) has been studied by 1 H (400 MHz) and 13C (100 MHz) n.m.r.spectroscopy. 1 H And 13C chemical-shift assignments have been made for the acyclic E and Z forms of each configurational isomer in 2 H 2 O. The 13C chemical shift assignments have been made primarily through the use of (1- 13C)-enriched compounds and 2D 13 C- 1 H shift-correlation spectroscopy. Analysis of the 1 H- 1 H spin-coupling