Chemical Forums
Chemistry Forums for Students => Organic Chemistry Forum => Organic Spectroscopy => Topic started by: uskydoo on December 01, 2015, 05:54:22 PM
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Hello forum!
I have recently undertaken to synthesise 2-methylheptan-2-ol from propanone and pentylmagnesium bromide.
I made a liquid with a bp of 154-158.6 deg. C. (Siwoloboff method) and RI of 1.4207. Literature values are given as 156 deg. C (yay!) and 1.4250 (yay-ish!). My IR spectrum satisfies me that I have a tertiary alcohol with a a bit of branching on it. the 13C NMR supports everything as you'd expect: 3 methyl groups, 2 on a tertiary carbon. DEPT gives me 4 methylene groups. All happy days.
The problem, dear forum, is this 1H NMR. I'm normally OK with these. But this has me flummoxed. An entire afternoon/ evening with the internet and I'm still no closer to resolving it. Apart from the CH3-CH2 at around 0.88 ppm and what I think is water contaminant in the singlet at around 1.5 (1.56ppm in CDCl3) I can't figure out this thing at all. The integration numbers have me baffled. Does that multiplet have a singlet sticking out of it? I just can't grasp it.
I thank you for any assistance you can render.
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since in the C-NMR everything looks fine I'd expect that you are a bit unlucky with overlapping peaks and couplings. Do you have a reference spectrum?
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Sadly not, the SDBS doesn't have this compound. Little info seems to be around- I'm guessing that outside the context of the educational lab there's not much call or use for 2-methylheptan-2-ol.
I did draw it in Chemdraw and use the predictor- everything seems too bunched together to get a clean read in that too. But the brief for the assignment was to confirm the structure from the NMR- it just seems I can't, not just like that. Would you agree?
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from the simple 1D proton spectrum I think there would be a lot of guessing involved... but if the 13C and DEPT look fine....