Rotational analysis of several bands in the high-resolution infrared spectrum of butadiene-1-13C1: assignment of vibrational fundamentals

Butadiene-1-13C1 was synthesized, and its high-resolution (0.002 cm−1) infrared spectrum was recorded for several bands in the mid-infrared region. A complete analysis of the rotational structure in the C-type band at 524.485 cm−1 for CH2 twisting and a partial analysis of the rotational structure in the C-type bands at 900.0 and 909 cm−1 were performed. Of these latter two bands, which are of comparable intensity, the higher frequency one is largely CH2 out-of-plane wagging and the lower frequency one is largely 13CH2 out-of-plane wagging. Taken together these bands correlate with one infrared-active au fundamental and one Raman-active bg fundamental of butadiene. The ground state rotational constants are A=1.3887919 (6), B=0.1436683 (3), and C=0.1302251 (3) cm−1, and upper state rotational constants are reported for the bands at 524.485 and 900.0 cm−1. Medium resolution infrared and Raman spectra gave a complete assignment of the vibrational fundamentals, including 11 fundamentals observed directly for the first time.