Studies in the chemistry of phenylhydrazine (1963)
AuthorsHapper, D. A. R.show all
This thesis is concerned with three aspects of the chemistry of phenylhydrazine. (1) The dissociation constants have been measured for the phenylhydrazine ion and nine of its meta and para substituted derivatives. The results are compared with the values obtained for the corresponding benzylammonium ions. Replacement of the methylene group (benzylamine series) by an amino group (phenylhydrazine series) appears to have little effect on the Hammett reaction constant (p); however, in the phenylhydrazine series, exalted substituent constants (σ) are required for para-M substituents. A possible explanation for the observed exaltations is suggested. (2) The reaction of phenylhydrazine with phenyl isothiccyanate has been examined. The effect on the ratios of the product 1-aryl and 2-aryl-4-phenylthiosemicarbazides of solvent change and of substitution in the phenylhydrazine nucleus, is recorded. The data obtained are consistent with the assumption that the same transition state gives rise to both isomeric thiosemicarbazides. The secondary amino group in the hydrazine appears to be considerably less sensitive to the electronic effect of substituents that is the amino group in aniline. (3) An investigation has been made into the mechanism of neutral hydrolysis of acetone-2-phenylsemicarbazone. A reaction scheme is suggested that accounts for the unexpected formation of 1-phenylsemicarbazide rather than 2-phenylsemicarbazide, as a major product. An Appendix to this section discusses briefly the kinetics of hydrolysis of acetone phenylhydrazone.