Hell-Volhard-Zelinsky reaction is of synthetic value in that the a halogen can be displaced by nucleophilic substitution ... 

Section 19.16 Halogenation at the a-carbon atom of carboxylic acids can be accomplished by the Hell-Volhard-Zelinsky reaction. An acid is treated with chlorine or bromine in the presence of a catalytic quantity of phosphorus or a phosphorus trihalide ... 

The a-halo acid is nonnally prepared by the Hell-Volhard-Zelinsky reaction (see Section 19.16). 

Hell-Volhard-Zelinsky reaction (Section 19.16) The phosphorus trihalide-catalyzed a halogenation of a carboxylic acid ... 

N. D. Zelinsky Institute of Organic Chemistry, Russian Academy of Sciences, Moscow 117913, Russia... 

O. V. Prokshits, Thesis, Zelinsky Institute of Organie Chemistry, Moseow, 1992 (in Russian). 

A. B. Sheremetev and N. N. Makhova (N. D. Zelinsky Institute of Organic Chemistry, Moscow, Russia) and W. Friedrichsen (University of Kiel, Germany) have reviewed the monocyclic furazans and furoxans. While much of the early work in this area was published in the German and Italian literature, more recently, a large amount has appeared in Russian journals, much of it being released for publication only during the last ten years. This survey should be of great utility to Western readers. 

Bromination of the substituted butyric acid, 26, by the Hell-Volhardt-Zelinsky procedure affords the a-halo acid bromide (27). Reaction of this with urea affords directly bromisovalum (28). 

Zelinsky, apparently overlooking Aschan s isopinene, has improperly appropriated the same name to a quite different terpene. 

Mojjo 1-4641. It does not form a crystalline hydrochloride or nitroso-chloride. Zelinsky assumes that a-pinene first absorbs hydrogen, with the formation of hydropinene, and that isopinene results from the latter, according to the following formulae —... 

---