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 Multiple Choice QuestionsMultiple Choice Questions

171.

Cycloalkane formed when 1,4-dibromopentaneis heated with sodium is

  • methyl cyclobutane

  • cyclopentane

  • cyclobutane

  • methyl cyclopentane


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172.

Least energetic conformation of cyclohexane is

  • chair conformation

  • boat conformation

  • cis conformation

  • E-Z form


A.

chair conformation

Cyclohexane exists in two forms and these are chair and boat conformations.In the chair form, all the C-H bonds on adjacent carbon atoms, are in the skew position. In the boat form, four of the C-H bonds are skew (1,2,3,4, 4, 5 and 6, 1) and two are eclipsed (2, 3 and 5, 6). At the same time, there will also be some bond opposition strain for these two pairs of eclipsed bonds and also steric repulsion between the hydrogen pointing towards each other at 1 and 4.

Hence, the total strain mn the boat conformation is larger than that in the chair conformation and consequently the former is less stable than the latter.


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173.

An alkyl bromide (X) reacts with sodium in ether to form 4,5-dIethyl octane, the compound X is

  • CH3(CH2)3Br

  • CH3(CH2)5Br

  • CH3(CH2)3CH(Br)CH3

  • CH3—(CH2)2—CH(Br)—CH2—CH3


174.

The correct statement is

  • Cyclohexadene and cyclohexene cannot be isolated with ease during controlled hydrogenation of benzene

  • One mole each of benzene and hydrogen when reacted gives 1/3 mole of cyclohexane and 2/3 mole unreacted hydrogen

  • Hydrogenation of benzene to cyclohexane is an endothermic process

  • It is easier to hydrogenate benzene when compared to cyclohexene


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175.

Number of possible alkynes with formula C5H8 is

  • 2

  • 3

  • 4

  • 5


176.

Benzene carbaldehyde is reacted with conc. NaOH solution to give the products A and B. The product A can be used as a food preservative and the product B is an aromatic hydroxy compound, where -OH group is linked to sp3-hybridised C-atom next to benzene ring. The products A and B respectively are

  • sodium benzoate and phenol

  • sodium benzoate and phenyl methanol

  • sodium benzoate and cresol

  • sodium benzoate and picric acid


177.

The arrangement of following compounds.

(i) Bromomethane

(ii) Bromoform

(iii) Chloromethane

(iv) Dibromomethane

In the increasing order of their boiling point is

  • III < I < IV < II

  • IV < III < I < IV

  • II < III < I < IV

  • I < II < III < IV


178.

An organic compound A on reduction gives compound B, which on reaction with trichloromethane and caustic potash forms C. The compound C on catalytic reduction gives N-methyl benzenamine, the compound A is,

  • nitrobenzene

  • nitromethane

  • methanamine

  • benzenamine


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179.

Which of the following has highest knocking ?

  • Olefins

  • Branched chain olefins

  • Straight chain olefins

  • Aromatic hydrocarbons


180.

Chlorination of benzene is not possible in the following reaction :

  • C6H6 + Cl2 FeCl3

  • C6H6 + HOCl H+

  • C6H+ I-Cl ZnCl2

  • C6H+ Cl2 AlCl3


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