Help urgent spectroscopy

Help. I don’t get why the line at 50 ppm isn’t included (c) it’s a c-o but it’s not in the overall structure why?? Btw the ms is here in purple but I don’t get why the c-o is not there

(edited 11 months ago)

Reply 1

user493

I think the line at 50 must just be another c-c bond as the line could really be either x

Reply 2

user493

I think the c=o is important for the aldehyde but the rest is to show that there is 4 c environments so that's why its needed

Reply 3

bl0bf1sh

Original post by Alevelhelp.1

Help. I don’t get why the line at 50 ppm isn’t included (c) it’s a c-o but it’s not in the overall structure why?? Btw the ms is here in purple but I don’t get why the c-o is not there

The molecular formula is C5H10O. Because it's an aldehyde, the only carbon-oxygen bond is the C=O for the aldehyde functional group. So there won't be a peak for C-O because there is no C-O in the molecule.

There are 5 carbons, and 4 peaks, one of which is the carbonyl carbon. This means that, for the remaining 3 peaks and 4 carbons, 2 of the carbons must be in the same chemical environment. As the molecule is an aldehyde, the C=O must be at one of the ends, and if you draw out all the possible structural isomers you'll find that the only one with a structure that would give a 13C NMR spectrum like the one shown in the question is (CH₃)₂CHCH₂CHO.

Reply 4

jack_harrison

The ~50 ppm peak is most likely the carbon next to the aldehyde C=O. The exact chemical shift of a carbon depends on the electron density that sits on it. Because this carbon is next to the aldehyde, which is electron withdrawing, it appears at a slightly higher chemical shift than your average alkyl carbon. It's a bit of a tricky one considering that it sits in the correct ppm range for C-O, but you should always remember that those ranges are just guidelines, and that other groups can give rise to those same chemical shifts.