Addition reaction

Just as the chemistry of alkenes is dominated by addition reactions, the preparation of alkenes is dominated by elimination reactions. Additions and eliminations are, in many respects, two sides of the same coin.

— Addition reaction

As a general rule, electrophiles undergo addition reactions with alkynes much as they do with alkenes. Take the reaction of alkynes with HX, for instance. The reaction often can be stopped after addition of 1 equivalent of HX, but reaction with an excess of HX leads to a dihalide product. For example, reaction of 1-hexyne with 2 equivalents of HBr yields 2,2-dibromohexane.

— Addition reaction

An addition reaction is a reaction in which a molecule adds to a molecule containing a double bond, converting the double bond into a single bond.Because of this property of readily combining with other substances such as the halogens, ethylene and related hydrocarbons are said to be unsaturated. Ethylene is the first member of a homologous series of hydrocarbons, called the ethylene series.

— Addition reaction

We turn our attention to alkenesand alkynes, compounds that contain one and two π bonds, respectively. Because π bonds are easily broken, alkenes and alkynes undergo addition, the third general type of organic reaction. These multiple bonds also make carbon atoms electron rich, so alkenes and alkynes react with a wide variety of electrophilic reagents in addition reactions.

— Addition reaction

Many alkenes possess defined stereochemistry (E and Z) and, as we shall see in our discussions, many of their addition reactions proceed in a stereochemically defined manner.

— Addition reaction