Microwave Spectrum and Structure of Propionitrile

Abstract

Rotational transitions of several isotopic species of propionitrile have been observed. This has permitted a determination of the structural parameters of the molecule. For C₂H₅C¹²N, B=4714.00 Mc, C=4235.07 Mc and for C₂H₅C¹³N, B=4689.77 Mc and C=4214.87 Mc. For CD₃CHDC¹²N, B=4169.43 Mc and C=3736.83 Mc. The following model reproduces these constants to within 1.5 Mc : r_C–C=1.5479 A (ethyl), r_C–C=1.4735 A (nitrile), r_C=N=1.1566 A, r_C–H=1.0914 A, ∠CCC=110°32′, ∠HCH=109°19′. The height of the barrier to internal rotation has been estimated to be 1150±100 cm^—1 or 3280±290 cal/mole for a torsional frequency of 226 cm^—1.