Orbital interactions of the types, ${sigma}-{pi},;{sigma}^*-{pi},;{sigma}-{pi}^*;and;{sigma}^*-{pi}^*$ are investigated for the rotamers of ${alpha}$-X-acetones (X = F and Cl) using STO-3G method of calculation. It was found that the interactions are possible only in gauche forms, and the ${sigma}^*-{pi}^*$ interactions are in general greater than the $sigma-pi$ interactions due to the greater overlap, in spite of the greater energy gap involved; the greater ${sigma}^*-{pi}^*$ interaction causes greater lowering of ${pi}^*$ level relative to the lowering of ${sigma}$ in the ${sigma}-{pi}$ interaction so that both ${sigma}-{pi}^*$ and $n-{pi}^*$ interactions are enhanced in the gauche forms. The extra stability of the gauche form and the red shift in the $n-{pi}^*$ transition are thus found to be natural corollaries of the greater ${sigma}^*-{pi}^*$ interaction in the gauche forms.