(i) `sp^(2)`-hybrid carbon in chlorobezene is more electronegative than a `sp^(3)`-hybrid carbon in cyclohexylchoride , due to greater s-character. Thus, C atom of chlorobenzene has less tendency to release electrons to Cl than carbon atom of cyclohexylchloride.
As a result, C - Cl bond in chlorobenzene is less polar than in cyclohexylchloride. Further, due to delocalization of lone pairs of electrons of the Cl atom over the benzene ring, C-Cl bond in chlorobenzene acquires some double bond character while the C - Cl in cyclohexy! chloride is a pure single bond. ln other words, C-Cl bond in chlorobenzene is shorter than in cyclohexyl chloride.
Since dipole moment is a product of charge and distance, therefore, chlorobenzene has lowar dipole moment than cyclohexylchloride due to lower magnitude of negative charge on the Cl atom and shorter C-Cl distance.
(ii) Alkyl halides are polar molecules, therefore, their molecules are held together by dipole-dipole attraction. The molecules of `H_(2)O` are hold together by H-bonds . Since the new forces of attraction between water and alkyl halide molecules are weaker than the forces of attraction already existing between alkyl halide-alkyl halide molecules and water-water molecules, therefore, alkyl halides are immiscible (not soluble) in water. Alkyl halide are neither able to form H-bonds with water nor are able to break the H-bounding network of water.
(iii) Grignard reagents are very reactive. They react with moisture present in the apparatus to form alkanes
`{:(R-Mg-X+H-OHrarr),(" "R-H+Mg(OH)X):}`
Thus, Grignard reagents must be prepared under anhydrous conditions.
