Theoretical calculations of chemical hardness and stability energy on C8H15O-X (X: OH, NH2, CH3) carried out by NBO at the B3LYP/6-311+G** level. C8H15O-X have been two distinguishable conformations: one CO-anti position, and the other CO-gauche position. This calculations confirm importance of LP2O16→ σ*C12-Y(Y=O, N, C) hyperconjugation interactions that can stable the CO-gauche conformers. Chemical hardness of CO-gauche conformers is in good agreement with the energy results. This results show that molecular interaction in the gauche geometries increases from compound with X=OH to X=CH3. Actually, the gauche effect with hyperconjugation factor play important role in the stability of the gauche geometries.