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proton n.m.r help :(

Hi internet,
So I'm taking a2 chemistry and I'm really struggling with proton n.m.r. I'm very confused in particular with question 6 in Jan 2012's paper in aqa.
Basically it says there's this species with 4 singlet peaks. And the chemical formula is C6 H12 O7. In the answers it says that the structural formula is:
CH3C=OCH2-C-(CH3)2 OH
(so the last group has two methyl and one alcohol group attached)
But in the question it said there were only singlets? Why isn't the peak for the CH3 split because I swear the two methyl groups are in the same chemical environment?
Thanks all you lovely people :smile:
So I'm taking a2 chemistry and I'm really struggling with proton n.m.r. I'm very confused in particular with question 6 in Jan 2012's paper in aqa.
Basically it says there's this species with 4 singlet peaks. And the chemical formula is C6 H12 O7. In the answers it says that the structural formula is:
CH3C=OCH2-C-(CH3)2 OH
(so the last group has two methyl and one alcohol group attached)
But in the question it said there were only singlets? Why isn't the peak for the CH3 split because I swear the two methyl groups are in the same chemical environment?
Reply 2
Avatar for shengoc
shengoc
12
Original post by username_username_
So I'm taking a2 chemistry and I'm really struggling with proton n.m.r. I'm very confused in particular with question 6 in Jan 2012's paper in aqa.
Basically it says there's this species with 4 singlet peaks. And the chemical formula is C6 H12 O7. In the answers it says that the structural formula is:
CH3C=OCH2-C-(CH3)2 OH
(so the last group has two methyl and one alcohol group attached)
But in the question it said there were only singlets? Why isn't the peak for the CH3 split because I swear the two methyl groups are in the same chemical environment?


there is not a proton on carbon adjacent to the CH3 group. hence no splitting there. you sure you grasp basic NMR?
Reply 3
Avatar for shengoc
shengoc
12
Original post by username_username_
Hi internet,
So I'm taking a2 chemistry and I'm really struggling with proton n.m.r. I'm very confused in particular with question 6 in Jan 2012's paper in aqa.
Basically it says there's this species with 4 singlet peaks. And the chemical formula is C6 H12 O7. In the answers it says that the structural formula is:
CH3C=OCH2-C-(CH3)2 OH
(so the last group has two methyl and one alcohol group attached)
But in the question it said there were only singlets? Why isn't the peak for the CH3 split because I swear the two methyl groups are in the same chemical environment?
Thanks all you lovely people :smile:


there isnt a proton on the carbon adjacent to that methyl group you mentioned. and yes, that two methyl groups are chemically identical due to free rotation about the single bond. the integral could tell you the ratio of hydrogen in this environment relative to the other protons in other environments

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