Alkene Nomenclature and Properties

Alkenes are a class of organic compounds that contain at least one carbon-carbon double bond. They are unsaturated hydrocarbons and have the general formula C(n)H(2n). Alkenes are important intermediates in many organic reactions and serve as the building blocks for a variety of industrial and consumer products. In this lesson, we will explore the nomenclature and properties of alkenes.

Nomenclature of Alkenes

The nomenclature of alkenes follows a similar set of rules as alkanes. The parent chain is identified and numbered so that the carbon atoms containing the double bond have the lowest possible numbers. The double bond is indicated by the suffix “-ene” and the position of the double bond is indicated by a number before the suffix.

If there are multiple double bonds, the suffixes “-diene”, “-triene”, and “-tetraene” are used to indicate two, three, or four double bonds, respectively. If the double bond is located on a ring structure, the naming convention is the same except the “cyclo” prefix is added to the molecule.

Visit our Organic Compound Namer to draw any molecule and get the IUPAC name and molecular formula!

Properties of Alkenes

The carbon-carbon double bond in alkenes is a region of high electron density, which makes the molecule susceptible to electrophilic attack. Alkenes undergo addition reactions, where an electrophile (an atom or molecule that is electron-deficient) adds to the double bond, forming a single bond and a new functional group.

Alkenes are generally more reactive than alkanes due to the presence of the double bond, which makes the molecule more susceptible to chemical reactions. The reactivity of alkenes is influenced by factors such as the degree of substitution, the size of the substituent groups, and the presence of functional groups.

Alkenes can also exhibit geometric isomerism, where the double bond restricts rotation around the carbon-carbon bond, leading to two different possible orientations of the substituent groups around the double bond. This is known as cis-trans isomerism, where the cis isomer has the substituent groups on the same side of the double bond, while the trans isomer has the substituent groups on opposite sides of the double bond.

Summary

Alkenes are unsaturated hydrocarbons that contain at least one carbon-carbon double bond. The nomenclature of alkenes follows a similar set of rules as alkanes, with the suffix “-ene” indicating the presence of the double bond. The carbon-carbon double bond makes alkenes susceptible to electrophilic attack, and they undergo addition reactions to form new functional groups. Alkenes can also exhibit geometric isomerism due to the presence of the double bond.

Test Your Knowledge:

What is the general formula for alkenes and why are they considered unsaturated hydrocarbons?

What is the difference between cis and trans isomers in alkenes?