Unsaturated Ester

[ggxoxo]

[I've simplified the qn]

The question gave C6H11COOCH3 and said it did not decolourised Bromine soln.

Then it asked if it was an unsaturated ester and since the CnH2n-1 rule applied I said yes.

But the answer said no because they said it is a cyclic ester because it did not react with Bromine.

Does that mean that the above rule is limited in esters; or is the answer wrong?

[Hellrocks]

Unsaturation should account for rings and double bonds though

[ggxoxo]

Hey are benzene rings not considered unsaturated is because its double bonds are unreactive? And how does the fact that its double bonds are conjugated/it is aromatic allows it not to react with Bromine?

[Fishyiscool]

Then it asked if it was an unsaturated ester and since the CnH2n-1 rule applied I said yes.

Can someone please explain the CnH2n-1 rule? Our textbook never said anything about that... D:

[bentennason]

^Same lol

[ggxoxo]

So normally you start with CnH2n+1 for saturated carboxylic acids; you can test this by drawing saturated molecules like ethanoic acid CH3COOH has C2H2(2)-1

But we know that a double bond removes 2 Hydrogens so if you have 2n+1 initially you remove 2 Hydrogens and so you get H2n+1-2--> H2n-1

So for every double bond you remove 2 Hydrogens

[Mao]

Hey are benzene rings not considered unsaturated is because its double bonds are unreactive? And how does the fact that its double bonds are conjugated/it is aromatic allows it not to react with Bromine?

Benzene is unsaturated.

The conjugated double bonds mean electrons are delocalised in the ring, and does not undergo the typical addition reaction because its double bonds don't 'break open'. It in fact doesn't have any double bonds, all the electrons are in the ring.

That's not to say it cannot react with Bromine, it just doesn't do so at room temperature.

[LukeHigham]

To correct a misconception:

Benzene rings are unsaturated. Cyclohexane would be its saturated derivative.

But benzene is less reactive than an alkene such as ethene due to its stability gained via resonance.

Benzene does not undergo addition readily. It undergoes substitution reactions more readily than addition.