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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: KurzickMushroom on November 05, 2009, 10:34:38 AM

Title: (anti-)Markovnikov's Rule
Post by: KurzickMushroom on November 05, 2009, 10:34:38 AM

Hi, my teacher said something about this that I did not agree with. When adding any acid, HX, to an alkene, Markovnikov's rule applies. The except to this is HBr. If HBr is added, anti-Mark's applies. My teacher told me anti Mark's rule applies only in the presence of Sulfuric Acid as a catalyst. I search on multiple websites and asked my tutor. H2SO4 is never mention as a catalyst.

Is this true? ( Does anti-Mark's rule apply only if HBr is in the presence of Sulfuric Acid?
Is H2SO4 needed as a catalyst for all Mark rule applications?

Thanks in advance.

Title: Re: (anti-)Markovnikov's Rule
Post by: JGK on November 05, 2009, 11:12:58 AM

My old texbook and the site listed below indicate that it is pthe presence or absence of peroxides which determine where the Br binds.

http://www.chemguide.co.uk/mechanisms/freerad/alkenehbr.html (http://www.chemguide.co.uk/mechanisms/freerad/alkenehbr.html)

Anti Markovnikov occurs in the presence of peroxides (also called the "peroxide effect")

Title: Re: (anti-)Markovnikov's Rule
Post by: KurzickMushroom on November 05, 2009, 12:42:46 PM

aww damn it! Thank you very much for the quick reply.