1.

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

Answer» <html><body><p></p><a href="https://interviewquestions.tuteehub.com/tag/solution-25781" style="font-weight:bold;" target="_blank" title="Click to know more about SOLUTION">SOLUTION</a> :Addition of HBr to propene is an ionic electrophilic addition <a href="https://interviewquestions.tuteehub.com/tag/reaction-22747" style="font-weight:bold;" target="_blank" title="Click to know more about REACTION">REACTION</a> in which the electrophile, i.e., `H^+` first <a href="https://interviewquestions.tuteehub.com/tag/adds-849677" style="font-weight:bold;" target="_blank" title="Click to know more about ADDS">ADDS</a> to give a more stable `2^@` carbocation. In the 2nd second, the carbocation is rapidly attacked by the nucleophile `Br^-` <a href="https://interviewquestions.tuteehub.com/tag/ion-1051153" style="font-weight:bold;" target="_blank" title="Click to know more about ION">ION</a> to give 2-bromopropane <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/PR_CHE_02_XI_C13_E08_016_S01.png" width="80%"/> <br/> In presence of benzoyl peroxide , the reaction is still electrophilic but the electrophile here is a `oversetdot(Br)` free radical which is obtained by the action of benzoyl peroxide on HBr <br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/PR_CHE_02_XI_C13_E08_016_S02.png" width="80%"/> <br/> In the first step, `oversetdot(Br)` radical adds to propene in such a way as to generate a more stable `2^@` radical . In the second step, the free radical thus obtained rapidly abstracts a hydrogen atom from HBr to give 1-bromopropane.<br/> <img src="https://d10lpgp6xz60nq.cloudfront.net/physics_images/PR_CHE_02_XI_C13_E08_016_S03.png" width="80%"/> <br/> it is evident that although both reactions (i.e., in presence or absence of benzoyl peroxide ) are electrophilic addition but it is due to different order or sequence of addition of H and Br atoms which gives different <a href="https://interviewquestions.tuteehub.com/tag/products-18828" style="font-weight:bold;" target="_blank" title="Click to know more about PRODUCTS">PRODUCTS</a>.</body></html>


Discussion

No Comment Found

Related InterviewSolutions