HOMO-LUMO, IRFRARED FREQUENCIES AND MOLECULARGEOMETRY COMPARSION STUDY OF THE STRENGTH OF BORONTRIHALIDES ACIDITY USING AM1 MOLECULAR MODELING

Abstract

AM1 Molecular Modeling has been used in the comparison of Lewis acid strength of
Boron Trihalide using available opportunities in this method such as HOMO-LUMO
gap , infrared frequencies and molecular geometry. HOMO-LUMO separation was
employed to evaluate acid strength of BX3, and results show that BI3 is more acidic than
others and acidity has decreased up to halogen group. When complex formation between
BX3 and dimethylamine was made , N—H bond stretching alters to red shift ( lower
frequency) .It was found that I3BNH(CH3)2 has the lowest frequency for this bond
.Geometry for these complexes , B—N bond length and degree of X-B-X angle of all
mentioned complexes were also studied and pyramidal structure for complexed BX3
were observed.