INTEGRATED SPECTRA PROBLEMS

SOLUTION for  PROBLEM #1

• In the MS, the molecular ion occurs at m/z = 72 indicating the MW = 72 g / mol.
• The IR shows a carbonyl C=O (1720 cm^-1), no -OH or -NH (above 3200 cm^-1), no C=C (1600 cm^-1)
• ¹³ C-nmr shows 4 types of C, including a C=O (210 ppm), and 3 hydrocarbon C (37, 29 and 8 ppm)
• H-nmr

d/ppm	multiplicity	integration	assignment
2.4	quartet	2	CH2 coupled to 3H
2.1	singlet	3	isolated CH3
1.1	triplet	3	CH3 coupled to 2H

• From the data, we can get a molecular formula of C₄H₈O matches the MW of 72 g / mol.
• This has an IHD = 1, and accounts for the p bond of the C=O.
• The following pieces can be deduced from the spectra  C=O, -CH₃, -CH₃, and -CH₂-.
• Given these pieces, there is only one way they can fit together:

• Checking the H-nmr, the coupling patterns observed are consistent with the isolated CH₃ and the -CH₂CH₃