Middle School Physical Science: Chemistry of Carbon - Hydrocarbons — Flashcards

A hydrocarbon is an organic compound consisting entirely of hydrogen and carbon. Hydrocarbons are examples of group 14 hydrides. Hydrocarbons are generally colourless and hydrophobic; their odor is usually faint, and may be similar to that of gasoline or lighter fluid.

Classification of Hydrocarbons    
Hydrocarbons can be classified in two basic classes. The classes are saturated hydrocarbons and unsaturated hydrocarbons. This classification is based on the number of bonds between carbon atoms.    
Saturated hydrocarbons contain only single bonds between carbon atoms. They are the simplest hydrocarbons. They are called saturated because each carbon atom is bonded to as many hydrogen atoms as possible. In other words, the carbon atoms are saturated with hydrogen. They may have straight-chain, branched-chain, or cyclic molecules.    
Unsaturated hydrocarbons contain at least one double or triple bond between carbon atoms. As a result, the carbon atoms are unable to bond with as many hydrogen atoms as they could if they were joined only by single bonds.    
This makes them unsaturated with hydrogen. Unsaturated hydrocarbons are classified on the basis of their bonds as alkenes or alkynes.    

- Alkenes are unsaturated hydrocarbons that contain at least one double bond. They may have straight-chain, branched-chain, or cyclic molecules. Cyclic alkenes are called aromatic hydrocarbons because they have a strong aroma. They have alternating single and double bonds between carbon atoms.    
- Alkynes are unsaturated hydrocarbons that contain at least one triple bond. They may have straight- or branched-chain molecules but rarely occur as cyclic molecules.