Microwave Spectrum, Internal Rotation, Dipole Moment, Quadrupole Coupling, and Structure of Nitrosomethane

Abstract

The microwave spectra of C~NO and CDaNO have been observed and analyzed. The barriers to internal rotation are 1137±5 and 1095±7 cal/mole for CHaNO and CDaNO, respectively, a difference of 42 cal/mole which is thought to be real. The barriers were calculated by the internal-axis method with retention of higher terms in the usual Fourier expansion of the rotational energy and computation of the torsional integrals in the harmonic-oscillator approximation. The theoretical parameters were fitted to the data by a least-squares method and the uncertainties reported are standard deviations. Transitions having comparable Stark and quadrupole energies were used to calculate the dipole moment. Secular equations of second or third order were solved for each of the data points. The dipole moment components are I'a= 2.240±0.OO1 D, I'b=0.522±0.006 D, and I'total = 2.300±0.OO2 D. The quadrupole coupling constants of C~NO are 0.50± 0.16, -6.016±0.031, and 5.518±0.031 for the components along the a, b, and c axes, respectively. The corresponding values for CDaNO are 0.60±0.07, -6.007±0.020, and 5.41l±0.020. The N=O and C-N distances are not well determined by the data. The CNO angle is 112.6±1.0o.

Determination of a High Potential Barrier Hindering Internal Rotation from the Analysis of the Ground State Spectrum: The Case of Ethyl Cyanide

“…Inspection of Table 2 shows that the potential determined from the ^-doublet transitions is significantly higher than that obtained from the other lines and that the difference increases with K. These facts probably indicate that the effective Hamiltonian (1) is not appropriate to explain satisfactorily the splittings of the ^-doublet transitions. Similar conclusions have already been obtained for some other molecules [22] and a centrifugal distortion effect on the methyl top was proposed as explanation [27]. It is in principle possible to introduce in the Hamiltonian additional terms to account for the nonrigidity effects [28].…”

Electronic structure of simple phosphorus containing molecules [C,xH,O,P] candidate for astrobiology (x=1, 3, 5)

“…The non linear CH 3 NO 50 shows less consistency with rotational constants that are closer to experiment at the equilibrium geometry than after correction for anharmonic effects; on another hand, anharmonic corrections are important for HCP. Looking in more details at the geometries, it appears that CH 3 PH 2 O and CH 3 PO are very similar with PQO bond lengths differing by less than 0.3% which lends confidence in the use of the same scaling factors.…”

Structure of the nitrosomethane molecule (CH3NO) in the ground electronic state: Testing of ab initio methods for the description of potential energy surface

“…The equilibrium geometric parameters of the CH 3 NO ( S 0 ) molecule calculated by the RHF, MP2, CASSCF(8‐6), CISD, and CCSD methods with the 6‐31G** and 6‐311++G** atomic basis sets are presented in Table I, where the experimental microwave data ( r s structure) are given for comparison 22, 23. The eclipsed conformation was predicted by all approaches as the global minimum on the PES.…”