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Urgent chemistry help needed

In Hnmr, when the question asks us for the splitting pattern of the adjacent carbons, how do we know which adjacent carbon to look at when there are more than two carbons in the molecule??????????

For example in CH3CH2CH2CH3

if it asks us for the splitting pattern of the CH2 carbon, how do we know which carbon to look at, is it a triplet or quartet??

Please help
Original post by s.aureus
In Hnmr, when the question asks us for the splitting pattern of the adjacent carbons, how do we know which adjacent carbon to look at when there are more than two carbons in the molecule??????????

For example in CH3CH2CH2CH3

if it asks us for the splitting pattern of the CH2 carbon, how do we know which carbon to look at, is it a triplet or quartet??

Please help


You have to look at all of the adjacent hydrogen atoms. Only non-equivalent hydrogens can split.

In the example above there are two environments only, CH3CH2, the next CH2 is identical to the first and the next CH3 is identical to the first.

So you have a triplet and a quartet, whse intensities (integrals) are in the ratio of 3 to 2
Reply 2
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Original post by charco
You have to look at all of the adjacent hydrogen atoms. Only non-equivalent hydrogens can split.

In the example above there are two environments only, CH3CH2, the next CH2 is identical to the first and the next CH3 is identical to the first.

So you have a triplet and a quartet, whse intensities (integrals) are in the ratio of 3 to 2


Okay thanks, but what if they ask for example, what is the splitting pattern of CH2, from CH3CH2CH2CH3, then is it a triplet or a quartet?? This what i mean when i say which adjacent carbon do we look at
Original post by s.aureus
Okay thanks, but what if they ask for example, what is the splitting pattern of CH2, from CH3CH2CH2CH3, then is it a triplet or a quartet?? This what i mean when i say which adjacent carbon do we look at

You look at both, but the CH2 is equivalent, and therefore doesn't affect it, therefore the CH3 changes the CH2 into a quartet.
Reply 4
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Original post by charco
You look at both, but the CH2 is equivalent, and therefore doesn't affect it, therefore the CH3 changes the CH2 into a quartet.

So your saying if there are the same CH groups next to each other, so the CH2CH2, then it won't split ?? For example does ethane, CH3CH3, not have a splitting pattern because CH3s are equivalent??
Original post by s.aureus
So your saying if there are the same CH groups next to each other, so the CH2CH2, then it won't split ?? For example does ethane, CH3CH3, not have a splitting pattern because CH3s are equivalent??


Correct :smile:
Equivalent protons cannot split one another.

Ethane has one singlet.

ethane_nmr.jpg
Reply 6
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Original post by charco
Correct :smile:
Equivalent protons cannot split one another.

Ethane has one singlet.

ethane_nmr.jpg


Hi okay, sorry im confused again, i get this but if you apply this to CH3CH2CH2CH3, shouldn't you have one quartet and one singlet then? Because CH2CH2 are equivalent and can't split each other
Original post by s.aureus
Hi okay, sorry im confused again, i get this but if you apply this to CH3CH2CH2CH3, shouldn't you have one quartet and one singlet then? Because CH2CH2 are equivalent and can't split each other

The CH2 protons get split into a quartet by the adjacent CH3 protons
Reply 8
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Original post by charco
The CH2 protons get split into a quartet by the adjacent CH3 protons

Riiiiiiiight okay, in your first explanation you said there's triplet and quartet in the ratio of 3:2, I understand where the two is from as there are two quartets from both CH2s, but where did the three on the triplets come from??, as there are only 2 CH3, and you said the CH2 wont initiate a split as it is equivalent
Original post by s.aureus
Riiiiiiiight okay, in your first explanation you said there's triplet and quartet in the ratio of 3:2, I understand where the two is from as there are two quartets from both CH2s, but where did the three on the triplets come from??, as there are only 2 CH3, and you said the CH2 wont initiate a split as it is equivalent


CH3 has three hydrogen atoms - this is where the three comes from
It is split into a triplet by the adjacent CH2 hydrogen atoms (n+1 rule)

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