REACTION OF STERICALLY CONGESTED PHENOLS
595
RCHOH + OH(Q)
RCHO + QH2( OH). (11)
di-tert-butyl-1,2-benzoquinone (VII) were obtained
by oxidation of the corresponding diphenols [19].
Here OH are semiquinone radicals, and Q are quino-
nes.
Initiation of the free radical transformations in the
model systems was performed by expose of them to
-irradiation (137Cs). Deaerated solutions were pre-
pared by bubbling high-purity (99.9%) argon for 1.5 h
through a chosen solvent (hexane or ethanol), and
then weighed portions of the compounds to be studied
were dissolved in thus prepared solvent under argon.
The solutions were placed into glass ampoules, sealed,
Reaction (11) underlies the suppression by com-
pounds III, IV, VI of 2,3-butanediol formation and
the increase of the yield of acetaldehyde in ethanol
radiolysis. Compounds I and IV under the same
conditions are unable to form quinones and react
instead with the CH3 CHOH radicals, thus decreasing
the yields of 2,3-butanediol and acetaldehyde.
and subjected to 137Cs irradiation. The absorbed dose
1
rates were 0.32 to 0.01 Gy sec , the used doses were
Thus, on the strength of the above results we can
draw the following conclusion: Phenolic and quinoid
compounds can not only inhibit oxidation, but also
effectively control various reactions of carbon-cen-
tered radicals. This property is intrinsic in diphenol
derivatives that are capable of forming quinoid struc-
tures in the course of homolytic transformations and
explains the higher reactivity of such derivatives
toward carbon-centered radicals.
within the range 0.2 4 kGy.
Analysis of hexane irradiation products (isomeric
dodecanes) was performed by GLC on a a Shimadzu
GC-17 AAF/APC chromatograph using a DB-5 quartz
capillary column (30.000 0.54 mm), initial tempera-
1
ture 100 C, programmed first at 8 deg min to 200 C
1
and then at 10 deg min to 270 C; flame ionization
detector, detector temperature 220 C, injector tem-
1
perature 250 C, carrier gas nitrogen (3.7 ml min ).
EXPERIMENTAL
Analysis of hexane free-radical oxidation products
(2- and 3-hexanols) was performed under the same
conditions except for the temperature program (initial
1
The H NMR spectra of compounds in CDCl3 were
obtained on a JNM PS-100 instrument against HMDS.
The mass spectra were recorded on a Shimadzu QP-
500 spectrometer at 70 eV with direct sample admis-
sion into the ion source.
1
temperature 60 C, programmed at 8 deg min to
180 C and then maintained at that temperature for
1
2 min) and rate of carrier gas (1.8 ml min ).
AKNOWLEDGMENTS
2,6-Di-tert-butyl-4-methylphenol (I) and 2,2 -
methylenebis(6-tert-butyl-4-methylphenol) (II) (Al-
drich) were purified by vacuum sublimation or crys-
tallization from hexane; hexane (Baker Analyzed,
99%) was used as received.
This study was financially supported by ISTC
(grant no. B-434)
REFERENCES
3,5-Di-tert-butylpyrocatechol (III) [17], 2,5-di-
tert-butylhydroquinone (IV) [18], and 4,6-di-tert-butyl-
resorcinol (V) were obtained by alkylation of pyro-
catechol, hydroquinone, and resorcinol, respectively,
with tert-butyl alcohol in the presence of sulfuric acid.
1. Roginskii, V.A., Fenol’nye antioksidanty. Reaktsion-
naya sposobnost’ i effectivnost’ (Phenolic Antioxi-
dants. Reactivity and Effectivity), Moscow: Nauka,
1988, p. 248.
4,6-Di-tert-butylresorcinol (V). To a solution of
5.5 g of resorcinol and 9 g of tert-butyl alcohol in
20 ml of glacial acetic acid, 6 ml of 98% sulfuric acid
was added dropwise at 20 25 C with stirring. After
1 h, the reaction mixture was poured into 200 ml of
water, the precipitate that formed was filtered off,
washed with water, and dried in air. Recrystallization
from hexane gave 7.5 g (67%) of compound V as a
2. Hallwell, B. and Gutteridge, J.M.C., Free Radicals in
Biology and Medicine, Oxford: Clarendon, 1999,
p. 937.
3. Muller, S.N., Batra, R., Senn, M., Giese, B., Kisel, M.,
and Shadyro, O., J. Am. Chem. Soc., 1997, vol. 119,
no. 12, p. 2759.
4. Shadyro, O.I., Yurkova, I.I., and Kisel, M.A., Int. J.
Rad. Biol., 2002, vol. 78., no. 3, p. 211.
1
colorless powder, mp 69 70 C. H NMR spectrum, ,
5. Shadyro, O.I., Sosnovskaya, A.A., and Vrublev-
skaya, O.N., Int. J. Rad. Biol., 2003, vol.79, no. 4,
p. 269.
6. Shadyro, O.I., in: NATO ASI, Ser. 3, High Technology,
Minisci, F., Ed., Dobrecht: Kluwer., 1997, vol. 27,
p. 317.
ppm: 7.11 s, (5H, 5CH), 6.07 s (2H, 2CH), 5.0 4.7
(1H, OH), 1.36 s (9H, 3CH3), 1.32 s (9H, 3CH3).
Mass spectrum, m/z (Irel, %): 222, (12) [M]+, 207
(100) [M
CH3].
2,5-Di-tert-butyl-1,4-benzoquinone (VI) and 3,5-
RUSSIAN JOURNAL OF GENERAL CHEMISTRY Vol. 75 No. 4 2005