Solvent-catalyst reaction

Olefin k rc) Solvent Catalyst Reaction (sec) (kcal.mole ) (eu) Ref. 

Alcohol No. OH groups Oxyalkylating agent Solvent Catalyst Reaction conditions Temp Pressure (°C) (psi) Ref. 

Dichloride Solvent Catalyst Reaction time, min Polymer, [rfl, dLg ... 

Influence of the solvents, catalysts, reaction temperatures and comparative oxidizing ability of tertiary-butyl hydro peroxide, hydrogen peroxide on the yield of compounds I and II has been investigated and obtained results are presented in Tables 1 and 2. 

The Kinetic Barrier. Aithough thermodynamicaiiy feasible at relatively low pressure and temperature, the transformation graphite-diamond faces a considerable kinetic barrier since the rate of transformation apparently decreases with increasing pressure. This kinetic consideration supersedes the orable thermodynamic conditions and it was found experimentally that very high pressure and temperature (>130 kb and >3300 IQ were necessary in order for the direct graphite-diamond transformation to proceed at any observable rate.f l These conditions are very difficult and costly to achieve. Fortunately, it is possible to bypass this kinetic barrier by the solvent-catalyst reaction. 

Solvent-Catalyst Reaction. The solvent-catalyst process was developed by General Electric Eind others. It establishes a reaction path with lower activation energy than that of the direct transformation. This permits a faster transformation under more benign conditions. As a result, solvent-catalyst synthesis is readily accomplished and is now a viable and successful industrial process. 

The representation of a chemical reaction should include the connection table of all participating species starting materials, reagents, solvents, catalysts, products) as well as Information on reaction conditions (temperature, concentration, time, etc.) and observations (yield, reaction rates, heat of reaction, etc.). However, reactions are only Insuffclently represented by the structure of their starting materials and products,... 

The understanding and simulation of chemical reactions is one of the great challenges of chemoinformatics. Each day millions of reactions are performed, sometimes with rather poor results because of our limited understanding of chemical reactivity and the influence of solvents, catalysts, temperature, etc. This problem has to be tackled by both deductive and inductive learning methods. 

Carbonylation of propargylic carbonates proceeds under mild neutral conditions (50 °C, I-10 atm) using Pd(OAc)2 and Ph ,P as a catalyst, yielding the 2,3-alkadienoates 18 in good yields[9,10]. The 2.3-alkadienoates isomerize to 2,4-dienoates during the reaction depending on the solvents and reaction time. 2-Decynyl methyl carbonate is converted into methyl 2-heptyl-2,3-butadienoate (19) in 82% yield. 

The Acetaldehyde Oxidation Process. Liquid-phase catalytic oxidation of acetaldehyde (qv) can be directed by appropriate catalysts, such as transition metal salts of cobalt or manganese, to produce anhydride (26). Either ethyl acetate or acetic acid may be used as reaction solvent. The reaction proceeds according to the sequence... 

Other than fuel, the largest volume appHcation for hexane is in extraction of oil from seeds, eg, soybeans, cottonseed, safflower seed, peanuts, rapeseed, etc. Hexane has been found ideal for these appHcations because of its high solvency for oil, low boiling point, and low cost. Its narrow boiling range minimises losses, and its low benzene content minimises toxicity. These same properties also make hexane a desirable solvent and reaction medium in the manufacture of polyolefins, synthetic mbbers, and some pharmaceuticals. The solvent serves as catalyst carrier and, in some systems, assists in molecular weight regulation by precipitation of the polymer as it reaches a certain molecular size. However, most solution polymerization processes are fairly old it is likely that those processes will be replaced by more efficient nonsolvent processes in time. 

Various processes involve acetic acid or hydrocarbons as solvents for either acetylation or washing. Normal operation involves the recovery or recycle of acetic acid, any solvent, and the mother Hquor. Other methods of preparing aspirin, which are not of commercial significance, involve acetyl chloride and saHcyHc acid, saHcyHc acid and acetic anhydride with sulfuric acid as the catalyst, reaction of saHcyHc acid and ketene, and the reaction of sodium saHcylate with acetyl chloride or acetic anhydride. 

Reaction and Heat-Transfer Solvents. Many industrial production processes use solvents as reaction media. Ethylene and propylene are polymerized in hydrocarbon solvents, which dissolves the gaseous reactant and also removes the heat of reaction. Because the polymer is not soluble in the hydrocarbon solvent, polymer recovery is a simple physical operation. Ethylene oxide production is exothermic and the catalyst-filled reaction tubes are surrounded by hydrocarbon heat-transfer duid. 

The refined grade s fastest growing use is as a commercial extraction solvent and reaction medium. Other uses are as a solvent for radical-free copolymerization of maleic anhydride and an alkyl vinyl ether, and as a solvent for the polymerization of butadiene and isoprene usiag lithium alkyls as catalyst. Other laboratory appHcations include use as a solvent for Grignard reagents, and also for phase-transfer catalysts. 

In this solvent the reaction is catalyzed by small amounts of trimethyl-amine and especially pyridine (cf. 9). The same effect occurs in the reaction of iV -methylaniline with 2-iV -methylanilino-4,6-dichloro-s-triazine. In benzene solution, the amine hydrochloride is so insoluble that the reaction could be followed by recovery. of the salt. However, this precluded study mider Bitter and Zollinger s conditions of catalysis by strong mineral acids in the sense of Banks (acid-base pre-equilibrium in solution). Instead, a new catalytic effect was revealed when the influence of organic acids was tested. This was assumed to depend on the bifunctional character of these catalysts, which act as both a proton donor and an acceptor in the transition state. In striking agreement with this conclusion, a-pyridone is very reactive and o-nitrophenol is not. Furthermore, since neither y-pyridone nor -nitrophenol are active, the structure of the catalyst must meet the conformational requirements for a cyclic transition state. Probably a concerted process involving structure 10 in the rate-determining step... 

Aziridines, like oxiranes, undergo hydrogenolysis easily with or without inversion of configuration, depending on the catalyst, reaction parameters, and various additives 65aJ08). For example, hydrogenolysis of 2-methyl-2-phenylaziridine in ethanol occurs mainly with inversion over palladium but with retention over platinum, Raney nickel, or Raney cobalt. Benzene solvent or alkali favor retention over palladium as well. 

Attempts have been made to catalyze the arrangement of 3-oxaquadricyclane to oxepins with transition-metal complexes.1 32 1 35 When dimethyl 2,4-dimethyl-3-oxaquadricyclane-l,5-dicarboxylate is treated with bis(benzonitrile)dichloroplatinum(II) or dicarbonylrhodium chloride dimer, an oxepin with a substitution pattern different from that following thermolysis is obtained as the main product. Instead of dimethyl 2,7-dimethyloxepin-4,5-dicarboxylate, the product of the thermal isomerization, dimethyl 2,5-dimethyloxepin-3,4-dicarboxylate (12), is formed due to the cleavage of a C O bond. This transition metal catalyzed cleavage accounts also for the formation of a 6-hydroxyfulvene [(cyclopentadienylidene)methanol] derivative (10-15%) and a substituted phenol (2-6%) as minor products.135 The proportion of reaction products is dependent on solvent, catalyst, and temperature. 

Transition-metal-based Lewis acids such as molybdenum and tungsten nitro-syl complexes have been found to be active catalysts [49]. The ruthenium-based catalyst 50 (Figure 3.6) is very effective for cycloadditions with aldehyde- and ketone-bearing dienophiles but is ineffective for a,)S-unsaturated esters [50]. It can be handled without special precautions since it is stable in air, does not require dry solvents and does not cause polymerization of the substrates. Nitromethane was the most convenient organic solvent the reaction can also be carried out in water. 

Chloroaluminate ionic liquids (typically a mixture of a quaternary ammonium salt with aluminum chloride see Table 6.9) exhibit at room temperature variable Lewis acidity and have been successfully used as solvent/catalyst for Diels-Alder reactions [57]. The composition of chloroaluminate ionic liquids can vary from basic ([FMIM]C1 or [BP]C1 in excess) to acidic (AICI3 in excess) and this fact can be used to affect the reactivity and selectivity of the reaction. The reaction of cyclopentadiene with methyl acrylate is an example (Scheme 6.31). 

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