[RoadWarrior]

How many signals does CH3CH2COOCH2CH3 have?

I think it is 2 or 3.. is the two -CH2 groups the same signal or different ones, because one -CH2 is bonded to a carbon and one to an oxygen.

[=gabriel=]

Originally Posted by RoadWarrior

How many signals does CH3CH2COOCH2CH3 have?

I think it is 2 or 3.. is the two -CH2 groups the same signal or different ones, because one -CH2 is bonded to a carbon and one to an oxygen.

Are we talking carbon or hydrogen NMR?

[RoadWarrior]

Originally Posted by =gabriel=

Are we talking carbon or hydrogen NMR?

Hydrogen.

[=gabriel=]

OK then just consider: What makes the hydrogen magnetic environments different? Are the hydrogens in this molecule same or different? I think you'll find there will be 4 signals, but think about it before writing it down

[boromir9111]

It's 2 peaks it will have, one for -CH3 and one for -CH2 with the relative peak areas of 3 and 2 with a total of 5 because of the different hydrogen's added up.

[Sanjetti]

This is ethyl ethanoate right? Surely it would have 4 peaks with relative abundance of 32:2?

Edit: Didn't realise it was you, RW

[=gabriel=]

Originally Posted by boromir9111

It's 2 peaks it will have, one for -CH3 and one for -CH2 with the relative peak areas of 3 and 2 with a total of 5 because of the different hydrogen's added up.

Sorry, but no.

[tullybow]

Mate, I would say you are looking at 4 peaks here...the protons are all in different environments. You have to look at not what only the H atom is connected to but also the next atom connected to that (if that makes sense!)

[boromir9111]

Originally Posted by =gabriel=

Sorry, but no.

I think it is because this is a question from an OCR exam paper and i did it a couple of days ago and the answer is 2 speaks straight from the mark scheme. That was for HNMR of course and if this is for that and then it has to be 2 peaks.

[tullybow]

If you need some more guidance, then message me (Just completed a Chem masters so should be able to, or at least try, to give you some insight :-) )

[RoadWarrior]

Originally Posted by =gabriel=

OK then just consider: What makes the hydrogen magnetic environments different? Are the hydrogens in this molecule same or different? I think you'll find there will be 4 signals, but think about it before writing it down

ah ok.. I've done all of it wrong then thanks

[Achilles99]

Boromir- that was probably the similar ether, this is an ester, draw it out if you still cant see it :P

[RoadWarrior]

Originally Posted by Sanjetti

This is ethyl ethanoate right? Surely it would have 4 peaks with relative abundance of 32:2?

Edit: Didn't realise it was you, RW

hehe Thanks for that

[=gabriel=]

Originally Posted by boromir9111

I think it is because this is a question from an OCR exam paper and i did it a couple of days ago and the answer is 2 speaks straight from the mark scheme. That was for HNMR of course and if this is for that and then it has to be 2 peaks.

I think you should check that mark scheme again. This is ethyl propionate and if you measure it's 1H NMR spectrum you'll get 4 peaks, simple as that. Even at A-level you'd be expected to recognise that the ethyls are not equivalent

[Achilles99]

They are significantly different, its hardly a complicated aspect!

[boromir9111]

Originally Posted by tullybow

aaa, if you got 2 then this is technically incorrect, but for A/S level or whatever they be overlooking some of the more complicated aspects of the NMR (inductive effect etc.) You could argue 2 peaks if if you were to ignore this.

Personally i thought it would be one because both of them are in the same environment but the mark scheme says 2 and i understand why they say that or at least i understand because the -CH2 is in different places.

[=gabriel=]

Originally Posted by tullybow

aaa, if you got 2 then this is technically incorrect, but for A/S level or whatever they be overlooking some of the more complicated aspects of the NMR (inductive effect etc.) You could argue 2 peaks if if you were to ignore this.

I've done A-level too and I'm pretty sure they would want to see 4 as an answer. Ethyl ether would give 2 signals, ethyl propanate gives 4. You don't need to understand inductive effects to see those protons are not the same.

[tullybow]

Mate, I think what they are getting at is you have a CH3 signal and a CH2 signal and then the ester functionality in the middle (withdrawing electron density) - you would get 4 peaks on the spectrum. Why do you think one mate? Got to think about the environment all the time....so if you're lookink at the proton on CH2 has it 'sees' 1 other proton, if CH3 it 'sees' two others - this affects the signal.

[tullybow]

Originally Posted by =gabriel=

I've done A-level too and I'm pretty sure they would want to see 4 as an answer. Ethyl ether would give 2 signals, ethyl propanate gives 4. You don't need to understand inductive effects to see those protons are not the same.

It was actually a First class Masters degree in Chem mate... the point is although 4 is the correct answer in practice different exam boards teach different things (sometimes these are not always correct). so to clarify...the answer is 4 but the the examiners may be marking from a scheme which sees the ester functionality as a unit rather than oxygen atoms in two different environments.

[EierVonSatan]

I've seen OCR give quite nasty NMR questions in the past...I would go with the 'real' answer of four peaks to be honest.