Grenda's method to convert arylamidine hydrochloride into benzimidazole with the aid of sodium hypochloride and a base has been applied to the previously untried N-arylamidines to synthesize the following : 5-chloro-2-phenylbenzimidazole (Y=96%), 5-methyl-2-phenylbenzimidazole (Y=96%), 2-benzylbenzimidazole (Y=50%), 2-benzyl-5-chlorobenzimidazole (Y=70%), 2-(2'-naphthyl)-benzimidazole (Y=75%), 5-chloro-2-(2'-naphthyl)-benzimidazole (Y=90%), 2-(p-tolyl)-benzimidazole (Y=95%), 5-chloro-2-(p-tolyl)-benzimidazole (Y=80%), 5-methyl-2-(p-tolyl)-benzimidazole (Y=80%).
Though primary alcohols are, in general, readily chlorinated with hydrogen chloride, neopentyl-type polyols such as pentaerythr.itol undergo chlorination with difficulty. Upon addition of a small amount of acetic acid, however, chlorination reaction is effected with ease. In order to clarify the catalytic mechanism of acetic acid, the chlorination of pentaerythritol and pentaerythritol dichlorohydrin has been studied. Though in the absence of acetic acid, pentaerythritol dichlorohydrin failed to react with hydrogen chloride, pentaerythritol trichloride was formed quantitatively when a proper amount of acetic acid was added. The true reactant, in this case, was found to be pentaerythritol dichloromonoacetatemonohydrin. Under the constant flow of hydrogen chloride gas, the reaction velocity was poportional to the first order of the true reactant concentration. In the presence of a proper amount of acetic acid, pentaerythritol was converted to the mono-, di-, or tri-chlorinated products with relatively good selectivity under given conditions.Dipentaerythritol tetrachlorodiacetate has been isolated as a by-product from the chlorinated product mixtures.
Chlorination of pentaerythritol tetraacetate (PETA), pentaerythritol dichlorodiacetate (PEDCDA), and pentaerythritol trichloromonoacetate (PETCMA) with gaseous hydrogen chloride has been investigated in the presence of zinc chloride PETA was chlorinated in a stepwise manner to form PETCMA . Essentially no pentaerythritol tetrachloride, the fully chlorinated product, was detected in the products. The reaction velocity of PETCMA was extremely small and was of the order of 1/170-1/370 that of the other reactions. Under the constant flow of hydrogen chloride gas, the chlorination velocity of PEDCDA was proportional to the first order of the reactant concentration and zinc chloride concentration. It is believed that zinc chloride first coordinates toward the carbonyl group of the reactant. Ligand exchange has then to occur to effect the desired reaction. The difficulty for zinc chloride to coordinate toward the carbonyl group of PETC MA would explain the difficulty in chlorination. Hydrogen chloride probably converts the Zn-OCOCH3 linkage formed by the ligand exchange into a Zn-Cl linkage, thus eliminating the acetic acid from the system to prevent the reverse reaction.
Esterif ication of cyanoacetic acid at 60.. in the absence of catalyst with various alcohols occured in the following order of readiness : methyl>ethyl>n-butyl>2-ethylhexyl>isobutyl>allyl>2-methoxyethyl . The reaction velocities, however, did not vary from each other to a significant extent except those for allyl alcohol and 2-methoxyethyl alcohol. The esterif ication reaction proceeded as a 2 nd order reaction for the cyanoacetic acid concentration, and the apparent activation energies for methyl alcohol, ethyl alcohol, allyl alcohol, isopropyl alcohol, 2-methoxyethyl alcohol, n-butyl alcohol, isobutyl alcohol, and 2-ethylhexyl alcohol were calculated to be 13.6, 14.6, 19.8, 22.8, 17.1, 17.4, 17.0, and 18.6, kcal/mol, respectively. Under the same conditions, esterif ication of monochloroacetic acid occured in the following order of readiness : methyl>n-butyl>ethyl>2-ethylhexyl> allyl> 2-methoxyethyl>isopropyl. The reaction was also of the 2 nd order for the concentration of mono-chloroacetic acid . The apparent activation energies for methyl alcohol, ethyl alcohol, allyl alcohol, isopropyl alcohol, 2-methoxyethyl alcohol, n-butyl alcohol, and 2-ethylhexyl alcohol were calculated to be 14.3, 16.4, 16.6, 22.9, 21.0, 16.3, and 15.6 kcal/mol, respectively. In the presence of sulfuric acid, esterification proceeded with ease and a quantitative yield was attained when benzene was used for the azeotropic removal of water.
An improved method was proposed for the preparation of guanyl-o-methylisourea salts based on the addition reaction between dicyandiamide and methanol. Zinc salts have been found to serve as effective catalysts and furthermore, they convert the isourea formed into insoluble zinc complex salts. Guanyl-o-methylisourea zinc complex was given in a good yield, especially when zinc nitrate or zinc sulfate was used as a catalyst. Since the complex is readily decomposed into guanyl-o-methylisourea and zinc hydroxide upon treatment with hot water, the process is useful for the production of the isourea on a large scale. Some properties of those comoupnds were also discussed.