NUMBER OF SIGNAL, MECHANISM OF SPLITTING AND SPIN-SPIN COUPLING IN NMR

NUMBER OF SIGNAL IN NMR :-

The number of signal in the NMR spectrum give the information about proton(hydrogen) arrangement in a molecule.

Each signal of NMR give information about each proton set.

Molecules give 1 nmr signal like benzene,

Molecules give 2 nmr signal like methanol,

Molecules give 3 nmr signal like ethanol

Molecules give 4 nmr signal like ethoxy acetic acid.

Some term related to the NMR spectra

1. Number of signal :- Indicated how many types of proton are present.

2. Position of signal :- Indicated about chemical shift and magnetic field of proton

3. Splitting of signal :- Indicated the number of near proton.

N+1 rule:-

This rule is used to calculated splitting of signal.

Equation is N+1 are used.

N= no.of proton present in nearby nuclei.

If N=0, 0+1=1 means singlet

If N=1, 1+1=2 means doublet

If N=2, 2+1=3 means triplets

Spin-spin coupling:-

Defination.:- the interaction between the spin of neighbouring nuclei in a molecule. May cause the splitting of nmr spectrum

Rule of spin spin coupling:-

1. Chemically equivalent proton do not show spin spin coupling.

2. Only non- equivalent proton couple .

3. Proton on adjacent carbon will couple

4. Proton separate by four or more bond will not couple.

Peak area ratio is according to the pascal’s triangle.

MCQ.

1. How many signal are detected in spectra of benzene ?

A. 1 nmr signal

B. 2 nmr signal

C. 3 nmr signal

D. 4 nmr signal

Ans. A

2. How many signal are detected in spectra of ethanol ?

A. 1 NMR signal

B. 2 NMR signal

C. 3 NMR signal

D. 4 NMR signal

Ans. C

3. Which rule is used to calculated splitting in NMR?

A. N+2

B. N+4

C. N+1

D.N +5

Ans.c

4. Spin spin coupling is occurring due to

A. Two near proton

B. Far proton

C. A and B

D. All of the

Ans. A

5. If N=0 how many signal shown in NMR spectra ?

A. Singlet

B. Doublet

C. A and b

D. None of this

Ans. A

6. Peak area ratio is according to the

A. Chemical shift

B. Ir range

C. Pascal scale

D. All of the

Ans. C

7. EDTA spectra has how many signal in NMR ?

A. 1

B. 2

C. 3

D. 4

Ans. D

8. In toluene, how many signal found in NMR?

A. 1

B. 2

C. 3

D.4

Ans. B

9.which condition is required for the spin spin coupling ?

A. equivalent proton do not show spin spin coupling.

B. Only non- equivalent proton couple .

C. Proton on adjacent carbon will couple

D. All of the above

Ans. D

10 In Acetone, how many signal shown in NMR ?

A. 1

B. 2

C . 3

D. 4

Ans. A

  1. Reference  taken from  Y R Sharma book Page no. 197 to 201.

2. Reference take analytical book of dr. Ravisankar third edition.

 

 

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