Abstract: N-formyl, N-acetyl pyrrolidine, piperdine, morpholine compounds are useful fine chimicals and intermediates. We have studied the substituent effects due to the presence of formyl and acetyl by ¹³C NMR. The equivalence of the chemical shift of C_a and C_a' and C_b and C_b' is lost because of the restricted rotation of the acetyl or formyl group due to the partial double bond character of the amide C(O)-N bond and steric compression.

Key words: N-formyl compound, N-acetyl compound, Pyrrolidine, Piperdine, Morpholine, Nonequivalence, Partial double bond character, Steric compression