Chapter 11.9, Problem 11.104P

Interpretation Introduction

Interpretation:

The product that will be formed in the given reaction has to be predicted.

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

Stereochemistry can also be determined for the product obtained by the way of addition of groups that adds across the double bond.  If the two groups add in the same side of the plane means it is known as syn addition and if the two groups add in the opposite side of the plane means it is known as anti addition.  This can be done by considering the given alkene in a planar form by using wedge and dash bonds.

In case of bromination in presence of water as solvent, always anti addition is preferred.  The two groups that are added are a bromine atom and a hydroxyl group.  Therefore, in this case the regiochemistry becomes relevant.  The hydroxyl group always goes to the carbon atom that is more substituted.  The complete reaction profile for the reaction of bromine with alkene in presence of water can be summarized as given below,