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Organic Chemistry – Some Basic Principles and Techniques

NEET 2018MCQHard📈 Topic in 38% papers+4−1
Ques. 1NEET 2018

Which of the following carbocations is expected to be most stable?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]

Answer

(3) [figure]

Solution

In each cation the positive charge is delocalised by resonance over the three carbons ortho and para to the sp3 (C–H, Y) carbon.

-NO2 is a strong electron-withdrawing group (−I, −R) ⇒ a positive charge on the carbon carrying -NO2 is strongly destabilised.

(1), (2), (4): -NO2 is ortho/para to the sp3 carbon ⇒ one resonance structure places on the carbon bearing -NO2 ⇒ destabilised.

(3): -NO2 is meta to the sp3 carbon ⇒ never comes on the carbon bearing -NO2 ⇒ least destabilised.

∴ Cation (3) is the most stable.

Answer: (3)

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Ques. 2NEET 2018

Which of the following molecules represents the order of hybridisation sp2, sp2, sp, sp from left to right atoms?

  1. HC C - C CH
  2. CH2 = CH - C CH
  3. CH2 = CH - CH = CH2
  4. CH3 - CH = CH - CH3
Ques. 3NEET 2017

The correct statement regarding electrophile is

  1. electrophile is a negatively charged species and form a bond by accepting a pair of electrons from another electrophile
  2. electrophiles are generally neutral species and can form a bond by accepting a pair of electrons from a nucleophile
  3. electrophile can be either neutral or positively charged species and can form a bond by accepting a pair of electrons from a nucleophile
  4. electrophile is a negatively charged species and can form a bond by accepting a pair of electrons from a nucleophile.
Ques. 4NEET 2017

The IUPAC name of the compound [figure]

  1. 5-formylhex-2-en-3-one
  2. 5-methyl-4-oxohex-2-en-5-al
  3. 3-keto-2-methylhex-5-enal
  4. 3-keto-2-methylhex-4-enal
Ques. 5NEET 2017

Which one is the correct order of acidity?

  1. CH CH > CH3-C CH > CH2=CH2 > CH3-CH3
  2. CH CH > CH2=CH2 > CH3-C CH > CH3-CH3
  3. CH3-CH3 > CH2=CH2 > CH3-C CH > CH CH
  4. CH2=CH2 > CH3-CH=CH2 > CH3-C CH > CH CH
Ques. 6NEET 2016 (Phase 1)

For the following reactions : (A) CH3CH2CH2Br + KOH CH3CH=CH2 + KBr + H2O (B) [figure] (C) [figure] Which of the following statements is correct?

  1. (A) is elimination, (B) and (C) are substitution reactions.
  2. (A) is substitution, (B) and (C) are addition reactions.
  3. (A) and (B) are elimination reactions and (C) is addition reaction.
  4. (A) is elimination, (B) is substitution and (C) is addition reaction.
Ques. 7NEET 2016 (Phase 1)

The pair of electrons in the given carbanion, CH3C C-, is present in which of the following orbitals?

  1. sp2
  2. sp
  3. 2p
  4. sp3
Ques. 8NEET 2016 (Phase 2)

In which of the following molecules, atoms are coplanar?

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
Ques. 9NEET 2016 (Phase 2)

In pyrrole the electron density is maximum on [figure]

  1. 2 and 3
  2. 3 and 4
  3. 2 and 4
  4. 2 and 5
Ques. 10AIPMT 2015

Which of the following statements is not correct for a nucleophile?

  1. Ammonia is a nucleophile.
  2. Nucleophiles attack low e- density sites.
  3. Nucleophiles are not electron seeking.
  4. Nucleophile is a Lewis acid.
Ques. 11AIPMT 2015 (Cancelled)

The total number of π-bond electrons in the following structure is [figure]

  1. 12
  2. 16
  3. 4
  4. 8

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