Modern NMR techniques for structure elucidation

Abstract

The rapid growth during the last decade of multiple pulse methods in one (1D) and two-dimensional (2D) NMR has produced over 100 new techniques of potential use in high-resolution NMR. This review sets out to identify and to illustrate those new methods which are most useful in the determination of molecular structure. Ten basic techniques are considered, including 2D homo-and hetero-nuclear chemical shift correlation by direct and by relayed coherence transfer, and 1D polarization transfer. Numerous variations on the basic techniques, for example multiple quantum filtration, are also discussed. Particular attention is paid to the problems of sensitivity and of the optimum choice of experimental techniques for different classes of structural problem.

A Comprehensive Review on Controlled Synthesis of Long‐Chain Branched Polyolefins: Part 3, Characterization of Long‐Chain Branched Polymers

“…[30] A good resolution of the carbon signal at branching points, as well as a large signal to noise ratio, are required in 13 C NMR quantitative analyses. [15,[31][32][33] Achieving such a high-quality 13 C NMR spectrum, however, is very difficult due to the low natural abundance of the 13 C isotope. Specifically, this low abundancy results that the signal intensity of branched carbons is a factor of 100-1000 lower than that of the backbone carbons.…”

“…It was found that viscosity data of strictly linear PEs prepared with single-site catalysts fit well to Cross equation, Equation (32) [177] 1 ( )…”

Assignment of Carbon and Proton Chemical Shifts of Methyl Neoabietate by One- andTwo-Dimensional NMR Spectroscopy

“…Additional NMR experiments such as two-dimen sional heteronuclear relayed-coherence transfer (RELAY) (Bax 1984) and two-dimensional homonuc lear correlation (COSY) (Morris 1986) were also per formed. The RELAY experiment, which detects adja cent protonated carbons, was not as useful (or as sensitive) as the long-range CH correlation experi ment which detects quaternary carbons as well.…”

Spirocyclohexane oxazines, thiazines and selenazines. Crystal structures and NMR comparative study

“…The two-dimensional experiments were performed by application of standard micro programs (Morris, 1986; SPIROCYCLOHEXANE OXAZINES, THIAZINES AND SELENAZINES (3) 5188 (3) 34 (4) 2389 (4) 1153 (2) 4921 (4) 40 (3) C 17 6268 (2) -723 (4) 5237 (4) 44 (4) 2351 (4) 1805 (2) 4238 (5) 60 (5) C18 5731 (2) -1328 (4) 4181 (4) 47 (5) 1006 (5) 2105 (2) 3298 (6) 79 (6) C19 6103 (3) -1852 (4) 3083 (4) 43 (5) -302 (5) 1769 (3) 3015 (5) 73 (6) C20 7007 (3) -1778 (4) 3028 (4) 48 (5) -287 (4) 1119 (3) 3674 (6) 72 (6) C21 7544 (2) -1176 (4) 408...…”

“…For the oxa derivative (I), two-dimensional NMR experiments were needed to interpret the spectra. Further details of two-dimensional NMR may be found in review articles (Freeman, 1980;Been & Gunther, 1983;Morris, 1986;Bax, 1982). In the following discussion, the molecular numbering defined in the X-ray structure analysis will be used.…”