Contribution of Hyperconjugation and Inductive Effects to the Pseudo -anomeric Effect in 4-Substituted Methoxycyclohexanes.

The importance of electrostatic nonconventional hydrogen bonds (NCHBs) to the pseudo -anomeric effect of 4-substituted methoxycyclohexanes is evaluated using theory [natural bond orbital (NBO)] to deconvolute electrostatic from other contributing effects. There is an interesting interplay between σ CH → σ CX * hyperconjugation and the electropositive charge on 3,5-axial hydrogens (H ax ). In essence, better σ CX * (or π CO * ) acceptors increase the charge on 3,5-CH ax , which in turn strengthens C δ+ H ax ··· δ- OMe NCHB interactions.