nmr split questions (singlet, triplet)

[joonkimdds]

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CH3-O-CH2-CH2-O-CH3


The correct answer is singlet and singlet.
But I think answer should be singlet and triplet.

Here is what I did.
The first C from the left has a adjacent atom with H=0 so we add one and it has singlet.

The 2nd C from the left has a adjacent carbon with H=2 so I added one and it should be triplet.

what am I doing wrong?

 

[iwannabadentist]

H H' H' H
| | | |
H-C-O-C'-C'-O-C-H
| | | |
H H' H' H

WOW that took me a while to draw. But count the bonds, if the Hs are more than 3 bonds apart, they won't split each other.
(count for yorself, and they should be 4 bonds apart in this molecule)

 

[joonkimdds]

H H' H' H
| | | |
H-C-O-C'-C'-O-C-H
| | | |
H H' H' H

WOW that took me a while to draw. But count the bonds, if the Hs are more than 3 bonds apart, they won't split each other.
(count for yorself, and they should be 4 bonds apart in this molecule)

I only see 3 bonds apart between H' of 2nd carbon to H' of the 3rd carbon. Maybe I am doing this wrong?
H'
|
C-C
...|
...H'
Above pic, there are 3 bonds between H' to another H'.

 

[doc toothache]

CH3-O-CH2-CH2-O-CH3

The correct answer is singlet and singlet.
But I think answer should be singlet and triplet.

Equivalent hydrogens will not split a signal. The ethylene hydrogens are equivalent and therefore only give a singlet.

http://www.sigmaaldrich.com/catalog...9|FLUKA&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC

 

[joonkimdds]

I got it ~!!!!
http://www.youtube.com/watch?v=UIVzpGUfjDQ
this was a really good video 🙂


By the way, does H in OH also count? and does it also have its own peak?

 

[bigstix808]

I got it ~!!!!
http://www.youtube.com/watch?v=UIVzpGUfjDQ
this was a really good video 🙂


By the way, does H in OH also count? and does it also have its own peak?

be careful and watch for symetry because that can really throw you off

yes, H in O-H will always have its own peak

 

[potbelly]

Equivalent hydrogens will not split a signal. The ethylene hydrogens are equivalent and therefore only give a singlet.

http://www.sigmaaldrich.com/catalog...9|FLUKA&N5=SEARCH_CONCAT_PNO|BRAND_KEY&F=SPEC

Hey,

In butane( CH3-CH2-CH2-CH3 ), don't H on C2 and C3 have the same environment and symmetry as well? How come it's not singlet?

 

[hsia2]

C2 and C3 are the same indeed
However, C1 would split C2 and C4 would split C3
So, you end up with
triplets (C2 splitting C1/ C3 on C4)
and Quadralit (4 peaks, C1 splitting C2, C4 splitting C3)

 

[joonkimdds]

Hey,

In butane( CH3-CH2-CH2-CH3 ), don't H on C2 and C3 have the same environment and symmetry as well? How come it's not singlet?

I guess CH2 doesn't count the other CH2 on his right(due to symmetry) but there are H on the left side which is CH4.

By the way, can someone post an example with OH and how many splits each will have?

For example, in OH-CH2CH2CH2CH3, does H from OH have triplet and will it be at downstream?