Chapter 14: Q27P (page 643)
Predict the splitting patterns for the signals given by compounds in Problem 4.
Short Answer
a.
b.
c.
d.
C-2,C-3,C-5,C-6 Shows doublet, while C-1, C-4 shows multiplet
e.
f.
g.
h.
i.
j.
k.
l.
m.
n.
o.
Step by step solution
Splitting patterns in NMR spectroscopy
NMR shows a different number of peaks. These are called the splitting patterns in NMR spectroscopy. We know that the simplest signal consists of one line is called a singlet, followed by a doublet, triplet, quartet, and multiplet.
Spitting is caused by the hydrogens on the same or neighboring carbons. Only non-equivalent protons cause splitting.
Splitting patterns in compounds
(a)
As a compound a contains plane of symmetry then spitting in the compound is as shown below;
Spliting in (a)
-CH3 group shows triplet as it couple with two neighboring hydrogen atoms while the -CH2 group shows quartet as it couples with three neighboring hydrogen atoms.
(b)
As the compound b contains plane of symmetry then spitting in the compound is as shown below;
Spliting in (b)
Both -CH2groups are equivalent so that they don’t couple with each other and show singlet.
(c)
Splitting in compound c is showm below:
Spliting in (c)
(d)
As a compound a contains plane of symmetry then spitting in the compound is as shown below;
Spliting in (d)
Hydrogen present on C-2 carbon does not split by hydrogens present on the C-3 carbon as both are equivalent. The hydrogen present on C-5 carbon does not split by hydrogens present on the C-6 carbon as both are equivalent.
C-2,C-3,C-5,C-6 Shows doublet, while C-1 , C-4 shows multiplet.
(e)
Splitting in e is shown below:
Spliting in (e)
As both the hydrogens are equivalent so they are not couple with each other and show singlet.
(f)
-CH3group next to carbonyl is show singlet as no neighboring hhydrogen is present.
Spliting in (f)
(g)
As a compound a contains plane of symmetry then spitting in the compound is as shown below;
Spliting in (g)
The middle -CH group shows quintet as it couple with four neighboring hydrogens. While -CH3 the shows triplet as it couples with two hydrogens. -CH2shows multiplet.
(h)
As a compound a contains plane of symmetry then spitting in the compound is as shown below;
Spliting in (h)
(i)
The group -CH3 shows doublet while -CH group shows quartet.
Spliting in (i)
(j)
The -OCH3 group shows singlet. While the -CH3 group shows singlet.
Spliting in (j)
(k)
As the given molecule contain plane of symmetry so all the benzene hydrogens are identical and show singlet
Spliting in (k)
Also the -CH3 group shows singlet.
(l)
As the given molecule contain plane of symmetry so hydrogen next to Br shows doublet while the hydogen present in between two group is showing singlet.
Spliting in (l)
(m)
As the given molecule contain plane of symmetry so hydrogen next to -NO2 shows doublet while the hydrogens on 3 rd carbon shows doublet of doublet.
Spliting in (m)
(n)
Double bonded -CH3group show doublet while the -CH3 group next to carbonyl group show singlet. Also the double bonded -CH shows quartet.
Spliting in (n)
(o)
As the both hydrogens are non equivalent so they show doublet.
Spliting in (o)
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