Aromatic compounds are compound with the benzene ring. When hydrogen atom is loss from the benzene molecule it became phenyl group. Derivatives of benzene are obtain when one or more of its hydrogen atom are substituted. These compounds are named by preceding the name benzene with the prefix of the substituent. E.g.

When they are more than one substituent on the benzene ring, we use number to indicate their position relative to the 1^st carbon atoms in the ring are generally in a clocic-wise direction. Prefix like o-(othos), mo (Meta), p (pera) are generally use to denote a relative position of two substituent groups where 1 of groups is at position 1

A. HYDROCARBONS

These are organic compound containing carbon and hydrogen atom only. All hydrocarbon have the general formulae of CxHy where x and y are whole numbers. They are classified into

1. Aliphatic; which are made up of straight and branch chain of carbon atom e.g. alkane, alkynes, alkenes etc.

1. Alicyclic; make of carbon atom arrangement in cycles or ring e.g. cyclo-propane.

1. Aromatic; made of compounds containing the benzene ring.

B. PETROLEUM OR CRUDE OIL

Petroleum in Greek means rock oil (petro=rock, oleum=oil).  Crude oil is a mixture of hydrocarbon.

It is believed that crude oil is formed by bacteria decomposition of animals and plants remained under pressure. It generally have no use in its raw form but once it is extracted and refined, it becomes one of the most useful chemicals.

C. REFINING OF CRUDE OIL

It is the separation of crude oil into its various useful fractions and this is by fractional distillation. In this process, the various fractions are separated base on the difference in their boiling point. This is carried out in refinery such as SONARA.

Petroleum is heated to a temperature of about 400 degree Celsius in an electric furnace and the resulting vapor enters a fractionative column which is divided  into several compartment, each maintained at a specific temperature range. As the column or tower is ascended, the temperature gradually reduces. The vapor obtained from heating the crude oil ascends the lower and the difference fraction condenses at the different compartment depending on their boiling points. The fraction with the highest boiling point condenses at the bottom while the fraction with the lowest boiling point condenses at the top. The following fractions are obtained:

• Residue: This is a non volatile fraction (40-50%) and it is basically made up of lubricating oil and bitumen used for construction e.g. vacilin.
• Gas oil: ( 13-25carbon atom). It has a temperature range of 150 to 360 degree C. it is usually used as heating fuel for engine of tractor, jet, car etc.
• Kerosene: (11-13carbon atom). It used as a domestic fuel in lamp and stoves for lighting and heating.
• Gasoline (petrol): (5-12carbon atom). It has a temperature range of 40 to 180 degree C. it is used for engines that require volatile liquid like the car engine. It is also used as a solvent for paint.
• Light Naphtha: (4 to 5carbon atom). These are low boiling points liquid. Generally used as organic solvent e.g. ether, benzene.
• Gas: (1 to 4carbon atom). Temperature below 20 degree C and used mainly as fuel for heating.

NOTE: Due to the ever increasing demand for the petrol fraction of crude oil, those whose demands are not high are converted into petrol to meet its high demand. This method is called cracking,