Formation of [C18H36]+ ˙ and [C7H7O2]+ in the mass spectrum of n-octadecyl benzoate

A series of deuterium-labeled n-octadecyl benzoates serves to extend the literature using lower homologues for study of the mass-spectral reactions characteristic of alkyl esters. The benzoic acid radical cation (a) arises largely via hydrogen migration from C(2), as expected for the conventional mechanism passing through a six-membered quasicyclic intermediate; the presence of contributions from other processes is simply noted in passing. The octadecene radical cation (b) and protonated benzoic acid (c) arise by paths seemingly closely related to each other but differing from the path dominant for a. The data are rationalized in terms of a reaction sequence passing through two ion-neutral complex intermediates. The first, (d), consists of octadecyl carbenium ion and benzoyloxy radical; the second, (e), consists of octadecene radical cation and benzoic acid. The ionized partner in d appears to undergo none to several hydride migrations, but most prominently one; that in e may dissociate promptly to yield b or may persist, undergoing multiple hydride migrations to effect essentially complete scrambling of hydrogens, before dissociating to yield c. The argument for this mechanistic sequence to form b and c rests basically on its ability to account plausibly for the experimental data, and literature precedents cited for specific aspects of it furnish additional support. The low critical energies and small kinetic energy releases observed in this work are in accord with the characteristics listed by McAdoo for decompositions mediated by ion-neutral complexes, and the selection of an octadecyl, as opposed to a smaller alkyl, ester predisposes the molecule to favor such low-energy processes.     

Decomposition of regular matroids

It is proved that every regular matroid may be constructed by piecing together graphic and cographic matroids and copies of a certain 10-element matroid.     

Synthesis of new photosensitive silicon-containing poly(salicylideneazomethynes)

Photosensitive silicon-containing poly(salicylideneazomethynes) have been synthesized. It has been shown that these polymers are characterized by the presence of intramolecular donor-acceptor interactions between valence shells of silicon and nitrogen atoms; as a result, polyconjugation appears according to the nonclassical mechanism. The photo-and electrophysical properties of the polymers have been examined. The introduction of an oxygen spacer into a polymer facilitates an increase in the photosensitivity and quantum yield of free charge carrier photogeneration, and it has almost no effect on the conductive behavior of the polymers.