KINETICS OF PHOTOLYTIC TRANSFORMATIONS
2143
which can be assigned to tBu, Me, and C=CH protons, ated quartz cells with the absorbing layer thickness of
respectively.
0.4 cm. The amount of CO released in the course of
photolysis was determined with a poly(ethylene gly-
col) manometer and a Tsvet-104 chromatograph
Photochemical transformations of IB upon irradia-
tion at 405 nm can be described by Eqs. (9) (13):
(1500 2.5-mm glass column, adsorbent NaX 5
,
column and detector temperature 30 C, thermal con-
IB + h
1IB*
3IB*,
(9)
2
ductivity detector, bridge current 250 mA, carrier gas
1
3IB*
3IB* + RH
3IB*
IB + h
,
(10) helium, flow rate 40 ml min ).
2
IB + RH,
IIB + CO,
IIA + R2.
(11)
The TLC analysis of photolysis products [11] was
(12) performed with Silufol UV 254 plates, eluent hexane
diethyl ether (4 :1). Elution was performed in a closed
chamber in an atmosphere saturated with the eluent
3IB* + 2RH
(13)
vapor. The spots were developed with iodine vapor,
and from their positions the Rf values of the mixture
components were calculated: Q Q 0.09, IA 0.45, IB
0.71, IIA 0.27, and IIB 0.62.
By kinetic analysis of the suggested scheme, we
obtained equations for the rate of photolysis of IB and
for the quantum yield of the process:
k12 + 2k13[RH]
Wphot,IB = Wexc,IB
, (14)
(15)
The IR and NMR spectra of the photolysis prod-
ucts were measured after preparative TLC separation
of the reaction mixture [1]. Areas with spots on silica
gel plates after the elution were separated from each
other, and the adsorbed substances were washed out
with ethyl acetate. Solutions obtained by treatment of
the same spots were combined. The residue was ana-
lyzed after thorough removal of the solvent.
k
10 + k12 + (k11 + 2k13)[RH]
k12 + 2k13[RH]
=
.
IB
k10 + k12 + (k11 + 2k13)[RH]
The yield of IIA is 0.15, and that of IIB, 0.82 mol
per mole of converted IB. From the kinetic curves of
the consumption of IB and of the accumulation of CO
and product IIB, we plotted the curve of accumulation
of the photoreduction product IIA (Fig. 3) and calcu-
lated the rate constants of the corresponding processes
and the quantum yields of the compounds (see table).
The IR spectra of photolysis products were re-
corded on a Shimadzu IR Prestige-21 device using
KBr pellets. The NMR spectra were taken at the Ana-
lytical Center of the Razuvaev Institute of Organo-
metallic Chemistry on a Bruker DPX-200 device
(operating frequency 200 MHz), with TMS as internal
reference.
EXPERIMENTAL
Q Q was prepared by the procedure described in
[5] and was characterized by the melting point (found
179 C; published data [5]: 178 C), IR spectra (found
6-tert-Butyl-4-(4-tert-butyl-2-methyl-3-oxocyclo-
penta-1,4-dienyl)-3-methyl-o-benzoquinone IB. IR
1
CO, cm : 1648, 1665, 1680; published data [5]:
1
1
1
spectrum, CO, cm : 1605, 1620, 1640. H NMR
spectrum (C6D6), , ppm: 1.35 s (9H, C6But), 1.56 s
(9H, C4 But) 1.946 and 1.953 both s (3H each, both
1648, 1670, 1680), and NMR spectra (CDCl3): H, ,
ppm: 1.28 s [18H, C(CH3)3], 1.91 s (6H, CH3), 6.57 s
(2H, C5,5 H); 13C, , ppm: 13.2 (CH3), 29.3 [C(CH3)3],
35.7 (CMe3), 134.3 (C5,5 H), 134.6 (C4,4 ), 144.8
(C3,3 ), 150.8 (C6,6 ), 179.4 and 180.6 (C=O). Organic
solvents (chemically pure grade) were dried by stand-
ard procedures [10]. Reaction mixtures were deaerated
by repeated freezing pumping thawing.
CH3), 6.96 s (1H, C5H), 7.77 s (1H, C5 H). 13C NMR
spectrum (CDCl3), C, ppm: 12.6 and 13.1 (both
CH3); 29.2 and 29.9 [both C(CH3)3]; 34.7 and 35.7
(both CMe3); 121.6 (C5H); 138.4 (C5 H); 145.1,
147.6, 147.9; 148.4, 148.7, and 150.4 (C3,4,6,1 ,2 ,4 );
180.2, 181.4, and 181.8 (all C=O).
Photolysis was performed on an installation with
the irradiation source (a DRSh-500 mercury lamp)
placed in a cooled cylindrical casing. Using a quartz
lens, we obtained a plane-parallel beam which was
passed through a set of standard color filters to cut out
the radiation of the required wavelength. The reaction
kinetics was monitored spectrophotometrically. The
UV visible spectra of reaction mixtures were recorded
ACKNOWLEDGMENTS
The study was financially supported by the Russian
Foundation for Basic Research (project no. 07-03-
00819-a) and Program of the President of the Russian
Federation for the support of leading scientific schools
with SF-46 and SF-2000 spectrophotometers in evacu- (no. NSh-4947.2006.3).
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 77 No. 12 2007