Chapter 11.5, Problem 11.55P

Interpretation Introduction

Interpretation:

The reagent that is used to carry out the given reaction has to be identified.

Concept Introduction:

Addition reactions are the one in which the groups are added to an unsaturated double bond.  The double bond is destroyed because the groups are added across the double bond.  If the considered alkene is a symmetrical one, then there is no difference in the product obtained but if the alkene is an unsymmetrical one, then regiochemistry decides the products that are obtained.

When two similar groups are added across a double bond, regiochemistry is irrelevant.  When adding two different groups across the double bond of an unsymmetrical alkene, the regiochemistry becomes relevant.  In simple words, it can be said that, when two different groups are added across a double bond, then regiochemistry becomes relevant.

Markovnikov Addition

    In the vinylic bond, if the bulky group gets substituted in the carbon atom that is more substituted means, it is known as Markovnikov’s addition.

anti-Markovnikov Addition

    In the vinylic bond, if the bulky group gets substituted in the carbon atom that is less substituted means, it is known as anti-Markovnikov’s addition.

If hydrogen halide is used in presence of hydrogen peroxide, anti-Markovnikov addition takes place.  This means the halide ends up on less substituted carbon atom.  This is because when peroxide is used the mechanism that the reaction undergoes is radical mechanism.  This involves a radical intermediate instead of ionic intermediate.  The main difference between ionic mechanism and radical mechanism is that proton is installed first in ionic mechanism while in radical mechanism, halide is installed first.  This is the reason why ionic mechanism gives Markovnikov product and radical mechanism gives anti-Markovnikov product.