Topic 7- Organic Chemistry

• Isomers are molecules that have the same molecular formula, but different structural formulas, this means they are made of the same atoms, but the atoms are arranged differently.
• Organic chemistry is about molecules that contain Carbon.
• Hydrocarbons are substances that only contain carbon and hydrogen atoms.
• Alkanes are a homologous series of molecules that contain:

  1. Only carbon and hydrogen atoms.
  2. Only single bonds (no double bonds).
• A homologous series is a group of organic compounds that have similar chemical properties, due to them having the same functional group.
• The general formula for alkanes is CnH2n+2.
• Hydrocarbons with only single bonds are saturated.
• Crude oil is a mixture of many different compounds. Most of the compounds are hydrocarbons.
• 1. Crude oil is formed from the remains of dead plants and animals, particularly plankton.
• Over millions of years, heat and pressure build up causing the remains to change chemically. This process forms crude oil.
• When crude oil is extracted from the ground, it contains impurities such as sand, salt and sulfur. These must be removed before refining can take place.
• Alkenes contain at least one carbon-carbon double bond (C=C).
• Alkenes can be represented by the general formula CnH2n.
• Alkenes are unsaturated hydrocarbons because they do not contain enough hydrogen atoms to form all possible single covalent bonds between their carbon atoms.
• Crude oil is a mixture of hydrocarbons with different boiling points.
• The first step in fractional distillation is to heat the crude oil to a very high temperature so that all of the compounds are evaporated from liquid to gas.
• The hot gaseous hydrocarbons then rise up the fractionating column because hot gas rises.
• As the hydrocarbons rise, they cool down, because the top of the column is cooler than the bottom.
• The hydrocarbons will condense when they become cooler than their boiling point, and the liquid hydrocarbons then collect in trays and drain out.
• The longer chain hydrocarbons condense at the bottom of the fractionating column because they have high boiling points.
• The shorter chain hydrocarbons condense at the top of the column because they have much lower boiling points.
• A feedstock is a raw material used to provide reactants for an industrial reaction.
• A petrochemical is a substance made from crude oil, via chemical reactions.
• Cracking is the process in which larger chain hydrocarbons are split into smaller, more useful hydrocarbons.
• Shorter chain alkanes have lower melting and boiling points, so are more flammable, and more volatile. 
• When a long chain alkane is cracked, there aren't enough hydrogen atoms to make two alkanes. Hence, cracking will always produce one alkane and one alkene. (Alkenes are hydrocarbons with a double bond between two carbon atoms).
• Bromine water (just bromine dissolved in water) by itself is an orange colour. But when it's mixed with alkenes, all of the bromine will react, and so the solution loses its orange colour, and turns colourless.