Strain effects in protonated carbonyl compounds: an experimental and ab initio treatment of acyclic carboxamides and ketones

Strain effects were quantitatively examined for a set of 22 compounds including ketones (R2CO), carboxamides (RCONH2) and N,N-dimethylcarboxamides (RCONMe2), where R = Me, Et, i-Pr, t-Bu, 1-adamantyl (1-Ad), in their neutral and protonated forms. Isodemic reactions which appear to give for the first time, quantitative measures of strain in the protonated species were established by using neutral and protonated methyl ketones as references.