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A review with comprehensive data on experimental indirect scalar NMR spin–spin coupling constants across hydrogen bonds

“…In several places of this review the problem of tautomerism in relation with nh J XY couplings has appeared. [67,71,83,87,88] Usually, to study tautomerism by NMR the tautomerizable proton is replaced by a methyl group and the properties of the resulting isomers compared with those of the tautomer. Obviously, this is not possible here since the proton is essential for the HB to exist.…”

“…In their first paper [83] it was demonstrated that the proton in 82 is on the N-phenyl substituent, settling the problem of tautomerism, while in symmetrical 81 it is exchanging between both N atoms. On 82 several couplings related to the N-H· · ·N HB were measured: 1 J NH = 88.6, 1h J NH = 4.4, 2h J NN = 8.6 Hz.…”

“…[110,111] In the first paper Brown et al measured 2h J NN for labeled compounds 82 and 83. The values, 7.3 and 8.0 Hz, respectively, are smaller than their solution values, 8.6 and 9.0 Hz, [83,97] that is, by about 1 Hz, while couplings across covalent bonds remain unchanged. [110] According to the authors, this indicates that solvent effects are affecting the J couplings across the HB but not those for the truly covalent bond.…”

Heavy atom motions and tunneling in hydrogen transfer reactions: the importance of the pre‐tunneling state

“…The dotted line was estimated using an empirical correction for quantum zero‐point vibrations of the H‐bonded proton and is assumed to be better able to reproduce experimental geometries as compared to the solid line 76, 77. The geometry of crystalline PALDIM ( Ic ) was estimated from the crystallographic N ... N distance and ab initio calculations 107, 108. The geometry of tetramethyldibenzotetraaza[14]annulene ( II )109, 110 was derived from the X‐ray crystal structure and dipolar ND couplings.…”

Deuterium isotope effects on 13C chemical shifts of negatively charged NH…N systems

“…This system is therefore ideal for studying isotope effects on chemical shifts in strongly intramolecularly hydrogen bonded N‐H…N ‐ systems. Deuterium isotope effects on chemical shifts have been used extensively to study hydrogen bonded systems both intermolecular and intramolecular ones . Deuterium isotope effects on 13 C chemical shifts have been investigated in detail in amides hydrogen bonded to a nitrogen in N‐substituted 3‐(cycloamine)propionamides, but also in similar systems with NH hydrogen bonded to oxygen, such as enaminones in Schiff bases, β ‐enamine derivatives of Meldrum's acid, in 1‐amionderivatives of anthraquinone and in 2,6‐cyclohexanediketo‐1‐amides but never in negatively charged systems with a ND donor and a negatively charged acceptor.…”