ISSN 0018-1439, High Energy Chemistry, 2006, Vol. 40, No. 6, pp. 375–381. © Pleiades Publishing, Inc., 2006.Original Russian Text © L.A. Maslovskaya, A.I. Savchenko, Yu.S. Polyakov, 2006, published in Khimiya Vysokikh Energii, 2006, Vol. 40, No. 6, pp. 421–427.

375

The attention given by researchers to the transfor-mations of quinones in various systems is due to thefact that the quinone moiety is present in molecules ofmany natural compounds, such as flavonoids and vita-mins, and pharmaceuticals and take part in biologicallyimportant processes, such as photosynthesis and elec-tron transfer [1–4].

ortho

-Quinones are formed in thediphenol inhibition of the oxidation of organic sub-stances. These oxidation processes occur under theaction of either chemical initiators or UV and

γ

-radia-tion as a result of two-electron transfer or the dispropor-tionation of phenoxyl radicals [5, 6]. The toxicity of anumber of medicaments [7, 8] and an increase in theefficiency of certain antioxidants (e.g., 2,6-di-

tert

-butyl-4-methylphenol) in the stabilization of polyole-fins and polystyrenes [9] were related to the accumula-tion of

ortho

-quinones and quinonoid compounds.

It is well known that quinones do not interact withperoxide radicals in organic solvents and the reaction ofquinones with alkyl radicals becomes predominant atoxygen deficiency [5, 6]. However, data on such reac-tions of

ortho

-quinones are scarce and primarily con-cern photochemical transformations [6, 10–12]. Theaim of this work was to study the effects of 4-

tert

-butyl-1,2-benzoquinone (

I

), 3,5-di-

tert

-butyl-1,2-benzo-quinone (

II

), and 4-methoxy-5-

ter

t-butyl-1,2-benzo-quinone (

III

) on the radical reactions of cyclohexane indeaerated solutions under the action of

γ

-radiation andto determine the reaction pathways and special featuresof the conversion of the additives.

EXPERIMENTAL

Compounds

I

–

III

were synthesized according topublished procedures [13–15]. The independent syn-thesis of spiro adduct

XXI

(see below) was performedby the reaction of 3,5-di-

tert

-butylpyrocatechol andcyclohexanone in accordance with a proceduredescribed by Cole et al. [16]. Cyclohexane was purifiedas described in [17], and cyclohexene was purified bydouble distillation. The solutions of quinones in cyclo-hexane with concentrations of up to

10

–2

mol/l wereused in the study. Deaerated cyclohexane samples andquinone solutions, which were placed in hermeticallysealed glass ampules, were irradiated on an LMB-

γ

-1å

source using

137

Cs radiation at a dose rate of 0.33 or0.058 Gy/s; the dose range was 1–10 kGy.

The final products were analyzed by gas–liquidchromatography (GLC) on a Varian CP-3380 chro-matograph with a flame-ionization detector. A CP-Sil5CB fused-silica capillary column 50 m in length and0.25 mm in diameter with a film thickness of 0.40

µ

mwas used. The oven temperature was programmed as fol-lows: heating from 150 to

160°ë

at a rate of 5

°

C/min,heating from 160 to

260°ë

at a rate of 25

°

C/min, and anisothermal segment of 20 min. The carrier-gas (hydro-gen) flow rate was 0.8 ml/min. The procedure used for

O

Ot-Bu

I

O

Ot-Bu

t-Bu

II

O

Ot-Bu

MeO

III

RADIATIONCHEMISTRY

Transformations of

ortho

-Quinones in the

g

-Radiolysisof Their Solutions in Cyclohexane

L. A. Maslovskaya

a

, A. I. Savchenko

b

, and Yu. S. Polyakov

a

a

Institute of Physicochemical Problems, Belarussian State University, ul. Leningradskaya 14, Minsk, 220050 Belaruse-mail: lmaslovskaya@mail.ru

b

Institute of Organic and Biomolecular Chemistry, Goettingen, Germany

Received January 12, 2006

Abstract

—The transformations of 4-

tert

-butyl-1,2-benzoquinone (

I

), 3,5-di-

tert

-butyl-1,2-benzoquinone (

II

),and 4-methoxy-5-

tert

-butyl-1,2-benzoquinone (

III

) in deaerated cyclohexane solutions under exposure to

γ

-radiation were studied. It was found by chromatography–mass spectrometry and

1

H and

13

C NMR spectros-copy that the addition of cyclohexyl radicals at the C=O bond in compounds

I

–

III

resulted in monoalkyl ethers,whereas cyclic ketal

XXI

was also formed in the case of compound

II

. Moreover, quinone

I

afforded mixed O-and C-alkylation products, and the adduct of cyclohexyl radicals and quinone

II

at the C=C bond was the sourceof dimeric products.

DOI:

10.1134/S0018143906060038

376

HIGH ENERGY CHEMISTRY

Vol. 40

No. 6

2006

MASLOVSKAYA et al.

the analysis of products by gas chromatography–massspectrometry (GC–MS) was described previously [17].

The mass spectra of products were measured on aVarian MAT 731 spectrometer using the NH

3

directchemical ionization technique.

The

1

H and

13

C NMR spectra were obtained on aBruker AM 250 spectrometer (operating frequencies of250 and 62.9 MHz, respectively) in deuterochloroform.

To specify quantitatively the products of addition ofcyclohexyl radicals to solutes, solutions of monoalkylethers of 4-

tert

-butylpyrocatechol, synthesised asdescribed in [18], were used. Radiation chemical yieldof the products was calculated using initial parts of thekinetic curves, and uncertainty of determination wasnot higher than 10%.

RESULTS AND DISCUSSION

It is well known that the action of ionizing radiationon hydrocarbons results in the formation of positivemolecular ions RH

+

,

e

–

, and excited molecules RH**,which are the direct precursors of alkyl radicals [19]. Inthe case of cyclohexane, the recombination of theresulting radicals gives bicyclohexyl with a yield of0.86 molecule/100 eV. The presence of quinones

I

–

III

in a concentration of (0.2–1.0)

×

10

–2

mol/l in irradiatedcyclohexane decreased the yield of bicyclohexyl to0.21 molecule/100 eV. The decrease in the yield can bedue to the ability of quinones to react with the interme-diate products of cyclohexane radiolysis: electrons, Hatoms, and cyclohexyl radicals. For example, it wasfound previously that

ortho

-quinones add electrons orhydrogen atoms at the carbonyl group in photochemicalreactions. In this case, ketyl radicals (or their anions)

are formed. Redistribution of electron density in theseradicals leads to semiquinones or their dissociatedforms

IV

and

V

[2, 6, 12] (scheme 1).

Alkyl radicals can combine with radicals

IV

or

V

[10, 11, 20]; in the case of

para

-quinones, they can addto the carbonyl group or C=C bonds in the ring [2, 5,21]. However, in the photochemical reactions of mono-nuclear and polynuclear

ortho

-quinones, such as naph-thoquinone, anthraquinone, and phenanthraquinone,the formation of 1,2- and (or) 1,4-addition products (

VI

and

VII

, respectively) only at the C=O bonds wasobserved [10, 11, 22, 23].

The occurrence of the above reactions leads to theconsumption of quinones and the formation of theirconversion products (table).

The GC–MS studies demonstrated that the conver-sion products of quinones

I

–

III

are structurally differ-ent. For example, in the case of compound

I

, adductswith molecular-ion masses of 248 (Fig. 1, products

2

,

3

), 330 (products

4

,

5

), and 412 (product

6

) wereformed, thus suggesting the addition of one, two, orthree cyclohexyl radicals, respectively. The degradationof M

+

(

m

/

z

248)

for products

2

and

3

gave a rearrange-ment ion of mass 166. According to scheme 2, 1,2- or1,4-adducts (

VI

or

VII

, respectively) can be formed inthe interaction of alkyl radicals with

ortho

-quinones.

O

OR

R

R

Re–(H)

O

O–(H+)R

R

R

R

O.

O–(H+)R

R

R

R

R = Alk, H IV

.

V

Scheme 1

O

O

O

R

OH

Scheme 2

R

1,2-

VI VII

adduct

. R.1,4-

adduct

OH

OR

20 25 30 35

t

, min

1

2

3

4

5

6

Fig. 1.

Chromatogram of an irradiated 4-

tert

-butylquinone(I) solution in cyclohexane (dose of 6 kGy). (1) Parentquinone (I). Monoalkyl ethers: (2) 2-cyclohexyloxy-4-tert-butylphenol (VIII) and (3) 2-cyclohexyloxy-5-tert-butylphenol (IX). Dialkylation products: (4) 2-cyclohexy-loxy-6-cyclohexyl-4-tert-butylphenol (XI) and (5) 2-cyclo-hexyloxy-3-cyclohexyl-5-tert-butylphenol (XII). Trialkyla-tion product: (6) 2-cyclohexyloxy-3,6-dicyclohexyl-4-tert-butylphenol (XIV).

HIGH ENERGY CHEMISTRY Vol. 40 No. 6 2006

TRANSFORMATIONS OF ortho-QUINONES 377

An NMR study of the structure of adducts demon-strated that isolated products 2 and 3 have the structuresof monoalkyl ethers VIII and IX [24]. They can beformed either by the recombination of a cyclohexyl rad-ical and semiquinone radical V (k = 2 × 107 l mol–1 s–1

[20]) or in a molecule–radical reaction. In this case, thereaction of ortho-quinones with cyclohexyl radicalscan occur through charge-separation intermediate Xyielding an 1,4-type adduct [25] (scheme 3, reactionroute A).

O

Ot-Bu c-Hex

.δ– .δ+O

Ot-Buc-Hex

O

Ot-Buc-Hex

OH

Ot-Buc-Hex

O

Ot-Bu

O

Ot-Bu

c-Hex

O

Ot-Bu

c-Hex

O

Ot-Bu

c-Hex

c-Hex

OH

Ot-Bu

c-Hex

c-Hex

.

.

.

.

. .

..

A

B

X

XIII

C

VIII

D

XI

Scheme 3

H

The dose dependence for the buildup ofmonoalkyl ethers VIII and IX is linear, and theiryield increases from 0.7 to 1.25 molecule/100 eV asthe concentration of parent compounds is increasedfrom 2 × 10–3 to 10−2 mol/l (table). The yieldincreases to 2.4 molecule/100 eV as the dose rate isdecreased to 0.058 Gy/s (Fig. 2). This change in theyield of the above products cannot be explained onlyin terms of interaction between cyclohexyl and semi-quinone radicals V (k = 2 × 107 l mol–1 s–1 [20]), sincethe reaction of H atom addition to the C=O bond(k = 7.8 × 108 l mol–1 s–1 [26]) practically cannotcompete with the reaction between atomic hydrogenand the cyclohexane molecule (kH + RH = 3 ×107 l mol–1 s–1 [27]) at a quinone concentration of 2 ×103 mol/l. Consequently, the formation of monoalkylethers was related to a considerable contribution of amolecule–radical reaction (scheme 3, reactionroute A).

The molecular-ion mass of products 4 and 5(Fig. 1) is 330, and the occurrence of fragment ionswith m/z 248 and 179 upon the degradation of M+

suggests that the addition of the second cyclohexylradical to the ring took place along with the alkyla-tion of either of the hydroxyl groups (compounds XIand XII) [24]. It cannot be excluded that the forma-tion of these products involves the interaction of thecyclohexyl radical with the C=C double bond (therate constant of methyl radical addition to para-

quinone at the C=C bond is k = 4.5 × 107 l mol–1 s–2

[2]) followed by the recombination of cyclohexadi-

0.8

0.6

0.4

0.2

0

c × 104, mol/l

1 2 3 4 5 6 7Dose, kGy

1 2

3

4

Fig. 2. The dose dependence of the buildup of (1, 2)monoalkyl ethers and (3, 4) dialkylation products in theirradiation of a 4-tert-butylquinone (I) solution(1 × 10−2 mol/l) in cyclohexane. Dose rate: (2, 3) 0.33 or(1, 4) 0.058 Gy/s.

378

HIGH ENERGY CHEMISTRY Vol. 40 No. 6 2006

MASLOVSKAYA et al.

ene-type radical adduct XIII with the second cyclo-hexyl (scheme 3, reaction route B).

The dose dependence of the buildup of adducts XIand XII exhibits an induction period (Fig. 2). The ini-tial yield of these adducts was no higher than 0.3 mole-cule/100 eV (table); however, it increased to 0.97 mol-ecule/100 eV starting with a dose of 3 kGy at a concen-tration of I equal to 2 × 10–3 mol/l. At the same time, adecrease in the dose rate resulted in a decrease in theyield. This suggests that the above compounds can

OH

Ot-Buc-Hex

VIII

OH

O

c-Hex

t-Bu

OH

Ot-Bu

c-Hex

c-HexIX XI

XII XIV

OH

O

c-Hex

t-Bu

c-Hex

OH

O

c-Hex

t-Bu

c-Hex

c-Hex

result from the successive addition of two cyclohexylradicals to quinone I with a considerable contributionof biradical reactions (scheme 3, reaction pathways B,C). With allowance for the existence of an inductionperiod in the buildup of products XI and XII, we cannotexclude the formation of them from monoalkyl ethersVIII and IX. Thus, the irradiation of monohexyl ethersof 4-tert-butylpyrocatechol (the preparation of theseethers was described elsewhere [18]) in cyclohexaneafforded dialkyl ethers and C-alkylation products withyields of 0.15 and 0.04 molecule/100 eV, respectively.Since dialkyl ethers were not detected among the radi-olysis products of quinone I, the formation of com-pounds XI and XII via reaction path D should beexcluded.

The degradation of the molecular ion of 6 at m/z 412gave fragments at m/z 330, 247, and 165, which corre-spond to the addition of three cyclohexyl radicals (struc-ture XIV). This product appeared with a yield of 0.15 mol-ecule/100 eV at an additive concentration of 10–2 mol/l.

According to GC–MS data when compound II wasirradiated in cyclohexane,, adducts with molecular-ionmasses of (1) 302, (2) 300, (3–5) 304, (6) 386, and (7)330 were formed (Fig. 3). In this case, the total yield of

Yields of the combination products of cyclohexyl radicals and quinones I–III in deaerated cyclohexane solutions at variousconcentrations of parent compounds and dose rates (P)

Parent compound Products (M+)

Radiation-chemical yield, molecule/100 eV

P = 0.30 Gy/s P = 0.005 Gy/s

Concentration, ×10–3 mol/l

2 5 10 5 10

I VIII + IX (248) 0.77 0.83 1.13 1.00 1.63

XI + XII (330) 0.30 0.25 0.22 0.20 0.12

XIV (412) 0 0 0.10 0 0

II XXI (302) 0.10 0.11 0.21 0.2 0.38

XV + XVI (304) 2.12 2.28 3.17 2.57 3.46

XVII ([M + H]+ 607) 0.20 0.37 0.81 0.58 1.12

XXIII (386) 0 0.07 0.39 0.02 0.15

XXIV (330) 0 0.08 0.14 0.10 0.22

III XXV + XXVI (278) 4.7 5.2 – – –

HIGH ENERGY CHEMISTRY Vol. 40 No. 6 2006

TRANSFORMATIONS OF ortho-QUINONES 379

the three main products with M+ 304 was as high as 3.98molecule/100 eV. The degradation of the molecularions M+ of products 3 and 4 afforded rearrangementions of mass 222, which corresponds to the structure ofmonoalkyl ethers XV and XVI [24].

The intensity of the molecular ion 304 of product 5was 28%, and the fragment ion with m/z 221 suggestedthe formation of a C–C-type adduct. However, theammonia direct chemical ionization mass spectrum ofthe isolated product exhibited the quasi-molecular ion[M + H]+ 606.9. According to X-ray diffraction [28]and 1H and 13C NMR-spectroscopic data, the isolatedcompound was unsymmetrical dimer XVII, which wasformed from adduct XIX as a result of cyclohexyl rad-ical addition to parent quinone II at the C=C doublebond. It is likely that this addition occurred in accor-dance with scheme 4.

The above reaction also resulted in the formation ofsymmetrical dimer XVIII, whose structure was deter-mined on the basis of ammonia direct chemical ioniza-tion mass spectra ([M + H]+ 606.9) and 1H and 13CNMR data.

Fragment ions at m/z 287 and 259 were formed bythe degradation of the molecular ion M+ (m/z 302)

OH

Ot-Bu

t-Bu

c-HexOH

O

c-Hex

t-Bu

t-Bu

XV XVI

O

c-Hex t-Bu

O

t-BuO

O

t-Buc-Hex

t-Bu

XVII XVIII

O

c-Hext-Bu

O

t-Bu O

O

c-Hex

t-Bu

t-Bu

unsymmetrical dimer symmetrical dimer

O

Ot-Bu

t-Bu .

XVII +O

Ot-Bu

t-Bu

c-Hex

O

Ot-Bu

t-Bu

c-Hex

+ XVIII

Scheme 4

.

.

(product 1). The 1H NMR spectrum exhibited signalsdue to aromatic protons at 6.71 and 6.75 ppm and mul-tiplets due to cyclohexyl protons in the region 1.40–2.10 ppm. The 13C NMR spectrum exhibited a charac-teristic signal due to the quaternary carbon atom at103.73 ppm. The coincidence of signals in the 1H and13C NMR spectra of the isolated product and a com-pound obtained in an independent synthesis, which wasalso described by Gautam et al. [29], allowed us toascribe structure XXI to this compound. It is wellknown that para-quinones can oxidize the adducts ofalkyl radicals and para-quinones [2]. The formation ofcyclic ketal XXI may also result from the oxidation ofcyclohexyl ether radical XX by parent quinone II at the–OCH group because of the presence of a labile hydro-gen atom in this group. Such a reaction was observed inthe case of 3,6-di-tert-butylpyrocatechol isopropylether [30] (scheme 5).

O

Ot-Bu

t-Bu.

+O

Ot-Bu

t-Bu

O

Ot-Bu

t-Bu

+ O

OHt-Bu

t-Bu.

XX

XXI

Scheme 5

22 24 26 28t, min

1

2

3

4 56

7

Fig. 3. Chromatogram of an irradiated 3,5-di-tert-butylquinone (II) solution in cyclohexane (dose of 6 kGy):(1) 4',6'-di-tert-butylspirocyclohexane-1,2'-[1,3]benzodiox-ole (XXI); (2) product with m/z 300 (XXII); (3, 4) themonoalkyl ethers 2-cyclohexyloxy-4,6-di-tert-butylphenol(XV) and 2-cyclohexyloxy-3,5-di-tert-butylphenol (XVI),respectively; (5) analysis product of unsymmetrical dimerXVII; (6) dialkyl ether XXIII; and (7) product with m/z 330(XXIV).

380

HIGH ENERGY CHEMISTRY Vol. 40 No. 6 2006

MASLOVSKAYA et al.

The formation of product 2 at m/z 300 (Fig. 3) canbe attributed to the reaction of the cyclohexene radicaland quinone II [11] because adduct XXI with molecu-lar-ion mass 300 and an analogous character of frag-mentation (fragment ions with m/z 285, 272, and 257)was the main product upon the irradiation of quinone IIin cyclohexene.

In the degradation of the molecular ion 386 of prod-uct 6, fragments at m/z 304 and 222 appeared, whichcorresponded to the structure of dicyclohexyl etherXXIII. This product could result from both the recom-bination of radical adduct XX with the second cyclo-hexyl and the secondary reaction of monoalkyl etherXV. The occurrence of the latter reaction was foundunder the irradiation of ether XV in cyclohexane. In thiscase, products XXIII and XXIV with molecular-ionmasses of 386 and 330 and yields of 0.5 and 0.1 mole-cule/100 eV, respectively, were formed.

The abundance of the molecular ion of product 7 atm/z 330 was 18%, and fragment ions with m/z 248 and165 suggested the formation of a mixed O–C and C–Cadduct with two cyclohexyl radicals, which corre-sponds to structure XXIV.

t-Bu

t-Bu

O

O

t-Bu

t-Bu

O c-Hex

c-HexO

XXII XXIII

XXIVt-Bu O c-Hex

OHc-Hex

As follows from the table, compound III affordedthe total yield of addition products equal to 4.6 mole-cule/100 eV. According to GC–MS data, two productswith the molecular-ion mass of 278 were formed in a2 : 1 ratio (Fig. 4). The degradation of M+ for either ofthe products gave a fragment ion of mass 196, whichcorresponds to the structure of monoalkyl ethers XXVand XXVI (products 1 and 2, respectively). The struc-ture of these products was found on the basis of 1H and13C NMR data.

The yields of monoalkyl ethers XV, XVI, XXV, andXXVI, as well as dimers XVII and XVIII, increasedwith increasing concentrations of parent compoundsand decreasing dose rates (table). This suggested theformation of these products in molecule–radical reac-tions via pathways A and B (scheme 3).

Note that dimeric products containing cyclohexylradicals were also isolated after the irradiation ofquinones I and III; however, additional studies arerequired for determining their structures.

Thus, we found that quinones I–III effectively reactwith alkyl radicals and afford a wide range of pyrocat-echol derivatives. The main products are monoalkylethers, which primarily result from the 1,4-addition ofcyclohexyl radicals at the C=O double bond in a mole-cule–radical reaction. Quinone I also gives mixed O-and C-alkylation products, whereas the adduct of thecyclohexyl radical and quinone II at the C=C bondresults in the formation of dimeric products.

ACKNOWLEDGMENTSWe are grateful to A. de Meijere (Institute of

Organic and Biomolecular Chemistry, University ofGöettingen, Germany) for the opportunity to performNMR-spectroscopic and GLC studies.

REFERENCES1. Jonah, C.D. and Rao, B.C., Radiation Chemistry—

Present Status and Future Trends, Amsterdam: ElsevierScience, 2001, vol. V, p. 287.

2. Neta, P., in The Chemistry of Quinoid Compounds,Patai, S. and Rappoport, Z., Eds., New York: Wiley,1988.

3. Jovanovic, S.V., Konya, K., and Scaiano, J.C., Can. J.Chem., 1995, vol. 73, no. 11, p. 1803.

4. Jovanovic, S.V., Steenken, S., Hara, Y., and Simic, M.G.,J. Chem. Soc., Perkin Trans. 2, 1996, no. 11, p. 2497.

5. Roginskii, V.A., Fenol’nye antioksidanty: reaktsionnayaaktivnost' i effektivnost’ (Phenolic Antioxidants: Reac-tivity and Performance), Moscow: Nauka, 1988.

6. Khudyakov, I.V. and Kuz’min, V.A., Usp. Khim., 1975,vol. 44, no. 10, p. 1748.

MeO OH

t-Bu O c-Hex

MeO O c-Hex

OHt-BuXXV XXVI20 22 24 26

t, min18

1

2

Fig. 4. Chromatogram of an irradiated 4-methoxy-5-tert-butylquinone (III) solution in cyclohexane (dose of 6 kGy).Monoalkyl ethers: (1) 4-tert-butyl-2-cyclohexyloxy-5-methoxyphenol (XXV) and (2) 5-tert-butyl-2-cyclohexy-loxy-4-methoxyphenol (XXVI).

HIGH ENERGY CHEMISTRY Vol. 40 No. 6 2006

TRANSFORMATIONS OF ortho-QUINONES 381

7. Singh, S., Jen, J.-F., and Dryhurst, G., J. Org. Chem.,1990, vol. 55, no. 5, p. 1484.

8. Largeron, M., Neudorffer, A., and Fleury, M.-B.,J. Chem.. Soc., Perkin Trans. 2, 1998, no. 12, p. 2721.

9. Kovarova, J., Rotschova, J., Brede, O., and Burgers, M.,Can. J. Chem., 1995, vol. 73, no. 11, p. 1862.

10. Bruce, J.M., Quart. Rev., 1967, vol. 21, no. 3, p. 405.

11. Maruyama, K., Ono, K., and Osugi, J., Bull. Chem. Soc.Jpn., 1969, vol. 42, no. 11, p. 3357.

12. El’tsov, A.V., Studinskii, O.P., and Grebenkina, V.M.,Usp. Khim., 1977, vol. 46, no. 2, p. 186.

13. Maslovskaya, L.A., Petrikevich, D.K., Timoshchuk, V.A.,and Shadyro, O.I., Zh. Obshch. Khim., 1996, vol. 66,no. 11, p. 1899.

14. Takata, T., Tajima, R., and Ando, W., J. Org. Chem.,1983, vol. 48, no. 24, p. 4764.

15. Mure, M. and Klinman, J.P., J. Am. Chem. Soc., 1995,vol. 117, no. 34, p. 8698.

16. Cole, E.R., Crank, G., and Minch, H.T.H., Aust. J.Chem., 1980, vol. 33, no. 3, p. 527.

17. Maslovskaya, L.A. and Timoshchuk, V.A., Khim. Vys.Energ., 1997, vol. 31, no. 6, p. 417 [High Energy. Chem.,1997, vol. 31, no. 6, p. 377].

18. Maslovskaya, L.A. and Savchenko, A.I., Zh. Obshch.Khim., 2003, vol. 73, no. 3, p. 422.

19. Saraeva, V.V., Radioliz uglevodorodov v zhidkoi faze(Radiolysis of Hydrocarbons in the Liquid Phase), Mos-cow: Mosk. Gos. Univ., 1986.

20. Mazaletskaya, L.I., Karpukhina, G.V., Komisarova, N.L.,and Belostotskaya, I.S., Izv. Akad. Nauk SSSR, Ser.Khim., 1982, no. 3, p. 505.

21. Goodspeed, F.C. and Burr, J.G., J. Am. Chem. Soc.,1965, vol. 87, no. 8, p. 1643.

22. Maruyama, K. and Otsuki, T., Bull. Chem. Soc. Jpn.,1971, vol. 44, no. 10, p. 2885.

23. Chesnokov, S.A., Cherkasov, V.K., Abakumov, G.A.,Kurskii, Yu.A., Shurygina, M.P., Malysheva, O.N., andShavyrin, A.S., Izv. Akad. Nauk, Ser. Khim., 2003, no. 3,p. 688.

24. Maslovskaya, L.A. and Savchenko, A.I., Zh. Obshch.Khim., 2005, vol. 75, no. 9, p. 1510.

25. Scott, G, in Development in Polymer Stabilization,Scott, G., Ed., London: Applied Sci. Publ, 1981, p. 1.

26. Richter, H.W., J. Phys. Chem., 1979, vol. 83, no. 9,p. 1123.

27. Pikaev, A.K. and Kabakchi, S.A., Reaktsionnayasposobnost' pervichnykh produktov radioliza vody(Reactivity of Primary Products of Water Radiolysis),Moscow: Energoizdat, 1982.

28. Meindl, K., Maslovskaya, L.A., Noltemeyer, M., andSavchenko, A.I., Acta Crystallogr., Sect. C: Cryst.Struct. Commun., 2005, vol. 61, p. 1950.

29. Gautam, D.R., Litinas, K.E., Fylaktakidou, K.C., andNicolaides, D.N., Phosphorus, Sulfur Silicon Relat.Elem., 2003, vol. 178, no. 9, p. 1851.

30. Abakumov, G.A., Cherkasov, V.K., Nevodchikov, V.I.,Druzhkov, N.O., Fukin, G.K., Kursky, Y.A., andPiskunov, A.V., Tetrahedron Lett., 2005, vol. 46, no. 23,p. 4095.