# Deducing compounds from spectroscopic data for isomers of formula C4H8O

Here's the problem:

I've already know the 3600 cm$^{-1}$ line indicates the $\ce{-OH}$ group and the 1640 cm$^{-1}$ line indicates the C double-bond C alkene.

From the $^{13}$C NMR data: the two carbons with chemical shifts of 100+ are sp$^2$ carbons and the remaining two are sp$^3$ carbons.

I have tried to work out compound D, and suggest this structure:

I am stuck on figuring out compound C. I suggest the structure below, but am unsure whether if it is correct.

Any help is appreciated thanks!

• What makes you unsure about it? – pH13 - Yet another Philipp Aug 10 '15 at 12:12
• @PH13 it's just the 1Hproton shifts that are confusing...especially for the Hb that I have labelled in compound C. I have interpreted 'qn' to mean 'quintet' but if it couples to 1x Ha and 3xHc, technically shouldn't it be a 'doublet of quartets'? – justbehappy Aug 10 '15 at 12:31
• That's not a "normal" quintet and thus it should not be named like one ... it's rather a multiplet or as you say at high resolution it would probably be a quarted of a doublet (vice versa). The coupling constants are very close to each other and this makes it a quintet at low resolutions. – pH13 - Yet another Philipp Aug 10 '15 at 12:46
• @PH13 ok! I see. Thanks for clarifying this. Do you also agree with my proposed structure for Compound D? – justbehappy Aug 10 '15 at 13:08