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Splitting pattern nmr

by katiecool
Tags: pattern, splitting
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katiecool
#1
Jul1-14, 02:12 PM
P: 4
I am struggling to understand how to determine splitting patterns for molecules. For example, (see attached) I was trying to determine the splitting pattern for CH2 in the molecule. On the right i believe n is equal to 1 and on the right it is equal to 3, but i am not sure if this is correct. A doublet quartet doesn't make any sense to me and that is what i seem to conclude. The addition of the OH is really throwing me off. Also, on top of that how would i begin to determine which is farthest down field! Any help would be great!
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Greg Bernhardt
#2
Jul8-14, 10:40 PM
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I'm sorry you are not generating any responses at the moment. Is there any additional information you can share with us? Any new findings?
katiecool
#3
Jul9-14, 02:31 PM
P: 4
I think that i am miss understanding how to determine which are equivalent hydrogen's. Equivalent hydrogen's act as a group. On both CH3's all the hydrogen's are equivalent. so "n" for both CH3's are equal to one. Thus i think it may be n=4 and n+1=5 so the splitting pattern would be a pentet? Can confirm that i am right?

sjb-2812
#4
Jul10-14, 01:57 AM
P: 427
Splitting pattern nmr

You were more right the first time. It may be that the J values are similar so it looks like a quintet, but this is just a resolution thing. As to which is more downfield, what kind of groups have downfield resonances in general?
katiecool
#5
Jul10-14, 12:40 PM
P: 4
I agree, but what i wrote the first time is something i learned outside of my notes. A pentet was something in my notes. So a pentet is possible? and i think that it would be the the part of the molecule with the fewest hydrogens.....so CH i think would be the farthest downfield?
sjb-2812
#6
Jul12-14, 02:59 AM
P: 427
A quintet would be more possible if you were only coupling to a nucleus with spin I=2, it's certainly not impossible.

I agree that the CH would be the most down field, but not because it has the fewest hydrogens. The CH in terminal alkynes for instance resonates at about δ3-4 from memory. Look into the electronic environment of the protons. I can see a similar thread on chemicalforums.com; it may be worth looking there too.


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