arenes - question

How would you distinguish between the following pairs of compounds using chemical tests? State observations
i) Cyclohexene and benzene
ii) Cyclohexane and benzene
iii) Buta-1,3-diene and benzene
iv) Methylbenzene and benzene

Thanks in advance

Reply 1

birdth

i)I think with Cyclohexene just add bromine cause it will react but not with benzene as you would need a catalyst.

Don't know about the others sorry!

Reply 2

hungry_hog

iii) Buta-1,3-diene and benzene

bromine water reacts with buta-1,3-diene, changing colour from brown to colourless

no reaction for benzene

Reply 3

Eau

Just a guess for iv) Methylbenzene and benzene

One of the above is more reducing. So you can use potassium permanganate to see the relative colour change?

Reply 4

vinny221

benzene is colourless and methylbenzene is light or pale yellow.

Reply 5

ChemistBoy

vinny221

benzene is colourless and methylbenzene is light or pale yellow.

Not a chemical test, also as far as I am aware toluene (methylbenzene) is colourless too (methyl is not a chromophore). You get benzoic acid upon reaction with potassium permanganate (I do believe that benzene doesn't react at all) so that is a perfectly valid chemical test. You could of course just distill it to see what temperature it comes off at, but again this is not a chemcal test.

Reply 6

Mandoragon

lets see; cyclohexene and benzene;

Reagent

a) Potassium manganate

b) Br(2) / dark

c) Br(2) / AlBr(3)

Benzene
a)no reaction

b)no reaction

c) substitution
Cyclohexene

a) rapid oxidation
b) addition
c) no reaction