A high-resolution FT-IR study of the fundamental bands v7, v8, and v18 of ethene secondary ozonide

Article abstract of DOI:10.1021/jp051647e

Ozonization reaction of ethene in neat film at 77 K was performed. Separation of ethene secondary ozonide from the other products of the reaction was performed by continuous pumping of the reactor. Only the products, which evaporated from the walls of the reactor at 185 K, were transferred to the gas cell. The high-resolution infrared absorption spectrum of gaseous ethene secondary ozonide (C₂H₄O₃) in a static gas long-path absorption cell has been recorded in the 900-1100 cm^-1 spectral region at 185 K. The spectral resolution was 0.003 cm^-1. Analyses of the v₇(A) band at 1037.0 cm^-1, the v ₈(A) band at 956.1 cm^-1, and the V₁₈(B) band at 1082.1 cm^-1 have been performed using the Watson Hamiltonian model (A, reduction; III^r, representation). A set of ground-state rotational and quartic centrifugal distortion constants have been obtained, and upper state spectroscopic constants have been determined for the bands investigated. A local resonance observed in v₁₈ is explained as c-Coriolis interaction with v₁₀+ v₁₁.

Full text of DOI:10.1021/jp051647e

J. Phys. Chem. A 2005, 109, 8719-8723
8719
A High-Resolution FT-IR Study of the Fundamental Bands ν7, ν8, and ν18 of Ethene
Secondary Ozonide
Valdas Sablinskas,*,† Flemming Hegelund,‡ Justinas Ceponkus,† Ruta Bariseviciute,†
Valdemaras Aleksa,† and Bengt Nelander§
Department of General Physics and Spectroscopy, Vilnius UniVersity, UniVersiteto street 3,
Vilnius-01513, Lithuania, Department of Chemistry, Aarhus UniVersity, Langelandsgade 140,
DK-8000 Aarhus C, Denmark, and Chemical Center, Department of Chemical Physics, Lund UniVersity,
P.O. Box 124, S-221 00 Lund, Sweden
ReceiVed: April 1, 2005; In Final Form: June 16, 2005
Ozonization reaction of ethene in neat film at 77 K was performed. Separation of ethene secondary ozonide
from the other products of the reaction was performed by continuous pumping of the reactor. Only the products,
which evaporated from the walls of the reactor at 185 K, were transferred to the gas cell. The high-resolution
infrared absorption spectrum of gaseous ethene secondary ozonide (C2H4O3) in a static gas long-path absorption
cell has been recorded in the 900-1100 cm-1 spectral region at 185 K. The spectral resolution was 0.003
cm-1. Analyses of the ν7(A) band at 1037.0 cm-1, the ν8(A) band at 956.1 cm-1, and the ν18(B) band at
1082.1 cm-1 have been performed using the Watson Hamiltonian model (A, reduction; IIIr, representation).
A set of ground-state rotational and quartic centrifugal distortion constants have been obtained, and upper
state spectroscopic constants have been determined for the bands investigated. A local resonance observed in
ν18 is explained as c-Coriolis interaction with ν10 + ν11.
1. Introduction
Among organic compounds present in troposphere, the
alkenes are unique as they are reactive toward ozone. The
currently generally accepted Criege mechanism1 assumes that
the ozonization reaction of alkenes proceeds in three steps: (I)
formation of primary ozonide (POZ), (II) decomposition of POZ
into a carbonyl compound R-CHO and a carbonyl oxide
R-COO, and (III) addition of the carbonyl compound to the
carbonyl oxide to form secondary ozonide (SOZ). The inter-
mediate products of the reaction are formed vibrationally
excited, and the fate of the reaction very much depends on the
possibilities for cooling of these products. Considerable colli-
sional cooling of the intermediate products is needed for the
reaction to proceed according to the Criege scheme. SOZ by
itself is a labile compound; its stability varies with the size and
shape of the radical, attached to the five-membered ring
COOCO. Ethene SOZ is the smallest and most unstable member
of the alkenes SOZ. In our experiments, this compound nearly
completely decomposes at room temperature during 12 h. It is
accepted that the Criege mechanism is valid for the ozonization
reaction in the condensed phase, but the reaction mechanism
in the gaseous phase has still not been established in full detail.2
The structure of ethene SOZ (C2H4O3) was established in
1972 by Gillies and Kuczkowski3 from microwave measure-
ments. They showed that the molecular point group is C2 with
the rotational axis coinciding with the b-axis of the molecule
(Figure 1). The vibrational spectrum of ethene SOZ isolated in
a solid-state argon matrix was measured by Ku¨hne and
Gu¨nthard4 in 1976, and most of the fundamental bands were
assigned. The vibrational assignment was recently modified by
Figure 1. Structure of ethene SOZ.
Samuni and Haas from their ab initio study of the normal modes
of the molecule.5
To our knowledge, no previous high-resolution infrared study
has been published for the ethene SOZ in the gas phase. In the
present paper, we investigate three fundamental bands in the
950-1100 cm-1 region: the weak CO symmetric stretching
mode ν7(A) at 1037 cm-1, the strong COC deformation mode
ν8(A) at 956 cm-1, and the strong asymmetric COC stretching
mode ν18(B) at 1082 cm-1. An improved set of ground-state
rotational and centrifugal distortion constants is obtained from
a simultaneous analysis of our present spectra of ν8 and ν18,
and the ground-state microwave measurements.3 Upper state
spectroscopic constants are obtained from separate fits of the
three bands, and a c-Coriolis perturbation observed in ν18 is
discussed in some detail.
2. Experimental Details
* Corresponding author. E-mail: valdas.sablinskas@ff.vu.lt.
† Vilnius University.
Ozone was prepared from oxygen by electric discharge in a
glass reactor cooled by L-N2. The reactor was filled with 100
‡ Aarhus University.
§ Lund University.
10.1021/jp051647e CCC: $30.25 © 2005 American Chemical Society
Published on Web 09/13/2005

8720 J. Phys. Chem. A, Vol. 109, No. 39, 2005
Sablinskas et al.
Torr L of oxygen and left for 1 h with electrical discharge
between electrodes fixed on the inner and outer walls of the
reactor. A mixture of ozone and oxygen was trapped on cold
walls of the reactor during the discharge. After the discharge
was stopped, oxygen was removed by pumping on the reactor
for 30 min. The saturated vapor pressure of oxygen at 77 K is
much higher than the saturated vapor pressure of ozone, and in
this way pure ozone was left in the reactor. Subsequently, ozone
was trapped on silica gel, cooled with dry ice.
The ethene SOZ has been prepared by reacting ozone and
ethylene in neat film, formed on the wall of the stainless steel
reactor at 77 K. Mixtures of ozone and olefins tend to be
explosive. To ensure better mixing of ozone with ethylene, the
reactants were introduced to the reactor in small portions, not
exciding 10 Torr L. This allowed the ozone and ethene to form
a sandwich-type structure consisting of consecutively deposited
thin films. This multilayer film was formed on a large surface
area in the reactor, and any localized build-up of reactants was
prevented. Attempts to use bigger portions of reactants produced
an explosive decomposition of the reaction mixture. Once the
reactants were in the reactor, cooling of the reactor was stopped
and the warming process was allowed to begin. Separation of
ethene SOZ from the other products of the reaction was
performed by continuous pumping of the reactor. Only the
products, which evaporated from the walls of the reactor at 185
K, were transferred to multipass IR gas cell, cooled to 185 K.
High-resolution infrared absorption spectra were recorded on
the Bruker IFS 120 HR Fourier transform spectrometer at the
Swedish national laboratory of synchrotron radiation MAX-
laboratory in Lund. The spectra were recorded at 0.003 cm-1
spectral resolution. To eliminate radiation >1100 cm-1, a high
transmission (T > 90%) 9-µm low pass optical filter was used.
For recording of the HR spectra, the globar light source, a KBr
beam splitter, and an HgCdTe detector were used.
A 200 L absorption gas cell, made of stainless steel, with
White optics, and equipped with CsI windows, was used to
obtain the HR spectra. The base length of the cell was 2.85 m.
A total number of 24 passes were used for recording of the
spectra. The pressure of ethene SOZ in the gas cell was less
than 10 Pa. Single-beam spectra were recorded with 0.003 cm-1
resolution without zero filling and with boxcar apodization. The
background spectrum of the empty cell was recorded at lower
resolution, using an appropriate zero filling factor. The final
absorbance spectra were free of the periodical interference
pattern, which comes from the cell windows and is rather strong
in single beam spectra.
Figure 2. HR FTIR absorption spectrum of ethene SOZ in spectral
region of ν7, ν8, and ν18 fundamental vibrations.
pick out the series. Also, the series start (i.e., for J ) Kc) is
straightforward to locate because this is the most intense line
in the series. In Figure 3, the assignment of a small part of the
R-wing of ν8 is shown. The strongest transitions RRK(K) are
easy to identify. There is also a tendency of clustering for lines
with the same value for 2J - Kc. This is because the molecule
is nearly planar, that is, A ≈ B ≈ 2C. Near the band center
R
P
region of ν8, a number of Q- and Q-branch series are seen.
Figure 4 shows the assignment to J and Kc of a part of the RQ-
branch. In the weak ν7 band, we were not able to establish
convincing Q-branch assignments.
As seen in Figure 2, a strong Q-branch appears near the band
center of ν18. Such a structure, which is not well resolved even
under high resolution, indicates a,c-band type. The rotational
fine structure in the P- and R-wing of ν18 is similar to that of
b-type bands with series spaced ca. 0.545 cm-1, each showing
a clear series start. Also, a tendency of clustering is clearly seen.
This appearance is typical both for a- and for b-type bands,
and we therefore conclude that ν18 is dominated by its
a-component. This is further confirmed by our assignment of
R
P
weaker Q- and Q-branch transitions. We have not been able
to assign c-type transitions in this band. In Figure 5a, small
part of the PP-branch assignment is shown and cluster structure
is indicated for 2J - Kc ) 30-32.
In our assignment procedure of the bands observed, we made
systematic use of ground-state combination differences (GSCDs).
The rotational ground-state constants from ref 3 were used to
predict GSCDs of the type RRK-1(J - 1) - PPK+1(J + 1), which
made possible the assignment of individual rotational lines in
the observed series to J and Kc. Also, Q- and P,R-branch
assignments were checked against each other by GSCDs. To
speed up and to complete the process of assignment, we used
a semiautomatic procedure based on computer-assisted Loomis-
Wood diagrams. These diagrams, which are based on our peak
lists, are ordered according to upper state quantum numbers and
take into account the GSCDs as originally suggested by
Nakagawa and Overend.6 The assignment and additional fit
programs have been developed at Aarhus University.
3. Assignment of the Bands
Ethene SOZ is a near oblate asymmetric top molecule of C2
symmetry with κ ≈ 0.918. Eleven of the normal vibrations of
the molecule, ν1-ν11, are totally symmetric (A). The remaining
10, ν12-ν21 are of B symmetry in the C2 point group. The totally
symmetric fundamentals give rise to b-type bands for which
the strongest transitions are governed by the oblate symmetric
top rotational selection rule ∆Kc ) (1. The fundamentals of
B-symmetry yield a,c-hybrid bands. For the strongest transitions
of the a-component, ∆Kc ) (1, and for the c-component,
∆Kc ) 0.
From the survey spectrum in Figure 2, it is seen that ν7 and
ν8 appear as typical b-type bands with a minimum of intensity
in the band center region. Intense series of PP- and RR-branches
(i.e., transitions with ∆Kc ) ∆J ) -1 and ∆Kc ) ∆J ) +1,
respectively) dominate the band structure. The individual lines
in the series are spaced A + B ≈ 0.545 cm-1, and it is easy to
Some details concerning the assignments of the fundamental
bands studied in the present work are summarized in Table 1.
About 1600 lines were assigned for ν8, and ca. one-half that
number were assigned for ν7 and ν18. Short asymmetry split
series were assigned for low Kc, typically for Kc < 5.
4. Results
4a. Ground-State Analysis. The vibrational ground state of
ethene SOZ was studied by microwave spectroscopy,3 and the

FT-IR Study of Ethene Secondary Ozonide
J. Phys. Chem. A, Vol. 109, No. 39, 2005 8721
Figure 3. A close-up on the infrared absorbance spectrum of the R-wing of the ν8 band of ethene SOZ. The figure shows the J-assignment of part
R
of the RR5- to the R15-branches.
Figure 4. A small portion of the central part of the infrared absorbance spectrum of the ν8 band of ethene SOZ. The figure shows the J-assignment
of the RQ5- to the RQ8-branches.
rotational ground-state constants were obtained; see Table 2,
column I. We have redetermined the ground-state parameters
for the molecule using our present infrared measurements.
Because the ν7 band is relatively weak, we only fitted GSCDs
obtained from the strong ν8 and ν18 bands. Both ν7 and ν8 are
b-type bands giving GSCDs of the same type, which makes ν7
less important for a ground-state analysis. A total of 1325
GSCDs mainly based on unblended lines were selected from
ν8 and ν18 for our ground-state fit. The Watson Hamiltonian
(A, reduction; IIIr, representation) was employed including all
five quartic centrifugal distortion constants.7 In column II of
Table 2, the ground-state constants obtained are given. Besides
the rotational constants, three of the quartic centrifugal distortion
constants ∆J, ∆JK, and ∆K have been determined for the first
time. The two nondiagonal quartic distortion constants δJ and
δK could not be obtained significantly from our data. The
standard deviation of the fit is 0.00059 cm-1, and the numerical
values of the residuals are well below 0.00180 cm-1. The
rotational constants obtained agree well with those from the
microwave analysis3 (column I). The largest deviation, which
corresponds to ca. four standard errors, is for the A-rotational
constant.

8722 J. Phys. Chem. A, Vol. 109, No. 39, 2005
Sablinskas et al.
Figure 5. A close-up on the infrared absorbance spectrum of the P-wing of the ν18 band of ethene SOZ. The figure shows clustering around the
P
leading PK(K) lines for Kc ) 30-32.
TABLE 1: Details of Assignment
band
band type
range of assignments
local crossings
ν7(A; 1037.0 cm-1
)
b, CO sym. stretch
b, COC deformation
a, COC asym. stretch
1 < Kc < 50, J < 53
Kc < 54, J < 58
1 < Kc < 47, J < 49
ν8(A; 956.1 cm-1
)
Kc ) 33
Kc ) 22,23
ν18(B; 1082.1 cm-1
)
TABLE 2: Ground-State Constants in cm-1 for Ethene
Secondary Ozonide (A, Reduction; IIIr, Representation)
TABLE 3: Upper State Constants in cm-1 for the ν7, ν8, and
ν18 Bands of Ethene Secondary Ozonide (A, Reduction; IIIr,
Representation)
Ia
IIb
IIIc
ν7
ν8
ν18
A
B
C
0.27498490(67)d 0.2749785(15)
0.27498377(73)
0.26998325(73)
ν0
1037.01111(5)a
0.2740553(100) 0.27482647(37) 0.2744217(31)
0.2693487(100) 0.26922995(37) 0.2685297(31)
956.06748(4)
1082.11501(5)
0.26998011(67)
0.15293046(33)
0.2699828(15)
0.15293094(52) 0.15293079(31)
0.1072(13)
-0.1395(33)
0.580(20)
1325
A
B
C
∆J × 106
0.1093(8)
-0.1437(22)
0.601(15)
1335
∆
JK × 106
0.15252428(13) 0.15256281(8)
0.15285078(27)
0.10105(41)
-0.1398(9)
1.075(7)
∆J × 106
0.10530(29)
-0.1332(7)
0.5183(41)
0.11527(16)
-0.16332(34)
0.7701(20)
∆K × 107
Ne
10
∆
JK × 106
∆K × 107
ΦK × 1011
δJ × 108
Nb
σf
0.00059
-0.627(14)
a I, rotational ground-state constants obtained in the MW study; ref
3. b II, ground-state rotational and centrifugal distortion constants
determined from a combined fit of the present GSCDs from ν8 and
ν18. c III, ground-state rotational and centrifugal distortion constants
determined from a combined fit of 10 MW measurements3 and the
GSCDs from ν8 and ν18. d Uncertainties quoted are one standard error.
0.379(15)
1548
0.00053
706
787
σc
0.00048
0.00051
a Uncertainties quoted are one standard error. b Number of observa-
tions in fit. c Standard deviation of fit, cm-1
.
e Number of observations in fit. f Standard deviation of fit, cm-1
.
4b. Upper State Analysis. To fit the assigned transition
wavenumbers in a band and to obtain upper state spectroscopic
parameters, we used the asymmetric rotor Hamiltonian of
Watson (A, reduction; IIIr, representation).7 In the fit, the
observed wavenumbers are converted to upper state energies
by addition of the proper ground-state energies, as calculated
from the set of ground-state constants given in column III of
Table 2. Thus, our fits are on upper state energies. No weighting
of the observed transitions is used in the fits.
We have also fitted our present GSCDs simultaneously with
the microwave transitions from ref 3. This added 10 observa-
tions. In this fit, we gave the microwave data a weight of 104
relative to our infrared GSCDs to take into account that the
accuracy of the microwave frequencies is higher by a factor of
ca. 100 as compared to our infrared wavenumbers. The constants
from this fit are given in column III of Table 2. As expected,
the inclusion of the microwave data increases the precision of
the ground-state parameters, in particular, the rotational con-
stants. The constants from the two fits (columns II and III) agree
within ca. three standard errors. A comparison with the
microwave values (column I) shows a slightly higher deviation
for the B-rotational constant, around four standard errors. We
consider the ground-state constants in column III as the best.
Table 3 summarizes the upper state constants obtained from
the fits of ν7, ν8, and ν18. The standard deviations of the fits are
around 0.00050 cm-1, which is ca. twice our estimated
wavenumber accuracy. In the fits, the band center, the rotational
constants, and the three quartic centrifugal distortion constants
∆J, ∆JK, and ∆K have been determined for the upper states.

FT-IR Study of Ethene Secondary Ozonide
J. Phys. Chem. A, Vol. 109, No. 39, 2005 8723
For the ν18 band, it was also necessary to include the sextic
distortion constants ΦK to obtain a good fit. As seen from Table
3, ΦK is obtained negative, and a comparison of ∆K with its
ground-state value (Table 2) reveals that this constant is
considerably larger than its ground-state value, ∆∆K ) 0.472-
(17) × 10-7cm-1. This indicates the presence of a global
c-Coriolis resonance lowering the Kc-levels of ν18. Thus, the
perturbing level is of higher vibrational energy than ν18. In
addition, a local resonance is observed for Kc ) 22, 23. The
effect of this resonance increases with J, giving rise to negative
residuals for Kc ) 22 and positive residuals for Kc ) 23. This
means that a crossing is present for which the perturbing level
is above the Kc ) 22 level in ν18 and below the Kc ) 23 level
in ν18. The observed sense of residuals indicates that the
perturber, producing crossing in ν18, also has higher vibrational
energy than ν18. Because the selection rules for c-Coriolis
resonance are ∆Kc ) 0, (2, (4, we suggest that the resonances
described above are due the same perturber, giving rise to global
c-Coriolis interaction (∆Kc ) 0) as well as local c-Coriolis
interaction for Kc ) 22, 23 (∆Kc ) (2). Assuming ground-
state values for the rotational constants of the perturber, we may
estimate the vibrational band center of the perturber to be located
11.3(3) cm-1 above the band center of ν18 from the position of
crossing observed in ν18. By symmetry, the perturber is predicted
to be of A-symmetry in the C2 group. Experimental band center
values for fundamental levels from solid-state infrared measure-
ments are given in ref 5. From these values, we may suggest
that the perturber is the binary combination of the ring
deformation vibration ν10 and the ring puckering vibration ν11,
ν10 + ν11(A), which is predicted at 1089 cm-1 from the data in
ref 4 neglecting anharmonicity. Our gas-phase study of ν18
locates ν10 + ν11 at 1093.4(3) cm-1 from the observed effect
of local c-Coriolis perturbation. The agreement is reasonable
taking into account that the measurements4 are for the solid state.
The c-Coriolis resonance might transfer intensity from ν18 to
the ν10 + ν11 band. However, we have not been able to assign
with confidence line series belonging to this combination band.
The upper state constants summarized in Table 3 have been
obtained from a fit leaving out 75 perturbed transitions of ν18
in the region of crossing.
be omitted. We have not been able to identify the perturber in
this case. As seen from Table 3, a significant value for the
quartic centrifugal distortion constant δJ may be determined.
This is certainly because we have been able to trace the typical
b-band series of low-Kc P- and R-branch transitions (in particular
for Kc ) 0 and 1 (Ka + Kc ) J + 1)) out to J ≈ 40. For the
weak ν7 band, no perturbation seems to be present.
A list of the assigned observed transitions used in the fits
described above may be obtained from F.H. or V.S.
5. Summary
In the present paper, we report the first recording of the high-
resolution spectra of ethene SOZ in the gas phase. Three bands,
ν7, ν8, and ν18, in the 950-1100 cm-1 region have been assigned
and analyzed. From a simultaneous fit of ν8, ν18 and the
microwave measurements by Gillies and Kuczkowski,3 we
obtain improved values of the ground-state rotational constants,
and three of the quartic centrifugal distortion constants ∆J, ∆JK,
and ∆K are determined for the first time. Upper state spectro-
scopic constants including band centers, rotational constants,
and quartic centrifugal distortion constants have been obtained
for the three bands studied. From a local resonance observed
in ν18, we may locate the binary combination level ν10 + ν11 at
1093.4(3) cm-1 assuming higher order c-Coriolis perturbation.
Acknowledgment. The running costs of the infrared beam
line at the Max laboratory were covered by the Swedish National
Science Council. Experiments at Max laboratory of V.S., J.C.,
R.B., and V.A. were supported partly by the European Com-
munity - Research Infrastructure Action under the FP6
“Structuring the European Research Area” Program (through
the Integrated Infrastructure Initiative “Integrating Activity on
Synchrotron and Free Electron Laser Science”) and partly by
Nordic Network of Chemical kinetics.
References and Notes
(1) Criegee, R. Angew. Chem. 1975, 87, 765-771.
(2) Horie, O.; Neeb, P.; Moortgat, G. K. Int. J. Chem. Kinet. 1997,
29, 461-468.
(3) Gillies, C. V.; Kuczkowski, R. L. J. Am. Chem. Soc. 1972, 94,
6337-6343.
(4) Ku¨hne, H.; Gu¨nthard, Hs. H. J. Phys. Chem. 1976, 80, 1238-1247.
(5) Samuni, U.; Haas, Y. Spectrochim. Acta 1996, A52, 1479-1492.
(6) Nakagawa, T.; Overend, J. J. Mol. Spectrosc. 1974, 50, 333-348.
(7) Watson, J. K. G. In Vibrational Spectra and Structure; Durig, J.,
Ed.; Elsevier: Amsterdam, 1977; pp 1-89.
In our analysis of the ν8 band, we observed a minor local
J-dependent resonance in the Kc ) 33 level. The observed sense
of the residuals indicates that the perturber is located above the
Kc ) 33 level. The neighboring Kc levels seem to be unper-
turbed, and in our fit only eight transitions for Kc ) 33 had to