Notes- Ultraviolet Absorption Spectra of Some Ortho-Anisyl Esters and Thiolesters

Abstract

notes 413 Fig, 1.Translucent picture made by superimposing the infrared spectra curves of compound I from West Indian mahogany and cycloeucalenol from Eucalyptus. In the few places where there is no perfect congruency of the two curves the lower line is that of compound 1

Molecular Addition Compounds of Boron. III. Trivinylphosphine-Trimethylborane and Related Adducts1,2

“…For two addition compounds of closely similar structure and molecular weight, the less stable exhibits the higher saturation pressure. 28 In Table X the volatility data for (CH2:CH)3P-BMe3 and Et3P-BMe3 show that trivinylphosphine is a weaker base than triethylphosphine. Thus the vinyl group has a weakening effect compared with the ethyl group on the electron-pair donor power of phosphorus.…”

“…Although such an effect would be analogous to the p,-pT bonding present in the alkylvinylboranes,26 its absence in the vinylphosphines is in agreement with the idea27 that in phosphorus compounds in which phosphorus shares electrons with three neighboring atoms the three bonds to phosphorus have little or no -character. It is interesting to note in passing that in the case of neutral organosulfur compounds in which a phenyl group is bonded to sulfur, evidence has been presented both for 28 and against29•30 the idea of mesomerism between the phenyl group's -electrons and the vacant sulfur d-orbitals.…”

The Expansion of the Sulfur Outer Shell.

“…The gain by the increased delocalization of the electronic system only slightly overbalances the energy of promotion of an electron to the d orbital and hence expansion does not occur in o-anisyl isomers (46). Bor dwell and Boutan (30) have criticized this view of the valency expansion of sulfur in thiolesters, but their objections have been answered (46). Knott (105) pointed out that in the aryl thiolesters studied by the author, steric hindrance should preclude or hinder structures with a decet configuration on sulfur.…”

“…Knott (105) pointed out that in the aryl thiolesters studied by the author, steric hindrance should preclude or hinder structures with a decet configuration on sulfur. This objection too has been answered (46). In fact, the geometrical requirements for d-orbital resonance are not the same as those required in resonating systems of octet structures.…”