Protonated methyl nitrite. A theoretical investigation on the structure and stability of (MeONO)H+ and the proton affinity of RONO (R = H, Me)

Ab initio calculations have been performed on the structure and stability of (MeONO)H+ and the proton affinity (PA) of RONO (R = H, Me). At the MP4/6-311G∗∗ // MP2(FULL)/6-31G∗ level of theory, the ion-dipole adduct MeOHNO+ 1 is by far the most stable promoter. At the G2 level, the dissociation enthalpy into MeOH and NO+ is computed as 25.3 kcal mol−1 and the PAs of MeONO and HONO amount to 187 and 188 kcal mol−1, respectively. This finding marks a departure from the expected order and parallels the anomalous trend recently ascertained in the PAs of the strictly related RONO2 (R = H, Me).