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Magazine Chapter 21: 78P (page 817)
An unknown compound D exhibits a strong absorption in its IR spectrum at 1692 cm-1 . The mass spectrum of D shows a molecular ion at m/z = 150 and a base peak at 121. The 1H- NMR spectrum of D is shown below. What is the structure of D?
Short Answer
Step by step solution
Spectroscopy
Spectroscopy is used to study the structure of compounds and can be used to predict or identify unknown compounds.
Mass spectrum of the given compound
The m/z value of molecular ion in mass spectrum gives the molecular mass of the compound.
The molecular mass of the compound is 150.
Therefore, the possible molecular formula of the compound is C9H10O2 .
Analyzing the IR and 1H-NMR spectrum of the given compound
The IR spectrum shows a strong absorption peak at 1692 cm-1 is characteristic of the carbonyl (C=O) group.
The NMR data:
Triplet at 1.5 corresponding to three hydrogen atoms indicates the carbon atom adjacent to the one bonded to the desired hydrogen contains two hydrogen atoms (-CH3CH2-) .
Quartet corresponding to three hydrogens at 4.1 ppm represents theCH2 group adjacent to a CH3 group.
Doublet at 7.0 ppm (2H) corresponds to two aromatic protons.
Doublet at 7.8 ppm (2H) corresponds to two aromatic protons.
(Since two peaks in the aromatic region correspond to two hydrogen atoms, each indicates that the benzene ring is para-substituted).
The singlet at 9.9 corresponds to the aldehydic proton.
Therefore, the structure of compound D is:
Structure of compound D
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