DEUTERIUM-ISOTOPE EFFECTS IN C-13 NMR-SPECTRA OF TRANS-AZOBENZENE

Deuterium isotope effects on C-13 chemical shifts have been determined in a series of deuteriated trans-azobenzene isotopomers. The longest effect observed is the one over ten bonds ((10)Delta) in 4-H-2-isotopo mer at C-4' atom amounting to 3.3 ppb. The magnitude and the extent of isotope effects in trans-azobenzene are related to those observed in isoelectronic and conformationally similar trans-stilbene. The sign al ternation pattern of the long-range isotope effects in trans-azobenzen e parallels that in isoelectronic trans-stilbene, cis-stilbene and tra ns-N-benzylideneaniline. (C) 1997 Elsevier Science B.V.