Chapter 2: Fundamentals of Organic Structures

In this chapter, we will discuss the fundamental structural features of organic compounds, the categorization and drawing of organic structures, functional groups, and nomenclatures.

Learning Objectives for this chapter:

• Draw, recognize and read different structure formulas that represent organic molecules correctly and skillfully.
• Understand and be able to recognize constitutional isomers. Draw all constitutional isomers with a given formula, by applying both structure knowledge and degree of unsaturation concept.
• Recognize and name simple organic molecules with common functional groups by applying IUPAC nomenclature.
• Understand the nature and structure effect on different intermolecular forces, and be able to predict and explain the physical property of substance based on the intermolecular force knowledge.

Organic Compounds Overview

Organic compounds are compounds that contain the carbon element. The simplest organic compound is a hydrocarbon, which is a compound containing only the elements carbon and hydrogen. Hydrocarbons are composed of several sub-categories: alkane, alkene, alkyne and aromatic, depending on the type of carbon-carbon bonds involved.

Hydrocarbons can be in chains (straight-chains or branched-chains) or rings. The hydrocarbon chain and ring form the “carbon backbone” of organic compounds, and functional groups connected to the backbone allow for a great diversity of organic structures. Functional groups are common and specific arrangements of atoms, usually heteroatoms (atoms other than carbon and hydrogen) like N, O, and Cl that show specific and relatively high reactivities. Knowledge about the common functional groups in this chapter will prepare us for the later discussion on organic reactions.

Hydrocarbons:

• Alkane and cycloalkane: contain only C-C (single) bonds
• Alkene and cycloalkene: contain one or more C=C (double) bonds
• Alkyne: contains one or more C≡C (triple) bonds
• Aromatic: contains a benzene ring and its derivative

Functional Groups involving heteroatoms (see details in Table 2.2, section 2.3):

• Alkyl halides (haloalkanes), alcohol, ether, nitrile, nitro, amine, aldehyde, ketone, carboxylic acid, ester, amide, anhydride