Ground-state rotational spectrum of CH3NC...HCN and the nature of hydrogen bonds involving triply-bonded carbon

Article abstract of DOI:10.1016/0022-2860(92)85046-J

The ground state rotational spectra of the hydrogen-bonded species CH3NC...HCN and CH3NC...DCN have been studied using the technique of pulsed-nozzle Fourier-transform microwave spectroscopy.The spectra were of the symmetric top type and their analysis led to the rotational constants B₀ = 969.0435(4) MHz and 964.7530(5) MHz for the parent and deuterated molecule, respectively.The centrifugal distortion constants, D_J and D_JK, were established to be 0.369(7) kHz for CH3NC...HCN, and 0.356(8) kHz and 39.4(2) kHz for the deuterium species, while the corresponding (14)N-nuclear coupling constants were χ(¹⁴N) = -4.23(11) MHz and -4.5(1) MHz.Analysis of the centrifugal constants D_J using a model of C_3v symmetry with the atoms arranged in the order H3CNC...HCN gave the quadratic force constant associated with stretching of the hydrogen bond as 9.3(1) N m^-1 and 9.7(1) N m^-1 in CH3NC...HCN and CH3NC...DCN, respectively.The distances in these isotopomers between the carbon nuclei adjacent to the hydrogen bond r(C...C), were found to be 3.433(3) Angstroem and 3.420(3) Angstroem, when using a model that compensates for the contributions of the intermolecular bending modes to the zero-point motion.