Search

The photochemical reaction between naphthalene and tetranitromethane in dichloromethane or acetonitrile gave predominantly (85–95%) products of nitro/trinitromethyl addition to the aromatic system, namely cis- and trans-1-nitro-4-trinitromethyl-1,4-dihydronaphthalene and trans-2-nitro-1-trinitromethyl-1,2-dihydronaphthalene. A small amount of trans-2-hydroxy-1-trinitromethyl adduct was also formed, presumably originating from an initial nitrito/trinitromethyl adduct.The minor reaction pathway directly gave product(s) of nitro substitution, the ratio of 1- to 2- nitronaphthalene being high ( 25) in dichloromethane and in the beginning of the acetonitrile runs (up to ≈ 40% conversion). The temperature dependence of this process suggests that coupling between (napthalene)+˙ and nitrogen dioxide is the major pathway leading directly to nitro products. 2-Nitronaphthalene, formed after long reaction periods in acetonitrile runs, was presumably formed via elimination of nitroform from the 1,2-adduct. cis-1-Nitro-4-trinitromethyl-1,4-dihydronaphthalene was isolated in pure form and shown to undergo facile base-catalysed elimination of nitroform in dichloromethane and acetonitrile to give 1-nitronaphthalene. It also underwent a slow spontaneous elimination in acetonitrile. It was stable under acidic conditions. GLC of the pure adduct gave exclusively 1-nitronaphthalene at a low injector-port temperature, whereas at higher temperatures a mixture of products was formed (naphthalene, 1- and 2-nitronaphthalene and 1-naphthonitrile).

Hexachloroosmate(V) cleanly oxidizes tetrabutylammonium tert-butylcyanoacetate to decaboxylative-coupling products, meso-and rac-2,3-di-tert-butylsuccinonitrile, thus constituting the first metal ion-based oxidant to be found to simulate properly this aspect of the Kolbe anodic oxidation of carboxylates.

Photolysis of tetranitromethane and 1,4-dimethylnaphthalene at low temperature in dichloromethane gives predominantly addition products, trans- and cis-1,4-dimethyl-1-nitro-4-trinitromethyl-1,4-dihydronaphthalene (1 and 2, together 90%), in addition to the side-chain nitration product (3, 7%). At higher temperature, 3 becomes the major product [ratio (1 + 2): 3 30 : 65]. With external acid present during the run, partial formation of the 2-nitro substitution product (4) was an additional feature.In acetonitrile, the phenomenology is similar, except that the corresponding nitrito adducts were also present at the beginning of the reaction (maximally 20%) and disappeared toward the end; the 2-nitro substitution product also appeared toward the end of the run at higher temperature.It was shown separately that pure 1 rearranges to an equilibrium mixture with 2 in both acetonitrile and dichloromethane (rate constants 0.11 and 8 × 10–4 min–1, respectively). From 2, the corresponding nitrito adducts are slowly formed in acetonitrile via a, presumably, homolytic nitro/nitrito rearrangement. The latter reaction has the 1-trinitromethylnaphthalenyl radical as the intermediate, capable of existing in equilibrium with both trinitromethanide ion/(1,4-dimethylnaphthalene)˙+ and trinitromethyl radical/1,4-dimethylnaphthalene. Chemical consequences of these equilibria were found in both acid/base promoted reactions and trapping of trinitromethyl radical by the spin trap, α-phenyl-N-tert-butylnitrone.‡ The 2-nitro substitution product 4, in all probability, was formed as a consequence of acid-induced reactions of 2, indicating that in the photochemical experiments 4 is also formed via this pathway.

The reaction between tris(4-X-phenyl)aminium ions (X = Br, Cl) and trinitromethanide ion in dichloromethane or acetonitrile takes place by one-electron transfer, eventually leading to nitro derivatives of the triarylamines.

The radical cation formed upon dissolution of bis(pentamethylphenyl)methane in trifluoroacetic acid has been shown to be that of 1,2,3,4,5,6,7,8-octamethylanthracene.

Le traitement d'hydrocarbures aromatiques polycycliques par N 2 O 4 dans le dichloromethane conduit a la production des derives mononitres avec une forte selectivite positionnelle avec des rendements presque quantitatifs

Like a proton or a base, an electron or a positive hole can act as a very efficient catalyst in an organic reaction that in itself does not involve a change in oxidation level in going from substrate to product. If an electron is added to or removed from a neutral molecule, a radical anion (cation) is formed (eqn. i), and can undergo reactions at the new oxidation level (eqn. ii). At a later stage of the reaction sequence, a return to the original oxidation level can be achieved by a chain transfer step, i.e. , a chemically different radical anion (cation) can reduce (oxidize) a new molecule of the starting material (eqn. iii). A familiar example of this reaction type is the S RN 1 reaction (developed and studied by Bunnett, Kornblum, Russell and Saveant in 1965–1980) which enables otherwise extremely slow aromatic nucleophilic substitution reactions to take place under mild conditions. Other examples, to be discussed in this paper, include the S OE 1 and S ON 2 reactions, cyclodimerizations and cycloreversions, cycloadditions in general, rearrangements, oligomerizations and ligand exchange reactions. In general, catalytic effects of the order of 10–20 k cal mol can be attained by electron transfer catalysis.

The Marcus theory for outer-sphere (non-bonded) electron transfer reactions is presented. In addition, it is applied to the problem of identifying compounds capable of generating radical ions and/or radicals via fast electron transfer to or from redox proteins. The use of the Marcus treatment is illustrated by several examples involving different types of xenobiotics.

Fur die Kern- und Seitenkettenchlorierung aromatischer Kohlenwasserstoffe durch Natriumperoxydisulfat/Lithiumchlorid in wasrigem Acetonitril - mit und ohne Kupfer(II)-chlorid -wird ein Radikalkation-Mechanismus vorgeschlagen. Die Untersuchung der relativen Reaktionsgeschwindigkeiten unter Verwendung verschiedener Substrate und die der Isomerenverteilung unter Verwendung von Toluol zeigt, das die Chlorierung in diesen Systemen konventionell unter Beteiligung von molekularem Chlor erfolgt. On the Mechanism of Chlorination of Aromatic Hydrocarbons with Sodium Peroxydisulfate/Lithium Chloride The chlorination of aromatic compounds by sodium peroxydisulfate/lithium chloride in aqueous acetonitrile in presence or absence of copper(II) chloride previously reported to proceed via a radical cation mechanism, has been studied with respect to the relative rates of reaction for different substrates and to the distribution of isomers in the chlorination of toluene. The results fully agree with the assumption that conventional chlorination mechanisms operate in these systems.

Cinetique des reactions a pH ∼ 7. Pour certaines reactions, le radical intermediaire forme dans la 1ere etape serait piege par la N-t-butyl-α-phenylnitrone

Etude des reactions entre le tris-(bromo-4 phenyl) ammoniumyle et les ions chlorure, bromure, iodure et cyanure

Application des concepts empruntes a la geometrie differentielle, des surfaces minimales et de la transformation de Bonnet a la reorganisation moleculaire. Interpretation de la racemisation et de l'isomerisation E/Z des doubles liaisons en termes de transformation de surface

Positional selectivity and the partition deuterium isotope effect (k/sub H//k/sub D/) have been determined in the chemical (with cerium(IV) ammonium nitrate (CAN), cobalt(III) acetate, and N-bromosuccinimide (NBS)) and electro-chemical side-chain oxidation of alkyl aromatics by using 5-R-hemimellitenes (R = H, t-Bu) and 1,3-dimethyl-2-(trideuterimethyl)-5-tert-butylbenzene as the substrates. Considering also the already available data for isodurene, it has been found that the positional selectivity is strongly influenced by the substrate structure in the anodic and CAN-promoted oxidations, both reactions exhibiting a very similar pattern. In conrast, Co(OAc)/sub 3/ selectivities do not correlate with those of the anodic oxidation but with the selectivities of the side-chain bromination promoted by NBS. These results have been interpreted by suggesting that, as in the anodic oxidations, CAN-induced reactions involve first the formation of a radical cation intermediate which then loses a proton to give a benzylic free radical in the selectivity-determining step. The data for Co/sup III/ would instead suggest a mechanism involving a hydrogen atom transfer, but this conclusion cannot yet be considered definitive. No simple correlation exists between selectivity data and the k/sub H//k/sub D/ values.