double_bond - 18-7-2006 at 04:21
hi
I studied that benzene is an unsaturated compound, but one of my collegue says that it is saturated and it gives a negative test for
unsaturation ie..bromine water test(Bayers test) and oxidation test using KMnO4 . He says that benzene is a saturated hydrocarbon, and benzoic acid
is saturated carboxylic acid? who is right me or my friend? please clear my doubt
Endo - 18-7-2006 at 05:13
Double,
I suggest you just break out your chemistry book and look up aromatic compounds[benzene]. Or, you could just use any of hundreds of tools available
to you and look up its structure. (saturated compounds have no double bonds). I really don't think you need to bother us to find this answer.
Flip - 18-7-2006 at 05:15
Hey there. So of course you are correct, aromacity is considered unsaturation. The biggest thing that could mess some people up when considering
this test on benzene is that aromatic rings are much less reactive than alkenes/ alkynes are. Throw in some free radical and ionic substitutions that
can discharge the bromine color and the casual observer could have a fair probability of a false negative. These aren't what I would use on aromatic
compounds though, a Friedel-Crafts test would work and you'd get to do a nifty reaction.
Nick F - 18-7-2006 at 05:16
It is unsaturated, but aromatic. This aromaticity stabilises the molecule by ~150 kJmol-1, which accounts for fact that benzene does not behave as a
"normal" unsaturated compound.
Nerro - 18-7-2006 at 05:34
As Flip said, when you do a Friedel-Crafts Alkylation (eg. C6H6 + Cl2 -AlCl3-> C6H5Cl + HCl) it could only work if the molecule is unsaturated. And
Hey presto! it works 
Tell your collegue that