The methylhydroxycyclohexadienyl radical: Ab initio computation and automation of the detection instrumentation.

摘要

Theoretical computations were used to study the methylhydroxycyclohexadienyl (MHCH) radical, and software was developed to automate an instrument designed to detect such radicals. The MHCH isomers were studied using ab initio and density functional theory methods. The ipso-MHCH and ortho-MHCH isomers were found to be significantly more stable, due in part to van der Waals attractions between the adjacent hydroxyl and methyl groups. This stability explains the disparate distribution of isomeric products formed by the photochemical oxidation of toluene. The differences in normal mode vibrational frequencies will aid in spectroscopically distinguishing the MHCH isomers. The LabVIEW graphical programming language was used to automate a laser ionization mass spectrometer which can be used to detect gaseous radicals at low concentrations. The program allows the user to control experiment parameters, and to collect and display two- and three-dimensional mass/REMPI spectra.