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Scalar Coupling Constants—Their Analysis and Their Application for the Elucidation of Structures
Author(s) -
Eberstadt Matthias,
Gemmecker Gerd,
Mierke Dale F.,
Kessler Horst
Publication year - 1995
Publication title -
angewandte chemie international edition in english
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 5.831
H-Index - 550
eISSN - 1521-3773
pISSN - 0570-0833
DOI - 10.1002/anie.199516711
Subject(s) - dihedral angle , coupling constant , scalar (mathematics) , proton , coupling (piping) , j coupling , constant (computer programming) , chemistry , chemical shift , molecule , computational chemistry , chemical physics , statistical physics , theoretical physics , nuclear magnetic resonance spectroscopy , computer science , physics , quantum mechanics , materials science , mathematics , hydrogen bond , stereochemistry , organic chemistry , geometry , programming language , metallurgy
Since their discovery in the early fifties, scalar/coupling constants have been of great interest to the NMR spectroscopist. Their impact on structure determination by NMR spectroscopy is founded on the fact that the size of the coupling constant is directly related to molecular conformation. Today, for most chemical substances the parameters for the Karplus relationship, which relates the vicinial (3‐bond) coupling constant to the dihedral angle, have been determined. In addition to proton–proton distances, the application of coupling constants in modern conformational analysis is indispensable. In the study of larger molecules which are of current interest, more and more involved experiments are necessary in order to overcome signal overlap and increasing line widths. A large number of experimental techniques for the determination of coupling constants has been developed; however, for this reason the choice of the most appropriate experiment to use has become more difficult. This decision must be made carefully to maximize instrument usage and obtain the largest number of couplings with the greatest accuracy possible. Many of the computer programs used in structure calculations can directly apply coupling constant restraints, similar to proton–proton distances developed from NOEs. Therefore, not only is the quality of the structure improved, but the molecular motions (internal dynamics) are better described. In this article, we review the techniques that exist today with particular attention paid to helping the non‐expert to choose the appropriate experiment for the problem at hand. In addition, the use of coupling constants in computer simulations are discussed.