670 J . Org. Chem., Vol. 61, No. 2, 1996
Risi et al.
Ta ble 4. Geom etr ic P a r a m eter s of
N-Meth yla zir id in e-2,3-d ion e (3a )
Sch em e 3
bond lengthsa PM2/6-31G*
bond anglesb
PM2/6-31G*
N(1)-C(2)
N(1)-C(3)
C(2)-C(3)
C(2)-O(4)
C(3)-O(5)
N(1)-C(6)
C(6)-H(7)
C(6)-H(8)
C(6)-H(9)
141.1
141.2
147.9
120.5
120.5
145.7
109.2
109.0
109.2
N(1)-C(3)-O(5)
N(1)-C(2)-O(4)
C(2)-N(1)-C(3)
C(2)-C(3)-O(5)
C(2)-N(1)-C(6)
C(3)-C(2)-O(4)
C(3)-N(1)-C(6)
N(1)-C(6)-H(7)
N(1)-C(6)-H(8)
N(1)-C(6)-H(9)
H(7)-C(6)-H(9)
H(8)-C(6)-H(9)
H(7)-C(6)-H(8)
142.1
142.0
63.2
159.5
148.2
159.6
148.6
109.2
108.1
109.5
109.7
110.1
110.2
a
b
pm. Degrees.
tions were made perpendicular to the window; then, the inlet
tube was rotated by 45° for the spectroscopy investigations.23
The deposition rate of gas mixtures was controlled with an
Air Liquide microleak (V.P/RX) and never exceeded 2 mmol/
h. This rate was chosen to minimize splitting of the vibra-
tional absorption bands due to alternative trapping sites.
F T-IR Sp ectr oscop y. The IR spectra were recorded on
a 7199 Nicolet spectrometer equipped with a liquid N2 cooled
MCT detector; the resolution was 0.12 cm-1 without apodiza-
tion. The integrated absorbances A (cm-1) were measured as
the area under a simulated peak (giving the best fit with the
experimental data) by use of the FOCAS program of the
Nicolet library.
P h otoir r a d ia tion Tech n iqu es. Irradiations were carried
out using an Osram 200 W high-pressure mercury lamp
equiped with a quartz envelope. The broad band was filtered
at λ g 335 nm, λ g 310 mn, and λ g 230 nm (Oriel filters).
Ab In itio Ca lcu la tion s. The ab initio molecular orbital
calculations were performed with the GAUSSIAN 92 program
package24 using the Møller-Plesset second-order (MP2) pro-
cedure with the standard split valence 6-31G* Gaussian basis
set.14,15 The geometry of 3a was optimized by means of
analytical gradient techniques. The bond lengths and bond
angles of molecule 3a are summarized in Table 4. The labeling
of the atoms is given in Scheme 3.
Syn th esis of 4-R-1,2,4-tr ia zolin e-3,5-d ion es. 4-Substi-
tuted-1,2,4-triazoline-3,5-diones were synthesized by oxidation
of the corresponding 4-R-1,2,4-triazolidine-3,5-diones (4-
substituted-urazoles) according to previously reported proce-
dures.3,25,26 These urazoles were dispersed in dichloromethane
and oxidized at 0 °C by bubbling dinitrogen tetraoxide to give
quantitatively the corresponding 4-substituted-1,2,4-triazoline-
3,5-diones (1a ,b). These triazolinediones were purified by
sublimation under high vacuum before use.
Spectra of solids were carried out using KBr pellets.
Vibrational transition frequencies are reported in wavenumber
(cm-1). Band intensities are assigned as very weak (vw), weak
(w), medium (m), strong (s), and broad (br).
4-P h en yl-1,2,4-tr ia zolin e-3,5-d ion e (1b) (86%): dark red
solid; mp 169 ( 2 °C (Aldrich 170 °C); 1H NMR (CDCl3, TMS)
δ 7.42 (s, 5H); 13C NMR (CD2Cl2) δ 158.3 (2C, CdO), 130.3
(2C, Cmeta), 130.0 (1C, Cpara), 129.8 (1C, Cipso), 124.6 (2C, Cortho);
IR (KBr) 3060 (w), 1768 (s, br), 1620 (w), 1585 (m), 1525 (m),
1503 (s), 1480 (w), 1400 (s), 1315 (w), 1289 (m), 1174 (s), 1070
(m), 1031 (m), 1000 (m), 910 (w), 892 (m), 765 (m), 724 (s),
678 (s, br), 605 (m) cm-1; UV (CH2Cl2) n f π* λmax 540 nm,
ꢀmax 118 mol-1 L cm-1, π f π* λmax 310 and 232 nm with
respectively ꢀmax 359 mol-1 L cm-1 and 6137 mol-1 L cm-1
.
Con clu sion
In this work, experimental data for the photochemical
reaction of 4-methyl- and 4-phenyl-1,2,4-triazoline-3,5-
diones trapped at 10 K in argon matrices were obtained.
The products of photolysis, CO, isocyanates, and aziri-
dine-2,3-diones, were identified. These results have to
be compared to those obtained by Wamhoff et al.7 on the
photolysis of 4-phenyl-1,2,4-triazoline-3,5-dione in solu-
tion (acetonitrile, benzene) at room temperature. Al-
though our final products are the same (N2, CO, isocy-
anate) we show that photolysis of the molecule isolated
in a cryogenic rare gas matrix gives in addition a strained
compound identified as N-R-aziridine-2,3-dione. The
latter which has been previously identified at 77 K by
Aoyma et al.11 decomposes spontaneously at tempera-
tures >77 K.
In our experiment the decomposition occurs at 10 K
under irradiation (λ g 230 nm). This compound is in
agreement with the hypothesis of an evolution via a
biradical intermediate able to exhibit decarbonylation or
cyclization.
4-Meth yl-1,2,4-tr iazolin e-3,5-dion e (1a) (81%): pink solid;
1
mp 112 ( 2 °C (Aldrich 107-109 °C); H NMR (CDCl3,TMS)
δ 3.05 (s, 3H); 13C NMR (CDCl3) δ 24 (1C, NsCH3), 157 (2C,
CdO); IR (KBr) 2966 (vw), 1782 (s, br), 1745 (s), 1540 (w), 1445
(m, br), 1392 (m), 1273 (m), 1101 (w), 1025 (vw), 952 (m), 739
(m), 673 (s, br), 626 (w), 554 (w). UV (CH2Cl2) n f π* λmax
535 nm, ꢀmax 184 mol-1 L cm-1, π f π* λmax 290 nm, ꢀmax 2000
Ack n ow led gm en t. The CNRS (IDRIS) and the
Region Provence-Alpes-Coˆte d’Azur (Centre Re´gional de
Calcul Scientifique) are gratefully acknowledged for
their financial support. F.R. thanks M. Monnier and
A. Allouche for fruitful discussions.
mol-1 L cm-1
.
(23) Pourcin, J .; Monnier, M.; Verlaque, P.; Davidovics, G.; Lauri-
cella, R.; Colonna, C.; Bodot, H. J . Mol. Spectrosc. 1985, 109, 186-
201.
(24) Frisch, M. J .; Trucks, G. W.; Head-Gordon, M.; Gill, P. M. W.;
Wong, M. W.; Foresman, J . B.; J onhson, B. G.; Schlegel, H. B.; Robb,
M. A.; Reploges, E. S.; Gompert, R.; Andres, J . L.; Raghavachari, K.;
Binkley, J . S.; Gonzalez, C.; Martin, R. L.; Fox, D. J .; Defrees, D. J .;
Baker, J .; Stewart, J . J . P.; Pople, J . A. Gaussian 92, Gaussian, Inc.;
Pittsburgh, PA, 1992.
Su p p or tin g In for m a tion Ava ila ble: Geometric param-
eters and observed and simulated IR spectra of 2a , IR spectra
of 1b photolysis reaction mixtures, and kinetic study (6 pages).
This material is contained in libraries on microfiche, im-
mediately follows this article in the microfilm version of the
journal, and can be ordered from the ACS; see any current
masthead page for ordering information.
(25) Stickler, J . C.; Pirkle, W. H. J . Org. Chem. 1966, 31, 3444.
(26) Mallakpour, S. E. J . Chem. Educ. 1992, 69, 238.
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