Lisachem

[sam0001]

Lisachem 2008 why is the ch2 split into 6 finer peaks in 1 propanol...

...I don't get t, shouldn't it be split into 12?

[charmanderp]

This is purely from memory, so excuse me if I'm wrong :p

The CH2 is in between a CH3 group and a CH2OH group. Therefore it's adjacent to carbons which in total are themselves directly attached to 5 hydrogen atoms. Using 5+1=6, we could get a sextet.

Why would it be split into 12? There aren't even 12 protons in total in propan-1-ol!

[Nobby]

Why would it be split into 12? There aren't even 12 protons in total in propan-1-ol!

In reality it should be 12, because the protons on the CH₂ can interact with the three on the CH₃, producing 4 fine peaks. But then these 4 peaks can each interact with the two on the other CH₂, producing 12 peaks.

But in VCE trial exams and study guides etc. I've only seen the (n+1) generalisation.

[sam0001]

Nobby, can vcaa test us on molecules such as 1 propanol? I was under the impression that they wouldn't.

[charmanderp]

They can, but as far as I know they only expect you to know the (n+1) rule. 2009 NEAP Short Answer Question 3.e asks you to draw the high resolution H-NMR spectrum of propan-1-ol and the answer provided has the --CH2-- peak split into six.

[sam0001]

Brilliant. Thanks for the help!