Acyclic alkanes analysis

Kolossvary I and W C Guida 1996 Low Mode Search An Efficient, Automated Computational Method for Conformational Analysis- Application to Cyclic and Acyclic Alkanes and Cyclic Peptides Journal of the American Chemical Society 118 5011-5019. 

Kolossvary I, Guida WC (1996) A low mode search. An efficient, automated computational method for conformatiraial analysis applicatirm to cyclic and acyclic alkanes and cyclic peptides. J Am Chem Soc 118 5011—5019... 

In this article (Part I) we have comprehensively reviewed the structural implications of the vibrational spectroscopic results from the adsorption of ethene and the higher alkenes on different metal surfaces. Alkenes were chosen for first review because the spectra of their adsorbed species have been investigated in most detail. It was to be expected that principles elucidated during their analysis would be applicable elsewhere. The emphasis has been on an exploration of the structures of the temperature-dependent chemisorbed species on different metal surfaces. Particular attention has been directed to the spectra obtained on finely divided (oxide-supported) metal catalysts as these have not been the subject of review for a long time. An opportunity has, however, also been taken to update an earlier review of the single-crystal results from adsorbed hydrocarbons by one of us (N.S.) (7 7). Similar reviews of the fewer spectra from other families of adsorbed hydrocarbons, i.e., the alkynes, the alkanes (acyclic and cyclic), and aromatic hydrocarbons, will be presented in Part II. 

Continuing interest in rotation barriers about single bonds in acyclic radicals, as determined by the interpretation of e.s.r. data, is illustrated in a study of R CHSR radicals and alkane-, arene-, and alkoxy-sulphonyl radicals (obtained by high-intensity u.v. irradiation of sulphinic acids in the presence of di-t-butyl peroxide at low temperatures). Further evidence for hindered rotation about the C—S bond in these species is obtained, - and an unusual order of proton hyperfine splittings a 0-H)> a (a-H) a (y-H) is reported for propanesulphonyl radicals. The potential of the e.s.r. method in conformational analysis is shown in studies of radical cations (3) from 2,5-bis(alkylthio)thiophens, where the S-cis-cis conformer (3) is identified as more stable than other rotamers this is assumed to be the case too for the neutral molecule. 

---