Enhanced conformational complexity by mono-chlorination: The case of 3-chloropropane-1,2-diol

By mono-chlorination of propane-1,2-diol its conformational complexity can be significantly enhanced. The Cl atom allows for a stabilization of conformers with an anti-periplanar arrangement of the OC-CO dihedral angle which has not been detected for any other vicinal diol in the gas phase. We assigned a total of eight different conformers in our chirped-pulse Fourier transform microwave (CP-FTMW) spectra with the 35 Cl and 37 Cl isotopologues for each case. Furthermore, the conformational landscape was analyzed in great detail including transition state calculations. In addition to the monomeric species, the Ne complex of the global minimum was also observed. From the nuclear quadrupole coupling constants, the presence of weak OH ⋯ Cl bonding is assessed. We further investigate the shifts induced in the energetic landscape by the chlorine atom with density functional and explicitly correlated wavefunction theory based methods. To understand the potential role of dispersion in the stabilization of some key conformers, local energy decomposition accompanied by dispersion interaction densities was employed.