Détermination de constantes d'acidité d'amidines N-N′-substituées. Relations entre les pKA et les vibrations IR — I. Acétamidines et métacrylamidines

Changes in the ultraviolet absorption spectra with pH in aqueous solution were used to determine the pK_A values of amidines. A new mathematical procedure was used to study sparingly soluble compounds. In this technique, all the experimental data are used to solve for the absorbance of the insoluble basic species and for the pK_A value by a ‘complex method’ of optimization, which is more general than the classical least-squares method. A relationship between a double bond vibration frequency and the acidity constants of these compounds has been demonstrated.