A CONFORMATIONAL STUDY OF BUTADIENE AND OF ITS HOMOLOGUES BY NMR SPECTROSCOPY

The NMR spectra of butadiene, of cis and trans pentadienes and of cis- and tran-t-butyl-butadienes were studied. The value of the coupling constant Js-vicinal varies with the temperature in butadiene and in its trans derivatives; it remains constant in the cis compounds. These results seem to indicate that in butadiene and in its trans-derivatives there is an equilibrium between a predominantly populated s-trans-conformation and a skewed conformation with the two double bonds not in the same plane. © 1969.