organic chemistry question

[ttran01]

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i had a few questions i am confused on from my practice test.

1. A hydrogen with 6 neighbors is split into 7 peaks. (a) what is the ratio of peak heights for each of the 7 peaks? (b) explain why the 7 peaks are not all of equal heights.

- for (a), i know to find the ratio you can use pascals triangle to figure out the ratio but for (b) im not sure how the peaks are different, the only thing i know is that it has to do with the alpha and beta but not sure how.

2. Saccharin has the molecular formula C7H5O3NS. What is the SODAR (degree of unsaturation) value for this artificial sweetener?
- i know theres an equation ( (2n + 2) - (#H +#Halogens - #N) ) / 2, but does the "S" affect the calculation in any way?

any help will be appreciated. thanks

 

[117296]

i had a few questions i am confused on from my practice test.

1. A hydrogen with 6 neighbors is split into 7 peaks. (a) what is the ratio of peak heights for each of the 7 peaks? (b) explain why the 7 peaks are not all of equal heights.

- for (a), i know to find the ratio you can use pascals triangle to figure out the ratio but for (b) im not sure how the peaks are different, the only thing i know is that it has to do with the alpha and beta but not sure how.

2. Saccharin has the molecular formula C7H5O3NS. What is the SODAR (degree of unsaturation) value for this artificial sweetener?
- i know theres an equation ( (2n + 2) - (#H +#Halogens - #N) ) / 2, but does the "S" affect the calculation in any way?

any help will be appreciated. thanks

For 1B, the seven peaks are of differing sizes because all of the six neighboring hydrogens may be in differing electromagnetic environments. For example, a hydrogen that is one carbon away will be in a different environment than a hydrogen two carbons away even if they are on the same molecule.

For #2: S is not a halogen, nor is it hydrogen or a nitrogen. I got 5... did you get the same?🙂 Good luck!

 

[gimpsd]

for part a, check out: http://orgchem.colorado.edu/hndbksupport/nmrtheory/splitting.html
the jist of what is said is that any given neighboring proton can be either in a alpha or beta spin state. Depending on which state it is in will cause the splitting pattern being observed. For instance, a hydrogen with two neighboring protons will have a 1:2:1 ratio because the chances of having both neighboring protons in a alpha orientation is 1 while having one in alpha and one in beta is 2 and having both in beta is 1. Not sure if this makes sense but if you look at my explanation and then at the webpage, I'm sure you'll understand it.

for part b:
S if you remember correctly is weird. It has that nasty habit of expanding octet. In this particular case you would add 4. Nitrogen adds one, halogen subtracts one and oxygen does nothing. I'm getting an answer of 8. If you look at the structure of a saccharin, it has a saturation of 8. However, this is not always intuitive because sometimes sulfer behaves like an oxygen so you would do nothing. I think the correct answer for this question was either 6 if you took sulfer to do nothing or 8 if sulfer took on an expanded octet.

 

[117296]

for part a, check out: http://orgchem.colorado.edu/hndbksupport/nmrtheory/splitting.html
the jist of what is said is that any given neighboring proton can be either in a alpha or beta spin state. Depending on which state it is in will cause the splitting pattern being observed. For instance, a hydrogen with two neighboring protons will have a 1:2:1 ratio because the chances of having both neighboring protons in a alpha orientation is 1 while having one in alpha and one in beta is 2 and having both in beta is 1. Not sure if this makes sense but if you look at my explanation and then at the webpage, I'm sure you'll understand it.

for part b:
S if you remember correctly is weird. It has that nasty habit of expanding octet. In this particular case you would add 4. Nitrogen adds one, halogen subtracts one and oxygen does nothing. I'm getting an answer of 8. If you look at the structure of a saccharin, it has a saturation of 8. However, this is not always intuitive because sometimes sulfer behaves like an oxygen so you would do nothing. I think the correct answer for this question was either 6 if you took sulfer to do nothing or 8 if sulfer took on an expanded octet.

you're probably right...my o chem teacher only briefly covered this point, and even looking at my notes, it doesn't seem that clear. Sorry for any confusion😳

 

[aboveliquidice]

for part a, check out: http://orgchem.colorado.edu/hndbksupport/nmrtheory/splitting.html
the jist of what is said is that any given neighboring proton can be either in a alpha or beta spin state. Depending on which state it is in will cause the splitting pattern being observed. For instance, a hydrogen with two neighboring protons will have a 1:2:1 ratio because the chances of having both neighboring protons in a alpha orientation is 1 while having one in alpha and one in beta is 2 and having both in beta is 1. Not sure if this makes sense but if you look at my explanation and then at the webpage, I'm sure you'll understand it.

for part b:
S if you remember correctly is weird. It has that nasty habit of expanding octet. In this particular case you would add 4. Nitrogen adds one, halogen subtracts one and oxygen does nothing. I'm getting an answer of 8. If you look at the structure of a saccharin, it has a saturation of 8. However, this is not always intuitive because sometimes sulfer behaves like an oxygen so you would do nothing. I think the correct answer for this question was either 6 if you took sulfer to do nothing or 8 if sulfer took on an expanded octet.

Sulfur is treated like oxygen when calculating...

 

[gimpsd]

Sulfer is treated like an oxygen but in this case you would have gotten the incorrect unsaturation if you didn't take into account sulfer's ability to expand it's octet.