question on NMR

[heywhatsup]

am i missing something here? why am i getting this one wrong? HELLPPP

Which of the following compounds will give a single
proton NMR signal?

I. hexane
II. 1, 2-dichloroethane
III. tert-butyl chloride
IV. 2-methyl-2-butene


A. III only
B. II and III
C. II and IV
D. I, II, and II
E. None of the above

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[Jaylee777]

whats given in the key? and what are you getting?

 

[Jaylee777]

oh ok I think I know what they are asking now and why you might be getting this wrong. I think they are asking for which ones give only a single signal (one type of proton) not which one will have a singlet. If this is the case then I believe the answer would be B because all the protons on those molecules are the same and would give the same signal due to overlap, thus producing only a single signal.

 

[Decan]

I agree...B

 

[AaBbZz]

I think that they are asking for singlet because T-Buytl chloride will give a single singlet because there are no adjacent hydrogens to the three methyl groups surrounding the carbon atom, so my answer is A.
Try drawing it out the other NMR's would be:
A: two triplets and a multiplet (however i am not sure on this one)
B: Doublet
C:Singlet
D:Quartlet and doublet

 

[heywhatsup]

I was only getting B, but the answer is B and C. it mentions they all have equivalent protons

 

[AaBbZz]

Yeah if the question is just 1 signal not just 1 signal which is a singlet then the answer is B. But i think I have the right types of signals listed each example. If someone could just confirm what I wrote for A that would be great.

 

[heywhatsup]

you guys are right! i was reading the question way too fast and got it all wrong..
thanks for your help!

 

[AdidasPete]

Draw out all of them...
As you should know by now, it all depends on the "environment" of the H's in the molecule.
1 has H's in a few environments, as part of a CH3 on the terminal ends, as well as part of CH2 in the center. It doesn't matter what it runs as, as long as you know its not a singlet. No go.
2 has H's all in the same environment, they are attached to a C that has another H attached as well as a CH2. All 4 H's have the same environment so they run as a singlet integrated x4. This works.
3 has 9 H's that are all in the same environment. They're all a part of a CH3 group that are attached to a carbon that is attached to 2 more CH3 groups as well as a Cl. It runs as a singlet integrated x9. This works too.
4 is also going to have H's in multiple environments. Some will be part of CH3 groups while the others will be attached on the terminal of the double bond. Two separate environments, not a singlet. Ixnay.
2+3 are the only two singlets... Go B
Hope that helps

 

[Jaylee777]

I was only getting B, but the answer is B and C. it mentions they all have equivalent protons

so by B and C....do you mean II and III? answer B?

 

[heywhatsup]

i meant B meaning II and III yes