FIR spectroscopy and DFT calculations involving 2-chloroethanol: Analysis of the ν19 + ν21←ν21 torsional hot band, and the solvated substitution reaction between ethylene glycol and hydrogen chloride

Abstract

We build upon a recent investigation of 2-chloroethanol (2CE) which focused on its high-resolution far-infrared (FIR) spectroscopy, and ab initio calculations that considered potential synthetic routes leading to its formation in interstellar molecular clouds. Here we report a rovibrational analysis of the normal isotopologue of 2CE (35ClCH2CH2OH) in the ν19 + ν21 – ν21 hot band (at ∼340 cm−1), that is complimented by density functional theory (DFT) calculations on the substitution reaction between hydrogen chloride and ethylene glycol in the presence of a simulated water environment. The spectroscopic analysis presented here involves the assignment of 2065 lines (J ≤ 79), and determination of rotational and centrifugal distortion constants up to sextic level using Watson’s A-reduction Hamiltonian. The calculations show that the reaction leading to 2CE proceeds in a qualitatively different way in a water-like environment in comparison to the gas phase, with a much broader barrier that is significantly lowered, and an early dissociation of HCl to give protonated ethylene glycol in the entrance channel.