Question

Why \[CCl4\] is used in halogenation?

Answer 1

Hint: Compared with hydrocarbons, organic halogen compounds have higher boiling points due to strong dipole-dipole and van der Waals forces. It is slightly soluble in water, but it is completely soluble in organic solvents.

Complete Step by Step Solution:
Halogenation:
1. Hydrogen atoms are replaced by halogen atoms in aliphatic or aromatic hydrocarbons, which results in alkyl halides (haloalkanes) and aryl halides (haloarenes).
2. An alkyl group contains halogen atoms attached to \(s{p^3}\)of the carbon atom, whereas an aryl group contains halogen atoms attached to \(s{p^2}\)of the carbon atom.
Use of \(CC{l_4}\)in halogenation:
1. The dipole moment of the Carbon-Chlorine (1.860 Debye) is higher than the other halogen atoms.
2. \(CC{l_4}\) exhibits effective back bonding, and thus, its negative charge stabilises in part by back donation to empty \(3d\pi \)orbitals of Chlorine. Due to \(2p\pi - 3d\pi \) back bonding, it is therefore a stronger acid than the other halogen atoms.
3. Carbon tetrachloride is a nonpolar compound, whereas water is highly polar. Nonpolar solvents are used to dissolve nonpolar compounds, and polar solvents are used to dissolve ionic and polar compounds respectively.
Additional information:
1. Aryl/Alkyl halides can be categorised as monohalogen, dihalogen, or polyhalogen (tri halogen, tetra halogen, etc.) compounds depending on which halogens are present in their composition and structure.
2. The free radical halogenation of alkanes produces alkyl halides and electrophilic substitution of arenes produces aryl halides.

Note: In alkyl halides, the carbon halogen bond is polarised; this means that the carbon atom has a partial positive charge, and the halogen atom has a partial negative charge.