Chemistry Reference
In-Depth Information
CH
3
O
OCH
3
H
δ
3.0
-
4.0
singlet
δ
6.5
-
7.5
singlet
area = 2 (4)
ar ea = 3 (6)
12.27
There are three possibilities. The number of different types of carbons is shown
under each structure.
H
3
C
O
C
H
3
H
3
C
O
C
H
3
H
3
C
O
C
H
3
8
8
8
The
1
H NMR spectrum would show a singlet (3H) near
δ
2.5 (aromatic CH
3
), a singlet
(3H) near
δ
3.5 (OCH
3
), and two doublets (2H each) near
δ
7.0.
12.28
The four isomeric butanols are:
OH
CH
3
CH
2
CH
2
CH
2
OH
CH
3
CH
2
CHC H
3
(CH
3
)
2
CHC H
2
OH
(C H
3
)
3
COH
1-butanol
2-butanol
2-methyl-1-propanol 2-methyl-2-propanol
(isobutyl alcohol)
(
tert
-butyl alcohol)
a.
The NMR spectrum is that of 2-methyl-2-propanol (
tert
-butyl alcohol). This is
the only isomer of butanol that has only two unique carbon atoms (three
equivalent methyl groups and the carbon bonded to the hydroxyl group).
b.
1-Butanol and 2-butanol have four different carbons and would each exhibit
four peaks in their decoupled
13
C NMR spectra. The
13
C-
1
H coupled
spectrum of 1-butanol would show one quartet for the methyl group (CH
3
)
and three triplets for the methylene (CH
2
) groups. This is quite different from
the coupled spectrum of 2-butanol, which would show two quartets for the
methyl groups, a triplet for the methylene, and a doublet for the methine (CH).
12.29
In a proton decoupled
13
C NMR spectrum, each of the unique carbons appears as a
separate peak, so one needs to know how many unique carbons there are in each
structure.
