3455are due to propyl torsions, features also noted in the spectra of n-propylbenzene and 4-n-propyltoluene, The observation of only three origins also substantiates the conclusion derived from the data on the ethylbenzenes that T~ = 90'.These results show (a) supersonic molecular jet spectroscopy is capable of observing specific molecular conformations which have very low barriers to conformational interchange, (b) aromatic ring methyl groups in the p-and m-xylenes can be considered as independent, nearly free rotors in So and SI, (c) the aromatic ring methyl groups in o-xylene are considerably more hindered in So and SI, and for SI, cross kinetic and potential terms must be introduced, (d) the barriers for rotation are greater in SI than So, (e) the dynamic nature of the motion of the ring methyl groups is contrasted by a more static, locked-in character of the aromatic ethyl and n-propyl substituents, (0 aromatic n-alkyl substituents have their first C-C torsion perpendicular to the plane of the aromatic ring, and (8) aromatic n-propyl substituents exist in anti and gauche conformations, as observed in these TOFMS/DE experiments.
Acknowledgment.We thank A. Kassman, W. Kuhn, B. LaRoy, and C. Lilly for the encouragement and support of this work.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.