Chemistry- Haloalkanes and Haloarenes

Haloalkanes

Organic compounds containing carbon, hydrogen, and halogen atoms, where one or more hydrogen atoms are replaced by halogen atoms.

Types of haloalkanes

1. Number of Halogen atoms attached:

   a. Monohaloalkane

   b. di-haloalkane

   c. tri-haloalkane

   d. tetra-haloalkane

2. Where is the halogen atom attached:

   a. Primary

   b. Secondary

   c. Tertiary

3. Structure

   a. Allylic

   b. Vinylic

In how many ways can you prepare haloalkane?

4 Ways:

1. Reaction with alcohols

2. Halogenation of alkanes

3. From alkenes

4. Halogen exchange

Which all reactants can be used with alcohol to produce haloalkane?

5 reactants:

1. HCl + ZnCl₂

2. NaBr + H₂SO₄

3. PX₃

4. PX₅

5. SOCl₂

Why is thionyl chloride preferred when haloalkane is prepared from alcohol?

Thionyl chloride (SOCl₂) is preferred because it produces higher yields of the desired haloalkane and generates by-products that are highly escapable gases (SO₂ and HCl), making separation easier.

Give General Reaction of halogenation of alkane to Haloalkane

G.R.

Alkane + Halogen \rightarrow Haloalkane + HX (in presence of sunlight)

Give general reaction of preparation of haloalkane from alkene

1. From X₂

   Alkene + X₂ ——> Haloalkane (By addition Reaction)

2. From HX

   a. For symmetric alkene it does not matter where the hydrogen and halogen atom is attached to form haloalkane

   b. For unsymmetric alkene, Markovnikov's rule applies, where the hydrogen atom attaches to the carbon with more hydrogen atoms.

Which are the 2 ways by which haloalkane can be prepared from halogen exchange?

1. Finkelstein Reaction(for iodides)

   NaI reacts with RCl or RBr to give RI(Alkyl iodide)

2. Swarts reaction(for fluorides0

   AgF/NaF reacts with RCl or RBr to give RF(Alkyl flouride)

Why is the boiling point for haloalkanes more than their parent alkanes?

Due to the electronegativity caused due to the C-X bond, There is an increased force of attraction between the atoms which lead to higher boiling point than their parent haloalkanes.

3 types of reactions showed by haloalkanes

1. Substitution Reaction

2. Elimination Reaction

3. Reaction with Metals

What kind of substitution reaction takes place in haloalkane?

Nucleophilic

Different types of substitution reaction that haloalkanes undergo

1. Hydrolysis with NaOH or KOH to form alcohols

2. Formation of amines with NH₃ where NH₂ gets attached to the alkyl group

3. formation of cyanides with KCN or HCN and formation of isocyanide with AgCN

4. Formation of alkyl nitrites with KNO₂ and formation of nitroalkane with AgNO₂

5. Williamson’s synthesis where haloalkane reacts with NaOR (sodium alkoxide) to give ether(ROR)

6. Formation of ester with the help of AgCOOH (silver salt of carboxylic acid)

7. Reduction with the help of LiAlH₄ to give alkane