Perfluoroalkylmanganese and silver compounds were prepared by the reaction of perfluoroalkyl halides with activated manganese and silver, respectively, under ultrasonic irradiation The organometallic compounds jroved to useful as potential "Grignard-type" perfluoroalkylating reagents for the preparation of a wide variety of perfluoroalkylated compounds.

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Ultrasonic irradiation was found to accelerate a solid-liquid two-phase aliphatic nucleophilic substitution by cyanide, acetate, and thiocyanate ions in nonpolar organic solvents. This ac- celeration was prominent when an adequate inorganic solid support, namely alumina for cya- nide and silica gel for acetate and thiocyanate, was present in a heterogeneous reaction mix- ture. An interesting phenomenon of sonochemical switching of reaction pathways from aro- matic electrophilic to aliphatic nucleophilic substitution was reported for the reactions of benzyl bromides, potassium cyanide, and alumina in aromatic solvents. The effects of organic and inorganic additives and ultrasonic pretreatment on this switching were studied. From these observations as well as the X-ray and SEM study of sonicated potassium permanganate crystals, the possible factors of ultrasonic acceleration of a solid-liquid two-phase reaction with solid inorganic salts were estimated as follows: (1) increase in surface area and active sites on inorganic salt crystals, (2) promotion of the interaction between inorganic salts and solid supports, and (3) acceleration of the reaction itself with and without intervening water molecules.

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Aqueous thymine solutions were sonicated in an ultrasonic cleaning bath with argon bubbling and the final degradation products were analyzed by high performance liquid chromatography. By comparison of the obtained data with those from γ-radiolyses of aerated and deaerated thymine solutions, it was found that hydroxyl radicals were produced through the scission of water molecules and this cleavage did not involve the degradation of hydrated electrons, implying the homolytic scission. It was also found that the yield of the hydroxyl radical obtained from 30 min sonication was equivalent to that from radiolytic degradation for the total dose of 800 Gy.

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It was found- that lithium naphthalenide can de prepared from metallic lithium and naphthalene in non-etherial solvents such as benzene-N, N, N' N'-tetramethy1-1, 2-ethane diamine (TMEDA) or benzene-N, N, N, N'-tetramethyl-1, 3-diamine (TMDAP) under ultrasound irradiation. Dimerization of isoprene [1] and synthesis of terpene alcohols by direct oxidation of isoprene dimer dianions can be achieved with lithium naphthalenide prepared in such non-etherial solvents.

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The magnetic field effect (≤260 mT) on the photoinduced hydrogen abstraction reaction of xanthone in sodium dodecyl sulfate (SDS) micellar solutions was studied by steady state and laser flash photolyses. In the SDS micellar solution, the excited triplet state of xanthone abstracts a hydrogen atom from a dodecyl sulfate anion very slowly. By the addition of xanthene to the solution, the hydrogen abstraction from xanthene occurs very effectively. In a magnetic field (260 mT), the relative quantum yield of disappearance of xanthone is reduced (25∼40%) by steady irradiation (Fig.3), while the relative yield of the photoproducts (i. e., xanthone dimer and xanthene dimer) increases remarkably (400%) (Fig.4). In the laser flash photolysis, the decay of a transient due to the 9-xanthenyl radical is also influenced significantly by the magnetic field (Fig.7). The results are interpreted in terms of a radical pair model of CIDNP.

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Recently, it has been found that the emission intensity of such reaction intermediates as OH, Na, and HPO in atmospheric flames is influenced by an external magnetic field. In order to elucidate the mechanism of this magnetic field effect on combustion, the emission intensity of each rotational transition of the A2 band of OH in flames has been investigated.
From the observed, spectra of the OH transitions in the absence and the presence of a magnetic field of 1.8 T (Fig. 's 1, 2, and 4), emission from the F1 sublevels of the 2E state was found to be enhanced by the field, while that from the F2 ones was insensitive to it. Large magnetic enhancement was observed for the Q1(4), Q1(5), and Q1 (6) transitions: the increments by a magnetic field of 1.8 T being 35, 23, and 34%, respectively (Table 2). The magnetically induced increase of the emission intensity for the transition from the sublevels with K'<4 or K'>6 was smaller than that from the one with K'=4, 5, or 6.
This magnetic field effect might be attributable to the increase of the formation rate of the F, sublevel with K'=4, 5, or 6 by a magnetic field. The magnetic field effect observed for OH has been compared with those for CN, Na, and HPO.

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Photochemical reactions of 1-isoquinolinecarbonitrile [1] J and 3-methyl-1-isoquinolinecarbonitrile [3] were carried out in ethanol, and magnetic-field and heavy-atom effects were investigated to elucidate the reaction mechanisms.
(1) Irradiation of [1] resulted in the formation of 1-(1-hydroxyethyl)isoquinoline [2] in ca.62% yield (Eq. (1)). The chemical yield of [2] increased quadratically with an increase in the field strength (magnetic field effect due to zig mechanism) (Fig.3). The reaction was quenched by the addition of propyl bromide (Fig.6), although the conversion remained almost constant (Fig.5). The results indicate that the photosubstitution reaction [1] [2] occurs from Si state through the formation of singlet hydrogen-bonded radical pair [2 a], whereas the triplet radical pair [2 b'] arising from T1 state undergoes diffusive separation (Scheme 2).
(2) In the case of [3], 1-(1-hydroxyethyl)-3-methylisoquinoline (4) and 3-methylisoquinoline [5] were obtained as photoproducts in ca.45% and 12% yields, respectively (Eq. (2)). The chemical yield of (4) decreased steeply by the application of a magnetic field of 40 mT (magnetic field effect due to HFI mechanism), and further increase in the field strength resulted in a quadratic increase in the yield (magnetic field effect due to tig mechanism) (Fig.4). On the other hand, the chemical yield of [ 5 ] was independent of an external magnetic field (Fig.4). Addition of propyl bromide caused a remarkable quenching for the reaction [3] [ 5 ], but did not so much for the reaction [3]+[4](Fig.6), the conversion having remained almost constant (Fig.5). The results indicate that the photosub stitution reaction [3] occurs from both S, and T1 states via the formation of radical pairs [4 a] and [4 b'], whereas the photodecyanation reaction [3] [5] proceeds via S1 state through the formation of biradical [5 a] (Scheme 3).

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Anodic generation of aminonitrenes from hydrazines N, N-disubstituted with the benzyl groups was investigated. The generation of aminonitrenes in the anodic oxidation of N, Ndibenzylhydrazine [1] and N-aminoisoindoline [2] could be confirmed on the basis of formation of hydrocarbons via the socalled abnormal reaction in hydrazine oxidation. Toluene and bibenzyl were formed in addition to 1, 1, 4, 4-tetrabenzyl-2-tetrazene and benzaldehyde dibenzylhydrazone from [1]. Compound [2] gave 1, 2, 5, 6-dibenzo-1, 5-cyclooctadiene as a hydrocarbon and a, ce-bis(2-isoindolinylimino)-o-xylene. Chemical oxidation of [1] with lead (IV) acetate, mercury(II) oxide and p-benzoquinone was also studied in comparison with the anodic oxidation. The reactivity of the aminonitrenes was found to be greatly affected by their methods of generation, electrolytic and reaction conditions, and oxidizing reagents used.

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The conversion of CO and NO has been widely carried out with various catalysts including metal oxides and zeolites at elevated temperature- in high pressure. The purpose n of this paper is to convert CO and NO using homogeneous metal complexes and electrode catalysts at room temperature in atmospheric pressure. The conversion reactions were activated in the following four different situations.
(1) The uptake of CO and NO by solution was enhanced by the addition of metal complexes. (2) The electrochemical conversion processes of CO and NO were activated by a chemically modified electrode: effective coatings were Everitt's salt for CO, and phthalocyaninatocobalt(II) or phthalocyanine for NO. (3) The activation of a semiconductor electrode by the illumination of light leads to stimulate the conversion efficiency, e. g., the holes produced at n-CdS under light can oxidize NO to NO₃- with a high efficiency. (4) At the three phase boundary(gas/solution/electrode), CO can be more effectively reduced than at two phase(solution/electrode), which is based on the fact that the diffusion of reaction gas to a reaction place is more favorable along the electrode surface than through the bulk solution.

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The anodic oxidation of β-substituted N-methoxycarbonyl amines [1] in methanol gave mixtures of products resulted from the cleavage of the a-carbon-hydrogen bond (route a) and the a-carbon-β-carbon (route b) through the intermediary formation of cation radicals. The ratio of a to b was found to be largely affected by β-substituents or stereochemistry of [1]. Route b took place exclusively in the anodic oxidation of [1] possessing β-substituents such as hydroxyl and methoxycarbonylamino groups, while route a predominated in the oxidation of [1] bearing an acyloxyl group at the β-position. A mixture of products resulted from routes a and b (52: 23) was obtained by the anodic oxidation of N-methoxycarbonylated 2-methoxyethylamine. The anodic oxidation of 2-oxazolidone or 2-imidazolidone gave exclusively the a-methoxylated products.
The products of route a were utilized for the synthesis of serine derivatives [2], and optically active amines were prepared through the anodic cleavage (route b) of optically active β-hydroxy amines [3].

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Pt-Solid Polymer Electrolyte prepared by a deposition of platinum on both surfaces of Nafion 415 using an electroless plating method was applied to methoxylation of furan. The methoxylation proceeded even in a direct oxidation system, though the current efficiency was low and the cell voltage was high because of deterioration of Nafion by by-products. The addition of a small amount of bromine remarkably improved the reaction efficiency, that is, the current efficiency was enhanced and the cell voltage was lowered. The added bromine formed a redox system, which mediated the methylation, leading to selective production of 2, 5-dimethoxy-2, 5-dihydrofuran at the lower cell voltage. The amount of bromine added was optimum at the concentration of 0.01 mol. dm^-3. While in a direct oxidation system the addition of water had a preferable influence, in the indirect mediatory system containing bromineAthe addition of water caused only an unpreferable effect lowering the current efficiency. Added bromine species were easily separated on work-up without forming any cumbersome by-product. The feasibility of application of SPE method to a mediatory system for electroorganic syntheses was elucidated, though the life of SPE composite electrodes still remains as a problem to be solved.

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The direct electrooxidation of 1, 3-dienes [1] in methanol gave 1, 4-dimethoxylated compounds [2] as main products along with 1, 2-adducts [3] and [4], whereas anodic oxidation of [1] utilizing sodium halides as supporting electrolytes gave [4] selectively. Sodium bromide gave better results than sodium chloride and sodium iodide (Table 1). The reaction proceeded not only regioselectively (Table 2) but also stereoselectively (Table 2, entries 5 and 6). This reaction was applied to the synthesis of a, a-unsaturated ketones. For example, 5-bromo-4-methoxy-2-pentene (15) synthesized from 1, 3-pentadiene by this anodic method was transformed to 3-penten-2-one [31] by the treatment of (15) with DBU followed by acid hydrolysis. Since 1, 3-dienes can be synthesized from aldehydes by the Witting reaction, this procedure is considered to be a new method for the transformation of aldehydes to a, /3unsaturated ketones with elongation of one or three carbon units. The transformation of 2-hexenal to 3-hepten-2-one (35) is a typical example of the one-carbon-unit elongation (eq.10), while three-carbon elongation is exemplified by the syntheses of 3-decen-2-one [39 a] and 3-tridecen-2-one [39 b] from heptanal and decanal, respectively (Eq.11).

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Films resulting from electrooxidative polymerization of various aniline derivatives (N-methyl-, N-ethyl-, 2, 5-dimethoxy- and 2, 6-dimethyl-anilines) on a Pt electrode in an acidic aqueous solution revealed a reversible, redox response in an aqueous supporting electrolytic solution and thus were found to be the electroactive. Their analysis by IR spectroscopy suggests that films were organic polymers possessing the 1, 4-disubstituted benzene structures as the unit structures and were formed by a coupling of the phenyl nuclei at 1- and 4- positions with respect to the amino group. Contrary to the films prepared in an acidic solution, the films prepared by electrooxidative polymerization of those aniline derivatives on the Pt electrode in a basic aqueous solution were electroinactive. From their IR spectroscopy, these films were considered to possess the 1, 3-disubstituted benzene structure. The redox response of these electropolymerized, electroactive films is considered to correspond to the oxidation reduction of the diamine/diimine redox couple. In the case of electrooxidative polymerization of the 4-substituted and 3, 5-disubstituted aniline derivatives, it was also found that the electrochemical behavior of the films prepared depends on the experimental conditions used for their electrochemical polymerization.

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Electron-transfer reaction and formation of active species induced by both applied potential and photoexcitation were studied by photoelectrochemical method.
A graphite electrode was coated with Nafion membrane, and then tris(2, 2'-bipyridine)- ruthenium (II) complex [Ru(bpy)32+] was adsorbed into the polymer layer. The modified electrode thus obtained was illuminated with visible light in the presence of methylviologen (MV2+) to give cathodic or anodic photocurrent depending on the applied potential. The cathodic photocurrent brought about formation of viologen cation radical (MV+). The cathodic photocurrent was enhanced about 9 times in the presence of oxygen due to oxidation of MV+.

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The formation of anion radicals from steroidal nitro compounds and their fate were examined using cyclic voltammetry and cathodic electrolysis. Nitro steroids examined were 6-nitro-5- cholestene and its C-3-substituted derivatives and several vic-nitro chlorides.6-Nitro-5-cholestene showed a reversible voltammogram in wide range of scan rates. The cathodic potential was -1.49 V (vs SCE). Structural-dependent voltammograms were recorded for above compounds, and these were interpreted as the difference in lifetimes of the anion radicals assuming coupled electron-transfer and chemical processes. Cathodic reduction of these compounds resulted in the formation of a dimer and/or a cyclosteroid depending on the nature and stereochemistry of the substituent.

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Reductive cleavage of some β-hydroxy sulfoxides (Tol-SOCH₂C(OH)R1R2) to the corresponding alcohols was examined by means of direct and indirect electrolyses. In the direct electrolysis at a mercury cathode irx acetonitrile there was a sharp difference with regard to yields of the corresponding alcohols and coulometric n-values between (1 a) (Ri=H, R2=Ph) and the other substrates, [1 b] (R1=-Me, R2-(CF12)2Ph) and Cl cD (R1=Me, (CH₂)8Me): With (1 b) and (1 c) the corresponding alcohols were obtained in 17 and 37% yields and the addition of phenol as a proton donor caused these yields to increase up to 31 and 41%, respectively, whereas [1 a] gave a very low yield(5%) even in the presence of excess phenol. The coulometric experiment in the presence of phenol gave n4-4 for (1 a) and nk-3 for (1 b) and [1 c].
Polarography and cyclic voltammetry showed that among anthracene, pyrene, and phenanthrene, pyrene was the most effective mediator for the reduction of (1 a)-(1 c). The rate of reduction of the substrate by an electrochemically generated pyrene radical anion was dependent on the type of the substrate the rate constant for [1 a] was higher than for [1 b] and [1 c]. A preparative reduction of (1 a) by means of the indirect electrolysis using pyrene produced the corresponding alcohol in a good yield. Also, in the indirect electrolysis of [1 b] and [1 c] the yields of the alcohols were higher than in the direct electrolysis.

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Electrochemical transformations of aspartic acid derivatives into nucleic acid pyrimidine bases were established. The three principal routes were exploited.
Dihydroorotic acid which is easily derived from aspartic acid was oxidized anodically to give uracil in a good yield. The method was extended to the synthesis of 1-substituted uracil. To generalize this method, the electrolysis of 5methyl-5, 6-dihydrouracil-5-carboxylic acid which is a positional isomer of dihydroorotic acid derivative was also carried out to afford thymine in a satisfactory yield. To develop a more practical method, the transformations of asparagine and aspartic acid β-methyl ester into uracil were examined. As a result, it was found that asparagine and aspartic acid a-methyl ester were efficiently transformed into uracil via Na-ethoxycarbonylasparagine and N-carbamoylaspartic acid p-methyl ester, respectively. The method was applied to the synthesis of 5-fluorouracil which has been used clinically as an antitumor agent.

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Anodic oxidation of o-xylene was studied in the presences of nitrate ion and oxygen. A divided cell with a sintered glass flit diaphragm was used and the anode was a platinum plate or a graphite rod. The electrolyte solution was acetonitrile containing AgNO₃, Cu(NO₃)23 H₂0, Fe(NO₃)3 H₂0, Ni(NO₃)2.6 H₂0 or the other nitrates. Furthermore, o-xylene was dissolved into the anolyte. The anode potential was normally controlled to be 2.1 or 2.3 V vs. SCE. The electrical charge passed was 2 faradays per 1 mol o-xylene. In the deoxygenized electrolyte solution, 2-methylbenzyl nitrate was the main product and the yield was 32.0% with AgNO₃. In the anodic oxidation under oxygen bubbling into the anolyte, the main product was o-tolualdehyde and yield was 41.8% with Fe(NO₃)3 H₂0 and was 40.6% with AgNO₃.

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Anodic oxidation of bis(4-nitrophenyl)sulfide [3] in a mixed solvent of acetic acid and coned. hydrochloric acid using carbon rods as an anode and a cathode in a divided cell gave bis(4-nitrophenyl)sulfone 1 J with high purity of more than 99.9% in a quantitative yield. The sulfone 1 J can be easily reduced to the corresponding diamino sulfone [2], which is of much use as a synthetic intermediate of many heat-proof resins, pesticides and pharmaceuti- cal drugs.
Since the product [ 1] is almost completely insoluble in the used solvent, it can be obtained by simple filtration of the reaction mixture. Furthermore, it was established that the filtrate can be repeatedly used many times as a solvent of the present anodic oxidation. The employment of sulfuric acid or perchloric acid as a supporting electrolyte in this electrochemical oxidation brought about the exclusive formation of bis(4-nitrophenyl) sul- foxide 4 with only a trace amount of M. From the experimental results, it is proposed that the sulfide [ 3] is chemically oxidized by chlorine, hypochlorous acid, or chlorine monoxide, generated by anodic oxidation of hydrochloric acid.

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Chemical reactivities of radical anions of dimethylbicyclo[2.2.1]hepta-2, 5-diene-2, 3-dicarboxylate(NE) and dimetyltetracyclo[3.2.0.02.04, 6]heptane-1, 5-dicarboxylate(QE) have been investigated by pulse radiolysis of hexamethylphosphorictriamide(HMPA) solutions and 77 K r irradiation of 2-methyltetrahydrofuran(MTHF) solutions. Solvated electrons were captured by QE in HMPA with a rate constant of 1.3 x 10 dmol-i-i at room temperature. The resultant radical anion of QE, which could not be detected, isomerized to NE radical anion very rapidly, even at 77 K.
On the other hand, the NE radical anion which was formed from NE and solvated electron with a diffusion-controlled rate, did not isomerize to QE radical anion but reacted with a neutral NE molecule with a rate constant of 1.2 x 107 dm3ol-1-'. The dimer anion thus formed shows a strong UV absorption band at wavelengths shorter than 330 nm and was estimated to be a a-bonded dimer. For the r radiolysis of HMPA solution of NE, it has been observed that G(E) depends on the concentration of NE and reached 142 at 0.04 molm^-3 of NE, suggesting a chain reaction to form polymeric products.

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It will be demonstrated that the reduced forms of Prussian Blue, Fe4Di[Fen(CN)6]3, and its analogs, iron-ruthenium cyanide, Fe41[Ruff(CN)6]3, iron-osmium Cyanide, Fe4m [Os5 (CN), ]3, do have catalytic activities for the reduction of molecular oxygen in aqueous acidic solutions. The above three complexes give a similar activity. It can be expected that Prussian Blue and its analogs have the capability of delivering two or four electrons, more or less simultaneously, to molecular oxygen in the crystals. The electrochemical behaviour of carbon paste electrodes containing Prussian Blue analogs has been also studied. The carbon paste electrodes show cyclic voltammograms identical with those of the respective modified electrodes with the thin-film form on substrates. This suggests that the technique using the carbon paste electrodes will be extended to various Prussian Blue analogs. The catalytic activities of the carbon paste electrodes are also discussed.

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Enhancement of electrode catalysis by under potential deposition (UPD) for the anodic oxidation of Cl fuels such as HCOOH, HCHO and Me0H was investigated in the acidic solution by means of the ordinary cyclic voltammetry and rotating disk electrode methods. An extraordinary large effect was observed with HCOOH oxidation by adding Pb2to the solution. The same effect was also detected with HCHO and Me0H but the effect was far smaller than that with HCOOH.
A good correlation between the coverage by under potential deposited Pb on a Pt electrode and the enhancement of the anodic current of HCOOH suggests that the coverage by Pb avoids adsorption of multisite intermediate such as COH on the unoccupied active site leading to the enhancement of the oxidation.
On the other hand, the addition of Me0H or CO to the solution containing HCOOH and Pb²⁺ extremely suppressed the enhancement of anodic current of HCOOH by UPD of Pb and in the case of Me0H or HCHO, stronger poison such as CO might be produced.
The electrolysis with the rotating disk electrode showed that the rate determining step on the smooth Pt surface is the surface electrode reaction, while on the Pb deposited Pt-Pt electrode the diffusion step controls the oxidation rate, resulting in a strong suppression of the poisoning by the intermediate.

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The current doubling behavior of formaldehyde was studied on an n-type ZnO polycrystalline semiconductor electrode. The increase in photocurrent due to formaldehyde was about 70% in neutral and alkaline electrolyte solutions. It was found that during the current doubling reaction the ZnO photoanode dissolved in the neutral aqueous solution but the dissolution reaction of ZnO was completely suppressed in the alkaline solution at a sufficiently high pH. From the experimental results a reaction mechanism is proposed.

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The behaviors of the electrochemical redox reaction of various substances were investigated with the quinonoid polymer modified electrode (SQE). The voltammograms of hydroquinones and quinones at SQE were similar to those at a glassy carbon electrode (GCE).
However a few species of hydroquinones having carboxyl or sulfo groups on the ring, such as 2, 5-dihydroxybenzoic acid and hydroquinonesulfonic acids showed different shaped voltammograms at a pH range where these hydroquinones dissociate into anions. The reductions of disulfides and unsaturated acids were obviously retarded with SQE. Furthermore, the oxidation of Fe2+ ion and the reduction of Fe ion could not be achieved with SQE.

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Triphenodioxazines [3] were prepared through the anodic oxidation of 2, 5-his(arylamino)- 3, 6-dichloro-1, 4-benzoquinones [2] which in turn were obtained by the reaction of anilines [1] with chloranil. The electrochemical reaction was carried out by passing 8 F/mol of electricity under a constant current in DMF-acetonitrile or DMF containing tetrabutylammonium bromide at 40-50&deg; C.

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Recoil implantation has been applied to synthesis of new chemical substances which, are not easily obtained by ordinary chemical procedures. The mechanisms of chemical reactions induced by recoil implantation are interesting because they can elucidate the related reactions in hot atom chemistry.
In this paper the recoil implantation reactions of Cr in R-diketonates mixed systerns such as [Fe(acac)3]-[Fe(dprr)3], [Cr(acac)3]-[Fe(dpm)3] and [Ci-(dpm)8]-[Fe(acac)3] were investigated. The source powders were irradiated with reactor neutrons, with r-rays of an electron linear accelerator, and with deutrons in a cyclotron, ana Cr recoil atoms produced by (n, r), and (d, xn) reactions were implanted in the catcher of diketonate mixed systems.
Implantation of "Cr by cyclotron irradiation in [Fe(acac)3]-[Fe(dpm)3] gave chemical species [51Cr(acac)x(dpm)3, ] where x-=0-3. The recoil replacement reaction type species [Cr(dpm)3] and [Cr(acac)3] were found more important than the abstraction type species [Cr. (acac)(dpiri)2] and [Cr(acat)2(dpin)] on the contrary of ROssler's observation on rhenium compounds. Moreover, the ratio [51Cr(dpm)3]/[51Cr(acac)3] was much larger than, unity when [Fe(dpm), ]/[Fe(acac)a] was unity, and it depended apparently on recoil energy. Observation of (n, r) and (r, n) reactions of chromium in the mixture systems [Cr(acac)3]- [Fe(dpm), ] and [Cr(dpm)3]-[Fe(acac)3] led us to the conclusion that there were threshold values of energy for formation of recoil replacement reaction type compounds.

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The radiation of r rays to butyl chloride solution of cis-transoid-cis-cyclobuta[1, 2-a: 4, 3- a']diindene (1) resulted in an efficient cleavage of the cyclobutane ring, giving indene more than 90% yield based on the, [1] unrecovered. Figure 2 shows, a linear doublereciprocal plot of the G value vs. the/concentration of [1]. from which the limiting G value was determined to be 67. The ring cleavage reaction was inhibited by compounds p?sessing lower oxidation potentials than 1.6 V vs. AgiAg+ (Fig.4). Kinetic analyses suggested that the active species responsible for the ring cleavage is the cation radical of butyl chloride stabilized by ion pairing with chloride anion or by a high degree of solvation and that the active species catalytically undergoes the ring cloeavage of [1] at a nearly diffusion-controlled limit without electron exchange; neutral molecules of indene are thus formed directly. It was, found that benzene and toluene can sensitize the ring-cleavage reaction (Fig.5). The sensitization was again interpreted in terms of catalysis by the cation radical ofthhydro- carbons. Similarly, the r radiolysis of [2] and [3] resulted in the ring cleavage to give indene, while no ring cleavage occurred in cases of [4], [5], and [6]. It was suggested that the through-bond interactions between the two ng electron systems involving the pertinent C-C bond of the cyclobutane ring are essential in the catalytic ring cleavage (Fig.6). The radiolytic reactions were compared with the redox-photosensitized reactions of the cyclobutane compounds that had been reported previously.

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