Reaction enthalpies for the hydrolysis of 3p, 4p and early 3d oxide bridges - how unique are the oligophosphates?

The hydrolysis of M-O-M bridges in binuclear oxyhydroxides of the 3p, 4p an d early 3d elements is investigated by quantum chemistry. The reaction enth alpies for the water addition reactions are compared. Hydrolysis of oxygen bridges is found endothemic for the Al-P, Ga-As and Sc-Mn species, but exot hermic for the S, Se, Cl and Br species. The hydrolysis of pyrophosphoric a cid is unique in displaying the reaction enthalpy, which is closest to zero . This fact is taken to explain why the oligophosphates are utilised in con trolling cellular reactions, as the hydrolysis energetics rely entirely on local conditions. (C) 2001 Elsevier Science B.V. All rights reserved.