摘要:
AbstractThe acidity constants of both Z and E conformational isomers of five N‐nitroso‐N‐alkyl‐α‐amino acids, ONN(R1)CH(R2)COOH, are determined by the observation of selected pH titrated 1H NMR signals. For two glycine derivatives (1, R1CH3, R2H, ONSar; 2, R1C2H5, R2H, ONEtGly) and two alanine derivatives (3, R1CH3, R2CH3, ONMeAla; 4, R1C2H5, R2CH3, ONEtAla) the E isomers appear to be stronger acids than the Z while for the third alanine derivative (5, R1n‐C3H7, R2CH3, ONPrAla) the opposite is observed. These results, also including anisotropy effects associated with the NNO group, are discussed in terms of conformations. A 7‐membered ring conformation with an NO…HOOC intramolecular hydrogen bond is proposed to be statistically important in the Z isomers of 1, 2, 3 and, to a lesser extent, 4.