Knowledge Bank

The Raman spectrum of methyl nitrite and methyl-$d3$-nitrite is reported in the gas, liquid, and crystalline solid phase. A temperature study of the Raman spectrum of the liquid allowed a direct assignment of the cis and trans fundamentals. The energy difference between the cis and trans conformers was estimated from the temperature dependence of two strong Raman bands near $600cm-1$ and agrees well with the NMR value estimated for the liquid (787 cal/mol at 200K by Raman, 803-866 cal/mol by $NMR1$). The room temperature far infrared spectrum of gaseous methyl nitrite and $methyl-d3$-nitrite is reported, together with the far infrared spectrum of the polycrystalline materials. Ab initio geometry optimizations of methyl nitrite at the 3-21G and 6-31G* levels of theory are reported as a function of the N=0 torsional angle. Frequency calculations using the 3-21G and 6-31G* levels of theory are reported for the cis and trans conformers and for a variety of N=0 torsional angles near the cis and trans limits. Considerable molecular relaxation appears in the calculation of optimized geometries, and the possibility of achieving experimental realization of these computational features is discussed.