Answer to Question #137485 in General Chemistry for mike

Question

For each molecule, predict the splitting pattern or patterns that would be seen in the peaks of
the high-resolution proton NMR spectrum.
a CH 3 CH 2 Cl

(1 mark)

b CH 3 COCH 3

(1 mark)

c CH 3 CHO

(1 mark)

d CH 3 CHClCH 3

Answer 1

We know that in proton NMR spectroscopy the number of splitting for a particular type of chemically equivalent proton is,

Number of splitting = (2N_iI + 1) when only one type of proton is present

N_i = number of neighborhood proton

I = nuclear spin quantum number

= (1/2)

So, (2N_iI + 1) = (N_i+1)

Ni = number of neighborhood proton

I = nuclear spin quantum number

= (1/2)

So, (2N_iI + 1) = (N_i+1)

When more than one type of protons are present, (2N_iI + 1)×(2N_jI + 1)×....

Ni or Nj = number of neighborhood proton

I = nuclear spin quantum number

I = 1/2

So, (2N_iI + 1)×(2N_jI + 1)×....

= (N_i+ 1)×(N_j+ 1)×....

a. CH3 CH2Cl

CH3

N_i= 2.

Splitting = (2+1)

=3

A triplet

CH2

N_i= 3

Splitting = (3+1)

= 4

A quartet

b. CH2 COCH3

CH3

N_i= 0

Splitting = (0+1)

=1

No splitting

COCH3

N_i= 0

Splitting = (0+1)

= 1

No splitting

c. CH3 CHO

CH3

N_i= 1

Splitting = (1+1)

=2

A doublet

CHO

Ni= 3

Splitting = (3+1)

= 4

A quartet

d. CH3 CHCl CH3

CH3

N_i= 1

Splitting

(1+1) =2

A doublet

CHCl

N_i= 3, N_j =3.

Splitting

(3+1)×(3+1)= 16

A multiplate

CH3

N_i =1

Splitting

=(1+1)

= 2

A doublet