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CHEM 221: Alkanes

AK Lectures

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image by Sean MacEntee


Introduction to Alkanes
Alkanes are the most basic members of a family of hydrocarbons. As the name implies, these molecules are composed of carbon and hydrogen connected by covalent bonds. The number of atoms and the overall shape of the molecule can vary greatly from one alkane to another but they do have underlining similarities, as discussed in the lecture.

Methyl Compounds
Methane is the simplest alkane molecule and it is composed of one carbon and four hydrogen atoms bonded covalently. If we replace one hydrogen atom with another atom or molecule, we will form a compound commonly known as the methyl compound. In this lecture, we will discuss the differences between these two types of compounds.

Methyl Cation, Methyl Anion and Methyl Radical Intermediates
Methane can be made into a reactive molecule by the dissociation of a hydrogen atom. If the hydrogen atom departs and takes both electrons with it, we will produce a methyl cation. If, on the other hand, the hydrogen that dissociates leaves both electrons on the former methane, we will form a methyl anion. Finally, if the detaching hydrogen takes a single electron with it, we will form a methyl radical.

Ethane
If we replace the substituent group in a methyl compound with another methane, we will produce the ethane compound, the second simplest alkane. In this lecture, we will explore this combination and discuss the bond produced.

Naming of Alkanes
Alkanes come in many different forms and shapes. Therefore, there exists a systematic approach to naming these hydrocarbons. As will be discussed in this lecture, several rules must be followed in order to ensure the proper name. In the following lecture, we will try a few examples using these rules.

Naming of Alkanes Examples
Alkanes come in many different forms and shapes. Therefore, there exists a systematic approach to naming these hydrocarbons. As will be discussed in this lecture, several rules must be followed in order to ensure the proper name. In this lecture, we will apply these rules to name the following several alkanes.

Isomers of Heptane
Isomers are molecules that have the same molecular formula but different structural arrangements of atoms. A favorite question in organic chemistry involves finding all the different types of isomers of some given alkane. Let us try to find all the isomers of heptane.

Boiling and Melting Points of Heptane
Since alkanes come in different forms and shapes, they have different temperatures under which they melt and boil. But what exactly determines this difference and why does it exist in the first place? These questions are addressed in this lecture.

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