carbon compound [part 2]

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: C_nH_2n+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: C_nH_2n+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 C₄H_2´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
  C_xH_y + (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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