KSR AKSHARA ACADEMY
Tiruchengode
TEST PAPER
Class 12 - Chemistry
1. Explain why [5]
i. the dipole moment of chlorobenzene is lower than that of cyclohexyl chloride?
ii. alkyl halides, though polar, are immiscible with water?
iii. Grignard reagents should be prepared under anhydrous conditions?
2. In the following pairs of halogen compounds, which compound undergo faster SN1 reaction. [5]
i. and
ii. and
3. Predict all the alkenes that would be formed by dehydrohalogenation of the following halides with sodium [5]
ethoxide in ethanol and identify the major alkene:
i. 1-Bromo-1-methylcyclohexane
ii. 2-Chloro-2-methylbutane
iii. 2,2,3-Trimethyl-3-bromopentane.
4. Give the names of the predominant products obtained when bromoethane is treated with following: [5]
i. An aqueous alkali
ii. Sodium metal in dry ether
iii. An alcoholic potassium hydroxide solution
iv. Magnesium followed by ethanol
v. Aminoethane.
5. Show how would you synthesise the following alcohols from appropriate alkenes? [5]
i.
ii.
iii.
iv.
6. Give structures of the products you would expect when each of the following alcohol reacts with (a) HCl -ZnCl2 [5]
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HBr and SOCl2.
i. Butan-1-ol
ii. 2-Methylbutan-2-ol
7. a. Complete the following reactions: [5]
LiAlH4
i. (C H 3 )2 C O −−−−→
ii.
b. Write the structure formulae of the organic compounds 'A', 'B', 'C' and 'D' in the following sequence of
reactions:
H2 O
'A' + CH2MgBr −−→
C onc.
C H3 − C H2 − C H − C H3 −−−−→
|
H2 SO4
OH
′
Br2 alc.KOH ′
′ ′ ′ ′
B −→
− C −−−−−→ D
8. a. How can you obtain Phenol from (i) Cumene, (ii) Benzene sulphonic acid, (iii) Benzene diazonium chloride? [5]
b. Write the structure of the major product obtained from dinitration of 3-methylphenol.
c. Write the reaction involved in Kolbe’s reaction.
9. Give plausible explanation for each of the following: [5]
i. Cyclohexanone forms cyanohydrin in good yield but 2, 2, 6 trimethylcyclohexanone does not.
ii. There are two -NH2 groups in semicarbazide. However, only one is involved in the formation of
semicarbazones.
iii. During the preparation of esters from a carboxylic acid and an alcohol in the presence of an acid catalyst, the
water or the ester should be removed as soon as it is formed.
10. Arrange the following compounds in increasing order of their property as indicated: [5]
i. Acetaldehyde, Acetone, Di-tert-butyl ketone, Methyl tert-butyl ketone (reactivity towards HCN)
ii. CH3CH2CH(Br)COOH, CH3CH(Br)CH2COOH, (CH3)2CHCOOH, CH3CH2CH2COOH (acid strength)
iii. Benzoic acid, 4-Nitrobenzoic acid, 3,4-Dinitrobenzoic acid, 4-Methoxybenzoic acid (acid strength)
11. i. How can you convert each of the following compounds to Benzoic acid? [5]
1. Acetophenone
2. Ethylbenzene
3. Bromobenzene
ii. Arrange the following compounds in increasing order of their property as indicated:
1. O2N - CH2 - COOH, F - CH2 - COOH, CN - CH2COOH
(Acidic character)
2. Ethanal, Propanal, Butanone, Propanone
(Reactivity in nucleophilic addition reactions)
12. i. How will you convert: [5]
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a. Benzene to acetophenone
b. Propanone to 2-Methylpropan-2-ol
ii. Give reasons:
a. Electrophilic substitution in benzoic acid take place at meta-position.
b. Carboxylic acids are higher boiling liquids than aldehydes, ketones and alcohols of comparable molecular
masses.
c. Propanal is more reactive than propanone in nucleophilic addition reactions.
13. A hydrocarbon ‘A’, (C4H8) on reaction with HCl gives a compound ‘B’, (C4H9Cl), which on reaction with 1 [5]
mol of NH 3 gives compound ‘C’, (C4H11N). On reacting with NaNO2 and HCl followed by treatment with
water, compound ‘C’ yields optically active alcohol, ‘D’. Ozonolysis of ‘A’ gives 2 mols of acetaldehyde.
Identify compounds ‘A’ to ‘D’. Explain the reactions involved.
14. Write the structure of A, B, C, D and E in the following reactions: [5]
15. Account for the following: [5]
i. Aniline is a weaker base compared to ethanamine.
ii. Aniline does not undergo Friedel-Crafts reaction.
iii. Only aliphatic primary amines can be prepared by Gabriel Phthalimide synthesis.
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