Question

why do alkanes and halo alkanes dissolve in toluene but fail to dissolve in water

Answer 1

Alkanes are saturated nonpolar hydrocarbons. Water, H2O, is a polar molecule. Organic molecules only mix readily with other molecules of the same polarity. Therefore, alkanes will not dissolve in water. Moreover, polar molecules dissolves with polar molecule only and non-polar molecule dissolves with non-polar only. It means like dissolves with like.

Same thing happen with halo alkanes, Because they cannot form H-bonds with water, so the water prefers to bond to itself.

In non-polar solvents the attraction between the haloalkanes and the solvent is a strong (or stronger) than the attraction of solvent for solvent particles.

Hope this helps