Raman Spectra of Gases. IV. Methylenecyclobutane and Trimethylene Sulfide

Abstract

The low frequency Raman spectra of methylenecyclobutane and trimethylene sulfide in the gaseous state have been recorded. The observed Q branches for the ring puckering vibration have been assigned as Δ v=2 transitions from a double minimum potential function. The Q branches for trimethylene sulfide agreed with those predicted from far infrared and microwave data and confirm the predicted energy difference for the v = 2 to 3 transition. This is the first direct observation of the ring puckering vibration for methylenecyclobutane. The determined potential function, V=4.104 × 105χ4−1.519 × 104χ2, differs from those proposed from the microwave and midinfrared studies but is capable of explaining not only the Raman results but also the previous data. The barrier to inversion was found to be 141± 5 cm−1.