Chapter 10 Haloalkanes and Haloarenes Topic 2 Class XII ppt By Kailash Bhatt

2. Topic-2 Method of Preparation
• A) Preparation from alcohols: In this method
the hydroxyl group of alcohol is replaced by by
halogen on reaction with conc. Halogen acid,
phosphorus halides, thionyl chloride.

3. B). Preparation of Hydrocarbon
• a) Free radical halogenation: Alkenes react
with halogens in presence of UV light to from
halo alkanes. The reaction process through
free radical mechanism.

4. From alkenes
• a) Addition of hydrocarbon: By the reaction with hydrogen halides
in alkenes is converted to the corresponding alkyl halides.
CH3-CH2-CH=CH2+ HBr CH3-CH2-CH-CH3
Br
But-1 ene 2-Bromo butane

6. Addition of Halogen
• In the laboratory addition of bromine to
an alkene in CCl4 resulting in distance in
discharge of radish brown colour of
bromine constitutes an important method
for the detection of double bond in a
molecule.

7. By Halide Exchange
a). Finkelstein Reaction
Alkyl iodides are prepared by this reaction. Alkyl chloride / Bromide with NaI
in dry acetone. This reaction is known as Finkelstein Reaction
Swarts Reaction
When alkyl halide treated with metallic fluorides (AgF, Hg2 F2,
CoF2, SbF3). Alkyl fluoride is formed. This reaction is own as
Swarts Reaction.

8. Preparation from Silver Salt of Acid
• Hunsdiecker Reaction: Bromoalkanes are
prepared by refluxing silver salt of acid with
bromine in CCl4. This reaction is known as
brodine Hunsdiecker.

9. Preparation of haloarenes
• a). Electrophilic Substitution of aromatic hydrocarbons: Aryl chloride and
bromides can be easily prepared by electrophilic substitution of arenes with
chlorine and bromine respectively in dark at ordinary temperature in presence of
Lewis Acid catalyst such as iron or ferric or aluminum halide.

10. From Diazonium Salts
• Diazonium Salt is prepared by treating aniline
dissolve cold aqueous material with acid with an
aqueous solution of sodium nitride at low
temperature diazonium salt is formed such reaction
is known as diazonium reaction.

11. Sandmeyer’s Reaction
• When Diazonium salt treated with cuprous
halide, aryl halide is formed such reaction is
known as Sandmeyer’s Reaction.