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H1 spectra of styrene

Attached i have the h1 nmr spectra of styrene (CH2=CH-C6H5) please can someone classify the peaks according to where they came from in the molecule?

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Reply 1

EierVonSatan

Any ideas yourself? :smile:

Reply 2

bluenicey

Original post by EierVonSatan

Any ideas yourself? :smile:

i think maybe the ch is the doublet as it sees ch2 but what i don't get is why there is a quartet as i cannot see anywhere in the structure where a proton can see 3 hydrogens

Reply 3

gingerbreadman85

look at the structure. The phenyl protons are pretty obvious, which only leaves 3 left to assign. Think about the coupling constants, there are 3 double doublets.

Remember how double bonds effect coupling.

Reply 4

EierVonSatan

Original post by bluenicey

i think maybe the ch is the doublet as it sees ch2 but what i don't get is why there is a quartet as i cannot see anywhere in the structure where a proton can see 3 hydrogens

Is this for A-level? The rules you learn at A-level won't let you explain the splittings here :nah:

Reply 5

gingerbreadman85

Original post by EierVonSatan

Is this for A-level? The rules you learn at A-level won't let you explain the splittings here :nah:

true, you've either got a bastard of a teacher or this is extension work.

I did stuff like this in uni Chem.

Reply 6

charco

Study Forum Helper

Original post by EierVonSatan

Is this for A-level? The rules you learn at A-level won't let you explain the splittings here :nah:

Although you are expected to understand geometric isomerism, so it's not a huge leap to see the non-equivalent environments in an alkene for NMR.

Reply 7

EierVonSatan

Original post by charco

Although you are expected to understand geometric isomerism, so it's not a huge leap to see the non-equivalent environments in an alkene for NMR.

When you only know the n+1 rule it might be, to be honest, especially when you need to start talking about the magnitude of J and some more complicated splittings such as double doublets and such :s-smilie:

Happy to go through it, but just wanted to make sure the OP knows that it's not really A-level material (if they're doing A-level/equivalent).

Reply 8

charco

Study Forum Helper

Original post by EierVonSatan

Happy to go through it, but just wanted to make sure the OP knows that it's not really A-level material (if they're doing A-level/equivalent).

Agreed, the degree of sophistication is beyond A' level, but an A' level student should be able to recognise that the protons are in different environments and likely to produce a more complex splitting pattern.