1. Make as many structures as you can from the molecular formula C5H12
Structural Isomerism
L.O. To be able to recognise structural isomerism.
To be able to assign the type of structural isomerism to an organic compound
Make as many structures as you can from the molecular formula C5H12
Now make as many structures as you can from the molecular formula C3H8O

2. ISOMERS EMPIRICAL FORMULA from % by mass composition
(Simplest ratio of atoms)
eg 24.2% C ; 4.0%H ; 71.8% Cl
 CH2Cl
MOLECULAR FORMULA
using empirical formula & Mr from mass spectrometer
(Actual number of atoms)
eg Mr = 99
 C2H4Cl2 Cl H Cl H
STRUCTURAL FORMULAS C C or
(Shows bonding of individual atoms)
ISOMERS
Molecules with SAME MOLECULAR FORMULA but DIFFERENT STRUCTURAL FORMULAS

3. ISOMERS STRUCTURAL ISOMERS STEREOISOMERS
= molecules with the same molecular formula but different bonding patterns of atoms
= isomers resulting from different spacial arrangements of same atoms in the same structural formula

4. FUNCTIONAL GROUP ISOMERS
STRUCTURAL ISOMERS
CHAIN ISOMERS
POSITIONAL ISOMERS
FUNCTIONAL GROUP ISOMERS
Isomers caused by different arrangements of the CARBON atoms to form straight or branched chains.
Isomers caused by different POSITIONS of the SAME functional groups
Isomers caused by different functional groups.

5. Chain Isomers C C Butane Methyl propane C C C Methyl butane Pentane
Dimethyl
propane

6. Positional isomers C Br OH 1-bromopropane 2-bromopropane Pentan-3-ol

7. Functional group isomers
1. Aldehydes and ketones
CH3CH2CH2CHO
CH3COCH2CH3
Butanal
Butan-2-one
2. Acids and esters
CH3CH2CH2COOH
CH3COOCH2CH3
Butanoic acid
Ethyl ethanoate
HCOOCH2CH2CH3
Propyl methanoate
CH3CH2COOCH3
Methyl propanoate