Organic Chemistry: Concepts and Applications - Headley Allan D. 2020

Alkanes, Cycloalkanes, and Alkenes: Isomers, Conformations, and Stabilities
4.1 Introduction

In the previous chapters, the properties and nomenclature of alkanes and alkenes were covered. In this chapter, there will be a closer examination of the three-dimensional arrangements of the atoms of these types of molecules and how different arrangements affect their stabilities and properties. The first concept that should be reviewed is that of isomers. By definition, isomers are compounds that have the same number and type of atoms but are arranged differently, resulting in different molecules. As a result, these compounds, although having the same molecular formulas, are different and hence have different properties. As the number of atoms of a molecule increases, so does the number of possible isomers (possible atomic arrangements), compared to molecules with fewer atoms. Structural isomers are one form of isomers; there are other types of isomers that are categorized as geometric isomers, conformational isomers, and stereoisomers. In this chapter, each type will be covered, and owing to the importance of stereoisomers, that category of isomers will be covered in the next chapter.