Compound #1 is a volatile liquid (boiling point 56 ^oC) that is used as a common organic solvent. Utilizing the Mass, IR, and ¹H NMR spectra, along with ¹³C NMR data, determine the structure of this compound.

Elemental Analysis: C, 62.04; H, 10.41; O, 27.55

Analysis

Elemental Analysis: C, 62.04; H, 10.41; O, 27.55

Based on the Mass Spectrum, the average molecular weight is 58, making the analysis correspond to a molecular formula of C₃H₆O .

Mass Spectrum

Infrared Spectrum

Proton NMR Spectrum

Carbon NMR Data

¹³C NMR Spectral Data:

singlet, 206.0 ppm
quartet, 27.0 ppm

Interpretation of the Data...

The Mass spectrum shows a molecular weight of 58 and a base peak of 43, suggesting the presence of the acylium ion (m/e = 43). The IR data are consistent with a simple aliphatic carbonyl compound. The proton NMR shows one singlet at 2.2 ppm, meaning that all 6 hydrogens in the compound are equivalent (i.e., two identical methyl groups). The chemical shift is consistent with hydrogens adjacent to a carbonyl. The carbon NMR data suggest a ketone (206 ppm) and a methyl group adjacent to a mild electron withdrawing group. Taken together, the data are consistent with a simple ketone with two identical methy groups.

Structure

m/e

58:

Molecular ion; the molecular weight of the compound is 58
43:

Base peak; m-15 (loss of a methyl group). The compound can lose a methyl group and form the stable acylium ion (m/e = 43; CH₃CO⁺)

Wave Number, cm^-1

3400:

no OH
3100:

no sp or sp² CH
2900:

medium absorbance suggesting sp³ CH
2200:

no unsymmetrical triple bonds
1700:

strong absorbance suggesting carbonyl is present
1600:

no carbon-carbon double bonds
Chemical Shift, ppm

2.2:

singlet, 6H, two equivalent methyl group; CH₃-X, where X is mildly electronegative (carbonyl, benzene ring, etc.)
¹³C NMR Spectral Data:

singlet, 206.0 ppm: singlet, ketone carbonyl region; R₂C=O
quartet, 27.0 ppm: quartet, mildly electronegative region; X-CH₃, where X is mildly electronegative (carbonyl, benzene ring, etc.)