Haloalkanes and Haloarenes — Important Questions

The bond is polar, Carbon bears partial positive charge, Halogen bears partial negative charge, Bond length increases from C-F to C-I

Halogens are more electronegative than carbon, making the C-X bond polar with carbon having δ+ charge and halogen having δ- charge. As we go down the halogen group, atomic size increases, so bond length increases from C-F (139 pm) to C-I (214 pm).

Nature of halogen, Nature of alkyl group, Nature of nucleophile, Temperature

Reactivity depends on: nature of halogen (I > Br > Cl > F), alkyl group structure (3° > 2° > 1° for SN1), nucleophile strength, and temperature. Color has no effect on reactivity.

Magnesium in dry ether

Grignard reagents (RMgX) are formed by the reaction of alkyl halides with magnesium metal in dry ether. The reaction must be carried out in anhydrous conditions to prevent reaction with water.

Resonance stabilization, sp² hybridization of carbon, Instability of phenyl cation, Electron repulsion

Aryl halides are less reactive due to: (1) resonance giving C-X partial double bond character, (2) sp² carbon being more electronegative than sp³, (3) phenyl cation instability ruling out SN1, and (4) electron-rich nucleophile repulsion by electron-rich benzene ring. Molecular weight doesn't affect reactivity.