organic chemistry MCQs

PPSC Lecturer Chemistry Test 39 Online Preparation MCQs

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Test Instructions:-
Test Name	Lecturer Chemistry
Subject	Chemistry Test 39
Test Type	MCQs
Total Questions	25
Total Time	20 Minutes
Total Marks	100

You have 20 minutes to pass to the quiz.

PPSC LECTURER OF CHEMISTRY TEST NO. 39

1 / 25

Which statement about the structure of benzene is not true?

The carbon-carbon bond lengths in benzene are greater than the carbon-carbon double bonds in aliphatic compounds.

The two Kekule structures of benzene are in equilibrium.

The stability of benzene ring is much greater than the stability of 1,3,5- cycloheptatriene.

The molecular geometry of benzene is best described as planar.

2 / 25

What is the term used for isomers that are in rapid equilibrium?

cis-trans isomers

constitutional isomers

conformational isomers

keto-enol tautomers

3 / 25

Which of the following is not a correct statement about the electrophilic substitution mechanism of benzene?

Formation of a carbocation intermediate is the rate-determining step.

Benzene functions as a nucleophile.

The addition product is a frequently observed minor product.

The carbocation intermediate contains an sp3 hybridized carbon in the ring.

4 / 25

Coal-tar is the main source of :

None of these

Heterocyclic compounds

Aromatic compounds

Aliphatic compounds

5 / 25

Which of the following reagents will react with methyl group rather than the benzene ring in methylbenzene?

CH3Cl in the presence of AlCl3

Chlorine in the presence of uv light

CH3COCl in the presence of AlCl3

Hydrogen in the presence of nickel

6 / 25

For reactions of ethylbenzene, the ethyl group is considered :

ortho director

ortho-meta director

meta director

ortho-para director

7 / 25

What purpose does FeCl3 serve in the electrophilic aromatic substitution reaction between chlorine and benzene?

It functions by destabilizing the carbocationic intermediate and thereby increases the rate of H+ loss.

It serves as a radical initiator to produce the chlorine radical needed to propagate the chain reaction.

It serves as a Lewis acid catalyst by reacting with the Cl2 and thereby activates it toward attack by benzene’s π electrons.

It serves as a Lewis base catalyst by reacting with Cl2 to generate chloride ions.

8 / 25

Which of the following statements is incorrect about benzene?

All twelve atoms lie in the same plane.

All of the carbon atoms are sp hybridized.

It has delocalized electrons.

The carbon-carbon bond lengths are all the same.

9 / 25

The delocalized π system in benzene is formed by a cyclic overlap of 6 orbitals.

sp2

10 / 25

What is the major organic product of the reaction between benzene and isobutyl chloride in the presence of AlCl3?

n-butylbenzene

tert-butylbenzene

chlorobenzene

isobutylbenzene

11 / 25

Aromatic hydrocarbons are also called :

Huckel's compounds

Alkoxy compounds

Trienes

Arenes

12 / 25

Which of the following statements are false about benzene?

It can be converted into cyclohexane by hydrogenation at 200°C in the presence of Ni catalyst.

It reacts with ethyl chloride in the presence of aluminium chloride to form ethylbenzene.

It is a planar molecule with bond angles 120°.

13 / 25

Which of the following fractions of coal-tar distillation contains benzene?

Light oil

Anthracene oil

Middle oil

Heavy oil

14 / 25

Which of the following statements are correct concerning benzene?

Benzene is a planar molecule.

The six carbon-carbon bonds have the same length.

(a) and (b)

15 / 25

Characteristic reactions of aromatic hydrocarbons are initiated by

Electrophiles

Uncharged molecules

Nucleophiles

Free radicals

16 / 25

Which of the following is not a correct statement concerning the Friedel- Crafts acylation of benzene?

The acylium ion is often produced from an acyl chloride.

An alkyl group substitutes for a hydrogen.

The benzene ring attacks an acylium ion.

The acylium ion is resonance stabilized.

17 / 25

Which of the following is aromatic?

cyclobutenyl anion

1,3-cyclohexadiene

cycloheptatrienyl cation

cyclopentadienyl cation

18 / 25

The carbon atoms in a benzene ring are :

sp3 hybridized

sp hybridized

None of these

sp2 hybridized

19 / 25

Toluene reacts with bromine in the presence of uv light to give

Benzoyl bromide

Benzyl bromide

m-Bromotoluene

o-Bromotoluene

20 / 25

The C–C bond length in benzene is

shorter than the C–C bond length in ethylene.

Same as that of C–C bond length in ethylene.

greater than the C–C bond length in ethane.

intermediate between C–C bond length in ethane and C–C bond length in ethylene.

21 / 25

Phenol on distillation with Zinc dust gives

Benzoic acid

Phenylzinc

Benzene

Cyclohexanone

22 / 25

Which of the following statements about benzene is correct?

It has no delocalized electrons.

The carbon-carbon bond length is longer than that of ethane.

All of the carbon atoms are sp3 hybridized.

It is a planar molecule.

23 / 25

Which of the following fractions of coal-tar distillation contains naphthalene?

Middle oil

Light oil

Anthracene oil

Heavy oil

24 / 25

Aromatic molecules contain __________ π electrons.

4n + 2 (with n being an integer)

4n + 2 (with n being 0.5)

4n (with n an integer)

25 / 25

Which of the following can be made by the action of CH3Cl on benzene in the presence of aluminium chloride?

Chlorobenzene

Ethylbenzene

o-Xylene

m-Xylene

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