Ethene photochemical reaction with

Photochemical Reactions of Pentacarbonyliron with Ethene Cocondensed in Low Temperature Matrices. We have also studied the photochemical reactions of pentacarbonyliron with ethene cocondensed in the nitrogen matrix (22). While the formation of Fe(CO) (C2H ) in UV photolysis of Fe(C0)5 cocondensed with C2H in argon matrix was inferred from the IR spectra (23), no MWssbauer parameters were reported on this relatively unstable product. In order to elucidate the detailed mechanisms of photochemical reactions with cocondensed species, we have compared the products from the homogeneous cocondensed matrix with those from the stratified matrix where Fe(C0)j and C2H constituted separate... 

The cation-radicals of ethenes, which are the primary products of one-electron oxidation, differ in their reactivity from the corresponding neutral compounds. This widens the possibilities of syntheses. Primary oxidation of ethenes (photochemically, with salts of transition metals or ammo-niumyl salts) makes it possible to obtain cation-radicals, which initiate reactions that are unusual for ethenes in an uncharged state. For instance, the cation-radical of phenylvinyl ether initiates head-to-head cyclodimerization as shown in Scheme 7.19 (Ledwith 1972, Farid and Shealer 1973, Kuwata et al. 1973). 

Various photochemical reactions of 3,4-dihydro-2/Apyrans have been reported in which formally a carbonyl group leaves the six-membered ring and a new bond is created between C2 and C5 forming cyclobutanes. However, this type of reaction is seldom of preparative interest due to low yields and the many byproducts formed. Mercury-i/ PjJ-sensitized decomposition of 3,4-dihydro-2//-pyran, at atmospheric pressure at 84.5°C, gave cyclobutanecarbaldehyde (1) in a maximum yield of 20% together with cyclobutane, carbon monoxide, ethene and acrylaldehyde.43... 

The reaction between ethyne and phosgene has also been studied under photochemical conditions (>220 nm) [2185a]. As in the analogous reaction with ethene (see Section 10.1.2), the phosgene merely acts as a convenient source of chlorine radicals the principal products were CO, CHj=CHCl, 1-chloro-l, 3-butadiene, benzene and polymer trace amounts of HC Cl and CgHjCl were also detected [2185a]. 

The iodonium salt (211) adds alkenes on irradiation. The photochemical reactions are carried with the salt as a suspension in acetonitrile or methylene chloride using a 400-watt lamp. The products obtained were identified as the dihydrofuran derivatives (212) and the best yields were obtained with electron-rich ethenes such as the enol ethers (Scheme 5). 

Photochemical decomposition of diazo(trimethylsilyl)methane (1) in the presence of alkenes has not been thoroughly investigated (see Houben-Weyl Vol. E19b, p 1415). The available experimental data [trimethylsilylcyclopropane (17% yield) and la,2a,3j8-2,3-dimethyl-l-trimethylsilylcyclopropane (23% yield)] indicate that cyclopropanation occurs only in low yield with ethene and ( )-but-2-ene. In both cases the formal carbene dimer is the main product. In reactions with other alkenes, such as 2,3-dimethylbut-2-ene, tetrafluoroethene or hexafluoro-propene, no cyclopropanes could be detected.The transition-metal-catalyzed decomposition of diazo(trimethylsilyl)methane (1) has been applied to the synthesis of many different silicon-substituted cyclopropanes (see Table 3 and Houben-Weyl Vol.E19b, p 1415) 3.20a,b,2i.25 ( iQp. per(I) chloride has been most commonly used for carbene transfer to ethyl-substituted alkenes, cycloalkenes, styrene, and related arylalkenes. For the cyclopropanation of acyl-substituted alkenes, palladium(II) chloride is the catalyst of choice, while palladium(II) acetate was less efficient, and copper(I) chloride, copper(II) sulfate and rhodium(II) acetate dimer were totally unproductive. The cyclopropanation of ( )-but-2-ene represents a unique... 

The photochemical reaction of A -methylphthalimide with 1,1-diphenyl ethene affords the phthalimide adduct (329) and the ether (330) in 44 and 12 % yield respectively. With imide (331) the byproducts are the ring opened adduct (332) and the ether (330) in yields of 31 and 44% yield respectively. The authors suggest that the formation of the ether is the result of a second electron transfer as illustrated in Scheme 11. ... 

Alkyl halides (RX X = Cl, I) are an important source of halogens in the atmosphere. The major tropospheric sinks of these compounds are photolysis (RBr, RI) and reaction with OH radicals. In the case of alkyl iodides (RI) relative kinetic studies of their OH reactions in photoreactors are complicated by fast reactions with the 0( P) atoms generated by the photochemical OH radical sources. Figure 1 below shows a In-ln plot of the kinetic data from an experiment performed in a large photoreactor to determine the OH rate coefficient for the reaction OH + CH3CH2CH2I relative to OH + ethene using the photolysis of methyl nitrite (CH3ONO) as the OH radical source. A recent example of the implementation of the relative kinetic technique for the determination of OH radical rate coefficients in a photoreactor can be found in Olariu et al. (2000). 

Several review articles have dealt with various aspects of cycloaddition reactions. A short review has presented examples to illustrate the use to which tethered alkenes can be put in the synthesis of cyclobutenes. The photochemical (2 + 2)-cycloaddition of enones to ethene has been studied from a theoretical standpoint. A review has highlighted the use of linear templates to control photochemical reactions such as (2 + 2)-photocycloadditions. The stereochemical control of photochemical reactions in clay-intercalated compounds has been discussed. A review has highlighted the interdisciplinary nature of photochemistry. ... 

Thermolysis of [(triphos)Ir(H)2Et] with styrene afforded [(triphos)IrH(ti2-CH2=CHI%)] which on photolysis underwent an insertion of iridium into a C-H bond to give a 1 1 mixture of the ( -) and (Z-) styryl complexes [(triphos)Ir(H)2(CH=CHPh)]. The ethene complexes lCpIr(L)(C2H4)] (L = CO, PPh3) were reported" to undergo two competing photochemical reactions in solution - isomerisation to a vinyl hydride and dissociation of ethene widi insertion of iridium into solvent C-H bonds. The mechanisms of these reactions were studied in detail. 

Re2 (li-H) (pa-a -CHCH2 ) (CO )0 reacts with ethene under photochemical reaction conditions to form the q -vinyl complexes Re2( U-H) (pa-Cf n -CHCHEt) (CO) 0 and the system is able to cataly tically generate but-l-ene and hex-3-ene. 

Hydrocarbons and other organic compounds in the atmosphere are assumed to oxidize through a series of steps of photochemical reactions. They do not react directly with sun-light, but react with photochemically formed species. The hydrocarbons identified in atmosphere are methane, ethane, ethene, ethylene, propane, n-butane, isopentane, etc. Hydrocarbons are removed from the atmosphere by several chemical and photochemical reactions. For instance, oxidation, to convert them into CO2, acids and aldehydes are formed. 

Kirmse and Streu have used the photocycloaddition of ethene to cyclopen-tenone and 3-methylcyclopentenone to yield the [2 + 2] adducts (32, R = H or Me) as a route to the synthesis of the norbornenones (33). Cyano Dewar heptalene (34) has been successfuUy synthesized using a multi-stage reaction in which the photocycloaddition of ethyne to the enone (35), yielding (36), played an important part. The Dewar heptalene (34) is photochemically labile and is converted into (37) on irradiation with 254 nm light, although it is... 

Although quinazolin-4(3//)-one itself does not undergo photochemical intramolecular [2 + 2] cycloaddition to alkenes, its 2-(trifluoromethyl) analog does perform such a reaction. Thus, irradiation of 2-(trifluoromethyl)quinazolin-4(3i/)-one in methanol under bubbling ethene gives the [2 + 2] cycloadduct, 2a-(trifluoromethyl)-2,2a-dihydro-l/y-azeto[l,2-a]quinazolin-4(377)-one as the sole product. In several cases, the initially formed adduct of 2-(trifluo-romethyl)quinazolin-4(3/7)-one with alkenes is further transformed under the irradiation conditions." ... 

In this reaction, triplet methylene inserts in the ethene molecule to produce an energized cyclopropane molecule, which may then either isomerize to propene or may be collisionally deactivated to give cyclopropane. Molecules may also be activated photochemically. Although most photochemical processes involve more than one electronic state of the molecule, it is possible in some cases to produce molecules in their electronic ground states with high vibrational excitation, and these may subsequently isomerize or dissociate. A typical example is the photoexcitation of cycloheptatriene followed by its isomerization to toluene. 

Additions to Cyclohexenones and Related Systems - Caldwell and his coworkers have studied the photochemical addition of 1,1-diphenylethene to 4,4-dimethylcyclohex-2-enone. The products from this reaction, carried out in cyclohexane, are shown in Scheme 1. Although other evidence (see reference 9b above and references cited therein) has suggested that an exciplex is not a key interaction in such (2+2)-photocycloaddition reactions Caldwell et al. conclude from their detailed study of this system that a triplet exciplex is involved. Schuster and his coworkers have reported that a variety of cyclic enones (17) -(19) add photochemically to fullerene. The yields of the adducts vary but with some of the less heavily substituted enones the yields can be reasonable as shown by the data under the appropriate structure. Suginome et aO report the synthesis of the cycloadducts (20) by the photochemical addition of various ethenes to the enone (21). The adduct (22) was also synthesized by photochemical addition of methoxycyclohexene to the enone (20). 

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