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Magazine Chapter 21: 77P (page 817)
An unknown compound C of molecular formula C6H12O3 exhibits a strong absorption in its IR spectrum at 1718 cm-1 and the given 1H NMR spectrum. What is the structure of C?
Short Answer
Step by step solution
Spectral data
Spectral data is used to identify unknown compounds.
Each atom or group present in a compound shows a characteristic absorption that is represented as a spectrum and hence the spectrum obtained for a compound can be used to predict its structure.
Inference from the IR data
The molecular formula of the compound is C6H12O3 and the compound shows an IR absorption at 1718 cm-1.
IR absorption at 1718 cm-1 is characteristic of carbonyl (C=O) stretching and therefore, the compound consists of a carbonyl group.
Inference from the 1H-NMR spectrum
The singlet at 2.2 ppm corresponding to three hydrogens indicates that the carbon adjacent to the one to which the concerned proton contains two hydrogen atoms.
(According to the n+1 rule, where n indicates the number of hydrogen atoms on the adjacent carbon).
Doublet at 2.7 corresponding to 2H (number of adjacent hydrogen atoms is 1).
The singlet at 3.2 corresponds to 6H (carbon adjacent to six equivalent hydrogens is not connected to a proton).
Triplet at 4.8 corresponds to 1H (adjacent carbon contains two protons).
Therefore, the predicted structure of compound C is:
Structure of compound C
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