Formulae of Organic Compounds
- Organic chemistry is the chemistry of carbon compounds
- Carbon forms a vast number of compounds because it can form strong covalent bonds with itself
- This enables it to form long chains of carbon atoms, and hence an almost infinite variety of carbon compounds are known
- Hydrocarbons are compounds that are made up of carbon and hydrogen atoms ONLY
The diagram shows examples of hydrocarbons
Ethanol is NOT a hydrocarbon as the molecule also contains an oxygen atom and is not solely made up of carbon and hydrogen
- Hydrocarbons can be placed into two categories
- Saturated molecules containing single carbon-carbon bonds only
- Unsaturated molecules containing double or triple carbon-carbon bonds
- The general formula is a formula that represents a homologous series of compounds using letters and numbers
- Eg. the general formula of alkanes is CnH2n+2
- A homologous series is a group of organic compounds that have the same functional group, the same general formula and the same chemical properties
- The structural formula is a formula that shows how the atoms are bonded to each carbon atom in a molecule
- The displayed formula is a 2D representation of an organic molecule showing all its atoms (by their symbols) and their bonds (by single, double or triple bonds)
- The skeletal formula is a simplified displayed formula with all the carbon and hydrogen (C-H) bonds removed
Overview of the Formulae of Organic Compounds Table
Worked example
Drawing skeletal formulae of molecules
Draw the skeletal formula of the following molecules:
- CH3(CH2)3OH
- (CH3)2CHCH2OH
- CH3CH2OCH2CH3
Answer:
Worked example
Drawing displayed formulae of molecules
Draw the displayed formula of the following molecules:
Answer
- The molecular formula shows the number and type of each atom in a molecule
- Eg. the molecular formula of ethanoic acid is C2H4O2
- The empirical formula shows the simplest whole number ratio of the elements present in one molecule of the compound
- Eg. the empirical formula of ethanoic acid is CH2O
Worked example
Deducing molecular & empirical formulae
Deduce the molecular and empirical formula of the following compounds:
Answer