The Quantum Yield of Singlet Oxygen in Thermal Degradation of Alcohol Hydrotrioxides

Article abstract of DOI:10.1134/S0018143918050089

The yield of singlet oxygen (¹О₂) in the decomposition of a number of hydrotrioxides of alcohols (cyclobutanol, cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol, L-menthol, 1,7,7-trimethylbicyclo[2.2.1]heptan-2-ol, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol, heptan-4-ol, propanol-2, and 1-cyclopropylethanol) has been determined using the IR chemiluminescence technique. It has been shown that cyclopentanol, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol and 1-cyclopropylethanol hydrotrioxides are efficient sources of singlet oxygen; the yield of ¹О₂ reaches up to 58%.

Full text of DOI:10.1134/S0018143918050089

ISSN 0018-1439, High Energy Chemistry, 2018, Vol. 52, No. 5, pp. 446–448. © Pleiades Publishing, Ltd., 2018.
Original Russian Text © L.R. Khalitova, A.V. Antipin, S.A. Grabovskii, N.N. Kabal’nova, 2018, published in Khimiya Vysokikh Energii, 2018, Vol. 52, No. 5, pp. 432–434.
CHEMILUMINESCENCE
The Quantum Yield of Singlet Oxygen in Thermal Degradation
of Alcohol Hydrotrioxides
a
a
a,
a
L. R. Khalitova , A. V. Antipin , S. A. Grabovskii *, and N. N. Kabal’nova
a
Ufa Institute of Chemistry, Ufa Federal Research Center, Russian Academy of Sciences, Ufa, 450054 Russia
e-mail: stas_g@anrb.ru
Received January 30, 2018
*
1
Abstract—The yield of singlet oxygen ( О ) in the decomposition of a number of hydrotrioxides of alcohols
2
(
cyclobutanol, cyclopentanol, cyclohexanol, cycloheptanol, cyclooctanol, L-menthol, 1,7,7-trimethylbicy-
clo[2.2.1]heptan-2-ol, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol, heptan-4-ol, propanol-2, and 1-cyclopro-
pylethanol) has been determined using the IR chemiluminescence technique. It has been shown that cyclo-
pentanol, 1,3,3-trimethylbicyclo[2.2.1]heptan-2-ol and 1-cyclopropylethanol hydrotrioxides are efficient
sources of singlet oxygen; the yield of О reaches up to 58%.
1
2
Keywords: singlet oxygen, hydrotrioxides, chemiluminescence
DOI: 10.1134/S0018143918050089
INTRODUCTION
In this study, we determined the yield of singlet
oxygen in the decomposition of a number of hydrotri-
oxides of secondary alcohols with the aim of searching
for efficient chemical sources of singlet oxygen.
1
1
Singlet oxygen O ( Δg), molecular oxygen in the
2
lowest electronically excited state, is formed in photo-
chemical and chemical processes. Its role is important
and diverse, ranging from that in chemical synthesis
and polymer degradation to a signaling molecule in
the cells of living organisms. Thus, the interest of
researchers in methods for obtaining singlet oxygen
and its properties has not been lost over more than the
last 50 years [1, 2]. Among the chemical sources, the
most effective and practical ones are systems involving
peroxides (hydrogen peroxide, phosphite ozonides,
and hydrotrioxides). Information on hydrotrioxides
EXPERIMENTAL
Hydrotrioxides were synthesized by ozonation of
alcohols at a low temperature in a solvent according to
the standard procedure [5]. The following alcohols
were chosen as the starting compounds: cyclobutanol
(
1), cyclopentanol (2), cyclohexanol (3), cyclohepta-
nol (4), cyclooctanol (5), L-menthol (6), 1,7,7-
trimethylbicyclo[2.2.1]heptan-2-ol (7), 1,3,3-
trimethylbicyclo[2.2.1]heptan-2-ol (8), heptan-4-ol
9), propanol-2 (10), and 1-cyclopropylethanol (11).
(
ROOOH) as a source of singlet oxygen is contradic-
tory and, as a rule, is based on the determination of the
(
1
O yield using the scavenging technique. The results
1
2
The H NMR spectra of hydrotrioxides 1a–11a are
identical to those reported earlier [5]. The concentra-
tion of hydrotrioxides was determined according to the
standard procedure with triphenylphosphine [6].
obtained by this method are unreliable [3], possibly,
because of the occurrence of the hydrotrioxide reac-
tion with a scavenger. The measurement of singlet
oxygen phosphorescence at 1270 nm is the most reli-
The yield of singlet oxygen in the thermolysis of
hydrotrioxides was determined using the IR chemilu-
minescence technique. The wavelength range of sin-
glet oxygen emission was isolated using an IKS-7 visi-
ble light cut-off filter (λ > 900 nm). The chemilumi-
nescence measurement unit was calibrated using a
source with a known singlet oxygen yield (Ф), triphe-
nyl phosphite ozonide, for which Ф = 1.0 [7]. All
experiments on the determination of the yield of sin-
glet oxygen were carried out maintaining constant
parameters, such as the reactor volume and geometry,
the total volume of the reaction mixture, the voltage
applied to a photomultiplier tube (FEU-83), and its
1
able and convenient method for studying O reac-
2
tions, including the determination of its yield of in the
decomposition of hydrotrioxides [3].
It was previously shown that the yield of singlet
oxygen in the degradation of alcohol hydrotrioxides,
as determined by measuring chemiluminescence (CL)
at 1270 nm in methylene dichloride, was 2.5, 13, or 8%
for methanol, ethanol, or 2-propanol hydrotrioxide,
respectively [3]. Later we found out that the degrada-
tion of a hydrotrioxide bearing a carbocyclic substitu-
ent (2-exo-hydroxybicyclo[2.2.1]heptyl-2) produced
1
O in CH Cl in as high a yield as 38% [4].
2
2
2
446

THE QUANTUM YIELD OF SINGLET OXYGEN
447
Table 1. The yield of singlet oxygen in thermolysis of hydro- with increasing degradation temperature, a change
trioxides 1а–11а (solvent, t-BuОMe)
that can be explained by an increase in the contribu-
tion of the radical chain reaction route. As tempera-
ture increases, the rate of decomposition of a hydrotri-
oxide into radicals increases, which leads to an
increase in its consumption in the radical chain pro-
cess [5]. The formation of singlet oxygen in that case
can result only from combination of peroxide radicals.
The yield of singlet oxygen by the combination of per-
oxide radicals bearing alkyl substituents does not
exceed 8% [9]. The contribution of this route in the
thermal degradation of hydrotrioxides la, 7a, and 8a is
apparently minimal, and there is an insignificant
[
ROOOH]0,
mol/L
ROOOH
Т, K Φ , %
0
1
2
3
4
5
6
а
а
а
а
а
а
0.15
288 32 ± 3
OOOH
2
73 34 ± 3
63 35 ± 3
288 40 ± 4
73 44 ± 4
63 58 ± 4
288 15 ± 2
73 18 ± 2
OH
2
0.14
0.17
0.14
0.13
0.03
OOOH
2
2
OH
OOOH
2
1
effect of temperature on the yield of O . In addition,
2
OH
263 23 ± 2
288 17 ± 3
during the thermolysis of hydrotrioxides, singlet oxy-
OOOH
gen can be present in the solvent cage along with a
273 29 ± 3
quencher, the parent alcohol and/or H O. Perhaps,
2
OH
263 35 ± 3
288 21 ± 3
quenching in the cage proceeds more efficiently with
increasing temperature and leads to a decrease in the
yield of singlet oxygen.
HO
OOOH
2
73 37 ± 3
63 51 ± 5
283 14 ± 2
63 24 ± 3
2
The yield of singlet oxygen in the degradation of
aliphatic secondary alcohols 9a and 10a in t-BuOMe
is ~30%. The introduction of the highly strained
cyclopropyl substituent significantly increases the
CH(Mе)2
2
OH
OOOH
1
yield of O , Φ = 56% in thermolysis of 11a.
2
7
8
9
а
а
а
0.03
0.04
0.1
283 21 ± 3
273 22 ± 3
OH
The degradation of hydrotrioxides of secondary
alcohols with the –OOOH group located on the cyclic
moiety in 1а–8а leads to the formation of singlet oxy-
gen with a yield of 23–58% (−10°С). Three types of
strain are known for cycloalkanes. The highest yield of
singlet oxygen is observed for hydrotrioxides 2a, 5a,
and 8a characterized mainly by Pitzer strain. The
263 25 ± 3
OOOH
OH
OOOH
283 47 ± 5
2
73 50 ± 5
263 51 ± 4
288 18 ± 2
73 22 ± 3
OOOH
OH
energies of this strain per CH – group in the cyclo-
2
2
pentane–cyclooctane series are 1.3, 0.0, 0.9, and 1.2,
respectively [10]. Indeed, for compounds 2a, 4a, and
5a with five, seven, and eight-membered cycles,
respectively, the yield of singlet oxygen increases to
263 31 ± 3
263 35 ± 3
1
1
0а
1а
0.2
0.1
OOOH
OH
OOOH
OH
5
8% relative to that with 3a and 6a (23%, −10°C). The
288 30 ± 3
degradation of hydrotrioxide 1a is characterized by a
1
2
73 45 ± 4
lower O yield than in the cases of 2a and 5a, which is
2
263 56 ± 5
probably due to the presence of Bayer strain in the
cyclobutane moiety (a significant change in the С–
С–С bond angle).
temperature (183 K). The yield of singlet oxygen was
calculated as described in [8]. Methyl tert-butyl ether
Bicyclic hydrotrioxides 7a and 8a are similar in
(
t-BuOMe) was used as a solvent, because the synthe- Pitzer strain and differ in steric strain. In the case of
sis of hydrotrioxides in it proceeds rapidly and with a isomer 8a, the steric strain due to the methyl groups in
high yield [3, 5].
the 3-position will be lower than for 7a, in where they
are in the 7-position [11]. The yield of singlet oxygen
in the thermolysis of 8a and 7a is 51 and 25%, respec-
tively.
RESULTS AND DISCUSSION
The yield of singlet oxygen was calculated (Table 1)
Thus, the increase in the yield of singlet oxygen can
from CL decay rate curves (Fig. 1) measured during be associated with an increase in Pitzer strain and a
the degradation of hydrotrioxides 1a–10a. For these decrease in Bayer and steric strains in the cyclic moi-
hydrotrioxides, the yield of singlet oxygen decreases eties of hydrotrioxides.
HIGH ENERGY CHEMISTRY Vol. 52 No. 5 2018

4
48
KHALITOVA et al.
I, arb. units
18
15
288 K
12
9
6
3
273 K
263 K
0
1000
2000
3000
4000
5000
t, s
Fig. 1. Decay rate curves of IR chemiluminescence during the degradation of 1-hydroxycyclopentylhydrotrioxide (0.14 mol/L)
in t-BuOMe at temperatures of 288, 273, and 263 K.
CONCLUSIONS
Kabal’nova, N.N., Izv. Akad. Nauk, Ser. Khim., 2007,
no. 2, p. 263.
The yield of singlet oxygen in the degradation of
5
. Grabovskii, S.A., Khalitova, L.R., Fedorova, A.V.,
Lobov, A.N., Rol’nik, L.Z., and Kabal’nova, N.N.,
Izv. Akad. Nauk, Ser. Khim., 2016, no. 2, p. 464.
the specified hydrotrioxides of secondary alcohols has
been found, using the IR chemiluminescence method,
to be significantly higher than that for the compounds
studied previously. In the series examined, 1,3,3-
trimethyl-2-hydroxybicyclo[2.2.1]heptyl-2-hydrotri-
oxide, 1-hydroxycyclopentylhydrotrioxide, and 1-
cyclopropylethylhydrotioxide are the best sources of
singlet oxygen.
6
. Shereshovets, V.V., Shafikov, N.Ya., Galieva, F.A.,
Sadykov,
R.A.,
Panasenko,
R.A.,
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Komissarov, V.D., Izv. Akad. Nauk SSSR, Ser. Khim.,
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Translated by V. Makhaev
HIGH ENERGY CHEMISTRY
Vol. 52
No. 5
2018