The Journal of Physical Chemistry A
Article
(7) Muller, R.; Wallis, J. D.; Philipsborn, W. V. Direct Structural
̈
this range. These results indicate the intermediacy of a nitrene
radical, in agreement with the well-known photochemistry of
aromatic azides. In DCM DMAPP is completely consumed
under similar irradiation periods, even in concentrated
solutions, yielding a quite different product distribution. The
assignment of the products is not unambiguous yet, but NMR
evidence shows that the phenyl ring is retained and strong
signals are observed in the aromatic region. Comparison with
calculated spectra indicates that in many products the former
phenylpentazole CN bond is replaced by a CC bond. Because
DCM absorbs at 193 nm, it is proposed that in this case radicals
formed from DCM decomposition, such as Cl• and CH2Cl•
start a chain reaction that leads to quantitative conversion of
DMAPP to products. The reaction pattern and mechanism in
DCM have yet to be elucidated; replacement of the azido group
by radical attack, in competition with N2 extrusion to form the
nitrene is a possible reaction route in this solvent.
The photochemistry of DMAPA at 193 nm is also studied. It
is found that in spite of the fact that DMAPA absorbs strongly
at 193 nm, only a small fraction reacts; 93.5% remains intact,
compared to 66% in the case of DMAPP. In contrast, near UV
excitation results in higher conversion. These results indicate a
fast internal conversion to the ground state directly from energy
levels near 6.4 eV.
Proof for the Pentazole Ring System in Solution by 15N NMR
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Chemistry: the Mechanism of the Reaction of Aryldiazonium
Chlorides with Azid Ion at −80 °C: Concerted versus Stepwise
Formation of Arylpentazols, Detection of a Pentazene Intermediate, a
Combined 1H and 15N NMR Experimental and ab initio Theoretical
Study. J. Chem. Soc., Perkin Trans. 2 1998, 2243−2247.
(9) Butler, R. N.; Stephens, J. C.; Burke, L. A. First Generation of
Pentazole (HN5, Pentazolic Acid), the Final Azole, and a Zinc
Pentazolate Salt in Solution: A new N-Dearylation of 1-(p-
methoxyphenyl) Pyrazoles, a 2-(p-methoxyphenyl) Tetrazole and
Application of the methodology to 1-(p-methoxyphenyl) pentazole.
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(11) Benin, V.; Kaszynski; Radziszewski, J. G. Arylpentazoles
Revisited: Experimental and Theoretical Studies of 4-Hydroxyphe-
nylpentazole and 4-Oxophenylpentazole Anion. J. Org. Chem. 2002,
67, 1354−1358.
(12) Schroer, T.; Haiges, R.; Schneider, S.; Christe, K. O. The Race
for the First Generation of the Pentazolate Anion in Solution is Far
From Over. Chem. Commun. 2005, 1607−1609.
(13) Portius, P.; Davis, M.; Campbell, R.; Hartl, F.; Zeng, Q.; Meijer,
A. J. H. M.; Towrie, M. Dinitrogen Release from Arylpentazole: A
Picosecond Time-Resolved Infrared, Spectroelectrochemical, and DFT
Computational Study. J. Phys. Chem. A 2013, 117, 12759−12769.
(14) Geiger, U.; Haas, Y.; Grinstein, D. The Photochemistry of an
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ASSOCIATED CONTENT
■
S
* Supporting Information
Use of H NMR to assign products of DMAPP photolysis, H
NMR spectra of ∼10−2 M DMAPP solution irradiated at 193
nm in MeCN and in DCM, H NMR spectra of ∼10−2
M
DMAPP solution irradiated at 340−400 nm in MeCN and at
240−400 nm in DCM, H NMR spectra of ∼10−2 M DMAPA
solution irradiated at 193 nm in MeCN and in DCM, H NMR
spectra of ∼10−2 M DMAPA solution irradiated at 340−400
nm in MeCN and at 240−400 nm in DCM. This material is
̈
(15) Ostmark, H.; Wallin, S.; Brinck, T.; Carlqvist, P.; Claridge, R.;
Hedlund, E.; Yudina, L. Detection of Pentazolate Anion (cyclo-N5−)
from Laser Ionization and Decomposition of Solid p-dimethylamino-
phenylpentazole. Chem. Phys. Lett. 2003, 379, 539−546.
(16) Vij, A.; Pavlovich, J. G.; Wilson, W. W.; Vij, V.; Christe, K. O.
Experimental Detection of the Pentaazacyclopentadienide (Pentazo-
late) Anion, Cyclo-N5−. Angew. Chem., Int. Ed. Engl. 2002, 41, 3051−
3054.
(17) Perera, S. A.; Gregusova, A.; Bartlett, R. J. First Calculations of
15N-15N J Values and New Calculations of Chemical Shifts for High
Nitrogen Systems: a Comment on the Long Search for HN5 and its
Pentazole anion. J. Phys. Chem. A 2009, 113, 3197−201.
(18) Gritsan, N. P.; Platz, M. S. Kinetics, Spectroscopy and
Computational Chemistry of Arylnitrenes. Chem. Rev. 2006, 106,
3844−3867.
AUTHOR INFORMATION
■
Corresponding Author
+97226585067.
Notes
The authors declare no competing financial interest.
(19) Gritsan, N.; Pritchina, E. The Mechanism of Photolysis of
Aromatic Azides. Russ. Chem. Rev. 1992, 61, 500−516.
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Photochemistry of Phenyl Azide. Russ. Chem. Rev. 1992, 61, 25−39.
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