Help spectroscopy

Help I don’t get why it’s 3 peaks isn’t it 2 because there’s 2 carbon environments the A’s labelled are all the same and the B in the middle so 2 c environments right??

For the bottom Q ignore the top

(edited 11 months ago)

Reply 1

TypicalNerd

Original post by Alevelhelp.1

Help I don’t get why it’s 3 peaks isn’t it 2 because there’s 2 carbon environments the A’s labelled are all the same and the B in the middle so 2 c environments right??

For the bottom Q ignore the top

2,2-dimethylpropane should only have 2 peaks on the 13C nmr spectrum for exactly the reasons you have posted.

I suspect there was a typo on the answer sheet (that, or they included the TMS peak, which they shouldn’t have and don’t appear to have done for the other molecule).

Reply 2

Alevelhelp.1

Original post by TypicalNerd

Tysm!!
also this q I don’t get how proton b is 3-4.2 ppm
because it just CH so would it not be 0.5-2.0ppm
using the table

even for the q6 i don’t get it 😭 plz help

(edited 11 months ago)

Reply 3

TypicalNerd

Original post by Alevelhelp.1

Tysm!!
also this q I don’t get how proton b is 3-4.2 ppm
because it just CH so would it not be 0.5-2.0ppm
using the table

even for the q6 i don’t get it 😭 plz help

It also has a CHO group next to it, so really it is a CH-C=O environment as opposed to just a CH. The CHO group contains a highly electronegative oxygen atom that increases the shift on the adjacent CH.

Edit: I looked at the wrong molecule, but a similar principle applies. There is an oxygen bonded directly to the CH, so it’s a CH-O environment.