Addition of HBr to propene yields 2-brom | Class 11 Chemistry Chapter Hydrocarbons, Hydrocarbons NCERT Solutions

Welcome to the NCERT Solutions for Class 11 Chemistry - Chapter Hydrocarbons. This page offers a step-by-step solution to the specific question from Exercise 1, Question 16: . With detailed answers and explanations for each chapter, students can strengthen their understanding and prepare confidently for exams. Ideal for CBSE and other board students, this resource will simplify your study experience.

Question 16:

Addition of HBr to propene yields 2-bromopropane, while in the presence of benzoyl peroxide, the same reaction yields 1-bromopropane. Explain and give mechanism.

Answer:

Addition of HBr to propene is an example of an electrophilic substitution reaction.

Hydrogen bromide provides an electrophile H+. This electrophile attacks the double bond to form 1° and 2° carbocations.

Secondary carbocations are more stable. Hence, the former predominates since it will form at faster rate. Thus, in the next step, Br- attacks the carbocation to form 2 - bromopropane as major product.

This reaction follows Markovnikov's rule where the negative part of the addendum is attached to the carbon atom having a lesser number of hydrogen atoms.

In the presence of benzoyl peroxide, an addition reaction takes place anti to Markovnikov's rule. The reaction follows a free radical chain mechanism as:

Secondary free radicals are more stable than primary radicals. Hence, the former predominates since it forms at a faster rate. Thus, 1 - bromopropane is obtained as the major product.

In the presence of peroxide, Br free radical acts as an electrophile. Hence, two different products are obtained on addition of HBr to propene in the absence and presence of peroxide.


Study Tips for Answering NCERT Questions:

NCERT questions are designed to test your understanding of the concepts and theories discussed in the chapter. Here are some tips to help you answer NCERT questions effectively:

  • Read the question carefully and focus on the core concept being asked.
  • Reference examples and data from the chapter when answering questions about Hydrocarbons.
  • Review previous year question papers to get an idea of how such questions may be framed in exams.
  • Practice answering questions within the time limit to improve your speed and accuracy.
  • Discuss your answers with your teachers or peers to get feedback and improve your understanding.

Latest Blog Posts

Stay updated with our latest educational content and study tips

Understanding Procrastination and Why Students Delay Studying | How To Fix It

One of the challenging things students face nowadays is procrastination. It hinders productivity, making it difficult for students to score well. We often associate procrastination as just being lazy. But there’s more to it. Various studies have shown that procrastination stems from negative feelings such as stress and anxiety. Oftentimes, when we start, we think […]

Read More

Effective Tips to Avoid Nervous Breakdown during CBSE Board Exam

The CBSE Board Exam is a crucial milestone for millions of students across India. The Central Board of Secondary Education is famous for its imparting quality education and knowledge which reaches out to a large share of students. Also, it is important to know that, the CBSE board takes a slight unconventional route, since it […]

Read More

HSSC CET Haryana 2025: Admit Card, Exam Dates, Fees, and More

Haryana government issued a notification on 31st December 2024 through its Gazette notification No. 42/119/2019-5HR-II for CET Haryana 2024. The Common Eligibility Test (CET) for Haryana is a significant opportunity for candidates seeking government jobs in Group C and Group D posts. Below is a comprehensive summary of the key information you need to know […]

Read More

Why Sleep is Crucial for Memory Retention and Learning?

Sacrificing your sleep to study more is doing more damage than you think. While it may seem like utilizing every hour of the day for study leads to better outcomes, the reality is quite the opposite. Lack of proper rest can negatively impact your brain, especially when it comes to sleep and memory retention. You’ll […]

Read More

Comments

  • Asmatullah
  • Apr 03, 2019

Why the HCl,HF and HI don't show peroxide effect


  • Asmatullah
  • Apr 03, 2019

Why the HCl,HF and HI don't show peroxide effect


Add Comment

Welcome to the NCERT Solutions for Class 11 Chemistry - Chapter . This page offers a step-by-step solution to the specific question from Excercise 1 , Question 16: Addition of HBr to propene yields 2-bromopropane, while in the presence of benzoyl peroxide, the sam....