Thermal gas-phase reaction of perfluorobuta-1,3-diene with NO2

Article abstract of DOI:10.1016/j.jfluchem.2007.12.001

The reaction of NO₂ with perfluorobuta-1,3-diene, CF₂{double bond, long}CFCF{double bond, long}CF₂ (C₄F₆), has been studied at 312.9, 323.0, 333.4, 396.0 and 418.0 K, using a conventional static system. The products formed in the temperature range 312.9-333.4 K were CF₂{double bond, long}CFCF(NO₂)CF₂(NO₂) (I), CF₂(NO₂)CF{double bond, long}CFCF₂(NO₂) (II), CF₂{double bond, long}CFCF(NO₂)C(O)F (III) and CF₂(NO₂)CF{double bond, long}CFC(O)F (IV) and FNO. The formation of these compounds was detected performing infrared and Raman spectra. The infrared spectrum shows a band at 1785 cm^-1, characteristic to the terminal -CF{double bond, long}CF₂ group and the Raman spectrum shows a band located at 1733 cm^-1, corresponding to -CF{double bond, long}CF- group. It indicates, that in this temperature range, NO₂ attacks initially only one double bound of CF₂{double bond, long}CFCF{double bond, long}CF₂. Since the intermediate radical CF₂{double bond, long}CFC{radical dot}FCF₂(NO₂) formed in this process is allylic in nature, so there is no isomerization involved in this process, but rather the allylic radical is able to add the second NO₂ either to CF₂ or CFCF₂(NO₂) end, forming the corresponding products. At 396.0 and 418.0 K different products were observed: CF₂(NO₂)CF(NO₂)C(O)F (V), NO, CF₃C(O)F, C(O)F₂ and traces of epoxide of tetrafluoroethene, showing that, at these temperatures, both double bonds are attacked by NO₂ and detachment of CF₂ group is produced. The mechanisms consistent with experimental results in the temperature range 312.9-333.4 and at 396.0 and 418 K are proposed.

Full text of DOI:10.1016/j.jfluchem.2007.12.001

Available online at www.sciencedirect.com
Journal of Fluorine Chemistry 129 (2008) 261–266
www.elsevier.com/locate/fluor
Thermal gas-phase reaction of perfluorobuta-1,3-diene with NO2
*
Joanna Czarnowski
´ ´
Instituto de Investigaciones Fisicoquımicas Teoricas y Aplicadas, INIFTA, Casilla de Correo 16, Sucursal 4, (1900) La Plata, Argentina
Received 10 September 2007; received in revised form 4 December 2007; accepted 4 December 2007
Available online 14 December 2007
Abstract
The reaction of NO2 with perfluorobuta-1,3-diene, CF2 CFCF CF2 (C4F6), has been studied at 312.9, 323.0, 333.4, 396.0 and 418.0 K, using a
conventional static system. The products formed in the temperature range 312.9–333.4 K were CF2 CFCF(NO2)CF2(NO2) (I),
CF2(NO2)CF CFCF2(NO2) (II), CF2 CFCF(NO2)C(O)F (III) and CF2(NO2)CF CFC(O)F (IV) and FNO. The formation of these compounds
was detected performing infrared and Raman spectra. The infrared spectrum shows a band at 1785 cmꢀ1, characteristic to the terminal –CF CF2
group and the Raman spectrum shows a band located at 1733 cmꢀ1, corresponding to –CF CF– group. It indicates, that in this temperature range,
NO2 attacks initially only one double bound of CF2 CFCF CF2. Since the intermediate radical CF2 CFCꢁFCF2(NO2) formed in this process is
allylic in nature, so there is no isomerization involved in this process, but rather the allylic radical is able to add the second NO2 either to CF2 or
CFCF2(NO2) end, forming the corresponding products. At 396.0 and 418.0 K different products were observed: CF2(NO2)CF(NO2)C(O)F (V),
NO, CF3C(O)F, C(O)F2 and traces of epoxide of tetrafluoroethene, showing that, at these temperatures, both double bonds are attacked by NO2 and
detachment of CF2 group is produced. The mechanisms consistent with experimental results in the temperature range 312.9–333.4 and at 396.0 and
418 K are proposed.
# 2008 Elsevier B.V. All rights reserved.
Keywords: Thermal gas-phase reaction; Perfluorobuta-1,3-diene; Nitrogen dioxide; 1,1,2,3,4,4–Hexafluoro-3,4-dinitrobut-1-ene; 2,3,4,4-Tetrafluoro-2-nitrobut-3-
enoyl fluoride; 1,1,2,3,4,4-Hexafluoro-1,4-dinitrobut-2-ene; 2,3,4,4-Tetrafluoro-4-nitrobut-2-enoyl fluoride; 2,3,3-Trifluoro-2,3-dinitropropanoyl fluoride
1. Introduction
vicinal dinitro compounds and nitrohaloacetyl halides and
XNO, where X = Br or Cl. The following basic common
reaction mechanism can be proposed:
The addition reactions of NO2 to halogenated olefins have
been subject of several studies [1–9]. These reactions are
generally employed for preparative purposes, because NO2
can act either as nitrating or as oxidating agent. From a
mechanistic point of view these processes are readily
understood in terms of free radical reaction schemes initiated
by the NO2 attack on the olefinic C atom. As several reaction
channels can be possible, the elucidation of the mechanism
of these reactions is of interest for organic and inorganic
chemistry.
ꢁ
NO2 þ CF2CX2 ! CF2ðNO2ÞCX2
ꢁ
CF2ðNO2ÞCX2 þ NO2 þ M ! CF2ðNO2ÞCX2NO2 þ M
ꢁ
CF2ðNO2ÞCX2 þ NO2 ! CF2ðNO2ÞCðOÞX þ XNO
In this mechanism and in the subsequent mechanisms of the
present work M is equal to effective pressure.
Detailed mechanistic studies, kinetic parameters and
product formation have been reported for several gas-phase
reactions of NO2 with perhalogenated ethenes CF2CX2, where
X = Br, Cl or F, at temperatures ranging from about 300 to
360 K [10–12]. The major products in these systems were
However the gas-phase reactions of NO2 with perfluor-
opropene, C3F6, [13] and with perfluorobutene-2, C4F8-2 [14]
follow a different pattern.
Perfluoropropene reacts with NO2 between 413.0 and
433.0 K [13], giving equivalent quantities of perfluoropropene
epoxide, PFPE, and NO as the major products and smaller
amounts of CF3CF(NO2)CF2(NO2), nitroperfluoroacetone and
FNO. The following mechanism was postulated for this
* Tel.: +54 221 4257291; fax: +54 221 4254642.
E-mail address: bdq782@infovia.com.ar.
0022-1139/$ – see front matter # 2008 Elsevier B.V. All rights reserved.
doi:10.1016/j.jfluchem.2007.12.001

262
J. Czarnowski / Journal of Fluorine Chemistry 129 (2008) 261–266
reaction:
appearing in the infrared spectra, assigned to SiF4, confirms
the presence of FNO. SiF4 forms on Pyrex cell surface
through the following reaction [9]:
CF3CF¼CF2 þ NO2 ! CF3CꢁFCF2NO2
SiO2 þ 4FNO ! SiF4 þ 2NO þ 2NO2:
At 396.0 and 418.0 K the NO2 was completely consumed
when introducing C4F6 to the reaction vessel as the second
reactant. The observed products were CF2(NO2)CF(NO2)-
C(O)F (V), NO, CF3C(O)F, C(O)F2 and traces of epoxide of
tetrafluoroethene.
CF3CꢁFCF2NO2 þ NO2 þ M ! CF3CFðNO2ÞCF2NO2 þ M
CF3CꢁFCF2NO2 þ NO2 ! CF3CðOÞCF2NO2 þ FNO
In the reaction of NO2 with C4F8-2 in the temperature range
418.5–470.0 K [14], equal amounts of perfluorobutene-2
epoxide, PFBE, and NO are formed. Above 430 K PFBE
decomposes generating CF3C(O)F and biradical :CFCF3. The
latter self-recombines reforming the parent C4F8-2 molecule.
The following mechanism consistent with experimental results
was postulated:
CF3C(O)F, C(O)F2, NO, FNO, SiF4 and epoxide of
tetrafluoroethene were identified by their known infrared
spectra. The compounds (I), (II), (III) and (IV) have been
assigned the structure consistent with their IR and Raman
spectra. The infrared absorption bands for the mixture of
CF2 CFCF(NO2)CF2(NO2) (I) and CF2(NO2)CF CFCF2
(NO2) (II) appear at 1785, 1620, 1371, 1333, 1275, 1243,
1175, 1133, 925 and 790 cmꢀ1. In the infrared spectra of
the mixture of CF2 CFCF(NO2)C(O)F (III) and CF2(NO2)
CF CFC(O)F (IV) the observed infrared bands were 1856,
1785, 1620, 1367, 1337, 1276, 1227, 1192, 1137, 931 and
813 cmꢀ1. In the Raman spectra of the mixture of compounds
(I) and (II) and that of (III) and (IV), bands located at 1780 and
1733 cmꢀ1 appeared. The infrared band at 1785 cmꢀ1 is
characteristic to the –CF CF2 group [15]. It was reported that
1783–1785 cmꢀ1 band in the infrared spectrum of polytetra-
fluoroethene is indicative of the presence of terminal olefin
groups in the structure of the polymer [16]. CF2 CFCF CF2,
CF3CF CF2, CClF CF2 and CBrF CF2 show the bands
corresponding to the C C stretching vibrations at 1796, 1789,
1790 and 1783 cmꢀ1, respectively. It was reported [17] that the
–CF CF– groups are not active in the infrared spectra. Indeed,
the infrared spectrum of the perfluorobutene-2, CF3CF CFCF3
shows a weak band corresponding to –CF CF– stretching
vibration at 1728 cmꢀ1. At the same time the vibrations
corresponding to internal double bond are usually active in the
Raman spectra of perfluoroolefins and appear in the region
1717–1730 cmꢀ1. The vibrations corresponding to terminal
olefin groups in the Raman spectra are located between 1775
and 1790 cmꢀ1. The bands at 1620 and 1333–1337 cmꢀ1 are
:CFCF3 þ :CFCF3 þ M ! C4F8-2 þ M
Continuing our studies on nitration of perhalogenated
olefins, the reaction of NO2 with perfluorobuta-1,3-diene, C4F6,
was investigated to elucidate the nitration mechanism of
molecules containing two double bonds.
2. Results and discussion
All experiments were carried out to the complete
consumption of NO2. Within the temperature range 312.9–
333.4 K the reaction proceeded with easily measurable
pressure decrease and the following products were formed:
CF2 CFCF(NO2)CF2(NO2)
(I),
CF2(NO2)CF CFCF2
(NO2) (II), CF2 CFCF(NO2)C(O)F (III) and CF2(NO2)
CF CFC(O)F (IV) and FNO. The band at 1029 cmꢀ1
Table 1
The comparison of experimental infrared and Raman spectra of A = CF2 CFCF(NO2)CF2(NO2) + CF2(NO2)CF CFCF2(NO2) and B = CF2 CFCF(NO2)
C(O)F + CF2(NO2)CF CFC(O)F
IR A
IIR
Raman A
IR
IR B
IIR
Raman B
IR
Tentative assigment
1856
1785
vs
s
1846
1780
1733
1699
1412
1341
vvs
C O
1785
s
1780
1733
1700
1412
1341
s
s
–CF CF2
–CF CF–
NO2
s
s
1620
1371
1333
1275
1243
1175
1133
925
vvs
m
s
vvs
s
1620
1367
1337
1276
1227
1192
1137
931
vvs
m
s
vvs
s
s
C–C
vs
NO2
vs
vs
m
m
w
vs
vs
m
m
w
CF2
C–C
C–F
C–F
C–N
790
w
813
m
NO2
IIR = intensity in the infrared spectra, IR = intensity in the Raman spectra, v = very, s = strong, m = medium and w = weak.

J. Czarnowski / Journal of Fluorine Chemistry 129 (2008) 261–266
263
Table 2
Analytical data of three experiments in the temperature range 312.9–333.4 K, where P(I) = [CF2 CFCF(NO2)CF2(NO2) + CF2(NO2)CF CFCF2(NO2)] and
P(II) = [CF2 CFCF(NO2)C(O)F + CF2(NO2)CF CFC(O)F]
Run
T (K)
Dp (Torr)
NO2i (Torr)
NO2f (Torr)
C4F6i (Torr)
C4F6f (Torr)
P(I) (Torr)
P(II) (Torr)
[FNO] (Torr)
9
8
7
312.9
323.0
333.4
25.5
23.0
26.8
33.5
30.1
32.9
–
–
–
34.5
30.8
28.3
17.9
15.7
12.0
8.7
8.0
8.0
7.0
6.0
7.9
6.9
6.1
10.4
The amounts of P(I) and P(II) were calculated from the quantities of C4F6 and NO2 consumed, that of FNO formed and Dp, the final pressure decrease of the reaction.
characteristic to the NO2 group [11–13,18]. The frequencies at
1367 and 1371 cmꢀ1 and those between 1276 and 930 cmꢀ1
indicate the presence of CF2, CF, C–C and C–N groups. The
absorption band located at 1856 cmꢀ1 shows the presence of
C(O)F group. It can be seen that the infrared and Raman
spectra of the compounds (I), (II), (III) and (IV) are consistent
with the structures proposed for CF2 CFCF(NO2)CF2(NO2),
CF2(NO2)CF CFCF2(NO2), CF2 CFCF(NO2)C(O)F and
CF2(NO2)CF CFC(O)F, respectively (see Table 1). The
additional support for the characterization of the above
compounds was obtained from the amounts of C4F6 and
NO2 consumed and that of FNO formed and the final pressure
decrease of the reaction (see Table 2).
1545 cmꢀ1 for chlorotrifluoroethene epoxide and at 1500 cmꢀ1
for 1,1-dichloro-2,2-difluoroethene epoxide [19].
For analyzing the reaction mixture of 8 experiments carried
out to the complete consumption of NO2, the reaction vessel was
rapidly cooled to liquid nitrogen temperature and the mixture
separated by fractional condensation. The fraction F1, volatile at
153 K, obtainedfromexperimentsmadeinthetemperaturerange
312.9–333.4 K wasFNOandthatfromexperimentsperformedat
396.0 and 418.0 K consisted of CF3C(O)F, C(O)F2, NO and
epoxide of tetrafluoroethene. Over the whole temperature range
312.9–418.0 K studied, the fraction F2, volatile at 233.0 K, was
the non-consumed reactant C4F6. The fraction F3, obtained as a
residue at 233.0 K from experiments made in the temperature
range 312.9–333.4 K, consisted of CF2 CFCF(NO2)CF2(NO2),
CF2(NO2)CF CFCF2(NO2), CF2 CFCF(NO2)C(O)F and CF2
(NO2)CF CFC(O)F, and that from experiments performed at
396.0 and 418.0 K was CF2(NO2)CF(NO2)C(O)F.
For the compound (V) the following structure has been
assigned: CF2(NO2)CF(NO2)C(O)F. Its infrared bands are
located at 1856, 1617, 1333, 1275, 1242, 1192, 1133, 992 and
792 cmꢀ1. These frequencies indicate the presence of the
structural groups: C(O)F, NO2, CF2, C–F, C–C and C–N. The
determination of the relative molecular mass of this compound
by gas-density measurement with a calibrated Pyrex bulb, gives
the value 222 ꢂ 11. The theoretical value of CF2(NO2)CF(-
NO2)C(O)F is 220.
CF2 CFCF(NO2)CF2(NO2), CF2(NO2)CF CFCF2(NO2),
CF2 CFCF(NO2)C(O)F and CF2(NO2)CF CFC(O)F cannot
be separated by fractional condensation, but, distilling at 253 K,
it was possible to obtain two fractions, one containing
CF2 CFCF(NO2)CF2(NO2) + CF2(NO2)CF CFCF2(NO2) and
In Table 1 the comparison of experimental infrared and
Raman spectra of the mixtures: A = CF2 CFCF(NO2)CF2
(NO2) + CF2(NO2)CF CFCF2(NO2) and B = CF2 CFCF
(NO2)C(O)F + CF2(NO2)CF CFC(O)F is presented.
another
CF2 CFCF(NO2)C(O)F + CF2(NO2)CF CFC(O)F,
with different relative amounts of these products thus allowing
the assignment of the infrared frequencies corresponding to each
mixture (see Table 1).
No data for CF2 CFCF(NO2)CF2(NO2), CF2 CFCF(NO2)
C(O)F, CF2(NO2)CF CFC(O)F and CF2(NO)2CF(NO2)C(O)F
were found in the literature. The formation of
CF2(NO2)CF CFCF2(NO2) in the reaction between N2O4 and
C4F6 in the autoclave and at room temperature was reported [5].
No band in the region 1500–1550 cmꢀ1 was observed,
indicating that epoxide is not produced in this reaction.
The fluorinated olefin epoxides generate a characteristic infrared
band in this zone, not given by other fluorocarbon compounds.
This band appears at 1551 cmꢀ1 for perfluoropropene epoxide
[13], at 1504 cmꢀ1 for perfluorobutene-2 epoxide [14], at
The analytical data of experiments in the temperature range
312.9–333.4 K are listed in Table 2, where indices i and f
signify initial and final. The quantities of C4F6 consumed and
that of FNO formed were obtained by fractional condensation.
The amount of [CF2 CFCF(NO2)CF2(NO2) + CF2(NO2)
CF CFCF2(NO2)] and that of [CF2 CFCF(NO2)C(O)F
+ CF2(NO2)CF CFC(O)F] were calculated from the quantities
of C4F6 and NO2 consumed, that of FNO formed and Dp, the
final pressure decrease of the reaction.
The analytical data of experiments performed at 396.0 and
418.0 K are summarized in Table 3, where indices i and f
Table 3
Analytical data of 5 experiments at 396.0 and 418.0 K
P
9.3
13.8
16.0
24.6
r
C4F6 (Torr)
Run
T (K)
NO2i (Torr)
NO2f (Torr)
CF2(NO2)CF(NO2)C(O)F (Torr)
P (Torr)
5
3
396.0
418.0
418.0
418.0
418.0
33.7
19.0
27.6
33.5
47.7
–
–
–
–
–
25.1
40.9
33.7
21.4
51.2
P
11.2
6.5
16.8
4
9.8
10
11
11.1
16.4
In this table C4F6r is the pressure of C4F6 remaining after the total consumption of NO2. P is the sum of the products [CF3C(O)F] + [COF2] + [NO] + [epoxide of
CF2CF2].

264
J. Czarnowski / Journal of Fluorine Chemistry 129 (2008) 261–266
r
denote initial and final. In this table C4F6 is the pressure of
bond of C4F6 and the compounds CF2 CFCF(NO2)CF2(NO2),
CF2(NO2)CF CFCF2(NO2), CF2 CFCF(NO2)C(O)F and
CF2(NO2)CF CFC(O)F are formed.
P
C4F6 remaining after the total consumption of NO2. P is the
sum of products [CF3C(O)F] + [C(O)F2] + [NO] + [epoxide of
CF2CF2].
The following mechanism, where C2F4O is the epoxide of
tetrafluoroethene, appears to be consistent with the experi-
mental results obtained at 396.0 and 418.0 K:
In the conditions of this work, the calculations done using
the equilibrium constant for N2O4 $ 2NO2 [20] indicate that
N2O4 is practically dissociated into NO2.
NO2 þ CF2¼CFCF¼CF2 ! CF2ðNO2ÞCꢁFCF¼CF2
NO2 þ CF2ðNO2ÞCꢁFCF¼CF2
! CF2ðNO2ÞCFðNO2ÞCF¼CF2
(10)
The reaction of C4F6 with NO2 gives different products
depending on the temperature region studied.
The following mechanism was postulated to explain the
formation of CF2 CFCF(NO2)CF2NO2 (I) and CF2 CFCF
(NO2)C(O)F (III) in the temperature range 312.9–333.4 K:
(20)
CF2¼CFCF¼CF2 þ NO2 ! CF2¼CFCꢁFCF2ðNO2Þꢃ
(1)
(7)
CF2¼CFCꢁFCF2ðNO2Þꢃ þ NO2 þ M
! CF2¼CFCFðNO2ÞCF2NO2 þ M
(2)
2 :CF2 ! CF2¼CF2
CF2¼CF2 þ NO2 ! C2F4O þ NO
C2F4O ! CF3CðOÞF
(8)
(9)
CF2¼CFCꢁFCF2ðNO2Þꢃ ! CF2¼CFCꢁFCðOÞF þ FNO
(3)
(4)
CF2¼CFCꢁFCðOÞF þ NO2 ! CF2¼CFCFðNO2ÞCðOÞF
(10)
(11)
C2F4O ! CðOÞF2 þ :CF2
As NO2 and C4F6 are stable compounds, the reaction must
proceed by the addition of NO2 to the double bond of the diolefin,
analogously to other reactions of NO2 with alkenes and dialkenes
[10–14,21–23]. It was found that the initial attack by NO2 occurs
at the terminal position of the non-halogenated diolefins by
C–N attachment giving R0CH CHꢁHCHR00(NO2) radicals
[21,24]. In presꢁence of molecular oxygen peroxy radicals,
R0CH CHC(O2) HCHR00(NO2), are formed, which combine
with NO2 to yield peroxy nitrates, R0CH CHC(O2NO2)
HCHR00(NO2) [21]. In the present work the generation of the
radical CF2 CFCꢁFCF2(NO2) was postulated, which may
undergo reaction with another molecule of NO2 giving
CF2 CFCF(NO2)CF2NO2 or can decompose leading to the
formation of FNO and CF2 CFCꢁFC(O)F radical. The latter
radical reacts with the second NO2 giving CF2 CFCF(NO2)-
CFCF(NO2)C(O)F.
Since the intermediate radical (NO2)CF2CꢁFCF CF2
formed by the addition of NO2 to C4F6 is allylic in nature
and there is no isomerization involved in this process, the allylic
radical is able to add NO2 either to (NO2)CF2CF or CF2 end.
Then the formation of CF2(NO2)CF CFCF2(NO2) (II) and
CF2(NO2)CF CFC(O)F (IV) can be explained by the reactions
of the second NO2 with the CF2 end group:
The experimental results at 396.0 and 418.0 K are
rationalized taking into account the data reported for the
reactions NO2 + C3F6 [13] and NO2 + C4F8-2 [14], where the
predominant process was the formation of NO and the
corresponding epoxides of perfluoropropene and perfluorobu-
tene-2. The formation of these products through the following
four-member ring intermediate, where R F or CF3, was
postulated:
The perfluoropropene epoxide and perfluorobutene-2 epox-
ide decompose above 460 and 430 K, respectively, the first
giving CF3C(O)F and :CF2 [25] and the latter CF3C(O)F and
:CFCF3 [14].
The lack of absorption band, characteristic to fluoro
epoxides in the 1500–1550 cmꢀ1 region of infrared spectra,
shows that a stable compound containing epoxide group is not
formed in this work.
Taking into account the above data, the concerted generation
of CF2(NO2)CF(NO2)C(O)F, :CF2 and NO through a following
four-center transition state is proposed:
ðNO2ÞCF2CꢁFCF¼CF2ꢃ þ NO2 þ M
! CF2ðNO2ÞCF¼CFCF2ðNO2Þ þ M
(5)
ðNO2ÞCF2CꢁFCF¼CF2ꢃ þ NO2
It can be explained in terms of concomitant weakening and
cleavage of C–C, C–N and O–NO bonds while C–O bond is
forming.
! CF2ðNO2ÞCF¼CFCðOÞF þ FNO
(6)
The absorption band at 1785 cmꢀ1 appearing in the infrared
spectrum, indicative of the presence of –CF CF2 group and the
band located at 1733 cmꢀ1 in the Raman spectrum showing the
presence of –CF CF– group, indicate that, in the temperature
range 312.9–333.4 K, NO2 does not attack the second double
The association of the two :CF2 leads to the formation of
CF2 CF2 and perfluorocyclopropane by addition of :CF2 to
tetrafluoroethene [25,26]. In presence of NO2, perfluorocyclo-
propane does not form, but the generation of perfluoroethene

J. Czarnowski / Journal of Fluorine Chemistry 129 (2008) 261–266
265
epoxide is observed, indicating that the reaction of NO2 with
CF2CF2 leading to the formation of C2F4O, is faster than the
addition of :CF2 to the double bond. It is well known, that the
perfluoroethene epoxide isomerizes to CF3C(O)F [27] and, at
higher temperatures, decomposes unimolecularly to give
C(O)F2 and :CF2 [28].
The nitric oxide NO did not add to the double bonds in this
work. The fluoro compounds containing –CF2NO group have a
characteristic intense blue color [29], which was not observed.
The reaction of C4F6 with FNO was discarded, because the
addition of the latter compound to the double bond requires
higher temperatures and pressures. No reaction between FNO
and perfluorobutene-2 occurred below 473 K [30].
33.5 Torr and that of C4F6 between 28.3 and 34.5 Torr. At 396
and 418.0 K the NO2 was completely consumed when
introducing C4F6 to the reaction vessel as the second reactant.
In this case the initial pressure of NO2 was varied between 19.0
and 47.7 Torr and the excess of non-consumed C4F6 varied
between 21.4 and 51.2 Torr. The analysis of reaction mixtures
was made by fractional condensation at 153 and 233 K. Three
additional experiments were made at 418.0 K to obtain greater
amounts of the compound CF2(NO2)CF(NO2)C(O)F (V) to
determine its relative molecular mass. In these experiments the
initial pressure of NO2 varied between 71.3 and 202.9 Torr and
the excess of non-consumed C4F6 varied between 78.5 and
234.0 Torr and only the fractional condensation at 233 K was
performed.
3. Conclusions
Acknowledgments
This work shows that below 335.0 K, NO2 attacks only one
double bond, giving three novel compounds: CF2 CFCF
(NO2)CF2(NO2), CF2 CFCF(NO2)C(O)F and CF2(NO2)CF
CFC(O)F, and that above 390.0 K NO2 reacts with the both
double bonds, leading to the formation of another not reported
compound CF2(NO2)CF(NO2)C(O)F.
This research project was supported by the Universidad
Nacional de La Plata, the Consejo Nacional de Investigaciones
´ ´ ´
Cientıficas y Tecnicas (CONICET, PIP 5777), the Comision de
´
Investigaciones Cientıficas de la Provincia de Buenos Aires
´ ´
(CICPBA), the Agencia Nacional de Promocion Cientıfica y
Density functional theory calculations to explore the
reaction mechanism and characterize the molecular properties
of these new molecules are underway [31].
´
Tecnologica (PICT 38444) and the Max Planck Institute for
¨
Biophysical Chemistry Gottingen through the ‘‘Partner Group
for Chlorofluorocarbons in the Atmosphere’’. The author
thanks the unknown reviewer for his very valuable suggestions,
Dr. Rosana M. Romano for performing the Raman and FTIR
spectra and Mr. Z. Czarnowski for helpful comments.
4. Experimental
The experiments were performed in a conventional grease-
free static system, allowing pressure measurements at constant
volume and temperature. The spherical quartz bulb (270 cm3),
connected to a sensitive quartz spiral gauge, used as a null
instrument, and to a mercury manometer, was employed as a
reaction vessel. The reactor was also connected to a standard
vacuum line for gas handling. The temperature was maintained
within ꢂ0.5 K using a Lauda thermostat, filled with Dow
Corning 200/300 Fluid for temperatures above 360 K and with
distilled water for those below 340 K. The infrared spectra were
recorded on Shimadzu IR-435 spectrometer, using 10 cm cell
provided with NaCl windows and the FTIR spectra on Nexus
Nicolet instrument equipped with an MCTB, using 10 cm cell
provided with Si windows with resolution of 1 cmꢀ1 and 256
scans at different pressures. A Bruker IFS166 was used to
record the FT Raman (6 mm tube, room temperature, excitation
line 1064) spectra with 2 cmꢀ1 resolution and 100 scans.
All reactants were purchased commercially. Perfluorobuta-
1,3-diene, C4F6 (PCR, 97–98%) was purified by repeated low-
pressure trap-to-trap distillation on vacuum line, the fraction
distilling between 218 and 173 K being retained each time.
Small amounts of NO present in NO2 were eliminated by a
series of freeze-pump-thaw cycles in presence of O2 until the
blue color due to the formation of N2O3 disappeared. The
degassed NO2 was purified by fractional condensation using
fraction that distilled between 213 and 243 K.
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