Benzaldehyde, heptanal, and cyclohexanone were reductively thiolated using sulfur in cyclohexane in the presence of molybdenum sulfide catalyst at 130-200°C to obtain the corresponding thiols in approximately 90% yield. It is assumed that the hydrogen sulfide possibly formed in situ upon reduction of sulfur would first add to the carbonyl groups to give thials or thiones VIA gem-olthiols or dithiols. The intermediates so formed would then be hydrogenated to form the product thiols. The reactions proceeded more readily than the analogous ones previously con-ducted using fatty acids and their derivatives as starting compounds.
Polypyromellitimide-amide polymer was prepared in two step reactions. Polypyromellitic acid hydrazide of high molecular weight was obtained when pyromellitic dianhydride was added to the dispersion of dicarboxylic acid dihy-drazide in dimethyl formamide, dimethyl acetamide, or dimethyl sulf oxide. The polymeric hydrazides, which were soluble in dimethyl formamide, dimethyl acetamide, dimethyl sulfoxide, and alkaline water, showed an inherent viscosity of 1.2-0.7. The solution was cast into essentially clear, flexible, and infusiblefilm. The polymer was amorphous as judged by X-ray diffraction patterns. The polypyromellitic acid hydrazide was then heated to form polypyromellitimide-amide. The cyclocondensation reaction of polypyromellitic acid-isophthalic hydrazide proceeds endothermally over the temperature range, 70-170°C as proven by differential thermal analysis as well as thermal decomposition studies. The polypyromellitic-isophthalic imide-amide can be wet-spun into fibers using an aqueous ethanol as a quenching liquid.
In order to confirm the authors' view that in the dissociation of substituted benzoic acids, the ortho effect is markedly influenced by the type of solvent, whereas in the hydrolysis of their esters, the ortho effect is essentially unaffected, the rates of alkaline hydrolysis of o-, m-, and p-substituted ethyl benzoates were measured in 3 wt.% ethanol-water at 25°C The rate of reaction was calculated based on the changes in optical density at 220-290mμ. The reaction rate of thenon-substituted benzoate in 3 wt.% ethanol-water was approximately 50 times as much as that observed in 85 wt.% ethanol-water, and the Hammett's p value, 1/2. However, the ortho effects, log (k ortho/k para), remained almost unchanged. Possible reasons for these facts have been discussed in the light of the ortho effect observed in the dissociation of substituted benzoic acids.
In order to confirm the previous observation that the ortho effect in the alkaline hydrolysis of substituted ethyl benzoates is not affected by the type of solvent, the rates of hydrolysis have further been measured in a mixture of water and dimethyl sulf oxide (DMSO), a typical dipolar aprotic solvent. The rates of hydrolysis of non-substituted benzoate in 65 vol.% DMSO-water, 85 vol . % DMSO-water, 95 vol. % DMSO-water, and 99 vol.% DMSO-water were found to be 56, 267, 1, 840, and 16, 000 times, respectively, as much as that observed in 85 wt % ethanol-water. The Hammett's p value increased with the concentration of DMSO and thus the value in 95.vol % DMSO-water was 3.1 in contrast to 1.33 in 3 wt. % ethanolwater. Despite such marked solvent effects, the ortho effect still remains almost constant. The accelerating effect characteristic to DMSO has been discussed based on the reaction rates of non-substituted benzoate, p values, and the ortho effects observed in mixtures of DMSO-water as well as ethanol-water . In 99 vol.% DMSO-water, the ortho effect induced by the o-methyl substituent essentially disppeared probably due to desolvation.