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Carbon‐13 NMR spectral investigations on allenic esters: Rationalization of carbon‐13 NMR chemical shifts and relaxation times ( T 1 )
Author(s) -
Gandhi R. P.,
Ishar M. P. S.
Publication year - 1991
Publication title -
magnetic resonance in chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.483
H-Index - 72
eISSN - 1097-458X
pISSN - 0749-1581
DOI - 10.1002/mrc.1260290706
Subject(s) - chemistry , chemical shift , carbon 13 nmr , rationalization (economics) , relaxation (psychology) , carbon fibers , computational chemistry , stereochemistry , additive function , psychology , social psychology , mathematical analysis , philosophy , materials science , mathematics , epistemology , composite number , composite material
Carbon‐13 NMR chemical shifts (CDCl 3 and C 6 D 6 solvents) and relaxation times ( T 1 ) were determined for carbons in a series of allenic esters [RR 1 CCCHCO 2 Et; (1) R = R 1 = H; (2) R = H, R 1 = CH 3 ; (3) R = H, R 1 = CH 3 CH 2 ; (4) R = R 1 = CH 3 ; (5) R = CH 3 , R 1 = CH 3 CH 2 ]. A comparison of the experimental δ 13 C values with those obtained by semi‐empirical additivity relationships revealed the inadequacy of these relationships to explain the obtained results. A rationalization of δ 13 C and relaxation time data is offered, inter alia , in terms of rotameric conformational preferences of the ester function.