1-Butene reaction with oxide ions

Iron molybdates were investigated by several authors. It is generally observed that iron is reduced first (Fe3+ - Fe2+), while deeper reduction is required to reduce the molybdenum ions as well. Both cations occur in partially reduced states during the reaction with butene. Pernicone [254] concludes from his ESR work that under stationary reaction conditions the iron ions stay in the reduced state and that the redox process only involves Mo6+ and Mos+. However, Trifiro and Pasquon [318] and Matsu ura and Schuit [207] are of the opinion that reoxidation initially may lead to Fe3+ which in turn (rapidly) oxidizes the Mos+ ions at the hydrocarbon reaction sites of the catalyst. However, direct evidence is not provided. 

A detailed study of the oxidation of alkenes by O on MgO at 300 K indicated a stoichiometry of one alkene reacted for each O ion (114). With all three alkenes, the initial reaction appears to be the abstraction of a hydrogen atom by the O ion in line with the gas-phase data (100). The reaction of ethylene and propylene with O" gave no gaseous products at 25°C, but heating the sample above 450°C gave mainly methane. Reaction of 1-butene with O gives butadiene as the main product on thermal desorption, and the formation of alkoxide ions was proposed as the intermediate step. The reaction of ethylene is assumed to go through the intermediate H2C=C HO which reacts further with surface oxide ions to form carboxylate ions in Eq. (23),... 

Nevertheless, the factors that affect the electrophilicity of alkyl halides operate here, and lead to synthetically useful levels of selectivity. At one extreme, in the presence of Lewis or protic acid, the epoxide opens towards the side that gives the more stabilised cation, which is usually the more substituted side, leading to regioselectivity appropriate to an S l reaction. At the other extreme, in the absence of Lewis or protic acid, the reaction is S 2 in character, and takes place on the side best able to support an SN2 transition structure, which is usually the less substituted side. A simple example is the opening of 1-butene oxide 4.176 with chloride ion, which gives each of the chlorohydrins as the major product, 4.177 in acidic and 4.178 in neutral conditions.402... 

Other Solid-acid Catalysts - Y-AI2O3 supported with different amounts of sulfate ion, and other carriers such as iron oxide, zinc oxide, silica, and silica-alumina impregnated with sulfate ion were used in the oligomerization reaction of a C4 olefin-containing material.Conversion of butene passed through a maximum at 80% when the catalyst sulfate ion content was around 20% by weight. Butene conversion was low for the different supports except for silica-alumina-supported sulfate ion, for which both the conversion and yield of trimer and tetramer were improved. 

Lewis and Bronsted acids [945] and modified or unmodified inorganic oxides [946] with various ions are the most popular catalysts for higher a-olefin oligomerization. The reactivity in the oligomerization reaction decreases in proportion to the increase of the olefin length (1-butene > 1-hexene > 1-octene > 1-decene) and the C=C bond position (1-butene > 2-butene). 

Dehydration of alcohols is catalyzed by boron phosphorous oxide. The reactivity of alcohols in the dehydration decreases as follows /ert-amyl alcohol > 3-pentanol > > 2-propanol > 1-pentanol > ethanol.The catalytic activities of the oxides composed of different amounts of B and P for propanol dehydration correlate with the total amount of acid sites.Butanol undergoes dehydration on boron phosphorous oxide. The maximum activity is obtained at the P/B ratio of 0.6. The activity correlates with the sum of Lewis and Bronsted acid sites. 2-Butanol, 2-methyl — 2-butanol, and 3-methyl — 2-butanol also undergo dehydration. The formation of tnw -2-butene and 2-methyl — 2-butene increases with increasing surface acidity. In these reactions, the carbenium ion mechanism is operating. 

The titanium-mediated photocatalytic oxidation of a pyridine solution was conducted by Low et al. (1991). They proposed that the reaction of OH radicals with pyridine was initiated by the addition of a OH radical forming the 3-hydro-3-hydroxypyridine radical followed by rapid addition of oxygen forming 2,3-dihydro-2-peroxy-3-hydroxypyridine radical. This was followed by the opening of the ring to give At-(formylimino)-2-butenal which decomposes to a dialdehyde and formamide. The dialdehyde is oxidized by OH radicals yielding carbon dioxide and water. Formamide is unstable in water and decomposes to ammonia and formic acid. Final products also included ammonium, carbonate, and nitrate ions. 

In 1993, Blatter and Frei [34] extended the Aronovitch and Mazur [28] photo-oxidation into zeolitic media, which resulted in several distinctive advantages as described below. Irradiation in the visible region (633 nm) of zeolite NaY loaded with 2,3-dimethyl-2-butene, 16, and oxygen resulted in formation of allylic hydroperoxide, 17, and a small amount of acetone. The reaction was followed by in situ Fourier-transform infrared (FTlR) spectroscopy and the products were identified by comparison to authentic samples. The allylic hydroperoxide was stable at - 50°C but decomposed when the zeolite sample was warmed to 20°C [35]. In order to rationalize these observations, it was suggested that absorption of light by an alkene/Oi charge-transfer complex resulted in electron transfer to give an alkene radical cation-superoxide ion pair which collapses... 

A thermal oxidation of 2,3-dimethyl-2-butene, 16, occurs in NaY when the temperature of the oxygen-loaded zeolite in raised above — 20°C [35], Similar thermally initiated oxidations were not observed for the less electron rich tram-or cix-2-butene. Remarkably, pinacolone was conclusively identified as one of the products of the reaction of 16, This ketone is not a product of the photochemical Frei oxidation (vide supra) and underscores the very different character of these two reactions and the complexity of the oxygen/16 potential energy surface, A rationale for the different behavior could lie in the different electronic states of the reactive oxygen-CT complex in the thermal and photochemical reactions. Irradiation could produce an excited triplet-state CT complex ( [16 O2] ) and/ or ion pair ( [16 02 ] ) with different accessible reaction channels than those available to a vibrationally excited ground-state triplet complex ( [16 "02]) and/... 

A reaction of particular relevance with respect to applied catalysis is the oxidative dehydrogenation (ODH) of hydrocarbon by VmOn ions according to reaction 2, which involves a two-electron reduction of the cluster. By means of a systematic study of the reactions of various YmOn ions as well as the related oxo-vanadium hydroxides VmO H+ ions with a set of C4-hydrocarbons, it was demonstrated recently that the ODH activity of the cluster ions shows a clear correlation with the formal valence of vanadium in the cluster ions with a maximum reactivity for formal vanadium (V) (Fig. 3) [84]. In such a kind of reactivity screening, it is essential to include more than a single reagent as a probe for the reactivity of the different ions in order to reduce interferences by kinetic barriers of one particular combination of neutral and ionic reactants [85]. Accordingly, the sums of the relative rate constants for the ODH reactions of the four different butenes are considered and normalized to the most reactive ion studied, which turns out to be the formally pure vanadium (V) compoimd In addition to isomeric... 

Evidence for the significant role of the alkoxyaluminohydride ions postulated by Trevoy and Brown11 4 has been secured experimentally by Fuchs and Vender Werf,w who examined the effect on product composition of altering the lithium aluminum hydride-ethylene oxide ratio. In the reaction of 1,2-epoxy-S-butene with approxinuuoU-stoichiometric quantities of reduoing agent, the principal product, l-buten-8-ol, was accompanied by a certain amount of the isomeric substance l-buten-4-ol (Eq, 374). The proportion of the latter mci[Pg.111]

Despite the enormous importance of zeolites (molecular sieves) as catalysts in the petrochemical industry, few studies have been made of the use of zeolites exchanged with transition metal ions in oxidation reactions.6338- 634a-f van Sickle and Prest635 observed large increases in the rates of oxidation of butenes and cyclopentene in the liquid phase at 70°C catalyzed by cobalt-exchanged zeolites. However, the reactions were rather nonselective and led to substantial amounts of nonvolatile and sieve-bound products. Nevertheless, the use of transition metal-exchanged zeolites in oxidation reactions warrants further investigation. 

The oxidation of A-alkoxyamines with lead tetraacetate generated aziridines, albeit in low yields (<20%)9 11. Despite the almost complete diastereoselectivity claimed in the preparation of A-methoxyazi ridine 1 from methoxyamine and ( )-2-butene loss of the geometrical purity was observed in the reaction of excess ( )- and (Z)-2-butene with A-(butoxy)aminc in dichloro-methane to give 2n. For this reason a two-step mechanism involving an intermediate N Pb species or nitrenium ion was proposed. However, the completely diastereoselective preparation of both trans- and cis-2 was successively claimed by different authors (GC-MS analysis)49. 

The selectivity of palladium and gold for alkene oxidation to aldehydes 28,29,170) was attributed initially to adsorption strength. However, electrooxidation in the presence of palladium ions indicates possible homogeneous alkene insertion, similar to the Wacker process 304). Homogeneous reaction is also involved in redox oxidations of hydrocarbons. In this case, the nature of the metal ions is expected to control selectivity. Indeed, toluene yields 20% benzaldehyde in electrolytes containing Ce salts, while oxidation proceeds to benzoic acid with Cr redox catalysts 311). In addition, the concentration of redox catalysts appears to affect yields in nonelectrochemical oxidation of ethylene large amounts of palladium chloride promote butene formation at the expense of acetaldehyde 312). Finally, the role of the electrolyte and solvent should not be ignored. For instance, electrooxidation of ethylene on carbon, in aqueous solution of acetic acid yields acetaldehyde 313) in the... 

---