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# Hnmr Help Please :) Watch

1. "compound E is an ester with molecular formula C4H802, it has a quartet at ? = 2.3 ppm. "

ppm at 2.3 is R-CO-CH

Now.. the answer it gave in the mark scheme is CH3CH2COOCH3 where as i got CH3C00CH2CH3...
I put it as that as to have a quartet using rule n+1 the carbon bonded to the double bonded C-O elements would need 3 hydrogens..

Sorry for the bad explanation, i expect to be wrong as this was a aqa mark scheme not just internet so any help on where im going wrong would be great. Thankyou
2. you got the right answer. yours is just flipped over
3. I dont think i have as the CH3 on their answer is bonded to an oxygen, so it wouldnt split the hnmr value would it?
..For example.. mine is ch3 bonded directly to the c=o compound.. where as theirs is bonded to an oxygen which is then bonded to the c=o compound.. if you get what im trying to say?
4. if the hydrogens at 2.3 ppm are quartets, they must be the hydrogens in the ch2 part of the molecule. this is because the carbon atom adjacent to the the ch2 cabon, has 3 hydrogens attached to it. so using the n+1 rule, the 2 carbons from the ch2 must be quartets. there are two of them so the peak area will be 2.
5. (Original post by LukeNunn)
I dont think i have as the CH3 on their answer is bonded to an oxygen, so it wouldnt split the hnmr value would it?
..For example.. mine is ch3 bonded directly to the c=o compound.. where as theirs is bonded to an oxygen which is then bonded to the c=o compound.. if you get what im trying to say?
yeah... i can see that now
6. Thankyou! Reated + :P
7. the hydrogens that are represented as quartets at 2.3 ppm are the ch2 hydrogens. these hydrogens have to be joined to the carbon that is directly attached to the c=o carbon. if the answer was the structure that you gave, the hydrogens at 2.3 ppm would be singlets, as the carbon they are joined to would be directly attached to the c=o carbon (using the n+1 rule, you're ch3 carbons would be attached to c=o which has no hydrogens, so the ch3 hydrogens would be singlets). so the alcohol group in the ester must be methyl, while the carboxylic acid group mast be ethanoate.

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Updated: December 18, 2010
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