PYQSide ExamsMy practice

Haloalkanes and Haloarenes · Question 21

JEE Main 2025 (Online) 2nd April Evening ShiftNumericalEasy📈 Topic in 13% papers+4
1

[figure] Consider the above sequence of reactions. 151 g of 2-bromopentane is made to react. Yield of major product P is 80\% whereas Q is 100\%. Mass of product Q obtained is g. (Given molar mass in g mol-1 H : 1, C : 12, O : 16, Br : 80)

Answer

184

Solution

Molar mass of 2-bromopentane, C5H11Br = 60 + 11 + 80 = 151 g mol-1

151 g = 1 mol

Dehydrohalogenation with alcoholic KOH follows Saytzeff rule; the more substituted alkene, pent-2-ene, is the major product P:

CH3-CH(Br)-CH2-CH2-CH3 alc. KOH CH3-CH=CH-CH2-CH3

moles of P = 1 0.80 = 0.80 mol

Addition of bromine gives 2,3-dibromopentane (Q):

CH3-CH=CH-CH2-CH3 Br2 CH3-CH(Br)-CH(Br)-CH2-CH3

Molar mass of Q, C5H10Br2 = 60 + 10 + 160 = 230 g mol-1

mass of Q = 0.80 230 = 184 g

Answer: 184

JEE Main 2025 (Online) 2nd April Evening Shift

Keep practising — Haloalkanes and Haloarenes

2

In the following substitution reaction : [figure] Product 'P' formed is :

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 29th January Morning Shift
3

The products A and B in the following reactions, respectively are A AgNO2 CH3-CH2-CH2-Br AgCN B

  1. CH3-CH2-CH2-ONO, CH3-CH2-CH2-CN
  2. CH3-CH2-CH2-NO2, CH3-CH2-CH2-CN
  3. CH3-CH2-CH2-ONO, CH3-CH2-CH2-NC
  4. CH3-CH2-CH2-NO2, CH3-CH2-CH2-NC
JEE Main 2025 (Online) 28th January Morning Shift
4

Given below are two statements : In the light of the above statements, choose the most appropriate answer from the options given below

  1. Both Statement I and Statement II are correct
  2. Statement I is incorrect but Statement II is correct
  3. Both Statement I and Statement II are incorrect
  4. Statement I is correct but Statement II is incorrect
JEE Main 2025 (Online) 28th January Morning Shift
5

The product B formed in the following reaction sequence is: [figure]

  1. [figure]
  2. [figure]
  3. [figure]
  4. [figure]
JEE Main 2025 (Online) 28th January Evening Shift
6

The major product of the following reaction is: [figure]

  1. 6-Phenylhepta-3,5-diene
  2. 6-Phenylhepta-2,4-diene
  3. 2-Phenylhepta-2,4-diene
  4. 2-Phenylhepta-2,5-diene
JEE Main 2025 (Online) 28th January Evening Shift

All Haloalkanes and Haloarenes PYQs →

PDFDownload Haloalkanes and Haloarenes PYQs as PDF Free, with answer key and a QR code to every solution — print it or study offline⬇
All JEE Main Chemistry chapters
Physical ChemistrySome Basic Concepts of ChemistryStructure of AtomStates of MatterThermodynamicsEquilibriumRedox ReactionsSolutionsElectrochemistryChemical Kinetics
Inorganic ChemistryClassification of Elements and Periodicity in PropertiesChemical Bonding and Molecular Structurep-Block Elements (Group 13 & 14)p-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 AcidsAminesBiomoleculesPrinciples Related to Practical Chemistry