Add time:08/23/2019         Source:sciencedirect.com

Publisher SummaryThere are several forms of carboxamides, and they are separated into three classes: primary, secondary, and tertiary. Primary carboxamides also exist in three forms: H(C=O)NH2, R(C=O)NH2, and ø(C=O)NH2. Secondary carboxamides exist in the forms: H(C=O)NHR, R(C=O)NHR’, R(C=O)NHø, ø(C=O)NHR, and ø(C=O)NHø. Tertiary carboxamides can have the basic structures as denoted for the secondary carboxamides with the replacement of the NH proton with R or ø. Each of these forms yields its own characteristic group frequencies. In the case of the primary amides the vasym. NH2, vsym. NH2, and vC=O modes occur at higher frequency in the vapor phase than in the neat phase. The vC=O for ø(C=O)NH2 (1719–1731 cm-1) occurs at lower frequency than vC=O for R(C=O)NH2 (1732–1780 cm-1) due to conjugation of the carbonyl group with the π system of the phenyl group.

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