Alkenes and Alkyls

The silver(III) complex [Ag(0H)(H)(I06)2] oxidizes primary and secondary alcohols to the corresponding carbonyls with 1 1 stoichiometry and the rate law (18) suggests a complexation mechanism. No evidence is found for radical formation. 

A similar rate law is observed in reaction of cyclic secondary alcohols by [Cu(0H)2H4Te06], where the rate is independent of ring size C5-C7. This points to rate-determining O-H rather than C-H bond scission in the proposed [CuOH2TeOsROH] complex. The reaction is catalyzed by OSO4. 

Limiting kinetic behavior in the [IrCUf oxidation of alcohols, R1R2CHOH (Ri, R2 = H, Me) points to formation of an intermediate complex which decomposes with C-H cleavage to give a carbon-centered radical in the rate-determining step. The absorbance at 488 nm increases and lack of CF inhibition points to a seven-coordinate geometry for the intermediate. 

In benzene solutionwith 1% acetic acid, oxidation of benzyl alcohols, ROH, to benzaldehydes by Pb(OAc)4 is second order in substrate, consistent with formation of an intermediate bis complex Pb(OAc)2(OR)2. No radicals are detected and a two-electron transfer oxidation of one of the coordinated alcohols is proposed. In the presence of pyridine, the reaction is first order in both alcohol and pyridine and a large isotope effect suggests proton abstraction by pyridine in the rate-determining step. 

Pulse radiolysis studies of the reactions between a -substituted alkyl radicals and [IrCU] indicate two distinct processes. Diffusion-controlled rates with a-OH and a-OR derivatives involve electron transfer, while, with alkyl and alkylchloride radicals, a chlorine atom transfer from [IrCU] to give [IrCl4(OH)2] predominates with considerably slower rate constants. The comparable reactions with [Fe(CN)6] are also slow and structure dependent but there is no evidence for CN transfer. 

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The second part of the theory, which is a logical consequence of the first, is that monomers that have more than one basic site, e.g., an aromatic ring or an oxygen atom, can form more than one type of complex with the carbenium ion this idea was first proposed by Plesch (1990) in the context of chemically initiated polymerizations. It helps to explain why aryl alkenes and alkyl vinyl ethers polymerize more slowly than isobutene and cyclopentadiene. The reason is that all the complexes formed by the alkyl alkenes are propagators, whereas for the aryl alkenes and vinyl ethers only a fraction of the population of complexes can propagate. 

A number of cis/trans 4,6-dialkyl-2,2-dimethyl-l,3-dioxanes were studied by C NMR spectroscopy (93JOC5251). The C NMR shifts of C -Me groups (Scheme 8) were found to be very sensitive to the 1,3-dioxane conformation [chair form Me(ax) ca. 19 ppm and Me(eq) ca. 30 ppm— pure 30.89 ppm in the twist-boat form both methyl carbons resonate at ca. 25 ppm (pure 24.70 ppm)]. With these values, AG° of the chair to twist-boat equilibrium was calculated (Table IV). For 13a (nitrile), 13b (alkyne), and 13e (methyl ester) (Scheme 8) in CH2CI2, the temperature dependence of the AG° values was determined. Depending on the substituent, small negative or positive entropy terms were found generally the enthalpy term dominates the -AG° value. In the tram isomers 13, the cyano and alkyne substituents favor the chair conformation, but CHO, ester, alkene, and alkyl substituents, respectively, clearly favor the twist-boat conforma-... 

Conjugate Additions of Reactive Carbanions to Activated Alkenes and Alkyls... 

Many authors note the fact that adsorption of alkenes and alkyl aromatics upon the alumosilicate surfaces leads to a marked increase in their proton acidity (e.g., Fame et al. 1972). Formation of cation radicals and their further deprotonation explain many features of the hydrocarbon catalytic transformations (Vishnetskaya et al. 1997). Scheme 1-44 (see below) represents this phenomenon. 

Primary amines react with nitrous acid to yield a diazonium salt, which is highly unstable and degradates into a carbocation that is capable of reaction with any nucleophile in solution. Therefore, reacting primary amines with nitrous acid leads to a mixture of alcohol, alkenes, and alkyl halides. 

Alcohol syntheses from alkenes and alkyl halides were summarized in Section 10-7.)... 

Pentafluorosulfanyl acetylene is a useful starting reagent for the synthesis of a variety of SF5 derivatives of saturated ethers, vinyl ethers, pyrazoles, cyclic alkenes, and alkyl-substituted phenyl-sulfur pentafluorides (134). It is also used for the preparation of a number of F5S-containing alkenes and alkynes (138, 139). 

Because oxidative decarboxylation of carboxylic acids by lead tetraacetate depends on the reaction conditions, the co-reagents, and the structures of the acids, a variety of products such as acetate esters, alkanes, alkenes, and alkyl hahdes can be obtained. Mixed lead(IV) carboxylates are involved as intermediates as a result of their thermal or photolytic decomposition decarboxylation occurs and alkyl radicals are formed. Oxidation of alkyl radicals by lead(IV) species gives carbocations a variety of products is then obtained from the intermediate alkyl radicals and the carbocations. Decarboxylation of primary and secondary acids usually affords acetate esters as the main products (Scheme 13.41) [63]. 

There is a significant production of conjugated di-alkenes and alkyl-cyclo-... 

Laszlo and co-workers have reported that K10 montmorillonites ion-exchanged with various transition metal cations are effident catalysts for Friedel-Crafts alkylation of aromatics with a wide range of alkylating agents such as alcohols, alkenes and alkyl halides.25... 

Termolecular interactions in excited states are an interesting aspect of recent organic photochemical studies. In general, terminal alkenes and alkyl vinyl ethers do not easily dimerize to give cyclobutanes under direct or sensitized photoieaction conditions. However, 1,4-di-cyanonaphthalene (DCN) can be used as an excellent sensitizer for the dimerization of alkyl vinyl ethers and trimethylsiloxyethene in benzene or toluene. In this process, the triplex [DCN--toluene--vinyl ether] generated from DCN, toluene, and vinyl ether has been postulated as a key reactive intermediate based on the observation that the... 

Very interesting are the results of recent investigations on the mechanisms of Co(II) mediated reductions of nitriles, alkenes and alkyl halides by LiAlH4 and NaBH4. Those studies have unambiguously identified borides and aluminides of cobalt as catalysts in all three reductions, a finding clearly at odds with commonly held notions about the mechanisms of such processes and which could also be relevant to other transition-metal—hydride systems [12]. 

Although rare, the direct C-H alkylation of p)fridine is known with both alkene and alkyl halide coupling partners in the... 

The formation of heterocyclic organoboranes from alkenes and alkylated diboranes has been recently reviewed 22b). 

Alkanes, Alkenes, and Alkyl Benzenes in l-Butyl-3-methylimidazolium... 

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