Scalar-coupling

Scalar coupling 0 Relaxation of the coupled spin or exchange Can be Important for T2 Further reading... 

Di Bari L, Kowalewski J and Bodenhausen G 1990 Magnetization transfer modes in scalar-coupled spin systems investigated by selective 2-dimensional nuclear magnetic resonance exchange experiments J. Chem. Rhys. 93 7698-705... 

Figure B2.4.1 shows the lineshape for intennediate chemical exchange between two equally populated sites without scalar coupling. For more complicated spin systems, the lineshapes are more complicated as well, since a spin may retain its coupling infonnation even though its chemical shift changes in the exchange.

In a selective-inversion experiment, it is the relaxation of the z magnetizations that is being studied. For a system without scalar coupling, this is straightforward a simple pulse will convert the z magnetizations directly into observable signals. For a coupled spur system, this relation between the z magnetizations and the observable transitions is much more complex [22]. 

Indirect or scalar coupling of nuclear spins through covalent bonds causes the splitting of NMR signals into multiplets in high-resolution NMR spectroscopy in the solution state. The direct or... 

The position of the second CC double bond in the structural fragment E follows finally from the correlation of the C signals at 5c = 37.8 and 49.8 with the //signals at 3h = 4.47 and 4.65. Note that trans protons generate larger cross-sectional areas than cis protons as a result of larger scalar couplings. 

We have previously considered ID and 2D spectra involving the coupling of nuclei through bonds scalar coupling, or f-coupling). Nuclei can... 

In the case of a COSY-NOESY spectrum having an unequal mixing, let us consider two nuclei (say, A and B) that are spatially close but belong to different coupling networks, and nuclei B and C, which have scalar coupling with each other but are spatially distant. The only transfers allowed in this situation are ... 

Scalar coupling Coupling interaction between nuclei transmitted through chemical bonds (vicinal and geminal couplings). 

Elucidation of the stereostructure - configuration and conformation - is the next step in structural analysis. Three main parameters are used to elucidate the stereochemistry. Scalar coupling constants (mainly vicinal couplings) provide informa-hon about dihedral bond angles within a structure. Another way to obtain this information is the use of cross-correlated relaxation (CCR), but this is rarely used for drug or drug-like molecules. 

Angular restraints are another important source of structural information. Several empirical relationships between scalar couplings and dihedral angles have been found during the last decades. The most important one is certainly the Karplus relation for -couplings. Another, relaxation-based angular restraint is the so-called CCR between two dipolar vectors or between a dipolar vector and a CSA tensor. 

D. F., Kessler, H. Scalar coupling constants - their analysis and their application for the elucidation of structures. Angew. Chem. Int. Ed. 1995,... 

Dipolar coupling and 3C shielding anisotropy cause unequal intensity of spinning side bands. The scalar coupling enabled magic angle rotation to distinguish two sets of sub-spectra.58... 

Evolution of the Hr magnetization under the heteronuclear long-range scalar coupling nJCH... 

Evolution of the Hd magnetization under the one-bond scalar coupling Vch... 

The 1 R,6R,7R,8S-as-fused structure and conformation of 102 were elucidated on the basis of their NMR spectroscopic data. The observed formation of only one sulfonium salt in this cyclization reaction was remarkable in that either sulfur atom might have been expected to participate in tosylate displacement. The H NMR spectrum of salt 102 shows a large three-bond scalar coupling of 10.6 Hz between H-6 (5 = 4.736) and H-7 (5 = 4.606) this indicates that they have an almost antiperiplanar relationship. The equatorial orientation of H-6 and the 3C6 conformation of its six-membered cycle are consistent with the strong NOEs observed between H-7 and both H-2axja and and... 

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