Fundamental Vibrational Frequencies in Ketene and the Deuteroketenes

Abstract

Accurate microwave relative intensity measurements have been made on rotational transitions of ketene and its deutero derivatives in the ground and first vibrational states. The results allow the three lowest fundamental frequencies of these molecules to be positively determined. For CH₂CO these modes are found to be 443, 527, and 617 cm⁻¹. The lowest frequency is nearly 100 cm⁻¹ lower than any fundamental previously cited from infrared data for ketene. To substantiate the microwave results solid‐state infrared spectra of the molecules at −192° have been investigated in the region 300–4000 cm⁻¹. The low‐frequency spectra are in good agreement with the microwave data, and a complete analysis allows the nine fundamentals of CH₂CO, CHDCO, and CD₂CO to be evaluated. The three lowest fundamentals of CH₂CO in the solid are found at 433, 513, and 613 cm⁻¹. The thermodynamic properties of ketene have been recalculated.