12th chemistry chapter11

 

Properties of alcohols

Physical properties

i. Lower alcohols are colourless liquids and the higher members are waxy solids.

Chain length C12-C18

ii. They have higher boiling points than the corresponding other organic compounds such as alkanes, aldehydes, ethers etc., this is due to the presence of intermolecular hydrogen bonding present in alcohols

.

iii. Among isomeric alcohols primary alcohols have higher boiling point and the tertiary alcohols have lower boiling points

iv. The lower members are highly soluble in water due to the formation of intermolecular hydrogen bonding with water.

Preparation of alcohols:

1. From Alkyl halides: 

2. From alkenes:

3. From Grignard reagent:

4. Hydroboration:

5. Reduction of carbonyl compounds:

1. From Alkyl halides: 

2. From alkenes:

3. From Grignard reagent:

4. Hydroboration:

5. Reduction of carbonyl compounds:

Preparation of glycol 

Ethelene glycol

Preparation of glycerol

The following tests are used to distinguish between 1 ° 2°  and 3° alcohols.

a) Lucas test:

When alcohols are treated with Lucas agent (a mixture of concentrated HCl and anhydrous ZnCl2 ) at room temperature, tertiary alcohols react immediately to form a turbidity due to the formation of alkyl chloride which is insoluble in the medium. Secondary alcohols react within 10 minutes to form a turbidity of alkyl chloride where primary alcohols do not react at room temperature. 

b) Victor Meyer’s test:

Chemical properties of alcohols

1.Nucleophilic substitution

Conversion of alcohol into alkyl halides: Other methods

3. Elimination reactions of alcohols

4.Oxidation of alcohols

5.Catalytic dehydrogenation

6.Esterification

Reactions of Glycol 

Dehydration reaction

Tautomerisation

Oxidation of glycol

nitric acid (or) alkaline potassium permanganate is used as the oxidizing agent

ii) Oxidation of glycol with periodic acid

periodic acid

Reaction of Glycerol

1.Nitration

2.Dehydration

3.Oxidation

3.Oxidation

Preparation of Phenols

a) From halo arenes(Dows process)
b) From benzene sulphonic acid
c) From aniline
d) From cumene

a) From halo arenes(Dows process)

b) From benzene sulphonic acid

c) From aniline

d) From cumene

Chemical Properties:

a) Reaction with Zn dust:

b) Reaction with ammonia:

c) Formation of esters:(Schotten-Baumann reaction)

d) Formation of ethers:(Williamson ether synthesis)

e) Oxidation:

f) Reduction:

a) Reaction with Zn dust:

b) Reaction with ammonia:

c) Formation of esters:(Schotten-Baumann reaction)

d) Formation of ethers:(Williamson ether synthesis)

e) Oxidation:

f) Reduction:

i) Nitrosation: 

ii) Nitration:

 iii) Sulphonation:

iv) Halogenation: 

v) Kolbe’s (or) Kolbe’s Schmit reaction:

vi) Riemer – Tiemann Reaction:

On treating phenol with  CHCl3 /NaOH

vii) Phthalein reaction:

viii) Coupling reaction:

Ethers:

IUPAC System:

Preparation of ethers: 

1. Inter molecular dehydration of alcohol

2. Williamsons synthesis

3.Methylation of alcohol

1. Inter molecular dehydration of alcohol

2. Williamsons synthesis

3.Methylation of alcohol

Chemical Properties of ethers:

1. Nucleophilic substitution reactions of ethers.

2.Autooxidation of ethers 

3.Some of the reaction of diethyl ether

Aromatic electrophilic substitution reactions:

i) Halogenation
ii) Nitration
iii) Friedel Craft’s reaction

i) Halogenation:

ii) Nitration

iii) Friedel Craft’s reaction

Bookback Questions

1. Identify the product (s) is / are formed when 1 – methoxy propane is heated with excess HI. Name the mechanism involved in the reaction 

Nucleophilic substitution reactions of ethers.(SN2)

2.Draw the major product formed when 1-ethoxyprop-1-ene is heated with one equivalent of HI

3.Suggest a suitable reagent to prepare secondary alcohol with identical group using Grignard reagent.

4.What is the major product obtained when two moles of ethyl magnesium bromide is treated with methyl benzoate followed by acid hydrolysis. 

5.Predict the major product, when 2-methyl but -2-ene is converted into an alcohol in each

of the following methods.

(i.) Acid catalysed hydration 

(ii.) Hydroboration

(iii.) Hydroxylation using bayers reagent

6. Arrange the following in the increasing order of their boiling point and give a reason for your ordering

(i.) Butan – 2- ol, Butan -1-ol, 2 –methylpropan -2-ol

(ii.)  Propan -1-ol, propan -1,2,3-triol, propan -1,3 – diol, propan -2-ol

7.Can we use nucelophiles such as

for the Nucleophilic substitution of alcohols

8.Is it possible to oxidise t – butyl alcohol using acidified dichromate to form a carbonyl compound. 

9. What happens when 1-phenyl ethanol is treated with acidified kmno4

10. Write the mechanism of acid catalysed dehydration of ethanol to give ethene.

11. How is phenol prepared from

i) chloro benzene

ii) isopropyl benzene

12. Explain Kolbe’s reaction

13. Write the chemical equation for Williamson synthesis of 2-ethoxy – 2- methyl pentane starting from ethanol and 2 – methyl pentan -2-ol

14. Write the structure of the aldehyde, carboxylic acid and ester that yield 4- methylpent-2-en-1-ol.

15. What is metamerism? Give the structure and IUPAC name of metamers of 2-methyoxy propane

16. How are the following conversions effected

i) benzylchloride to benzylalcohol 

ii) benzyl alcohol to benzoic acid

17. Complete the following reactions

18.0.44g of a monohydric alcohol when added to methyl magnesium iodide in ether liberates at STP 112 cm3 of methane with PCC the same alcohol form a carbonyl compound that answers silver mirror test. Identify the compound.

19. Complete the following reactions

20. Phenol is distilled with Zn dust followed by friedel – crafts alkylation with propyl chloride to give a compound B, B on oxidation gives (c) Identify A,B and C.

21.

Identify A,B,C,D and write the complete equation

22. What will be the product (X and A)for the following reaction

23. How will you convert acetylene into n-butyl alcohol.

24. Predict the product A,B,X and Y in the following sequence of reaction

25. 3,3 – dimethylbutan -2-ol on treatment with conc.sulphuric acid to give tetramethyl ethylene as a major product. Suggest a suitable mechanism