Haloalkane

Question 1

How to prepare haloalkane
1.
2.

Answer 1

1. Conversion of alcohols to haloalkane

2. Conversion of alkene to haloalkane

Question 2

Hydrolysis of haloalkane

Answer 2

Reagent: aq NaOH
Condition : reflux
Product : 1 OH ( for one halogen)
2 OH and H ( 2 halogen) - - > aldehyde
2 OH and CH3 ( 2 halogen) - - > ketone
3 OH and CH3 ( 3 halogen) - - > COOH

Question 3

Reaction of ammonia with Haloalkane

Answer 3

Reagent : NH3
Condition : ethanolic, reflux
Product : amine and HX

Question 4

Reaction of haloalkane with KCN

Answer 4

Reagent : KCN
Condition : ethanolic, reflux
Product : nitrile

Question 5

Reduction of nitrile

Answer 5

Reagent : H2
Condition: Ni (catalyst), 180°C
Product : amine

Question 6

Acidic hydrolysis of nitrile

Answer 6

Reagent : H2O and H+
Condition: Reflux
Product : COOH and NH4+

Question 7

Alkaline hydrolysis of haloalkane

Answer 7

Reagent: OH- and H2O
Condition: reflux
Product : salt and NH3

Question 8

Elimination of haloalkane

Answer 8

Reagent : NaOH
Condition : ethanoic NaOH, reflux
Product : alkene and HCl
Obey Saytzeff’s rule

Question 9

Define Saytzeff’s rule

Answer 9

In the elimination of HX from haloalkane, the alkene with the most number of alkyl groups is the major product.

Question 10

SN2 (Biomolecular necleophilic substitution)
What haloalkane
What order

Answer 10

Mechanism: The halogen atom will repel the approaching OH- ion. Thus, the OH- ion attacks the carbon atom from the back. An activated complex is formed.

Second order of reaction
Primary haloalkane

Question 11

Sn1 ( unimolecular nucleophilic substitution)
What haloalkane
What order

Answer 11

C become C+, Br separated and become Br-
Br- become OH-
OH connected to the C
Both neutralise no charges

Tertiary haloalkane
First order

Question 12

Test for halogen in haloalkane

Answer 12

Reagent : AgNO3
Condition : ethanolic solution, heat
Product : Chloro - white ppt
                  Bromo - pale yellow ppt
                  Iodo- yellow ppt

Question 13

Test for reactivity of haloalkane

Answer 13

Reagent : AgNO3
Condition: ethanolic solution, room temp
Product: chloro - white ppt formed after several                    mins
Bromo- pale yellow ppt after one minute
Iodo- yellow ppt after few seconds

Question 14

Test for reactivity of primary, secondary and tertiary haloalkane

Answer 14

Reagent : AgNO3
Condition : ethanolic solution, room temp
Product : primary - cloudiness after several mins
Secondary - cloudiness after 1 min
Tertiary- cloudiness after few seconds