the absence of p alpha-p beta interchange and the complete lack of positional 18o isotope exchange of the pyrophosphate moiety are compatible with tight ion pairing of intermediates in the coupled isomerization-cyclization of geranyl pyrophosphate and establish a remarkably tight restriction on the motion of the transiently generated pyrophosphate anion with respect to its cationic terpenyl reaction partner .
C0022023
ion
C0007447
cationic