A Short Guide to Organic Chemistry

A short Organic guide to Chemistry

Organic chemistry is the part of chemistry that looks and deals with the properties, structures and reactions of organic compounds which contain carbon covalent bonding. We will be looking at hydrocarbons, molecules that consist of carbon and hydrogen only, and their reactions to form alcohols, carboxylic acids, and polymers.

Hydrocarbons are found in crude oil, which forms over millions of years when dead plants and animals fall to the bottom of the sea; under pressure changes the chemical properties. Within crude oil there are many di erent fractions, which is determined by the length of the hydrocarbon. e larger the molecule, the higher the boiling point, which can be used to separate crude oil.

Crude oil can be separated using fractional distillation. Distillation is the process of separating a mixture of di erent liquids. A fraction is a group of molecules with similar boiling points. e fractions have a range of di erent uses. For example, petroleum gas, which is a fraction with a low boiling point, is used as a fuel for gas barbecues and grills and bitumen, a fraction with a high boiling point, is used in paving and roo ng application.

Sometimes there is not enough of a fraction to keep up with the demand of people using it, so cracking is used to increase the supply of some fractions. Cracking is the process of larger less useful alkanes being broken down into smaller more useful alkanes and alkenes. For cracking to occur the larger hydrocarbons are heated until they vaporise at 600-700°C over a catalyst of alumina or silica.

ere are two main types of hydrocarbons: alkanes and alkenes. Alkanes are saturated hydrocarbons which means that there are only single bonds between carbon atoms. Alkenes are unsaturated hydrocarbons as they have one carbon-carbon double bond. e general formula for alkanes is CnH2n+2 and alkenes is CnH2n. As alkenes have a double bond, this can open up and bond with the same alkene resulting in addition polymerisation.

ere are multiple ways to make alcohol, one is the hydration of ethene with steam and the other is anaerobic fermentation of glucose. e general formula of alcohols is CnH2n+1OH which means that the equivalent of a water (H2O) molecule has been added to ethene to make ethanol. is happens when ethene is mixed with steam and vaporised whilst being passed over a phosphoric acid catalyst at 300 degrees Celsius and a pressure of 60-70 atmospheres. Whereas fermentation of glucose requires anaerobic conditions and a catalyst of yeast. Fermentation is a slow and batch process, but the equipment is easily assembled and is also a renewable process. However, hydration of ethene with steam is a continuous process, equipment is hard to assemble and is a non-renewable process.

Alcohol can be oxidised to form a weak carboxylic acid; these acids have the general formula CnH2nCOOH. An example of a carboxylic acid is vinegar. If there is a mixture of alcohols and carboxylic acid, then they will react to form an ester and water. Esters have the functional group COO. Esters have strong smells and are o en used in perfumes and avourings. If a molecule has a functional group at either end of the molecule then the molecule can react to form a polymer; this type of polymerisation is called condensation polymerisation as water is produced as a byproduct.

Sacha Jennings