Due to the polar halogen-carbon bond in haloalkanes, they are more soluble than hydrocarbon in water. But the solubility is still very low because the overall influence of the dipole-dipole interaction is small.


But why does the influence of the halogen decreases as the length of the carbon chain increases?

Shouldn't this be increasing the solubility of haloalkanes in water instead? As an increase of carbon in the chain translate to more electrons and more movements of electrons increase the dispersion forces. This increase in inter-molecular forces means that its closer to of the strength of hydrogen bonding in water

  • $\begingroup$ The hydrophobic chain becomes larger so the hydrophobicity increases, whereas the hydrophilicity remains similar. So it becomes less soluble. $\endgroup$ Aug 2 '20 at 12:30
  • $\begingroup$ As Safdar said the increases size of the hydrocarbon in length or branching causes increase in hydrophobic character. Moreover, the C-X bond is not polar enough to form hydrogen bond with water. Only dipole forces exist between molecules of haloalkanes, not hydrogen bonds. $\endgroup$ Aug 2 '20 at 12:40
  • $\begingroup$ Because the chain has hydrophobic character. More hydrophobic character decreases the solublity $\endgroup$ Aug 2 '20 at 12:47
  • $\begingroup$ Hydrogen bonds do exist between chlorine atom and hydrogen. But these bonds are rather weak, with respect to usual hydrogen bonds with N, O or F. $\endgroup$
    – Maurice
    Aug 2 '20 at 13:28
  • $\begingroup$ @Maurice Hydrogen bonds may exist between Cl and H, but for that to be efficient doesn't the chlorine also require a high partial negative charge on it. Like HF is associated with H bonds because of the high polarity of the H-F bond itself. Such a high charge seperation cannot from the relatively small polarity of the C-Cl bond. I doubt if the C-F bond will be polar enough, though for hydrogen bonding. $\endgroup$ Aug 2 '20 at 15:10

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