CNMR problem!

[utdent20]

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Ok So i have a problem and wanted to to share it with you all so solving for the CNMR?
on
CH3CH2-C=OCH2CH2CH3... what is the answer , number the carbons from left being # 1.
I got # 1= quartet. # 2=Triplet, # 3 zero or one??? #4 Triplet, #5 triplet, #6 Quartet??
What do you all think share your views?

 

[Maygyver]

Do you mean HNMR? I didn't think that CNMR showed splits? I thought it just showed the number of carbons/symmetry.

 

[utdent20]

i dont' know i am tyring to figure it out myself.. so if its shows Carbon/symmetry how does that work on this problem??I don't know how to get started on that

 

[Maygyver]

i dont' know i am tyring to figure it out myself.. so if its shows Carbon/symmetry how does that work on this problem??I don't know how to get started on that

Can you give me the exact problem?

 

[anesthesia_209]

C-NMR doesn't show mulitplicity. It only shows the number of chemically distinct carbons on the molecule.

 

[Isradoc1983]

here is a website that can help you out
http://arrhenius.rider.edu/nmr/nmr_tutor/selftests/problems_fs_start.html

it has different C13 NMR problems. Also, I thought about C13 as you did cause I read Kaplan, but I guess it just shows the distinct carbons.

 

[utdent20]

maguyver..the problem is posted a top..

 

[utdent20]

isodoc..what kind of question can be shown ont he DAT>. about c-13..like a graph given and identify the carbons with their ranges.? that website sorta helped but also confused me.

 

[Isradoc1983]

I didn't take the DAT yet, but the most they can ask as I see it is how many distinct C signals you're going to have from a certain mol' or which one will be upfield/downfield . I never studied CNMR in College and was confused by Kaplan explanation about it, but overall it's similar to 1H NMR. I think there is one version of the DAT that has about 5 questions on IR, 1H NMR, and CNMR which is ridicolous cause its 2 much 🙂 so I am memorizing IR and 1H NMR groups.

 

[Albuterol]

I understand HNMR...CNMR is simimlar except you are counting how many distinct C there are on the molecule right?

And also can someone explain what symmetry does to the HNMR and CNMR signals?
CH3-CO-CH3 for example.

 

[Isradoc1983]

I understand HNMR...CNMR is simimlar except you are counting how many distinct C there are on the molecule right?

And also can someone explain what symmetry does to the HNMR and CNMR signals?
CH3-CO-CH3 for example.

For 1H NMR there will be only one peak representing CH3 and it'll be shifted to the left because of the C=O
for CNMR you'll have 2 picks 1 would come from the 2 * CH3 and one from C=O. The peak from C=O will be more to the left because of the O.

Hope it helps

 

[Albuterol]

thanks for clarifying man

 

[utdent20]

how do we know when its going to the left or right.. as in upfield and downfield? and also isradoc.why would there be only 2 peaks.. if we are counting the carbons wouldnt we have 3 peaks. 2 from CH3 and one from C=0?

 

[Isradoc1983]

well we know if it goes upfield/ downfield by how close it is to O, N, Cl etc....
so the closer it is the more it'll shift to the left (downfield) and the farther it is the more it'll be upfield ( to the right)
There are only 2 peaks for acetone because the two CH3 are in similar "environment" and will produce one big pick i.e if you'll have CH3CH2C=OCH2 CH3 you'll have 3 distinct peaks 1 from 2*CH3 ;1 from 2*CH2; and one from C=O; also notice the the peaks from CH2 will be more downfield cause they are closer to the carbonyl group
here is a link to the full spectrum of acetone
http://www.muhlenberg.edu/depts/chemistry/chem201woh/13Cacetone.htm
the big peak on the right is from the two CH3
hope it helps

 

[Maygyver]

maguyver..the problem is posted a top..

...just count the number of unique carbons then... You didn't post a question, just a formula.

 

[Maygyver]

how do we know when its going to the left or right.. as in upfield and downfield? and also isradoc.why would there be only 2 peaks.. if we are counting the carbons wouldnt we have 3 peaks. 2 from CH3 and one from C=0?

I thought he explained it well but, as repeated, CNMR only shows the number of unique carbons. Try the question you posted and I'll tell you what I got. How many peaks would your compound have?