Novel dihydrate formation in p-nitrophenylglyoxal

It is novel that the reaction of p-nitrophenyl-glyoxal with biochemically relevant compounds has a long lag time before the reaction commences. While utilizing NMR spectroscopy to investigate factors that may affect the lag, it has been discovered that a dihydrate form of pNPG is in equilibrium with a monohydrate while in the presence of water. This behavior is not present in the related phenylglyoxal molecule. Quantum chemical computations on the nonhydrated, hydrate, and dihydrate forms of pNPG, as well as phenylglyoxal and its hydrated forms, using both the B3LYP and MP2 levels of theory indicate that nitro group creates the necessary environment for hydration of pNPG whereas this is not present in standard phenylglyoxal. The equilibrium constants and their relationship with temperature as well as the heat of reaction and change in entropy have been determined experimentally. This data should provide new insights into the behavior of this and related systems in biochemical processes.