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Structural studies on aryl‐substituted enaminoketones and their thio analogues. Part II. Experimental and DFT calculated carbon–carbon coupling constants, n J (CC)'s ( n = 1–3)
Author(s) -
Bugaj Marta,
Baran Piotr A.,
KamieńskaTrela Krystyna,
Krówczyński Adam
Publication year - 2009
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.2481
Subject(s) - chemistry , thio , aryl , coupling constant , computational chemistry , carbon fibers , coupling (piping) , stereochemistry , organic chemistry , mechanical engineering , alkyl , physics , materials science , composite number , engineering , composite material , particle physics
Spin–spin carbon–carbon coupling constants across one, two and three bonds, J (CC), have been measured for a series of aryl‐substituted Z‐s‐Z‐s‐E enaminoketones and their thio analogues. As a result, a large set, altogether 178, of J (CC)s has been obtained. It consists of 82 couplings across one bond, 31 couplings across two bonds and 65 couplings across three bonds. Independently, the DFT calculations at the B3PW91/6‐311++G(d,p)//B3PW91/6‐311++G(d,p) level yielded a set of theoretical J (CC) values. A comparison of these two sets of data gave an excellent linear correlation with parameters a and b close to ideal; a = 0.9978 which is not far from unity and b = 0.22 Hz which is close to zero. The 1 J (CC) couplings determined for the crucial fragment of the molecules, i.e. CCCO (or CCCS), are: 1 J (CC) ≈ 68 Hz (67 Hz) and 1 J (CC) = 60.5 Hz (60.0 Hz). The corresponding couplings found for the Z‐s‐Z‐s‐E isomer of the parent enaminoketone, 4‐methylamino‐but‐3‐en‐2‐one are 64.1 and 59.3 Hz, respectively. The most sensitive towards substitution of the oxygen atom by sulfur are two‐bond couplings between the α‐vinylic and aromatic C ipso carbon atoms, which attain 12 Hz in the enaminoketone derivatives and decrease to 5 Hz in their thio analogues. Copyright © 2009 John Wiley & Sons, Ltd.