Aromatic hydrocarbon, Benzene-structure, properties and uses, derivatives of Benzene e.g. methyl benzene. Alkanols – sources, general molecular formula, nomenclature, classification, types, preparation, properties and uses.  Test for alkanols.

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TOPIC: AROMATIC HYDROCARBONS

 

CONTENT

Benzene, structure, properties and Uses

Derivative of Benzene

Aromatic Hydrocarbons

These are hydrocarbons that have the same structure as benzene.

 

Benzene: Benzene is a typical aromatic compound with molecular formula of C₆H₆.  It has the structure of:

Preparation:- 

1. From coal tar: The destructive distillation of coal produced coal tar which contain      benzene
2. From petroleum; The dehydrogenated of alkane using valladim(v)oxide (v₂O₅) as     catalyst at 500^oC and 20 atmos give benzene

C₆H₁₄     V₂O₂               C₆H₆  +  4H₂

The process is known as catalytic reforming.

3. From polymerization of ethyne

3 ( H – C = C – H )           C₆H₆

 

Evaluation

1. Describe three (3) ways of preparing benzene.
2. Draw the structure of benzene.

 

Physical properties

1. It has a pleasant odour.
2. It has boiling point of 80^oC.
3. Benzene can dissolve in water.
4. It burns with sooty flame.

 

Chemical Properties

Benzene can undergo both additional reaction and substitutional reaction.

1. Additional Reaction.

1. Hydrogenaton:  Benzene reduces to cyclo-hexane if hydrogen gas is passed through       finely divided nickel at 150^oC.
2. Halogenation:  In the presence of ultra-violet light, benzene reacts with halogen to  produce cyclic compound.

C₆H₆  + 3 Cl₂       UV

Light

2. Substitution Reaction.
3. Benzene undergoes substitution reaction due to the presence of its single bonds.
4. Halogenation e.g. Cl₂, Br₂, I₂

 

 

 

 

 

+  Br₂

Benzene                                            Bromobenzene

1. Nitration: This occurs in the mixture of HNO₃ and H₂SO₄ together with benzene

 

HNO₃             Nitrobenzene.

iii. Sulphonation: Benzene reacts with conc., H₂SO₄ to form benzene sulphonic acid.

 

3. Alkylation: It involves reactions of benzene with halo-alkanes in the presence of AlCl₃.

 

Uses.

1. It is used as a solvent to dissolve organic.
2. It is used as fuel in petrol.
3. It is used in the manufacture of aromatic compound e.g. benzoic acid.

 

Evaluation

1. State two (2) uses of benzene
2. Identify two (2) chemical properties of benzene with examples.

 Derivatives of Benzene

 

 

Evaluation

1. Give another name to the following compounds

(a ) Phenol               (b) Toluene

2. State  four (4) derivatives of benzene.

 

READING ASSIGNMENT

New School Chemistry By .O.Y. Ababio, pg 492-494.

 

WEEKEND ASSIGNMENT

1. Benzene can be prepared from the following except

(a) Coal tar              (b) petroleum         (c) Alkanol   (d) Ethyne

2. Benzene can undergo additional reaction due to presence of

(a) double bonds  (b) single bonds     ( c) hydrogen     ( d) carbon.

3. Benzene undergoes the following reaction except.

(a) substitution        (b) addiction   (c) Hydrogenation   ( d) polymerization

4. The technique used in separating a mixture of common salt and water is

(a) evaporation     (b) sublimation  (c) decantation (d) chromatography.

 

Theory

1. a. State two (2) uses of Benzene
2. identify two (2) physical properties of benzene.
3. a. How would you prepare benzene?
4. State two (2) chemical properties  of benzene.

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