Draw the structure identified by the following H and C NMR spectra. The molecular formula is ...

Question:

Draw the structure identified by the following H and C NMR spectra. The molecular formula is {eq}C_{10}H_{12}O {/eq}.

a. 3 hydrogens at 1.2 signal.

b. 2 hydrogens at 2.3 signal.

c. 2 hydrogens at 3.8 signal.

d. 2 hydrogens at 7.0 signal.

e. 2 hydrogens at 7.2 signal.

f. 1 hydrogen at 9.8 signal.

Chemical shifts on a NMR

The chemical shifts on a proton NMR spectra gives valuable information about the chemical environment of the protons. It is almost impossible to interpret a spectrum without knowing the effect of different functional groups on the chemical shifts of protons.

Some examples include:

The proton associated with a carboxylic acid will be in the region of 10.5 - 12 ppm

The protons next to a double bond can be expected at 5 - 7 ppm

The proton on a carbon that is also attached to a halide can be expected in the region of 3 - 5 ppm

Answer and Explanation:

The molecule is 4 proypylbenzaldehyde as shown below.

The chemical shifts of protons on a carbon chain can typically be found between 1 and 3 ppm

The protons on a benzene ring is in the region of 7 ppm and since there are only 2 types of protons, it has to be a para substituted ring (corresponding to the 4 protons mentioned in that region).

The 1 hydrogen at 9 ppm corresponds to an aldehyde. This is also confirmed by the formula mentioning 1 oxygen atom

The hydrogens have been labelled on the proposed structure below

a. 3 hydrogens at 1.2 signal.

b. 2 hydrogens at 2.3 signal.

c. 2 hydrogens at 3.8 signal.

d. 2 hydrogens at 7.0 signal.

e. 2 hydrogens at 7.2 signal.

f. 1 hydrogen at 9.8 signal.


Learn more about this topic:

How to Read NMR Spectra of Organic Compounds
How to Read NMR Spectra of Organic Compounds

from Organic Chemistry: Help & Review

Chapter 2 / Lesson 2
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