Mendeleev Commun., 2014, 24, 222–223
1
13
12
11
10
9
8
7
6
5
d/ppm
Figure 2 1H NMR spectrum of salicylaldehyde-d1.
Zn(OAc)2·2H2O
Ni(NO3)2·6H2O
1
3
5
7
13
12
11
10
9
8
7
6
5
d/ppm
O
H
Figure 4 The 1H NMR spectra of the H/D exchange of salicylaldehyde in
the presence of 1, Zn(OAc)2·2H2O or Ni(NO3)2·6H2O.
9
OD
11
13
Innovation in Chemistry (PERCH-CIC). We are grateful to Miss
Tan Geok Kheng and Hong Yimian (National University of
Singapore) for the solution of the crystal structure.
210
170
130
90
50
10
d/ppm
Online Supplementary Materials
Supplementary data associated with this article can be found
in the online version at doi:10.1016/j.mencom.2014.06.011.
Figure 3 The HSQC spectrum and proposed structure of salicylalde-
hyde-d1.
After 5.5 h, the hydroxyl proton peak completely disappears and
other peaks remain unchanged (Figure 2). From HSQC spectrum,
all positions of C and H are the same as those of salicylaldehyde
except no proton at hydroxyl group (Figure 3). The peak assign-
ment indicated in the spectrum tentatively suggests the structure
of salicylaldehyde-d1. To confirm the H/D exchange reaction of
the salicylaldehyde, the organic product was analyzed by GC-MS
(Figure S3). The product ion of m/z 123 at a retention time of
22.20 min produces fragment ions with m/z 121 and 65. They
resulted from the loss of a deuterium atom from the ion at m/z 123
and the formation of the [M–C5H5]+ ion, respectively. Since the
molecular weight of salicylaldehyde is 122, only one active H in
its structure was exchanged for a deuterium atom. The similar
reaction was also performed using DMSO. The product ion
mass spectrum of m/z 122 at a retention time of 20.92 min
shows fragment ions at m/z 121 and 65 (Figure S4). However, the
molecular ion of m/z 123 was found in this reaction. The intensity
of this ion in DMSO-d6 is higher than that in DMSO. The mole-
cular weight of salicylaldehyde-d1 causes a slow mobility of the
substance and results in an increase of the retention time.20 The
GC-MS analysis and 1H NMR spectroscopy confirmed the H/D
exchange reaction. Ni(NO3)2·6H2O or Zn(OAc)2·2H2O was tested
as a catalyst under identical conditions (Figure 4). The hydroxyl
proton immediately manifests itself as a broad peak at 10.67 ppm
in the presence of Zn(OAc)2·2H2O and this peak remained
unchanged after 6 h. When using Ni(NO3)2·6H2O as a catalyst,
there is no reaction after 6 h. Thus, the heterometallic ion pair
compound is an efficient catalyst in the H/D exchange of salicyl-
aldehyde. Zn(OAc)2·2H2O can also catalyze the H/D exchange
reaction, however, the reaction is not complete within 6 h. The
Lewis acidity of the zinc salt may be the source for promoting
the catalytic activity. Other alcohol substrates, namely, tert-butanol,
diphenylmethanol and phenylethanol were tested under analogous
conditions with complex 1 as a catalyst, but no reaction was
observed within 6 h.
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This work was supported by Khon Kaen University under
Incubation Researcher Project and the Center of Excellence for
Received: 12th August 2013; Com. 13/4177
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