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Chemical shift assignments in N , N ‐disubstituted trifluoroacetamides
Author(s) -
Graham Laurine L.
Publication year - 1972
Publication title -
organic magnetic resonance
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0030-4921
DOI - 10.1002/mrc.1270040213
Subject(s) - chemistry , chemical shift , alkyl , medicinal chemistry , proton , oxygen atom , carbon atom , stereochemistry , molecule , organic chemistry , physics , quantum mechanics
Due to hindered rotation about the central CN bond in N , N ‐disubstituted trifluoroacetamides, CF 3 CONR 1 R 2 , two resonance peaks are usually observed for each proton in R 1 and R 2 . Chemical shift assignments are made for the following amides: 1 , R 1 = R 2 = Me; 2 , R 1 = R 2 = Et; 3 , R 1 = Me, R 2 = 2‐Propyl; 4 , R 1 = Me, R 2 = 1‐Butyl; 5 , R 1 = Me, R 2 = Cyclohexyl; 6 , R 1 = R 2 = 2‐Propyl; 7 , R 1 = 2‐Propyl, R 2 = Cyclohexyl. Amides 6 and 7 show an inversion of the relative chemical shift for both the methine and methyl protons of the 2‐propyl group as compared with 3 . For non‐fluorinated amides, aromatic solvents shift the trans alkyl peaks to higher field faster than those cis (to the carbonyl oxygen atom); however, this generalization does not apply to all trifluoroacetamide proton peaks.