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#1 2009-09-07 10:22:15

orgopete
Administrator

NMR of butyl acetate, unknown of C6H12O2

Yahoo!Answers in chemistry wrote:

Organic Chem help please?
The H NMR spectrum of a compound with molecular formula C6H12O2 is shown here.
Draw its structure.

http://www.curvedarrow.com/chem/ZZ78750D01.jpg
Identify the compound with MF = C6H12O2.

IHD = (2x+2-y)/2
IHD = (12+2-12)/2 = 1

This problem may have had an IR associated with it to more easily identify a C=O bond being present. We could argue that it could have a ring with two oxygens placed at various points, but there are only two hydrogens attached to an oxygen (peak at 4.1 ppm).

The integral is 2:3:2:2:3. Therefore one of the six carbons does not have a hydrogen attached. The others are CH3 and CH2 units. That makes it pretty simple.
The peaks at 4.1 ppm has an adjacent CH2. Therefore, it must be a OCH2CH2.
The peak at 2 ppm has no adjacent hydrogens as it is a singlet. It cannot be a CH3CH2 or CH3O, therefore it must be a CH3C=O.
The peak at 0.9 has an adjacent CH2, therefore it must be a CH3 with an adjacent CH2, CH3CH2.
Putting the pieces together, the compound is butyl acetate, CH3C(=O)OCH2CH2CH2CH3

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