ALKANA

Addition of Accidified potassium manganate (VII), KMnO4

Alkene CnH2n + [O] + H2O (l) CnH2n(OH)2

Represent oxygen atom Diol
derived from KMnO4 Type of Alcohol

Eg : C2H4 (g) + [O] + H2O (g) C2H4(OH)2 (l)

Ethene Oxidising Agent Steam Ethane-1,2-diol
KMnO4

vThe purple colour of KMnO4 solution decolourised immediately to
produce a colourless organic liquid

vAccidified KMnO4 solution can be used to identify the presence of a
C – C double bond in a chemical test

ALKANES AND ALKENES

SIMILARITIES
AND

DIFERENCES

SIMILARITIES Do not conduct electricity
at any state

Insoluble in water but soluble in organic compound

Physical state changes when number of molecules increase

Low densities, increase gradually with increasing number
of carbon atoms per molecule

Low melting and boiling points. When the number of
carbon atoms per molecule increases, both melting and
point increase too.

DIFFERENCES (CHEMICAL PROPERTIES)

Hexane DIFFERENCES Hexene
vSaturated hydrocarbon Test vUnsaturated hydrocarbon
vContains C – C single vContain C – C double

bonds bonds
vUnreactive vReactive

Observation Observation

vBurns with yellow Sootiness of flame vBurns with yellow flame
flame

vNo change Reaction with vBromine decolourised
vBromine slowly Bromine, Br2 rapidly :
1,2-dibromohexane
decolourised in (In darkness: produced
sunlight Shake bromine
solution with vAccidified KMnO4
vNo change alkane/alkene decolourised rapidly :
vHexane does not react Hexane-1,2-diol formed
Reaction with
with accidified KMnO4 Accidified KMnO4

(ADD + SHAKE)