[vande060]

In the NMR spectra of ethyl iodide, the peaks for methyl hydrogens appear at 1.9 ppm and the peaks for methylene hydrogens appear at 3.2 ppm with j= 8 Hz the number of peaks given by the methyl hydrogen is __a__ with the approx area ratio __b__. These peaks are separated by__c__ Hz. The number of peaks given by the methylene group is __d__ with the approx ratio__e__ . These peaks are separated by__f__ Hz. The ratio of the total area of the methyl peaks is __g__. Of these two groups of peaks, the __h__ peaks are further down field. The chemical shift difference between these peaks of 1.3 ppm corresponds in a 60MHz instrument to __i__.

okay:

a 3
b 1:2:1
c. ?
d 4
e 1:3:3:1
f 8Hz
g 3:2
h methylene
i 1.6*60 = 78Hz

are any of this right, do you have suggestions for those that are not right? Thank you for you time.

[MissPhosgene]

To answer C, think about how coupling constants relate sets of protons. When sets of protons are coupled, they ------ a coupling constant.

[AC Prabakar]

I couldn't make clear"area ratio"!!!!
Is it mean the proton count or splitting patter?
If it is about splitting pattern your correct. Other wise pls change to appropriate answer.
Pls let me know if your not agree with what I said.


Would u like to have the C or do u have the answer with u?

Any way, i just thought of sharing regarding "C"

Case-1:-If the question is about coupling constant then:

Here only 2 sets of protons available.
Let us consider as "a-Set:methyl protons" and "b-Set:methylene proton"

If "a" and "b" are interacting with other to afford splitting, both will show the same extend of interaction which will result in the same value of J (coupling constant).
Case-2:-If the question is about the separation from TMS then:-

For-C:-1.9*60=114
f:-3.2*60=192

I didn't got how u taken 1.6 for "i".I think it should be 1.3 only..
Correct me if i am wrong..

[vande060]

I couldn't make clear"area ratio"!!!!
Is it mean the proton count or splitting patter?
If it is about splitting pattern your correct. Other wise pls change to appropriate answer.
Pls let me know if your not agree with what I said.


Would u like to have the C or do u have the answer with u?

Any way, i just thought of sharing regarding "C"

Case-1:-If the question is about coupling constant then:

Here only 2 sets of protons available.
Let us consider as "a-Set:methyl protons" and "b-Set:methylene proton"

If "a" and "b" are interacting with other to afford splitting, both will show the same extend of interaction which will result in the same value of J (coupling constant).
Case-2:-If the question is about the separation from TMS then:-

For-C:-1.9*60=114
f:-3.2*60=192

I didn't got how u taken 1.6 for "i".I think it should be 1.3 only..
Correct me if i am wrong..

thanks for the reply, both of you

well, i think the question for b and c is asking for the relative area between the peaks for those equivalent hydrogens. and then for g i think it wants the relative area between the two groups of nonequivalent hydrogens. does that sound right?

[vande060]

To answer C, think about how coupling constants relate sets of protons. When sets of protons are coupled, they ------ a coupling constant.

i thought they would share the coupling contant, and that the width between the adjacent peaks of the protons are the same, the only thing that changes is the overall width of the signal(ie a triplet is 3J and a quatet is 4j) that is what it thought, but im not sure at all. the question seems like it is asking what the adjacent peaks are seperated by.

[MissPhosgene]

To answer C, think about how coupling constants relate sets of protons. When sets of protons are coupled, they ------ a coupling constant.

i thought they would share the coupling contant, and that the width between the adjacent peaks of the protons are the same, the only thing that changes is the overall width of the signal(ie a triplet is 3J and a quatet is 4j) that is what it thought, but im not sure at all. the question seems like it is asking what the adjacent peaks are seperated by.

They do share a coupling constant. The J value is determined by finding the distance between both prongs of a doublet (or the distance between prongs of a triplet pitchfork) and doing some multiplication. Since it is a measure of the strength of an . interaction, etc, it's the same for the protons which interact. If you think about it, it doesn't make sense for it to be different for protons which participate in the same interaction.

Triplets actually can't be pitchforks because pitchforks have four prongs, but I think you know what I mean.

[vande060]

They do share a coupling constant. The J value is determined by finding the distance between both prongs of a doublet (or the distance between prongs of a triplet pitchfork) and doing some multiplication. Since it is a measure of the strength of an . interaction, etc, it's the same for the protons which interact. If you think about it, it doesn't make sense for it to be different for protons which participate in the same interaction.

Triplets actually can't be pitchforks because pitchforks have four prongs, but I think you know what I mean.

if i interpret this correctly, then c anf f should both be 8Hz right, since it asks for what the peaks are separated by; and you pointed out the peaks for both groups will be separated by j, because the share a coupling constant

[MissPhosgene]

yup

[vande060]

yup

thanks for all your help, did everything else look fine? i know that letter i should say 1.3*60

[MissPhosgene]

Yeah, everything looks good. i looked like a type-o because 1.6 * 60 = 96