Organic chemistry

• Compounds with the same molecular formula can have different structural formulae due to the different arrangement of their atoms in space
• For conventional reasons, metal carbonates, carbon dioxide, and carbon monoxide are not included in organic compounds
• Displayed Formula

  Shows the spatial arrangement of all the atoms and bonds in a molecule
• Organic Chemistry is the scientific study of the structure, properties, and reactions of organic compounds
• Hydrocarbons are compounds that contain only hydrogen and carbon atoms
• Homologous Series: a series or family of organic compounds that have similar features and chemical properties due to them having the same functional group
• Structural Formula

  Enough information is shown to make the structure clear, but most of the actual covalent bonds are omitted
• Organic compounds contain carbon
• Ways to represent organic compounds

  • Displayed Formulae
  • General Formulae
  • Structural Formulae
• The functional group is a group of atoms bonded in a specific arrangement responsible for the characteristic reactions of each member of a homologous series
• Structural isomers are compounds that have the same molecular formula but different structural formulae
• General Formulae of Common Homologous Series

  • Alkanes: Cn H2n+2
  • Alkenes: Cn H2n
  • Alcohols: Cn H2n+1 OH
  • Carboxylic Acids: Cn H2n+1 COOH
• Saturated compounds have molecules with all carbon-carbon bonds as single bonds
• Examples of unsaturated compounds are alkenes with the general formula C H
• Homologous Series

  • All members have the same general formula
  • Same functional group
  • Similar chemical properties
  • Gradation in physical properties
  • Difference in molecular formula between members is CH
• Worked Example

  1. A compound has the formula C H. To which homologous series does this compound belong to?

  2. Answer: There are 12 carbon atoms, so n = 12, There are twice the number of hydrogen atoms than carbon atoms = 2n, General formula = C H, Compound belongs to alkenes
• Naming Organic Compounds: Prefix indicates the number of carbon atoms in the longest continuous chain
• Unsaturated compounds have one or more carbon-carbon bonds that are not single bonds
• Worked Example

  1. What is the formula of an alcohol that contains 5 carbon atoms?

  2. Answer: Number of carbons = 5, Number of hydrogens = 2 x 5 + 1 = 11, Formula = C H OH
• Alkenes can form more bonds with other atoms by opening up the C=C bond
• Examples of saturated compounds are alkanes with the general formula C H
• The names of organic compounds have two parts: the prefix (or stem) and the end part (or suffix)
• Common fossil fuels

  • Coal
  • Natural gas
  • Methane
  • Propane
• Most common fossil fuels include coal, natural gas, and hydrocarbons obtained from crude oil
• A fuel is a substance that, when burned, releases heat energy which can be transferred into electricity
• The fractions in petroleum are separated through fractional distillation
• Prefix in organic compound names


  Tells how many carbon atoms are present in the longest continuous chain in the compound
• Further Rules for Naming Compounds

  When there is more than one carbon atom where a functional group can be located, each carbon is numbered to describe where the functional group is located
• Naming Organic Compounds

  Make sure you can draw and name the structures given above
• Hydrocarbons are made from hydrogen and carbon atoms only
• Each component part of petroleum, called a fraction, has different applications
• Suffix in organic compound names

  Indicates the functional group present in the compound
• Main constituent of natural gas is methane, CH4
• Petroleum is a complex mixture of hydrocarbons, also known as crude oil, found under porous rock
• The boiling point and viscosity of each fraction increase as the carbon chain gets longer
• Propan-1-ol

  • Alcohol with an -OH functional group located on the first carbon atom
• Colour


  As carbon chain length increases, the colour of the liquid gets darker as it gets thicker and more viscous
• Methane is an alkane and is the major component of natural gas
• Uses of Fractions

  • Refinery gas: heating and cooking
  • Gasoline: fuel for cars (petrol)
  • Naphtha: raw product for producing chemicals
  • Kerosene: for making jet fuel
  • Diesel: fuel for diesel engines
  • Fuel oil: fuel for ships and for home heating
  • Lubricating oil: for lubricants, polishes, waxes
  • Bitumen: for surfacing roads
• Volatility


  • Refers to the tendency of a substance to vaporize
  • With increasing molecular size, hydrocarbon liquids become less volatile
  • Attraction between molecules increases with increasing molecular size