The structures of pentanoyl chloride, CH3(CH2)3COCl, contained in supersonic expansions of argon gas

We report the first structural study of pentanoyl chloride. Vapor above a sample of pentanoyl chloride was mixed with a supersonic expansion of argon gas. Once in this state a chirped pulse Fourier transform microwave spectrometer was used to obtain pure rotational spectra for the target compound between 8 GHz and 16 GHz. Within this experiment two conformers were detected. In both cases rotational constants, quartic centrifugal distortion constants and chlorine nuclear electric quadrupole coupling tensors were obtained for the first time. Quantum chemical calculations have provided structures with rotational constants closely matching the experimental values. The values of the chlorine nuclear quadrupole coupling tensor are compared to those of other acyl chlorides and are consistent with a standard acyl chloride Cl35 χzz value of −59(1) MHz.