The enthalpies of hydrogen bonding (Delta H-hb) and tautomeric transformation (Delta H-tt) of hydrophosphorylic compounds of different space groups have been determined. It was found that acyclic and six-membered cyclic phosphoric acids, except calicylic derivatives exist in a form with P(O)H fragment and have Delta H-tt values in the gaseous phase of about 70 kJ mol(-1); 1,3,2-dioxophospholanic analogues are about 40 kJ mol(-1).