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

Q16.

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.

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.

👍 0
👎 0
✍️ Add Answer
🚩 Report

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.

Important Questions & Answers

Why is this answer important for exams?

This question is important because it tests key concepts from the NCERT syllabus and is frequently asked in CBSE exams.

Which NCERT concept is used in this question?

This question is based on core NCERT concepts explained in the chapter and should be revised thoroughly before exams.

What is the correct answer to: 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.?

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.


...

How do you solve 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. step by step?

Step-by-step explanation:
• 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

What common mistakes should be avoided in this question?

Students often lose marks by skipping steps, writing incomplete explanations, or misunderstanding keywords used in the question.

Latest Blog Posts

Stay updated with our latest educational content and study tips

Simple and Compound Interest Formulas with Questions

Simple and Compound Interest Formulas with Questions

Interest is one of the most significant ideas in maths and financial calculations. It is very common in banking, loan applications, investments, saving account and competitive exams. Simple Interest and Compound Interest make it easier to find out how much more is earned and/or paid on a principal during the period of time. These Interest … Read more

Read More
Spoken English Course Topics for Beginners in 2026

Spoken English Course Topics for Beginners in 2026

In 2026, students, professionals, and job seekers must have a high level of spoken English. Spoken English is a beginner level course to enhance learners’ communication skills in English, their pronunciation, vocabulary, grammar structure and confidence in speaking English fluently. Today, the emphasis of spoken English courses is placed on actual conversations, everyday speech practice … Read more

Read More
Difference Between AI and Machine Learning

Difference Between AI and Machine Learning

Artificial Intelligence (AI) and Machine Learning (ML) are two of the most sought-after technologies in today’s digital era. Although these terms are often used together, they are not the same. Machine Learning is, in fact, a component of Artificial Intelligence that enables systems to learn and enhance on their own, without direct programming. AI is … Read more

Read More
Time, Speed and Distance Formulas

Time, Speed and Distance Formulas

Time, Speed, and Distance are some of the most important concepts in mathematics and aptitude. These are the concepts which are used to calculate the speed of an object, time taken for an object to move and the distance traveled during the motion. Questions from this topic are frequently seen in School Tests, Competitive Tests, … Read more

Read More

Student Discussion

Asmatullah
Class · · , · Apr 03, 2019
Why the HCl,HF and HI don't show peroxide effect
👍 👎 Reply
Asmatullah
Class · · , · Apr 03, 2019
Why the HCl,HF and HI don't show peroxide effect
👍 👎 Reply

ADD NEW COMMENT

        Can’t find your school? Type full name and submit.