Photolytic transformations of p-quinones

Article abstract of DOI:10.1134/S1070363208080112

Quantum yields, apparent photolysis rate constants, and energies of activation of the dark stages in the decomposition of 3,6-di-tert-butyl-2,3- epoxy-5-hydroxycyclohex-2-ene-1,4-dione, 1,4-naphthoquinone, and 9,10-anthraquinone under irradiation at λ 313 nm and of 1,4-benzoquinone under irradiation at λ 232-254 nm were determined. Products of photochemical transformations of these compounds in saturated hydrocarbons were identified, and a probable mechanism of these transformations was proposed.

Full text of DOI:10.1134/S1070363208080112

ISSN 1070-3632, Russian Journal of General Chemistry, 2008, Vol. 78, No. 8, pp. 1529–1532. © Pleiades Publishing, Ltd., 2008.
Original Russian Text © O.G. Mishchenko, S.V. Maslennikov, I.V. Spirina, Yu.A. Kurskii, V.I. Faerman, V.P. Maslennikov, 2008, published in Zhurnal
Obshchei Khimii, 2008, Vol. 78, No. 8, pp. 1294–1297.
Photolytic Transformations of p-Quinones
O. G. Mishchenkoa, S. V. Maslennikova, I. V. Spirinaa, Yu. A. Kurskiib,
V. I. Faermana, and V. P. Maslennikova
a Research Institute of Chemistry, Lobachevskii Nizhnii Novgorod State University,
pr. Gagarina 23-5, Nizhnii Novgorod, 603950 Russia
e-mail: spirina@ichem.unn.ru
b Razuvaev Institute of Organometallic Chemistry,
Russian Academy of Sciences, Nizhnii Novgorod, Russia
Received October 10, 2007
Abstract—Quantum yields, apparent photolysis rate constants, and energies of activation of the dark stages in
the decomposition of 3,6-di-tert-butyl-2,3-epoxy-5-hydroxycyclohex-2-ene-1,4-dione, 1,4-naphthoquinone, and
9,10-anthraquinone under irradiation at λ 313 nm and of 1,4-benzoquinone under irradiation at λ 232–254 nm
were determined. Products of photochemical transformations of these compounds in saturated hydrocarbons
were identified, and a probable mechanism of these transformations was proposed.
DOI: 10.1134/S1070363208080112
The main path of photochemical transformations of
p-quinones involves their reduction through
intermediate formation of ketyl radicals [1]. The
quinone molecule in the ground state frequently acts as
a reagent toward the excited p-quinone molecule [2].
There are no published data on the kinetic relations
holding in these processes. In the present work we
examined primary steps in the photolysis of 3,6-di-tert-
butyl-2,3-epoxy-5-hydroxycyclohex-2-ene-1,4-dione
(I), 1,4-benzoquinone (II), 1,4-naphthoquinone (III),
and 9,10-anthraquinone (IV) in saturated hydrocarbons
with a view to estimate their reactivity and identify
products of their photochemical transformations.
The electronic absorption spectra of compounds I–
IV are characterized by absorption maxima at λ 300 (I,
III, IV) and 240 nm (II). Therefore, their solutions
were irradiated at λ 313 and 232–254 nm, respectively.
The color of solutions of compound I (c0 ~10–4 M)
remained unchanged, whereas originally light yellow
solutions of II–IV turned colorless. In order to identify
the photolysis products, solutions of the compounds
under study in hexane with a concentration of 10–2
M
were irradiated for a long time. During the process, a
black solid separated from solutions of II and III, and
it became colorless upon subsequent irradiation. The
photolysis was accompanied by reduction in the
intensity of absorption maxima in the UV spectra (λ
310, 241, 321, and 327 nm for compounds I–IV,
respectively). In the electronic spectrum of I, a new
absorption maximum appears at λ 270–280 nm (Fig. 1).
The kinetics of decomposition of compounds I–IV
were monitored by spectrophotometry, following
variation of the optical density of the reaction
mixtures. The kinetic curves thus obtained are shown
in Fig. 2. The orders of the reactions were determined
from the linear log relations between the initial rate of
photolysis and initial concentration (see table). Table
also contains the apparent rate constants, energies of
activation, and quantum yields of photolysis of
compounds I–IV. The quantum yields do not depend
on the intensity of incident light in the range from 1017
O
O
OH
O
O
O
II
I
O
O
O
III
O
IV
1529

1530
MISHCHENKO et al.
D
0.8
0.6
0.4
3.0
1
2
2.5
2.0
1.5
1.0
0.5
0.0
3
4
5
4
3
0.2
0.0
2
1
0
10
20
30
40
230
270
310
350
τ, min
λ, nm
Fig. 2. Variation of the concentration of quinones I–IV in
nonane during photolysis; c0 = 2.4×10–4 M, temperature 298 K:
(1) compound III, λphot 313 nm, I0,sp = 1.8×1018 quantum s–1 l–1;
(2) compound II, λphot 232–254 nm, I0,sp = 4.8×1017
Fig. 1. Electronic absorption spectra of a solution of
compound I in nonane (c0 = 2.49× 10–4 M) under irradiation
at λ 313 nm, I0,sp = 3×1018 quantum s–1 l–1, temperature 298 K:
(1) before irradiation, (2) after 7 min, (3) after 20 min,
(4) after 45 min, and (5) after 90 min.
quantum s–1 l–1; (3) compound I,
λphot 313 nm, I0,sp
6.04×1018 quantum s–1 l–1; (4) compound IV, λphot 313 nm,
I0,sp = 5.9×1018 quantum s–1 l–1.
to 1019 quantum s–1 l–1, but they are proportional to the
initial substrate concentration.
1.5 month, the conversion did not exceed 3%.
Simultaneously, an equivalent amount of carbon(II)
oxide liberated. NMR and GC analysis of the reaction
mixture obtained in the photolysis of diketone I under
irradiation at λ 313 nm revealed formation of 3,5-di-
tert-butyl-2-hydroxycyclopenta-2,4-dien-1-one and an
equimolar amount of carbon dioxide (9 mol %,
calculated on the initial diketone), 4,6-di-tert-butyl-6-
hydroxycyclohex-4-ene-1,2,3-trione, 3,5-di-tert-butyl-
4-hydroxy-6-oxo-6H-pyran-2-carbaldehyde, and 1,3-
di-tert-butyl-2-hydroxy-4-oxocyclobut-2-ene-1-carbal-
dehyde (and the corresponding amount of CO, 77%).
Stepovik et al. [3] were the first to synthesize
compound I; the authors presumed that these
compound is formed through intermediate cyclo-
hexene-1,2-dione which undergoes isomerization into
the 1,4-dioxo isomer.
O
O
O
O
O
HO
O
OH
According to the GC–MS data, the main products
of photolytic decomposition of quinones II and III
were phenol ethers differing by the structure of hexyl
radical and the corresponding hydroquinones at a ratio
of 1:2 (II) or 99:1 (III).
In the electronic spectra of o-quinones, π–π*
transition in the carbonyl groups gives rise to
absorption in the region of 400 nm. When a solution of
I in nonane was irradiated at λ 405 nm over a period of
In keeping with published data [2], photolysis of
compound IV gives dihydroanthraquinone in almost
Kinetic and activation parameters and quantum yields of photolysis of compounds I–IV; c = (0.5–3)× 10–4 M, I0,sp = 1017–
1019 quantum s–1 l–1, temperature 298 K
Comp.
kap×104, s–1
Eact, kcal mol–1
φ×102
Order of reaction
λmax/λphot, nm
no.
310/313
241/(232–254)
327/313
0.9 0.1
1.03 0.07
1.25 0.05
1.5 0.1
0.23 0.02
3.4 0.4
3.2 0.3
13 2
–
3.4 0.3
20 2
I
2.3 0.5
5 1
II
35 4
III
IV
320/313
7.2 0.9
4.0 0.5
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 8 2008

PHOTOLYTIC TRANSFORMATIONS OF p-QUINONES
1531
O
OH
O
O
O
OH
−CO2
−CO
O
H
O
HO
H
O
O
O
O
O
HO
O
HO
I:
W = w0k5/(k1[RH] + k5); φ = k5/(k1[RH] + k5);
quantitative yield. Precipitation of a black solid from
solutions of II and III during irradiation indicates
formation of a quinhydrone complex which undergoes
dissociation as the initial compound is consumed [4].
Analogous transformations for compounds I and IV
are impossible because of serious steric hindrances.
II, III: W = w0(k2[RH] + 2k6[Q])/{(k1 + k2)[RH] + k6[Q]};
φ = (k2[RH] + 2k6[Q])/(k1 + k2[RH] + k6[Q]);
IV: W = w0k2/(k1 + k2); φ = k2/(k1 + k2).
EXPERIMENTAL
OH
O
OH
Compound I was kindly provided by Stepovik et al.
[3]; quinone II was synthesized by the procedure
described in [5], mp 116.5°C; published data [5]: mp
116°C. Quinones III and IV were commercial
products of chemically pure grade. Hexane and nonane
of chemically pure grade were dried by standard
procedures [6] and distilled, fractions boiling at 68.6–
69.0°C and 150–151°C, respectively, being collected.
X
X
X
X
X
X
+
+ RH
OH
O
OR
X = H, XX = CH=CHCH=CH.
On the basis of our experimental results and
published data, we propose the following scheme for
the photolysis of compounds I–IV (Q).
The setup for photolysis of compounds I–IV and
procedures for measurement of the incident light
intensity and TLC analysis of the transformation
products were described in [7].
hν
Q → Q*,
The amounts of liberated carbon(II) oxide and
carbon(IV) oxide were determined by gas chromato-
graphy on a Tsvet-104 instrument equipped with a
1500×2.5-mm glass column packed with STK
activated charcoal (grain size 0.2–0.4 mm); oven
temperature 70°C, detector temperature 70°C; thermal
conductivity detector (bridge current 250 mA); carrier
gas helium, flow rate 30 ml min–1.
k1
Q* + RH → Q# + RH#,
k2
Q* + RH → QH• + R•,
k3
QH• + R• → QRH,
k4
QH• + RH → QH2 + R•,
GC–MS analysis was performed on a Trance GC
Ultra/DSQII instrument using a 60-m×0.25-mm TR 5
capillary column; injection volume 0.01 μl; injector
temperature 300°C; carrier gas helium (M 60), flow
rate 1 ml min–1; oven temperature programming from
50 to 300°C; a.m.u. range 50–400. The components
were identified using NIST 2003 library.
k5
Q* → [P0] → P1 + CO; P2 + CO2; P3 + P4,
k6
Q* + Q → Q2,
2R• → R2.
Application of the quasistationary concentration
principle gave the following expressions for the rates
and quantum yields of photolytic decomposition of
compounds I–IV:
The NMR spectra were recorded on a Bruker
Avance DPX-200 spectrometer at 200 MHz for 1H and
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 8 2008

1532
MISHCHENKO et al.
50 MHz for 13C; chloroform-d was used as solvent,
and tetramethylsilane, as internal reference.
and 39.1 (CMe3), 69.8 (C1), 140.4 (C3), 163.0 (C4),
195.6 (CHO), 195.9 (C2).
4-Hexyloxyphenol. Mass spectrum, m/z (Irel, %):
110 (100), 137 (3), 194 (2).
3,5-Di-tert-butyl-2-hydroxycyclopenta-2,4-dien-
1-one. H NMR spectrum, δ, ppm: 1.27 s and 1.38 s
1
(9H each, t-Bu), 6.39 s (1H, 4-H), 7.62 s (OH,
exchangeable with D2O). C NMR spectrum (DEPT),
δC, ppm: 28.8 and 30.4 (CH3), 34.4 and 35.1 (CMe3),
136.1 (C4), 149.6 and 151.3 (C3, C5), 183.9 (C2), 188.7
(C=O).
4-Hexyloxynaphthalen-1-ol. Mass spectrum, m/z
(Irel, %): 132 (13), 160 (100), 187 (15), 242 (5).
13
REFERENCES
1. Einführung in die Photochemie, Becker, H.G.O., Ed.,
4,6-Di-tert-butyl-6-hydroxycyclohex-4-ene-1,2,3-
trione. H NMR spectrum, δ, ppm: 1.00 s and 1.23 s
(9H each, t-Bu), 2.65 br.s (1H, OH), 7.43 (1H, 5-H).
13C NMR spectrum (DEPT), δC, ppm: 24.8 and 27.6
(CH3), 33.1 and 37.8 (CMe3), 77.4 (C6), 152.8 (C5),
161.7 (C4), 188.1 (C3), 195.6 (C2), 203.4 (C1).
Berlin: Wissenschaften, 1976.
1
2. Ranby, B. and Rabek, J.F., Photodegradation,
Photooxidation, and Photostabilization of Polymers.
Principles and Applications, London: Wiley, 1975.
3. Stepovik, L.P., Gulenova, M.V., Shavyrin, A.S., and
Fukin, G.K., Russ. J. Gen. Chem., 2006, vol. 76, no. 8,
p. 1275.
4. Tumanskii, B.L., Prokof’ev, A.I., Bubnov, N.N.,
Solodovnikov, S.P., and Khodak, A.A., Izv. Akad. Nauk
SSSR, Ser. Khim., 1983, no. 1, p. 268.
5. Preparatyka Organiczna, Polaczkowa, W., Ed.,
Warszawa: Panstwowe Wydawnictwa Techniczne, 1954.
Translated under the title Preparativnaya organicheskaya
khimiya, Moscow: Khimiya, 1964, p. 679.
3,5-Di-tert-butyl-4-hydroxy-6-oxo-6H-pyran-2-
1
carbaldehyde. H NMR spectrum, δ, ppm: 1.34 s and
1.46 s (9H, t-Bu), 9.70 d (1H, CHO, J = 1.3 Hz), 13.23
d (1H, OH, J 1.3 Hz, exchangeable with D2O). 13C
NMR spectrum (DEPT), δC, ppm: 28.7 and 30.7 (CH3),
31.9 and 35.5 (CMe3), 112.0 (C3), 126.6 and 157.4 (C5,
C2), 161.9 and 166.3 (C6, C4), 199.2 (CHO).
6. Spravochnik khimika (Chemist’s Handbook), Nikol’-
1,3-Di-tert-butyl-2-hydroxy-4-oxocyclobut-2-ene-
1-carbaldehyde. H NMR spectrum, δ, ppm: 1.17 s
1
skii, B.P., Ed., Moscow: Khim. Lit., 1951, vol. 2.
7. Klement’eva, S.V., Mishchenko, O.G., Maslennikov, S.V.,
and Spirina, I.V., Russ. J. Gen. Chem., 2007, vol. 77, no. 4,
p. 607.
and 1.36 s (9H each, t-Bu), 6.97 br.s (1H, OH,
exchangeable with D2O), 9.75 s (1H, CHO). 13C NMR
spectrum (DEPT), δC, ppm: 26.7 and 28.5 (CH3), 33.1
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 78 No. 8 2008