Chemistry: determing name of a compound.

[kakxy]

Homework Statement

A compound only contains C, H and O. An elemental analysis of the compound gives the result C: 40.00%; H: 6.71%. The 13C NMR, IR spectrum and mass spectrums are in the graph below.

Graphs: http://s512.photobucket.com/albums/t323/antiuniverse/graphs.gif

I need to determine the name of the compound.

Homework Equations

N/a

The Attempt at a Solution

I'm not entirely sure. From the elemental analysis:

If we had 100g of compound, we'd have:
40g C
6.71g H
53.29 O

Work out the moles:
40g / 12 = 3.3333 moles of C
6.71g / 1 = 6.7100 moles of H
53.29g / 16 = 3.3306 moles of O

Divide by smallest ratio:
2.8571 / 2.8571 = 1 atom of C
6.7100 / 2.8571 = 2 atoms of H
1.1652 / 2.8571 = 1 atom of O

So the empirical formula would be H2CO (or C2H4O2?). I think the mass spectrum is telling me that the empirical formula must be H2CO (which has a molecular weight/mass of 30).

From the 13C NMR spectra I believe it's either an aldehyde or ketone. I know that H2CO is formaldehyde (methanal) which is an aldehyde and correlates with what I found in the 13C NMR spectra.

Could anybody look over this and let me know if it's correct?

 

[Gannon]

I think you're solid; the IR spectrum spike between 1750/cm denotes a C=O bond. The NMR spectrum implies that all hydrogens in the molecule produce the same signal, and must have the same environments (symmetrical on the molecule); this spike is also pretty far from the starting point which would mean that the hydrogens are attached to something close to oxygen (like a carbonyl carbon). I don't know how to read mass spec (for some reason my organic teacher never went over this). Your calculations look good, and CH2O seems like it's probably the answer.

 

[Blueshift5]

Your analysis is correct. Based on the given data, the compound is most likely formaldehyde (H2CO). The 13C NMR spectrum shows a peak at around 200 ppm, which is characteristic of a carbonyl carbon in an aldehyde or ketone. The IR spectrum also shows a strong peak at around 1700 cm^-1, which is indicative of a C=O bond. Additionally, the mass spectrum shows a peak at 30 m/z, which corresponds to the molecular weight of formaldehyde. Overall, your reasoning and conclusion are sound.