Investigation of the process of aqueous acid enolization of 2,3;4,6-di-0-isopropylidene-2-keto-1-gulonic acid

Autor: E. V. Aganova, V. V. Beregovykh, I. D. Frizen, G. P. Yurevich, E. D. Goryacheva, I. A. Rubtsov, M. M. Avrutskii
Rok vydání: 1986
Předmět:
Zdroj: Pharmaceutical Chemistry Journal. 20:129-132
ISSN: 1573-9031
0091-150X
DOI: 10.1007/bf00766908
Popis: Methods of enolization of (I) catalyzed by a mineral acid such as hydrogen chloride are widely used. These methods may be grouped into three main.groups, To the first group belong those that are effected in hydrochloric acid of various concentration. The reaction is complete in 6 h and the yield of acid (V) does not exceed 80% according to [2, 3, 6, 10-12]. In the second group are methods of enolization carried out in organic solvents (including such compounds as chloroform, dichloroethane, trichloroethylene, aromatic hydrocarbons, and-their halogen substituted derivatives) with the participation of hydrogen chloride dissolved in CI-C4 alcohols. The reaction time oscillates between 12 and 48 h and the yield of (V)may vary from 50 to 87% according to [3, 4, 6]. The third group includes enolization processes occurring in the mentioned solvents using concentrated hydrochloric acid. The reaction time in this case was reduced to 6 h, the yield of acid (V) was within the limits 78-85% [2, 9]. In view of the absence in these variants of the method of alcohols to homogenize the reaction mixture the reaction was~heterogeneous during the whole process (boththereactants and the majority of the reaction products has low solubility in the solvents used). The role of the solvent is mainly the creation of a continuous phase in the reaction mixture providing favorable conditions for the interaction of reactants present in the dispersed phase. It was also shown in [8] that the application of emulsifying surfactants at 0,05-10 wt.% assigned the breaking up of the dispersed phase which increased thereactionrate. The duration of the process was reduced to 4-6 h and the yield of acid (V) reached 94%.. This method may be considered as the most promising for further investigation.
Databáze: OpenAIRE
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