How many unique c13 nmr signals exist in the spectrum for the compound?

How many unique 1H & 13C NMR signals exist in the spectrum of the following compounds?How many unique 1H NMR signals exist in the spectr

Answer

General guidance

Concept and Reason
This problem is based on the concept of NMR spectroscopy. NMR spectroscopy is a very good tool to analyze organic compounds. H-NMRsignal indicates number of ‘different sets’ of protons present in the molecule. 13 C-NMRindicates number of ‘different sets’ of carbon atom present in the molecule.

Fundamentals

A set of protons with the same magnetic environment are called equivalent protons and give only one signal in the H-NMRspectrum. Therefore, number of sets of protons reveal how many signals appear in the spectrum. Similarly, a set of carbon atoms with the same magnetic environment are called equivalent carbons and give only one signal in the13 C-NMRspectrum. Therefore, number of sets of carbon atoms reveal how many signals appear in the spectrum.

Step-by-step

Step 1 of 10

(1.a) The structure of the compound representing the value of chemical shift is as follows: 2
.00
3 Signals

Part 1.a

Number of H-NMRsignals is .


This compound contains three types of hydrogen atoms. As the molecule is symmetrical, therefore ,there will be only three distinct hydrogen atoms. Thus, compound will give three H-NMRsignals.

Step 2 of 10

(1.b) The structure of the compound representing the value of chemical shift is as follows: 1. HO-
2.30
2.30
3 Signals

Part 1.b

Number of H-NMRsignals is .


This compound contains three types of hydrogen atoms. Due to symmetry, both carboxyl group and methylene group give one signal each and one distinct signal is observed for the other methylene group. Thus, compound will give three H-NMRsignals.

Step 3 of 10

(1.c) The structure of the compound representing the value of chemical shift is as follows: 1-86
7-20
5 signals

Part 1.c

Number of H-NMRsignals is .


This compound contains five types of hydrogen atoms. As both the substituents on benzene ring are different, different signals are obtained for every hydrogen present on the benzene ring and one separate signal is observed for the methyl group present on the benzene ring. Thus, compound will give five H-NMR signals.

Step 4 of 10

(1.d) The structure of the compound representing the value of chemical shift is as follows: 4.92 HS
5.11
3 Signals

Part 1.d

Number of H-NMRsignals is .


This compound contains three types of hydrogen atoms. Due to symmetry, same signal is observed for both the methyl groups and two separate signals are observed for the hydrogen present in the methylene group. Thus, compound will give three 1H NMR signals.

Step 5 of 10

(2.a) The structure of the compound representing the value of chemical shift is as follows: 177 178
4 Signals

Part 2.a

Number of 13 C-NMRsignals is .


This compound contains four types of carbon atoms. As both the substituents present on the cyclopentane ring are same, the carbon atoms are equivalent. Thus, compound will give four 13 C-NMRsignals.

Step 6 of 10

(2.b) The structure of the compound representing the value of chemical shift is as follows: MAN
3 Signals

Part 2.b

Number of 13 C-NMRsignals is .


This compound contains three types of carbon atoms. Due to symmetry both the carbon atoms of the methyl groups are same and the both the carbons attached via double bond are chemically inequivalent. Thus, compound will give three 13 C-NMR signals.

Step 7 of 10

(2.c) The structure of the compound representing the value of chemical shift is as follows: 24-3
3 Signals

Part 2.c

Number of 13 C-NMRsignals is .


This compound contains three types of carbon atoms. As both the substituents attached on benzene ring are same, there is same signal observed for both the methyl groups. Also, both the ipso carbon, carbons ortho to the methyl substituents are also equivalent. Thus, compound will give three 13 C-NMR signals.

Step 8 of 10

(2.d) The structure of the compound representing the value of chemical shift is as follows: 134-7
121-9
131-5
Br
1306
4 Signals

Part 2.d

Number of 13 C-NMRsignals is .


This compound contains four types of carbon atoms. As both the substituents attached on benzene ring are same, both the ipso carbon and carbons ortho to the bromo group are equivalent and give two signals. Carbon sandwiched between the two bromo substituents is chemically inequivalent from other carbon atoms and the carbon meta to both the bromo group is also giving a different signal. Thus, compound will give four13 C-NMR signals.

Step 9 of 10

(2.e) The structure of the compound representing the value of chemical shift is as follows: 14,3
1326 2015
3 Signals

Part 2.e

Number of 13 C-NMRsignals is .


This compound contains three types of carbon atoms. As the molecule is symmetrical therefore there will be only three distinct carbon atoms Thus, compound will give three 13 C-NMRsignals.

Step 10 of 10

(2.f) The structure of the compound representing the value of chemical shift is as follows:

HO118-4
778-ОН
З 37
3 Signals

Part 2.f

Number of 13 C-NMRsignals is .


This compound contains three types of carbon atoms. Due to symmetry, both the carboxylic group and both the methylene group will give two distinct signals and a distinct signal is observed for the other methylene carbon. Thus, compound will give three NMR signals.

Answer

Part 1.a

Number of H-NMRsignals is .

Part 1.b

Number of H-NMRsignals is .

Part 1.c

Number of H-NMRsignals is .

Part 1.d

Number of H-NMRsignals is .

Part 2.a

Number of 13 C-NMRsignals is .

Part 2.b

Number of 13 C-NMRsignals is .

Part 2.c

Number of 13 C-NMRsignals is .

Part 2.d

Number of 13 C-NMRsignals is .

Part 2.e

Number of 13 C-NMRsignals is .

Part 2.f

Number of 13 C-NMRsignals is .

Leave a Comment