chemistry
Appendix
APPENDIX
1
Chemical tests for functional groups
Homologous series/
Typical compound
Functional group(s) Alkanes
CH3CH3
ethane
C – C and
C–H
Alkenes
CH2 = CH2 ethene C=C
Chemical tests/Observations
Add liquid bromine in ultraviolet light (or sunlight):
White fumes of HBr liberated; decolourisation of bromine occurs slowly
(a) Add Br2 in CCl4 at room temperature:
Decolourisation of bromine occurs immediately
CH2 = CH2 + Br2 → CH2BrCH2Br
(b) Add acidified KMnO4 at room temperature:
Decolourisation of KMnO4 occurs immediately
CH2 = CH2 + [O] + H2O → CH2 – CH2
⏐
⏐
OH OH
(a) Insert a glowing splint into the hydrocarbon hydrocarbons: Burns with smoky flame
Aromatic hydrocarbons (b) Add concentrated nitric(v) acid and concentrated sulphuric acid at 55 °C:
Yellow oil with bitter almond smell produced
benzene
NO2
+ HNO3 (HONO2)
Alkylbenzenes
– CH3
CH3
+ H2O
Add alkaline KMnO4 and boil:
Decolourisation of KMnO4; brown precipitate of MnO2 formed ⎯ CH3 + 3[O]
methylbenzene
H2SO4
⎯ COOH + H2O
Comment Oxidation of the side chain is more effective in alkaline than acidic conditions.
Haloalkanes
R–X where R is an alkyl group; X is Cl, Br or I
C–X
Add silver nitrate in alcohol and warm:
White precipitate for C – Cl group; cream-coloured precipitate for C – Br group; yellow precipitate for C – I group Alcohols
CH3CH2OH
ethanol
– OH
(a) Add solid PCl5:
White fumes of HCl liberated
C2H5OH + PCl5 → C2H5Cl + POCl3 + HCl(g)
(b) Add glacial ethanoic acid and a few drops of concentrated sulphuric acid and heat:
Fragrant fruity smell of ester liberated
CH3COOH + C2H5OH → CH3COOC2H5 + H2O
Appendix
Ace Ahead Chem (Appendix) 3rd (11/11/08).indd 1
1
11/13/08 12:36:33 PM
Homologous series/
Typical compound
Aldehydes
CH3CHO ethanal Functional group(s) H
⏐
–C=O
Chemical tests/Observations
(a) Add 2,4-dinitrophenylhydrazine at room
APPENDIX
1
Chemical tests for functional groups
Homologous series/
Typical compound
Functional group(s) Alkanes
CH3CH3
ethane
C – C and
C–H
Alkenes
CH2 = CH2 ethene C=C
Chemical tests/Observations
Add liquid bromine in ultraviolet light (or sunlight):
White fumes of HBr liberated; decolourisation of bromine occurs slowly
(a) Add Br2 in CCl4 at room temperature:
Decolourisation of bromine occurs immediately
CH2 = CH2 + Br2 → CH2BrCH2Br
(b) Add acidified KMnO4 at room temperature:
Decolourisation of KMnO4 occurs immediately
CH2 = CH2 + [O] + H2O → CH2 – CH2
⏐
⏐
OH OH
(a) Insert a glowing splint into the hydrocarbon hydrocarbons: Burns with smoky flame
Aromatic hydrocarbons (b) Add concentrated nitric(v) acid and concentrated sulphuric acid at 55 °C:
Yellow oil with bitter almond smell produced
benzene
NO2
+ HNO3 (HONO2)
Alkylbenzenes
– CH3
CH3
+ H2O
Add alkaline KMnO4 and boil:
Decolourisation of KMnO4; brown precipitate of MnO2 formed ⎯ CH3 + 3[O]
methylbenzene
H2SO4
⎯ COOH + H2O
Comment Oxidation of the side chain is more effective in alkaline than acidic conditions.
Haloalkanes
R–X where R is an alkyl group; X is Cl, Br or I
C–X
Add silver nitrate in alcohol and warm:
White precipitate for C – Cl group; cream-coloured precipitate for C – Br group; yellow precipitate for C – I group Alcohols
CH3CH2OH
ethanol
– OH
(a) Add solid PCl5:
White fumes of HCl liberated
C2H5OH + PCl5 → C2H5Cl + POCl3 + HCl(g)
(b) Add glacial ethanoic acid and a few drops of concentrated sulphuric acid and heat:
Fragrant fruity smell of ester liberated
CH3COOH + C2H5OH → CH3COOC2H5 + H2O
Appendix
Ace Ahead Chem (Appendix) 3rd (11/11/08).indd 1
1
11/13/08 12:36:33 PM
Homologous series/
Typical compound
Aldehydes
CH3CHO ethanal Functional group(s) H
⏐
–C=O
Chemical tests/Observations
(a) Add 2,4-dinitrophenylhydrazine at room