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Hydrocarbons · Question 31

AIPMT 2015MCQMedium📈 Topic in 12% papers+4−1
1

2,3-Dimethyl-2-butene can be prepared by heating which of the following compounds with a strong acid?

  1. (CH3)3CCH=CH2
  2. (CH3)2C=CHCH2CH3
  3. (CH3)2CHCH2CH=CH2
  4. (CH3)2CH- CH3 |CH-CH=CH2

Answer

(1) (CH3)3CCH=CH2

Solution

2,3-Dimethyl-2-butene is (CH3)2C=C(CH3)2 ( C6H12). On heating with a strong acid an alkene is protonated to a carbocation, which can rearrange to a more stable one and then lose H+.

(CH3)3C-CH=CH2 H+ (CH3)3C- CH-CH3 (2°)

1,2-Methyl shift ⇒ (CH3)2 C-CH(CH3)2 (3°, more stable)

Loss of H+ ⇒ (CH3)2C=C(CH3)2 (most substituted, Saytzeff alkene)

Options (2) and (3) have the 2-methylpentane skeleton (one branch) ⇒ they give 2-methylpent-2-ene; option (4) has seven carbon atoms.

∴ only (CH3)3CCH=CH2 gives 2,3-dimethyl-2-butene.

Answer: (1)

AIPMT 2015

Keep practising — Hydrocarbons

2

The oxidation of benzene by V2O5 in the presence of air produces

  1. maleic anhydride
  2. benzoic acid
  3. benzaldehyde
  4. benzoic anhydride.
AIPMT 2015
3

A single compound of the structure, [figure] is obtainable from ozonolysis of which of the following cyclic compounds?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2015 (Cancelled)
4

The reaction of C6H5CH=CHCH3 with HBr produces

  1. C6H5CH2CH2CH2Br
  2. [figure]
  3. C6H5 Br |CHCH2CH3
  4. C6H5CH2 Br |CHCH3
AIPMT 2015 (Cancelled)
5

What products are formed when the following compound is treated with Br2 in the presence of FeBr3? [figure]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
AIPMT 2014
6

Some meta-directing substituents in aromatic substitution are given. Which one is most deactivating ?

  1. -COOH
  2. -NO2
  3. -C N
  4. -SO3H
NEET 2013
7

Which of the following compounds will not undergo Friedel-Crafts reaction easily?

  1. Nitrobenzene
  2. Toluene
  3. Cumene
  4. Xylene
NEET 2013
8

Nitrobenzene on reaction with conc. HNO3/H2SO4 at 80-100 C forms which one of the following products?

  1. 1, 4-Dinitrobenzene
  2. 1, 2, 4 - Trinitrobenzene
  3. 1, 2-Dinitrobenzene
  4. 1, 3-Dinitrobenzene
NEET 2013
9

Which of the following reagents will be able to distinguish between 1-butyne and 2-butyne?

  1. NaNH2
  2. HCl
  3. O2
  4. Br2
AIPMT 2012 (Mains)
10

Among the following compounds the one that is most reactive towards electrophilic nitration is

  1. benzoic acid
  2. nitrobenzene
  3. toluene
  4. benzene
AIPMT 2012 (Prelims)
11

Liquid hydrocarbons can be converted to a mixture of gaseous hydrocarbons by

  1. oxidation
  2. cracking
  3. distillation under reduced pressure
  4. hydrolysis
AIPMT 2010 (Prelims)

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