Reactions of Alkenes

Alkenes represent a chemically rich functional group with many possible transformations. This tutorial looks at a number of typical reactions of alkenes as they appear in a sophomore organic chemistry. The typical reactions of alkenes are:

Catalytic Hydrogenation of Alkenes

–is a reaction between an alkene and hydrogen leading to the formation of alkane or a cycloalkane. Reaction is typically catalyzed by Pt, Pd, or Ni and presents an important reaction for both synthetic chemists and industry.

Halogenation of Alkenes

–is a reaction between and alkene and halogen leading to the formation of a vicinal dihalide. The reaction is typically only performed with Cl₂ or Br₂ and is stereospecific (anti-addition).

Oxyhalogenation of Alkenes

–is a reaction that is very similar to the halogenation of alkenes in both the mechanism and its stereospecificity. The main difference is that the nucleophile in this reaction is water which is taken in a large excess.

Alcoxyhalogenation of Alkenes

–is just like the oxyhalogenation reaction but the nucleophile in this reaction is an alcohol. Alcoxyhalogenation is a useful way to make functionalized ethers.

Hydrohalogenation of Alkenes

–is, perhaps, one of the most “typical” reactions of alkenes that is covered in a lot of details in organic chemistry. In this reaction and alkene reacts with either HCl, HBr, or HI to yield a corresponding alkyl halide.

Catalytic Hydration of Alkenes

–is the reaction between an alkene and water catalyzed by a strong acid. It is generally only used with simple molecules due to the possibility of carbocationic rearrangements and harsh conditions.

Catalytic Addition of Alcohols to Alkenes

–is the reaction that is very similar to the hydration of alkenes. It suffers from the same drawbacks and has a limited usefulness.

Radical Hydrohalogenation of Alkenes

–is a very useful reaction that places a halogen on the less substituted carbon of the double bond.

Oxymercuration-Reduction (Oxymercuration-Demercuration) of Alkenes

–is a reaction that places the hydroxyl (-OH) group on the more substituted carbon of the double bond.  Also, due to the nature of the mechanism of this reactions, no carbocationic rearrangements are observed.

Alcoxymercuration-Reduction of Alkenes

–is very similar to the oxymercuration-reduction. The reaction produces ethers and is very useful for synthetic chemists.

Hydroboration-Oxidation of Alkenes

–is an extremely useful reaction that results in the hydroxyl group (-OH) onto the less substituted carbon of the double bond. It is also different from many other reactions of electrophilic additions to an alkene is its stereospecificity being one of the few syn addition reactions.

Epoxidation of Alkenes

–is a fairly common reaction of alkenes that converts the double bond into a three-membered ring with the oxygen atom. This a cyclic functional group is called an epoxide or oxirane.

Ozonolysis of Alkenes

–is a reaction that cleaves the double bond oxidizing the carbons to carbonyls or carboxylic acids.

Dihydroxylation of Alkenes

–is one of the more narrowly specialized reactions that selectively converts an alkene into a vicinal diol.

Cyclopropanation of Alkenes

–is one of the few reactions that effectively yields highly strained three-membered rings (cyclopropanes).

Reactions of Alkenes Combined Spiderweb