Two Forms of 1,3 Butadiene

Abstract

IN a previous publication¹, experimental evidence was adduced for the existence of butadiene molecules in two forms, s-cis and s-trans. This evidence came from a study of the ionization potentials of butadiene gas, both by spectroscopic and electron impact methods. The existence of the two forms has recently received strong confirmation from the thermodynamic studies of Aston, Szasz, Woolley and Brickwedde². A conflict of opinion has, however, appeared as to which of the isomers is the lower-energy form. Rasmussen, Tunnicliff and Brattain³ concluded that the s-cis form had the lower energy ; Aston et al. followed Mulliken⁴ in believing that the s-trans was the lower-energy form. We wish to note here that the ionization potential data indicate that the s-trans isomer is the lower-energy form.