FSc Notes Part 2 Chemistry Important Chemicals Ester COO, Ether O and Phenol

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Ester COO

Definition

Organic compounds that contain divalent functional group – COO – are called ester.

General Formula

They are denoted by RCOOR where R may be any alkyl group. The alkyl groups of ester may be similar or different. The general formula of ester is

CnH2n+1 – COO – CnH2n+1

Where n may be any natural number.

Structure

The structural formula of ester shows that it contains a Carbonyl group.

RCOOR

Examples

1. Dimethyl Ester (CH3COOCH3)

Uses of Ester

1. It is used as a good solvent for paints, varnishes, oils, fats, gums, resins, cellulose etc.
2. It is used as plasticizer.
3. It is used in the preparation of artificial flavours and essences.

Ether O

Definition

Organic compounds which contain divalent functional group – O – are called ether.

General Formula

They are denoted by ROR where R may be any alkyl group. The alkyl groups of ether may be similar or different. The general formula of ether is

CnH2n+1 – O – CnH2n+1

Where n may be any natural number.

Examples

1. CH3-O-CH3 (DiMethyl Ether)
2. CH3-O-C2H5 (Ethyl Methyl Ether)

Preparation

Ether can be prepared by the following methods.

1. From Ethyl Alcohol

William son prepared diethyl ether from alcohol by using sodium metal or sulphuric acid therefore this method is also William son synthesis.

2. From Ethyl Chloride

When ethyl chloride is heated with dry silver oxide then diethyl ether is formed.

2C2H5Cl + Ag2O —-> C2H5 – O – C2H5 + AgCl

Chemical Properties

Reactivity

Due to greater stability diethyl ether is relatively unreactive. When diethyl ether reacts with strong acid such as hydrogen iodide then oxonium ion is formed, which reacts with strong nucleophile and convert into ethyl alcohol and ethyl iodide.

C2H5-O-C2H5 + HI —-> C2H5-OH-C2H5 + I

C2H5-OH-C2H5 + I —-> C2H5-OH + C2H5I

Uses of Ether

1. Ether is used as solvent.
2. It is used as general anaesthetic.
3. Ether is used in the manufacture of smokeless powder.

Phenol

Definition

Aromatic alcohols are called Phenols.

OR

Those derivations of benzene in which hydrogen atom is replaced by OH group are known as Phenol.

Classification of Phenol

On the basis of hydroxyl group (OH) bonded with benzene ring, Phenol are classified into following three classes.

1. Mono Hydric Phenol
2. Di Hydric Phenol
3. Tri Hydric Phenol

1. Mono Hydric Phenol

Those aromatic phenols which contains only one OH group are called Mono Hydric Phenol.

2. Di Hydric Phenol

Those aromatic phenols which contain two OH groups are called Di Hydric Phenol.

3. Tri Hydric Phenol

Those aromatic phenols which contain three OH groups are called Tri Hydric Alcohols.

Preparation

Phenol can be prepared by following methods.

1. From Chloro Benzene (Down’s Process)

When chloro benzene is heated with 10% NaOH solution at 300ºC under 200 atm pressure then sodium Phenoxide is formed, which on further heating with HCl convert into Phenol.

2. From Benzene Sulphonate

When benzene sulphonate is fused with NaOH at 25ºC ten sodium Phenoxide is formed, which on further heating with HCl convert into Phenol.

Physical Properties

1. At ordinary temperature and pressure, phenol exist as colourless, crystalline solid.
2. Phenol has peculiar smell.
3. Phenol is a poisonous compound.
4. The melting point of phenol is 43ºC and its boiling point is 182ºC.
5. Above 68.5ºC Phenol is completely soluble in water.

Chemical Properties

The important chemical reactions of Phenol are

1. Reaction with Sodium Hydroxide (NaOH)

When phenol reacts with NaOH then sodium Phenoxide and water are formed. This reactions shows the acidic nature of phenol.

2. Reaction with Zinc Dust

When vapours of phenol are passed through red hot zinc dust then benzene is formed.

3. Hydrogenation

Introduction of hydrogen in a compound is called Hydrogenation. In presence of catalyst nickle when phenol is heated with hydrogen at about 150ºC then hydrogenation takes place as a result cyclo hexanol is formed.

4. Reaction with Bromine Water

In presence of water, when bromine reacts with phenol then 2, 4, 6 – tri bromo phenol is formed.

5. Reaction with Concentrated Nitric Acid

When phenol reacts with concentrated nitric acid then 2, 4, 6 – tri phenol (Picric Acid) is formed.

Diagram Coming Soon

6. Reaction with Dilute Nitric Acid

When Phenol react with dilute nitric acid then a mixture of ortho and Para nitro Phenol is formed.

Diagram Coming Soon

7. Reaction with Sulphuric Acid

When phenol reacts with H2SO4 then ortho phenol sulphonic acid and para phenol sulphonic acid are formed. The amount of product depending upon the temperature, lower pressure i.e. (15 – 20ºC) favours the production of ortho phenol sulphonic acid where as high temperature about 100ºC favours the production of para phenol sulphonic acid.

Uses

1. Phenol is uses as antiseptic.
2. Phenol is used in the manufacture of soaps, plastics etc.
3. Phenol is used in the preparation of Picric Acid and Aspirin.
4. It is used as link Preservative