Please do not adjust margins
ChemComm
Page 3 of 3
DOI: 10.1039/C7CC04952H
Journal Name
COMMUNICATION
It is impossible to determine ꢀ due to the nonꢀquantitative nature of TLC plates in standard plate sizes, also incorporating a fluorescent
TLC analysis ꢀ whether the intense spot C at the origin of the silica compound, such as manganeseꢀactivated zinc silicate, for use in
gel TLC plate (bottom) is representative of unreacted phenol in the combination with standard UVꢀlamps, remains to be developed.
reaction mixture or is due to 2ꢀphenoxytetrahydropyran being Similarly, processes for the fabrication of ranges of granule size of
decomposed on the silica gel stationary phase. TLC is also a rapid mesoporous silicon diimide gel for use as the stationary phase in
process compared to column chromatography, which can take many chromatography columns will also need to be developed. This would
hours. This makes acidꢀlabile compounds more susceptible to allow this new, highly stable and basic chromatographic stationary
decomposition during column chromatography. To determine the phase to have considerable potential use in GLC, GPC and HPLC
unstable nature of 2ꢀphenoxytetrahydropyran over silica gel and applications.
silicon dimimide a second experiment was designed. Identical
solutions (1 mol L−1) of 2ꢀphenoxytetrahydropyran in In summary, we have shown that mesoporous silicon diimide gel
tetrahydrofuran were stirred over of either mesoporous silicon Si(NH)(NH2)2 is a suitable, efficient, and stable stationary phase for
diimide gel or silica gel at room temperature and the pH monitored thin layer chromatography. It has been shown using a model system
after 3 hours and 12 hours, table 1. The solution in contact with that mesoporous silicon diimide gel has the capacity to separate
silica gel became acidic (pH = 4) quickly, i.e., less than 3 hours. The organic compounds chromatographically without decomposing acidꢀ
test mixture containing silicon diimide gel gradually became basic sensitive functions or bonds. It provides an alternative to either basic
(pH = 9), over 12 hours, due to the presence of silicon diimide gel. alumina, baseꢀdoped silica gel or silicon oxynitride for use as a
This pH change in the presence of silica is expected to be large chromatographic stationary phase in the identification and
enough to decompose acidꢀlabile materials.
purification of acidꢀlabile organic compounds, such as
pharmaceutical intermediates or final products.
Notes and references
1.
2.
3.
L. F. Giraldo, B. L. Lopez, et al., Macromol. Symp., 2007,
258, 129ꢀ141.
I. M. ElꢀNahhal and N. M. ElꢀAshgar, J. Organomet. Chem.,
2007, 692, 2861ꢀ2886.
H. Wan, X. Xue, Y. Du and X. Liang, Anal. Methods, 2012,
4, 3524.
5.5
5.4
5.3
5.2
5.1
5.0
4.9
4.8
4.7
6.0
5.9
5.8
5.7
5.6
5.5
5.4
5.3
5.2
5.1
5.0
4.9
4.8
X
:
parts per Million : 1H
X : parts per Million : 1H
A
B
Fig. 4. NMR Spectra of 2ꢀphenoxytetrahydropyran after 3 hours
stirring over silica, A, and 2ꢀphenoxytetrahydropyran after 3 hours 4.
stirring over silicon diimide, B.
H. Wan, Q. Sheng, H. Zhong, X. Guo, Q. Fu, Y. Liu, X. Xue
and X. Liang, J. Sep. Soc. 2015, 38, 1271.
H. Wan, H. Zhong, X. Xue, X. Liang, J. Sep. Sci. 2016, 39,
3860.
5.
The THF solvent was removed from the 3 hour samples and the
NMR recorded using CDCl3 as solvent and TMS as internal
standard, figure 4. NMR A shows that the Hβ triplet (5.34 ppm) was
gradually replaced over 3 hours by a composite peak comprised of
the Hα broad phenolic singlet (5.21 ppm) and the Hγ hemiacetal
triplet, (4.89), in the presence of silica gel. The number of protons
represented by this composite peak also increased relative to the
number of protons of the phenyl ring, in agreement with the
replacement of one Hß by one Hα plus one Hγ. The formation of the
Hγ hemiacetal triplet and Hα broad phenolic singlet was not observed
in NMR B. This is evidence that gradual decomposition of 2ꢀ
phenoxytetrahydropyran occurs in the presence of silica gel. While
TLC may be a too rapid process to see significant degradation of 2ꢀ
phenoxytetrahydropyran, it is clear that silicon diimide would be the
preferred stationary phase to protect against acidꢀlabile
decomposition.
6.
7.
8.
J. J. Kirkland, J. Chromatographic Sci., 1996, 34, 309ꢀ313.
Y. Mao and B. M., J. Chromatography A, 1997, 790, 9ꢀ15.
M. Grun, A. A. Kurganov, et al., J. Chromatography A,
1996, 740, 1 ꢀ9.
C. J. Vanoss, R. F. Giese, et al., J. Adhesion Sci. Technol.,
1992, 6, 413ꢀ428.
E. Chibowski, Abstracts Amer. Chem. Soc., 1992, 203: 262ꢀ
COLL.
W. Wu, R. F. Giese, et al., 1996, 89, 129ꢀ132.
R. Rovai, C. W. Lehmann, et al., Angew. Chem. Int. Ed.
Eng., 1999, 38, 2036ꢀ2038.
F. Cheng, S. Clark, et al., J. Amer. Cer. Soc., 2004, 87,1413ꢀ
1417.
F. Cheng, S. M. Kelly, et al., J. Membrane Sci., 2006, 280,
530ꢀ535.
F. Cheng, S. M. Kelly, et al., Chem. Mater., 2006, 18, 5996ꢀ
6005.
S. P. Kitney, F. Cheng, S. Khan, C. N. Hope, W. McNab and
S. M. Kelly, Liq. Cryst., 2010, 38(8): 1027 ꢀ 1033.
9.
10.
11.
12.
13.
14.
15.
16.
THP is a typical protecting group used for alcohols and phenols in
organic synthesis. 2ꢀphenoxytetrahydropyran utilises the THP
protecting group and we have shown that it is hydrolysed to form
phenol and tetrahydropyran by the acidic nature of the silica gel. No
such changes were observed in the solution in contact with the
silicon diimide gel under identical conditions. The triplet at 5.35
ppm was still observed with the same relative intensity after 24
hours of stirring in the presence of silicon diimide.
An upꢀscaled process for the reproducible fabrication of uniform
This journal is © The Royal Society of Chemistry 20xx
J. Name., 2013, 00, 1-3 | 3
Please do not adjust margins