Diethyl Ether → Chloral

Participants

Reaction Steps

As a result of their studies on the process, Kondo, Suda and Tunemoto found that it was possible to obtain the 2,2,2-trichloro-1-(N-hydrocarbylpyrryl-2)-ethanol adduct in almost quantitative yield by reacting chloral with N-hydrocarbylpyrrole at from -10° C. to about 36° C. without using a Lewis acid catalyst such as zinc chloride. As reported in their above refered to co-pending application, it was discovered that the rate of this reaction-which is preferably conducted in the presence of solvents which do not directly affect on the reaction, for example, ethereal solvents such as diethyl ether, dioxane, THF, and the like, and hydrocarbons such as benzene, toluene, hexane, and the like--is dependent on the origin (or the purity) of chloral used. Chloral from a freshly opened bottle did not react with N-methylpyrrole at room temperature and only after prolonged reflux (sometimes several days) was the adduct formed. In contrast, chloral from an old bottle reacted instantly at room temperature. Acting on the hypothesis that trichloroacetic acid, which is formed easily by the oxidation of chloral, does catalyze this reaction, they found that the addition of organic acid such as trichloroacetic acid, acetic acid or p-toluene-sulfonic acid to the reaction mixture accelerates this reaction. They further report that among these three acids p-toluene-sulfonic acid appears more effective than the others and that in carrying out the process in the presence of a protonic acid added preferably in the form of an organic acid or a cation exchange resin, the adduct (i.e., the 2,2,2-trichloro-(N-hydrocarbylpyrryl-2)-ethanol) has been readily formed in almost quantitative yield.

Provenance & Evidence