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Organic Chemistry – Some Basic Principles and Techniques

NEET 2013 (Karnataka)MCQMedium📈 Topic in 12% papers+4−1
Ques. 1NEET 2013 (Karnataka)

Homolytic fission of the following alkanes forms free radicals CH3-CH3, CH3-CH2-CH3, (CH3)2CH-CH3, CH3-CH2-CH(CH3)2. Increasing order of stability of the radicals is

  1. (CH3)2 C-CH2CH3 < CH3- CH-CH3 < CH3- CH2 < (CH3)3 C
  2. CH3- CH2 < CH3- CH-CH3 < (CH3)2 C-CH2-CH3 < (CH3)3 C
  3. CH3- CH2 < CH3- CH-CH3 < (CH3)3 C < (CH3)2 C-CH2CH3
  4. (CH3)3 C < (CH3)2 C-CH2CH3 < CH3- CH-CH3 < CH3- CH2

Answer

(2) CH3- CH2 < CH3- CH-CH3 < (CH3)2 C-CH2-CH3 < (CH3)3 C

Solution

Stability of alkyl free radicals: 3° > 2° > 1°, due to hyperconjugation (and +I effect of alkyl groups).

CH3- CH2 (1°) < CH3- CH-CH3 (2°) < 3° radicals

Between the 3° radicals: (CH3)3 C has 9 α-hydrogens, (CH3)2 C-CH2-CH3 has 8 α-hydrogens.

⇒ (CH3)3 C is the most stable.

∴ CH3- CH2 < CH3- CH-CH3 < (CH3)2 C-CH2-CH3 < (CH3)3 C

Answer: (2)

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Ques. 2NEET 2013 (Karnataka)

Which of the following chemical system is non aromatic?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 3AIPMT 2012 (Prelims)

Which nomenclature is not according to IUPAC system?

  1. Br-CH2-CH=CH2 1-Bromoprop-2-ene
  2. [figure] 4-Bromo-2,4-dimethylhexane
  3. [figure] 2-Methyl-3-phenylpentane
  4. [figure] 5-Oxohexanoic acid
Ques. 4AIPMT 2011 (Prelims)

Which one of the following is most reactive towards electrophilic reagent?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 5AIPMT 2011 (Prelims)

The correct IUPAC name for the compound is [figure]

  1. 4-ethyl-3-propylhex-1-ene
  2. 3-ethyl-4-ethenylheptane
  3. 3-ethyl-4-propylhex-5-ene
  4. 3-(1-ethylpropyl)hex-1-ene
Ques. 6AIPMT 2010 (Mains)

Which of the following species is not electrophilic in nature?

  1. Cl
  2. BH3
  3. H3 O
  4. NO2
Ques. 7AIPMT 2010 (Mains)

The IUPAC name of the compound CH3CH=CHC CH is

  1. pent-4-yn-2-ene
  2. pent-3-en-1-yne
  3. pent-2-en-4-yne
  4. pent-1-yn-3-ene
Ques. 8AIPMT 2010 (Prelims)

Which one of the following is most reactive towards electrophilic reagent?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 9AIPMT 2009

The IUPAC name of the compound having the formula CH C-CH=CH2 is

  1. 1-butyne-3-ene
  2. but-1-yne-3-ene
  3. but-1-en-3-yne
  4. 3-butene-1-yne.
Ques. 10AIPMT 2009

The state of hybridisation of C2, C3, C5 and C6 of the hydrocarbon, [figure] is in the following sequence

  1. sp3, sp2, sp2 and sp
  2. sp, sp2, sp2 and sp3
  3. sp, sp2, sp3 and sp2
  4. sp, sp3, sp2 and sp3
Ques. 11AIPMT 2008

Base strength of [figure] is in the order of

  1. (i) > (iii) > (ii)
  2. (i) > (ii) > (iii)
  3. (ii) > (i) > (iii)
  4. (iii) > (ii) > (i)

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