Investigate The Variety Of Organic Compounds - Session 1

Compounds that contain carbon and hydrogen atoms are called organic compounds. In addition to carbon and hydrogen atoms, organic compounds also contain other atoms such as oxygen, nitrogen, phosphorous or halogens. Some examples of organic compounds include glucose, carboxylic acids and ethanol. Carbon shows unique characteristics in organic compounds. It is tetravalent. This means it can form maximum of four covalent bonds.

Carbon atoms combine with other carbon atoms to form long chains of compounds. This self linking property of carbon atoms is called catenation. Due to catenation, carbon atoms are able to form numerous compounds. Heptane contains seven carbon atoms connected as a chain. Benzene contains six carbon atoms connected in circular form.

Hydrocarbons are compounds that are made up of only carbon and hydrogen atoms. Hydrocarbons can be classified into saturated hydrocarbons and unsaturated hydrocarbons. Saturated hydrocarbons have only single bonds between carbon atoms. An example of saturated hydrocarbon is propane. Unsaturated hydrocarbons have one or more double or triple bonds between carbon atoms. An example of unsaturated hydrocarbon is ethene.

Linear or branched-open-chain hydrocarbons are called Aliphatic hydrocarbons. They are classified into alkanes, alkenes and alkynes. Alkanes contain single bonds between carbon atoms. General molecular formula of alkanes is shown here. n represents number of carbon atoms in the molecule. For example, propane is an alkane. It contains three carbon atoms. Its molecular formula is C₃H₈. Alkanes are also called saturated hydrocarbons.

Alkenes contain one or more than one double bonds between carbon atoms. General molecular formula of alkenes is shown here. n represents number of carbon atoms in the molecule. For example, ethene is an alkene. It contains a double bond between two carbon atoms. Its molecular formula is C₂H₄. Alkenes are also called unsaturated hydrocarbons.

Alkynes contain one or more triple bonds between carbon atoms. General molecular formula of alkynes is shown here. n represents number of carbon atoms in the molecule. For example, ethyne is an alkyne. It contains a triple bond between two carbon atoms. Its molecular formula is C₂H₂. Alkynes are also called unsaturated hydrocarbons.

Aromatic hydrocarbons are a group of organic compounds that contain one or more circles of carbon atoms with alternating single and double bonds. They are called aromatic because they have specific aroma or smell. The most well known aromatic hydrocarbon is benzene. Benzene has a circle of six carbon atoms. Aromatic hydrocarbons are also used in production of plastics, dyes and in pharmaceuticals.

Functional groups are specific groups of atoms or bonds within a molecule that determine the properties, reactivity, and behaviour of the molecule in chemical reactions. For example, the hydroxyl group -OH is a polar functional group that is often found in alcohols. An example of alcohol containing hydroxyl group -OH is ethanol. The carboxyl group -COOH is found in carboxylic acids. Carboxyl group is acidic in nature. An example of carboxylic acid containing carboxyl group is ethanoic acid.

Alkoxy functional group R-O-R are there in ethers. R represents any alkyl group. When we remove one hydrogen atom from alkane, it becomes an alkyl. For example CH3CH2- is an alkyl group. It is called ethyl. -COH group is called aldehyde group. It is there in aldehydes. R-CO-R is the general formula of ketones. Ketones contain -CO- group. This group is called carbonyl group. Some more examples of functional groups are given in the illustration.

Aliphatic hydrocarbons are named using a systematic nomenclature system called the International Union of Pure and Applied Chemistry system. The IUPAC system uses a prefix to indicate the number of carbon atoms in the chain. It is then followed by the suffix "-ane" to indicate that the molecule is an alkane. For example, the alkane with one carbon atom is called methane. The alkane with two carbon atoms is called ethane.

If there are branches or substituents on the carbon chain, the IUPAC system uses a numbering system to identify the position of the branch or substituent. The longest continuous carbon chain is identified first. Then the branches or substituents are named using prefixes. The location of the branch is indicated by a number that corresponds to the position of the carbon atom on the main chain that is attached to the branch.

For example, the alkane with five carbon atoms and a methyl branch on the second carbon atom would be named 2-methylpentane . The prefix 2- indicates that the methyl group is attached to the second carbon atom. pentane indicates that there are five carbon atoms in the main chain. The numbering of longest continuous chain starts from the end closer to substituent.

Aliphatic hydrocarbons can also contain other functional groups, such as halides, alcohols, and amines. These functional groups are named using suffixes that indicate the type and location of the functional group. For example, an alkane with an alcohol group -OH attached to it would be named propanol. The suffix ol indicates the presence of alcohol group -OH . ethan indicates that there are two carbon atoms in the main chain. Some of the IUPAC suffixes of different functional groups is given in illustration.