This is Part 2 of the long series of Berry Berry Easy essential and concise notes for SPM Chemistry (Form 5) topic on Carbon Compounds. In case you miss out, the previous notes focused on definitions on the types of compounds, hydrocarbons, combustions (with equation), homologous series (which you should already memorise by now) and sources of hydrocarbon. We hope you have taken the baby step to master the aforementioned parts.
So let us hop straight into the very important topic of IUPAC naming convention. This will be something you will not regret learning, as you will use this not only in Form 5, but also in Form 6, foundations, A-levels, degree, masters and up to PhD level. (No exaggeration as we do personally know of PhD level candidates learning and relearning IUPAC naming convention from scratch). Besides that you can also look at the trends of properties in a series. Also, not forgetting halogenation. This will be a rather difficult topic to master but worth every effort to do so.
SPM Chemistry Form 5 – Terminology and Concepts: Carbon Compounds (Part 2)
A) IUPAC (International Union of Pure and Applied Chemistry) – is used to name organic compound.
Organic compound is divided into three portions which is Prefix + Root + Suffix.
- Prefix – name of the branch or side chain.
General formula: CnH2n+1 –Where n = 1, 2, 3, … (n = number of carbon)
Formula Branch or name of group CH3 - methyl C2H5 - ethyl C3H7 - propyl C4H9 - butyl C5H11 - pentyl
Alkyl group signifies that it is not part of the main chain.
Two or more types of branches are present, name them in alphabetical order.
Number of side chain Prefix 2 Di- 3 Tri- 4 Tetra- 5 Penta- 6 Hexa-
More than one side chains are present, prefixes are used.
- Root – the parent hydrocarbon (denotes the longest carbon chain).
Number of carbon atoms Root name 1 meth- 2 eth- 3 prop- 4 but- 5 pent- 6 hex- 7 hept- 8 oct- 9 nan- 10 dec-
- The longest continuous (straight chain) carbon chain is selected.
- Identify the number of carbon.
- Suffix – functional group.
Homologous series Functional group Suffix Alkane - C – C - -ane Alkene - C = C - -ene Alcohol – OH -ol Carboxylic acid – COOH -oic Ester – COO – -oate
Prefix + Root + Suffix
B) Family of Hydrocarbon – Alkane
1. General formula: CnH2n+2
Where n = 1, 2, 3, … (n = number of carbon)
2. Each carbon atom in alkanes is bonded to four other atoms by single covalent bonds.
Alkanes are saturated hydrocarbon.
|Name of alkane||Molecular formula of alkane|
Molecular formula is a chemical formula that shows the actual number of atoms of each type of elements
present in a molecule of the compound.
Example: molecular formula of butane is C4H2´4+2 = C4H10
|Name||Condensed structural formula of alkane|
Structural formula is a chemical formula that shows the atoms of elements are bonded (arrangement of atoms) together in a molecule by what types of bond.
3. Physical properties of alkanes
|Name||Molecularformula||RMM||Density(g cm-3)||Physical state at 25°C|
Alkanes with more than 17 carbon atoms are solid.
- Solubility in water – all members in alkanes are insoluble in water but soluble in many organic solvent (benzene and ether).
- Density of alkane – the density of water is higher than density of alkane.
When going down the series, relative molecular mass of alkanes is higher due to the higher force of attraction between molecules and alkane molecules are packed closer together.
- Electrical conductivity – all members in alkanes do not conduct electricity.
Alkanes are covalent compounds and do not contain freely moving ions.
- Boiling and melting points – all alkanes in general have low boiling points and melting points.
Alkanes are held together by weak intermolecular forces.
4. Chemical properties of alkanes
- Reactivity of alkanes
Alkanes are less reactive (saturated hydrocarbon).
Alkanes have strong carbon-carbon (C – C) bonds and carbon-hydrogen (C – H) bonds.
All are single bonds which require a lot of energy to break.
Alkanes do not react with chemicals such as oxidizing agents, reducing agents, acids and alkalis.
- Combustion of alkanes
Complete combustion of hydrocarbons
CxHy + (x + y/4) O2 –> xCO2 + y/2 H2O
CH4 + 2O2 –> CO2 + 2H2OIncomplete combustion
occurs when insufficient supply of oxygen
CH4 + O2 –> C + H2O
2CH4 + 3O2 –> 2CO + 4H2O
- Substitution reaction of alkanes (Halogenation)
Substitution reaction is one atom (or a group of atoms) in a molecule is replaced by another atom (or a group of atoms).
Substitution reaction of alkanes take place in ultraviolet light.
Alkanes react with bromine vapour (or chlorine) in the presence of UV light.
CH4 + Cl2 –> HCl + CH3Cl (Chloromethane)
CH3Cl + Cl2 –> HCl + CH2Cl2 (Dichloromethane)
CH2Cl2 + Cl2 –> HCl + CHCl3 (Trichloromethane)
CHCl3 + Cl2 –> HCl + CCl4 (Tetrachloromethane)
The rate of reaction between bromine and alkanes is slower than the rate of reaction between chlorine and alkanes.