No abstract

The investigation of structural isomers and proton transfer phenomena of the 2-hydroxypyridine system in the cation ground state (Do) has been performed by two-color (1 +l') resonantly enhanced multiphoton ionization (REMPI) zero kinetic energy photoelectron spectroscopy. The adiabatic ionization energies of keto/enol tautomers have been determined to be 68 137 f 5 and 72 093 f 5 cm-' for 2-pyridinone and 2-hydroxypyridinol, respectively. Although the structural isomers have been reported in the neutral excited state (SI) for the keto tautomer, the observed ionization energies for these isomers were found to be the same within our experimental accuracy. This indicates that no structural isomers of the keto tautomer exist in the Do state. The keto tautomer adopts a planar geometry in the Do state similar to that in the neutral ground state. In addition, no spectroscopic evidence for fast proton transfer from the enol form to the keto form in the DO state has been obtained from the analysis of the spectral line width.

The dipole moments of ethylene glycol dimethyl ether (N=1), diethylene glycol dimethyl ether (N=2), triethylene glycol dimethyl ether (N=3), and tetraethylene glycol dimethyl ether calculated on the assumptions that: (i) the dipole moments of these chain molecules are given by the vector sum of the polar groups of ether whose group moment is 1.20 D, and (ii) all the internal rotations of a chain molecule are free. The calculated values of N= 1, N= 2, N=3, and N=4 are 1.67D, 2.03D, 2.33D, and 2.60D, respectively. The agreement between the observed and the calculated values is satisfactory. The solvent effect and the temperature dependence of the observed dipole moments have also been discussed in terms of chain flexibility.

The electric dipole moments of diphenyl sulfide, sulfoxide, and sulfone and their derivatives were determined in benzene solutions at 25°C. The observed moments are used to estimate the mesomeric moments on the assumption of the vector addition of group moments. The mesomeric moments of the phenylmercapto, phenylsulfinyl, and phenylsulfonyl groups are estimated to be −0.12, 0.10, and 0.44 D, respectively. The steric effect of ortho-substituents is also discussed on the basis of the dipole moment data.

In the solution polymerization of vinyl chloride with benzoyl peroxide, it was found that the initial rate of the polymerization was remarkably increased by adding dimethylaniline, but that conversion became constant at lower conversion. It was observed that when the rate became constant the benzoyl peroxide was completely decomposed and the reaction could be reinduced by adding more benzoyl peroxide. On the basis of these results, it seems possible that the polymerization is instituted by the benzoate radical and not by the dimethylaniline radical as suggested by Horner. The benzoate radical is produced through the reaction of dimethylaniline with benzoyl peroxide. In view of such considerations, we postulate a reaction mechanism for the polymerization of vinyl chloride.