SPM Chemistry Form 5 Notes – Terminology and Concepts: Carbon Compounds (Part 2)

by BerryBerryTeacher

in Berry Reference (Notes)

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.

  1. 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.

  2. 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.
  3. 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

    Example: 4-methylhept-2-ene.

    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
Methane CH4
Ethane C2H6
Propane C3H8
Butane C4H10
Pentane C5H12
Hexane C6H14
Heptane C7H16
Octane C8H18
Nonane C9H20
Decane C10H22

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
Methane CH4
Ethane CH3CH3
Propane CH3CH2CH3
Butane CH3CH2CH2CH3
Pentane CH3CH2CH2CH2CH3
Hexane CH3CH2CH2CH2CH2CH3
Heptane CH3CH2CH2CH2CH2CH2CH3
Octane CH3CH2CH2CH2CH2CH2CH2CH3
Nonane CH3CH2CH2CH2CH2CH2CH2CH2CH3
Decane CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

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
Methane CH4 16 - Gas
Ethane C2H6 30 - Gas
Propane C3H8 44 - Gas
Butane C4H10 58 - Gas
Pentane C5H12 72 0.63 Liquid
Hexane C6H14 86 0.66 Liquid
Heptane C7H16 100 0.68 Liquid
Octane C8H18 114 0.70 Liquid
Nonane C9H20 128 0.72 Liquid
Decane C10H22 142 0.73 Liquid

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.
    Example:
    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.

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