10.4 Methods of Preparation of Haloalkanes
10.4.1 From Alcohols
10.4.2 From Hydrocarbons
NEETprep Audio Note:
Free radical chlorination or bromination of alkanes gives a complex mixture of isomeric mono- and polyhaloalkanes, which is difficult to separate as pure compounds. Consequently, the yield of any single compound is low (Unit 13, Class XI).
Example 10.3
Identify all the possible monochloro structural isomers expected to be formed on free radical monochlorination of (CH3)2CHCH2CH3.
Solution
In the given molecule, there are four different types of hydrogen atoms. Replacement of these hydrogen atoms will give the following
(CH3)2CHCH2CH2Cl (CH3)2CHCH(Cl)CH3
(CH3)2C(Cl)CH2CH3 CH3CH(CH2Cl)CH2CH3
(II) From alkenes
(i) Addition of hydrogen halides: An alkene is converted to corresponding alkyl halide by reaction with hydrogen chloride, hydrogen bromide or hydrogen iodide.
NEETprep Audio Note:
(ii) Addition of halogens: In the laboratory, addition of bromine in CCl4 to an alkene resulting in discharge of reddish brown colour of bromine constitutes an important method for the detection of double bond in a molecule. The addition results in the synthesis of vic-dibromides, which are colourless (Unit 13, Class XI).
10.4.3 Halogen Exchange
Alkyl iodides are often prepared by the reaction of alkyl chlorides/ bromides with NaI in dry acetone. This reaction is known as Finkelstein reaction.
NEETprep Audio Note: 
NaCl or NaBr thus formed is precipitated in dry acetone. It facilitates the forward reaction according to Le Chatelier’s Principle.
The synthesis of alkyl fluorides is best accomplished by heating an alkyl chloride/bromide in the presence of a metallic fluoride such as AgF, Hg2F2, CoF2 or SbF3. The reaction is termed as Swarts reaction.
NEETprep Audio Note: 