THEORETICAL CALCULATIONS OF MINIMUM ENERGY STRUCTURES AND THERMODYNAMICS FOR THE FORMATION OF CYCLIC AMIDINES AND IMIDATES BY INTRAMOLECULAR NUCLEOPHILIC ADDITION ELIMINATION REACTIONS/

Theoretical calculations of minimum energy structures and thermodynami c terms using SCF theory with thermodynamic and solvation corrections have been made of the cyclisation of 1-amino-8-(acetylamino)naphthalen e to give 2-methylperimidine with the liberation of water and of the r elated reaction of 1-hydroxy-8-(acetylamino)naphthalene to 2-methylnap htho[1,8-d,e][1,3]oxazine. The calculations predict that in the gas ph ase the former reaction is strongly thermodynamically favourable (Delt a G = -37.9 kJ mol(-1), Delta H = -0.6 kJ mol(-1) and T Delta S = +37. 3 kJ mol(-1) at 298.2 K) whereas the latter is much less favourable (D elta G = -2.0 kJ mol(-1), Delta H = +31.1 kJ mol(-1) and T Delta S = 33.1 kJ mol(-1) at 298.2 K), The results are in qualitative agreement with experimental observations for the reactions in solution, Reasons for the different behaviour of the two reactions are discussed.