[davidenarb]

That is indeed 7 signals!
I have two questions :

1) Although it is 7 signals, it is still 10 unrelated protons right?

2) Can you tell me which method did you use to predict the 7 signals ?

[discodermolide]

No the protons are all related to each other via the H-H coupling.
To get 7 I counted the groups of protons. CH₃, CH₂, CH₂, CH, CH₃, CH₂, CH₃.
In the ideal world that would give 7 sets of signals.

[davidenarb]

but as you can see in the website when you put the mouse on each hydrogen, they will be separated.
Also, this makes sense because the methyl group on carbon C3 will create different electronic environments on the other hydrogens

[discodermolide]

Don't forget that bonds rotate and these effects will be averaged out. Only in a case of restricted rotation will such second order effects be seen.

[davidenarb]

OK.

One last question. How many signals you would expect for the R 2-bromopentane ?

[discodermolide]

5

[clarkstill]

You are correct, there are 10 theoretically resolvable proton environments.  Chemdraw doesn't deal well with diastereotopic methylene units, but in reality you would probably be able to distiguish them with a big enough magnet.

There are 7 unique proton environments in 2-bromopentane.

The issue of whether the protons are experimentally distinguishable is another one entirely...

[davidenarb]

You are correct, there are 10 theoretically resolvable proton environments.  Chemdraw doesn't deal well with diastereotopic methylene units, but in reality you would probably be able to distiguish them with a big enough magnet.

There are 7 unique proton environments in 2-bromopentane.

The issue of whether the protons are experimentally distinguishable is another one entirely...

Thank you very much for your post. I was really confused.