Long range ¹³C¹³C coupling constants. A review

Abstract

A large number of 13G13C coupling constants from a aiversity of compounds are now available. Attempts have been made to classify this information in order to illustrate how these data are obtained, how signs are determined and how both two-and three-bond couplings can lead to structural information. Coupling constants in aromatic compounds are now well documented, substituent effect trends have been estabIished and correlations with bond orders are noticed. Comparison of "G1'C couplings with 13C-'H couplings is mentioned. Theoretical calculations are dealt with, and these can now be properly evaluated as both magnitudes and signs of the experimental couplings are known. Finally, the occurrence of long range couplings in biosynthetic material is briefly surveyed.

A versatile component-coupling model to account for substituent effects: Application to polypeptide ϕ and χ1 torsion related 3J data

“…Among the pertinent effects are angular dynamics [14][15][16][17][18] as well as variations in the local spin topology [4,[19][20][21]. The quantitative flavodoxin study [8] corroborated common qualitative experience that side-chain related coupling constants are affected indeed by topological variation across different amino-acid types, such as to cause misinterpretation of torsion angles if disregarded.…”

“…Incremental coupling constants, also known as component couplings, depend on both the type of a substituent and its position relative to the interacting coupled nuclei [20,21]. Two types of substituents shall be distinguished.…”

Spectral Assignment of Phenanthrene Derivatives Based on 6H-Dibenzo[C,E][1,2] Oxaphosphinine 6-Oxide by NMR and Quantum Chemical Calculations

“…The general structure of DOPO (1) and its derivatives exhibits an almost planar geometry with an extended conjugated system that favors the occurrence of long-range couplings. 37,38 Several models have been proposed to understand long-range spin-spin couplings in organophosphorus systems, ranging from hyperconjugative mechanisms to angle-dependant models involving P-C bonds and planes of the Pi-electron systems. 39,40 Thus, it was interesting to examine the P-H and P-C longrange couplings observed for DOPO (1) and its derivatives and compare them with the existing literature.…”

Carbon‐carbon [nJ(CO, C)] and carbon‐fluorine coupling constants [nJ(CF)] of ortho‐substituted benzoic acids and acid fluorides: INDO‐SOS calculations and evaluation of rotational effects

“…The fluoride 5 gives average values, as a methyl group in the meta position has no directing effect on the COF group. The 2J(C=0, C) values are very similar for 3 and 4, as was also observed for 1 and 2.…”