Infrared Study of n -Alkanes in CCl 4,CDCl 3 /CCl 4,and CDCl 3 0.5% Solutions

Abstract

Three factors appear to affect n-alkane molecular vibrations in CHCl₃/CCl₄ solutions. These are: (1) Physical restriction of the vCH₃ and vCH₂ vibrations by solvent molecules. (2) Inter molecular hydrogen bonding between n-alkane protons and the free pair of electrons on Cl atoms of either CCl₄ or CDCl₃. The positively charged alkane protons arise during the dipole moment changes, δP/δQ, occurring during a full cycle of the vCH₃ and vCH₂ modes. (3) The physical restriction of solvent molecules, which is greater in the case of CDCl₃ than in the case of CCl₄ due to a high degree of CDCl₃ orientation about n-alkane molecules due to repulsion of the C-D of CDCl₃ by the n-alkane vCH₃ and vCH₂ protons, which allows stronger C-D:Cl bonds to be formed between solute and solvent.