This is literally driving me crazy (1 Viewer)

[Cleverusername5321]

My teacher told us that toluene is not an alkene because it's not actually double bonds that occur in it. We tested this by adding bromine water to toluene, which did not discolour it, which would seem to suggest that it indeed does not have double bonds. My teacher also showed our class an image of the bonds that actually occur, but I forgot the name. Anyone know the name of these bonds?

 

[enigma_1]

Sorry I don't get what you mean. Can you perhaps explain in a different way?

 

[Cleverusername5321]

Sorry I don't get what you mean. Can you perhaps explain in a different way?

Those are not double bonds but they are called something else. My teacher tells me that it's drawn as double bonds for convenience. I want to know what they are actually called.

 

[enigma_1]

Those are not double bonds but they are called something else. My teacher tells me that it's drawn as double bonds for convenience. I want to know what they are actually called.

Oh ok yeah, above harrypotterfan got it, it's benzene ring where there are 3 double bonds which keep shifting around.

 

[Fizzy_Cyst]

Did your teacher use the term resonating or sp2 hybridised (hopefully not that latter, cuz you really need Molecular Orbital Theory) to explain that

 

[Cleverusername5321]

Did your teacher use the term resonating or sp2 hybridised (hopefully not that latter, cuz you really need Molecular Orbital Theory) to explain that

Maybe resonating, I'm not sure. It was the first HSC experiment. It had something to do with overlapping.

I think it has something to do with this.

Is it sigma bonds?

 

[Fizzy_Cyst]

Ur probs thinking Pi bonds, not sigma

 

[Cleverusername5321]

Ur probs thinking Pi bonds, not sigma

So is that what they're actually called?

 

[Fizzy_Cyst]

Pi and Sigma are two different types of bonds. Sigma bonds are much stronger.
In benzene, the resonance is due to delocalised Pi electrons.

 

[LizzyGrant]

The benzene ring has resonance, they are not actual double bonds. Anyway, not really needed for the HSC I believe.

 

[screwuhsc]

dw about it use other egs

 

[someth1ng]

It's beyond the syllabus - the same thing occurs for all carbon rings based on benzene. Basically, what actually happens is that the double bonds you see in the structure, the electron pair that makes the double bond can be passed on to the adjacent single bond. What you actually see is a structure that is the mix of both extremes - each bond is about 1.5x the strength of a single bond. They are NOT jumping between the two structures, the actual structure is in between both structures.

Anyway, the point is all bonds between the members of the ring are identical, not double bonds. We call this resonance.