PYQSide ExamsMy practice

Organic Chemistry – Some Basic Principles and Techniques · Question 14

NEET (UG) 2022 (Phase 2)MCQMedium📈 Topic in 38% papers+4−1
1

Which of the following is the most stable carbocation?

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

Answer

(1) [figure]

Solution

(1) The positive carbon is tertiary and lies between two C=C bonds, so the charge is delocalised over three carbon atoms by resonance (pentadienyl-type cation); hyperconjugation with the CH3 group and the ring C–H bonds adds further stability.

(2) Secondary carbocation, allylic to only one C=C bond.

(3) Primary carbocation, no resonance.

(4) Secondary carbocation, no resonance.

∵ As per NCERT, a carbocation is stabilised by resonance (delocalisation of the positive charge) and by hyperconjugation; resonance has the larger effect.

∴ The carbocation in option (1) is the most stable.

Answer: (1)

NEET (UG) 2022 (Phase 2)

Keep practising — Organic Chemistry – Some Basic Principles and Techniques

2

The correct structure of 2, 6-dimethyl-dec-4-ene is

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET (UG) 2021
3

A tertiary butyl carbocation is more stable than a secondary butyl carbocation because of which of the following?

  1. +R effect of -CH3 groups
  2. -R effect of -CH3 groups
  3. Hyperconjugation
  4. -I effect of -CH3 groups
NEET (UG) 2020
4

The number of sigma ( ) and pi ( ) bonds in pent-3-en-1-yne is -

  1. 11 bonds and 2 bonds
  2. 13 bonds and no bonds
  3. 10 bonds and 3 bonds
  4. 8 bonds and 5 bonds
NEET (UG) 2019
5

Which of the following is correct with respect to -I effect of the substituents? (R = alkyl)

  1. -NH2 < -OR < -F
  2. -NR2 < -OR < -F
  3. -NH2 > -OR > -F
  4. -NR2 > -OR > -F
NEET 2018
6

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

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
NEET 2018
7

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
NEET 2018
8

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.
NEET 2017
9

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
NEET 2017
10

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
NEET 2017
11

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.
NEET 2016 (Phase 1)

All Organic Chemistry – Some Basic Principles and Techniques PYQs →

PDFDownload Organic Chemistry – Some Basic Principles and Techniques PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All NEET Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolid StateSolutionsElectrochemistryChemical KineticsSurface Chemistry
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular StructureHydrogens-Block Elementsp-Block Elements (Group 13 & 14)Environmental ChemistryGeneral Principles of Isolation of Elementsp-Block Elements (Group 15–18)d- and f-Block ElementsCoordination Compounds
Organic ChemistryOrganic Chemistry – Some Basic Principles and TechniquesIsomerismHydrocarbonsHaloalkanes and HaloarenesAlcohols, Phenols and EthersAldehydes, Ketones and Carboxylic AcidsAminesBiomoleculesPolymersChemistry in Everyday LifePrinciples Related to Practical Chemistry