Influence of counterion on the methylation of some ambident nucleophiles: DFT study

摘要: The reactions of ambident anions YCHX− and nucleophiles YCHXNa (X, Y = CH2, O, S) with CH3F were investigated in the gas phase THF solution. For this purpose M06-2X/6-311+G(d,p) theoretical model was engaged combination CPCM solvation model. goal work to examine influence counterion (Na+ case) reaction systems. It found that order reactivity non-ambident both media is as follows: $${\text{CH}}_{2} {\text{CHCH}}_{2}^{ - }$$  > OCHO− > SCHS−. On other side, follows different order: CH2CHCH2Na > SCHSNa > OCHONa. latter agreement chemical intuition it inversely proportional hardness respective nucleophilic atoms: C < S < O. Ambident behave differently two media, thus indicating solvents also examined reactions. Namely, HOMO–LUMO gaps are smaller gas-phase, whereas charge distribution more favorable Owing these facts, C-methylation than S- O-methylations, S-methylation less unfavorable O-methylation gas-phase. In solution O- S-methylations kinetically controlled, competitive C-methylations thermodynamically controlled. way, applicability hard–soft acid–base theory systems confirmed. Furthermore, findings offer robust confirmation our approach which involves counterions examinations. Counterions do exist systems, their should not be neglected.