Cryogenic photolysis studies. Part 2.—Infrared spectrum of nitrosomethane monomer

Abstract

The photolysis of trans-t-butyl nitrite in an argon matrix at 20 K gave rise to absorptions due to acetone, nitrosomethane and cis-t-butyl nitrite. Isomerisation was dominant at higher concentrations ; decomposition was dominant at lower concentrations. Vaporisation of nitrosomethane dimer and trapping of the products at 20 K yielded the spectrum of nitrosomethane monomer and the trans dimer. Ultra-violet irradiation dissociated the dimer, leaving nitrosomethane monomer. On warming to room temperature and recooling to 20 K the cis-nitrosomethane dimer was obtained, which could be dissociated by photolysis to regenerate the monomer. A vibrational assignment of the monomer is presented.

Infrared spectra of tautomers and rotamers of 9-methylguanine. An experimental and theoretical study

“…The effect of the UV irradiation on the distribution of intensity in the spectrum from the different rotamers isolated in the low-temperature matrix and the relaxation in the dark observed here is very similar to observations for a number of other molecules reported previously (25)(26)(27)(28).…”

One-dimensional models of internal rotation in CX3NO molecules (X=H, D, F)

“…The calculated torsional energies and kinematic coefficients are given in Table 3. On the whole, the results of the ab initio calculations for the isotopomers CX 3 NO (X = H, D) are in good agreement with experiment, the agreement being improved as the AO basis set is Table 2 Vibrational frequencies of the CX 3 Table 4, and the corresponding frequencies are listed in Table 5. The geometric parameters of the molecules change only slightly in moving from the minimum to the saddle point, the changes in the harmonic vibrational frequencies being also small.…”

“…For the sections constructed by the IRC and GE methods, accurate calculation and projection gave virtually the same estimates for ZPE. The exceptions are only in the vicinities of the stationary points, where these changes are substantial, but this fact is probably associated with numerical instability in the Table 7 Symmetry coordinates and the assignment of vibrational frequencies (PED, all contributions larger than 10% are given) of the CX 3 calculations according to the IRC scheme in the case of small energy gradients. For the MEP, the projection of the force constant matrix, as expected, has a substantial effect on the value and degree of change in the ZPE.…”

“…We used the results of the studies [1][2][3][4][5][6][7][8][9][10] for comparison with the results of ab initio calculations. Before proceeding to numerical experiments (Section 3), let us describe the concepts forming the background for the use of one-dimensional potential curves for internal rotation.…”

“…These molecules are sufficiently small for high-level ab initio calculations and they are characterized by a simple form of the internal rotation potential. In addition, the structures of the molecules under consideration were experimentally studied by microwave [1,2], vibrational [3,4], and vibronic [5][6][7][8][9][10] spectroscopy.…”