The interaction of the two amines means that some reactions
may not occur to a significant extent. In this case, the fact that AMP
is present in excess and has a pKa similar to PZ means that much less
PZ will be protonated than in a PZ only solution. Also the presence
of PZ means that formation of AMP carbamate is unlikely to make a
significant contribution to net absorption due to its low stability relative
to the PZ carbamate. Regressions were carried out including
all possible reactions and it was found that AMP carbamate formation,
PZ protonation and PZ monocarbamate protonation were
poorly defined by the data and could be excluded. The equilibrium
constants and enthalpies for these reactions were fixed to
the previously regressed values. Alternatively the formation of the
dicarbamate PZ species was well defined by this dataset.