Deuterium isotope effects on 15N, 13C and 1H chemical shifts of proton sponges

摘要: Abstract Deuterium isotope effects on 15N, 13C and 1H chemical shifts have been measured in the protonated forms of DMAN, 4-bromo, 4-picryl, 4-nitro 2- 2,7-chloro derivatives. Structures geometry optimised using BPW91/6-31(d)G density functional theory (DFT) methods show good correspondence to experimental X-ray data. are calculated GIAO/DFT methods. Chemical for two tautomers calculated. Equilibrium constants determined from 1J(N,H) coupling constants. A comparison 1J(N,D) couplings non-symmetrical derivatives that upon deuteriation equilibrium is shifted towards dominant form. The deuterium effect DMANH+ shows only small values despite apparently strong intramolecular hydrogen bonds as judged primary effects. counter ion has little one-bond effect. Secondary 15N divided into intrinsic contributions. close 0.3 ppm related charge delocalisation proximity positive charge. contributions at nitrogens carbons seen increase throughout series parallel with constant. For resonances found aromatic hydrogens. An important feature analysis DMANs multi-isotope approach.