Organic Chem question.

What type of reaction is isomerisation? Neither my syllabus states anything about it nor any text book of A level tells that isomerisation is any kind of reaction! But the past papers gives this question and the mark scheme states its answer as C, i.e Isomerisation...

(edited 13 years ago)

Reply 1

EierVonSatan

If two different compounds have the same molecular formula, then they are isomers of each other :smile:

Reply 2

mobius323

Looks to me as if the fluorine on the 1st Carbon has swapped with the chlorine on the 2nd Carbon.

The molecular formula of the molecule will not have changed. The structural formula has. Isomers are molecules with the same molecular formulae but different structural formulae.

Reply 3

SalBhatti

Original post by EierVonSatan

If two different compounds have the same molecular formula, then they are isomers of each other :smile:

Original post by mobius323

Oh, wow. Thanks - I didn't even notice that. Btw isomerisation isn't any TYPE of reaction, right?

Reply 4

shengoc

Original post by Zishi

Oh, wow. Thanks - I didn't even notice that. Btw isomerisation isn't any TYPE of reaction, right?

well bonds are broken and bonds are formed, so i would consider it to be so.

Reply 5

SalBhatti

Original post by shengoc

well bonds are broken and bonds are formed, so i would consider it to be so.

Hmm, thanks. I got it. :yay:

Reply 6

mobius323

Original post by Zishi

Oh, wow. Thanks - I didn't even notice that. Btw isomerisation isn't any TYPE of reaction, right?

(edited 13 years ago)

Reply 7

Maker

Original post by mobius323

It's a tricky one, because (and this is just a hunch, but it makes sense), in the reaction above for example, a C-F bond is broken and a C-Cl bond is broken. Now after that, a C-Cl bond is made in place of the broken C-F bond, and a C-F bond is made in place of the C-Cl bond.

Now, going back to the dreaded Energetics (more precisely, bond enthalpies), you should know that making bonds is exactly as exothermic and breaking bonds is endothermic. This meant that the Enthalpy Change of Reaction would be zero. This would mean total energy in = total energy out.

I'd say it's a reaction, yeah.

I don't think the assumption is neccesaily true. Diffferent groups bonded to a C atom will change the bond energy of other groups attached to the same C atom. For example, the C-H bond energy in choloromethane is different to the C-H bond in methane.

(edited 13 years ago)

Reply 8

mobius323

Original post by Maker

Hmmm, perhaps. If you model each Carbon as a seperate molecule, then I can see what you're talking about. I can see how the polarisation of the Carbon atoms would be different.

Reply 9

butterflyeffect1

As said above, the molecular formula is the same for each compound. They are structural isomers of each other. I don't think the enthalpy change of the reaction will be zero either because the environment of the C-Cl bond in C-Cl3-C and CCl2F-C are different which would effect how the carbon atom attracts electrons and therefore the enthalpy of the bond