What is the difference between saturated and unsaturated hydrocarbons?

Alkanes are the simplest family of hydrocarbons and are known for their single bonds between carbon atoms. They follow the general formula \(C_nH_{2n+2}\), where \(n\) is the number of carbon atoms. Alkanes are called saturated because each carbon atom is fully surrounded by hydrogen atoms, with no capacity to hold any more.

For example, methane (\(CH_4\)) is the simplest alkane with only one carbon atom, while ethane (\(C_2H_6\)) has two. The structures of alkanes can be linear, branched, or cyclic, but importantly, they do not contain any double or triple bonds, making them quite unreactive chemically. This lack of reactivity makes them suitable for use as fuels.

In contrast to alkanes, alkenes and alkynes are unsaturated hydrocarbons. Alkenes contain at least one double bond \(C=C\) and follow the general formula \(C_nH_{2n}\) for non-cyclic structures. Ethene or ethylene \(C_2H_4\) is the simplest alkene.

Alkynes are even less saturated, containing at least one triple bond \(C\equiv C\), with acetylene \(C_2H_2\) being the simplest example. They follow the general formula \(C_nH_{2n-2}\). Both types of hydrocarbons are more reactive than alkanes due to the presence of multiple bonds, which can participate in chemical reactions such as polymerization and hydrogenation.

Hydrocarbon saturation refers to the state of a hydrocarbon molecule being saturated with hydrogen. When a hydrocarbon is saturated, it means all the carbon atoms are linked by single bonds (\(C-C\)) and have as many hydrogen atoms as possible. Alkanes are an example of saturated hydrocarbons.

Unsaturated hydrocarbons, on the other hand, have double or triple bonds between carbon atoms. These multiple bonds reduce the number of hydrogen atoms the structure can hold, thus not being fully saturated with hydrogen. Alkenes and alkynes fall into this category, and their ability to add atoms or groups of atoms in reactions is a property utilized in various chemical industries.

Single, double, and triple bonds refer to the types of bonds that can occur between carbon atoms in hydrocarbons. A single bond (\(C-C\)) is a bond where two electrons are shared between two atoms and is the most stable type of bond. Double bonds (\(C=C\)) involve four sharing electrons and triple bonds (\(C\equiv C\)) have six sharing electrons.

These bonds not only differ in the number of shared electrons but also in their bond lengths and strengths – single bonds being the longest and least strong while triple bonds are the shortest and strongest. This range in bonding offers a variety of properties and reactivities among the hydrocarbons. It's the reason why alkenes and alkynes are more chemically active than the more stable alkanes.

The general formula of hydrocarbons is a way to represent the composition of these molecules based on the number of carbon atoms and the type of bonding present. For alkanes, the general formula is \(C_nH_{2n+2}\), which indicates that for every carbon atom, there are two hydrogen atoms plus two additional ones. For alkenes, the formula is \(C_nH_{2n}\) since the double bonds reduce the number of hydrogen atoms by two. Alkynes have an even lower ratio of hydrogen to carbon, represented by \(C_nH_{2n-2}\) due to the presence of triple bonds.

These formulas are fundamental in organic chemistry as they provide a quick way to predict the number of hydrogen atoms in a molecule and provide insight into the molecule's structure and potential reactivity.