Haloalkanes And Haloarenes

(i) Wurtz-Fittig Reaction: Reaction of an aryl halide with an alkyl halide and sodium metal to form substituted benzene.
C H X + 2Na + R-X C H -R + 2NaX
(ii) Ullmann Reaction: Heating an aryl iodide with copper powder to form biaryl.
2 C H I + 2Cu C H -C H (Biphenyl) + 2CuI
(iii) Gattermann Reaction: Modification of Sandmeyer reaction using Copper powder instead of CuCl.
C H N Cl C H Cl + N
(iv) Hunsdiecker Reaction: Reaction of silver salt of carboxylic acid with Bromine to form alkyl bromide (Decarboxylation).
R-COOAg + Br R-Br + CO + AgBr
(v) Balz-Schiemann Reaction: Preparation of fluorobenzene from diazonium salt using HBF .
C H N Cl + HBF C H N BF C H F + N + BF

1. Steps: SN is a two-step reaction (formation of carbocation, then nucleophile attack). SN is a single-step concerted reaction (bond breaking and making happen simultaneously).
2. Kinetics: SN is first order (Unimolecular), Rate [Alkyl Halide]. SN is second order (Bimolecular), Rate [Alkyl Halide][Nucleophile].
3. Stereochemistry: SN leads to racemization (retention + inversion). SN leads to complete inversion of configuration (Walden inversion).
4. Reactivity Order: For SN : (due to carbocation stability). For SN : (due to steric hindrance).

Optical activity is the property of certain organic substances to rotate the plane of plane-polarized light when it is passed through their solution.
If the compound rotates light to the right (clockwise), it is dextrorotatory ( or +).
If it rotates light to the left (counter-clockwise), it is levorotatory ( or -).
This property arises due to molecular chirality (lack of a plane of symmetry).

Step 1: Diazotization: Aniline is treated with Sodium Nitrite (NaNO ) and Hydrochloric acid (HCl) at a low temperature (0-5 C) to form Benzene Diazonium Chloride.
C H NH + NaNO + 2HCl C H N Cl + NaCl + 2H O
Step 2: Sandmeyer Reaction: The Benzene Diazonium Chloride is treated with Cuprous Chloride (Cu Cl or CuCl) in HCl.
C H N Cl C H Cl + N
The product C H Cl is Chlorobenzene.