Dehydration and Dehydrogenation

With various catalysts, butanediol adds carbon monoxide to form adipic acid. Heating with acidic catalysts dehydrates butanediol to tetrahydrofuran [109-99-9] C HgO (see Euran derivatives). With dehydrogenation catalysts, such as copper chromite, butanediol forms butyrolactone (133). With certain cobalt catalysts both dehydration and dehydrogenation occur, giving 2,3-dihydrofuran (134). 

The 1,4-isomer has been similarly generated from terephthalonitdle [623-26-7] (56) using a mixed Pd/Ru catalyst and ammonia plus solvent at 125 °C and 10 MPa (100 atm). It is also potentially derived (57) from terephthaUc acid [100-21-0] by amination of 1,4-cyclohexanedimethanol (30) [105-08-8], Endocyclization, however, competes favorably and results in formation of the secondary amine (31) 3-a2abicyclo[3.2.2]nonane [283-24-9] upon diol reaction with ammonia over dehydration and dehydrogenation catalysts (58) ... 

Dehydration and dehydrogenation combined utihzes dehydration agents together with mild dehydrogenation agents. Included in this class are phosphoric acid, sihca-magnesia, silica-alumina, alumina derived from aluminum chloride, and various metal oxides. 

A similar difference in the adsorption coefficients of the starting reactant of branched reactions was also found in the parallel dehydration and dehydrogenation of isopropyl alcohol on some oxide catalyst (123) here, of course, the chemical nature of both branches is clearly different. It is of interest, however, to note that for the series of catalysts with varying... 

The Genesis and Principle of Catalysis at Oxide Surfaces Surface-Mediated Dynamic Aspects of Catalytic Dehydration and Dehydrogenation on TiO2(110) by STM and DFT 317... 

Schwab and Schwab-Agallides (7) have studied the competitive dehydration and dehydrogenation of ethanol over y- and a-alumina and... 

IrCl2H(cod)]2 catalyzed the synthesis of substituted quinolines, where the reachon of aniline derivahves, aromatic and alkyl aldehydes efficiently proceeds under an oxygen atmosphere (Scheme 11.34) [46]. The plausible mechanism consists of a Mannich reaction, a Friedel-Craft-type aromahc substituhon, dehydration, and dehydrogenation. This can be recognized as a formal [4+2] cycloaddition of N-aryl imine and enol (Scheme 11.35). 

Although the specific role of each type of center (acid or base) in each process (dehydration-dehydrogenation) is still only incompletely elucidated, many authors have correlated the initial rates of dehydration and dehydrogenation with the acidity and basicity, respectively, of the solid. Thus, the number of basic sites has been correlated with the rate constants for dehydrogenation or with the ratio of the rate constants for dehydrogenation and dehydration (74,80,89,90,94). 

A number of routes are available for the synthesis of 2,2 -bipyridines where one of the pyridine rings is built up from simpler entities. For example, condensation of 2-(aminomethyl)pyridine (31) with acetaldehyde or acetylene over a silicon-alumina catalyst at 450°C gives 2,2 -bipyridine, ° whereas 2-cyanopyridine reacts with acetylene at 120°C in the presence of a cobalt catalyst to afford 2,2 -bipyridine in 95% yield.2-Acetylpyridine with acrolein and ammonia gives 2,2 -bipyridine in the presence of dehydrating and dehydrogenating catalysts, and related condensations afford substituted 2,2 -bipyridines. ° In a similar vein, condensation of benzaldehyde with 2 mol of 2-acetylpyridine in the presence of ammonia at 250°C affords 2,6-di(2-pyridyl)-4-phenylpyridine, ° and related syntheses of substituted 2,2 6, 2"-terpyridines have been described. Likewise, formaldehyde with two moles of ethyl picolinoylacetate and ammonia, followed by oxidation of the product and hydrolysis and decarboxylation, affords a good... 

Like 2,2 - and 2,3 -bipyridines, 2,4 -bipyridine is formed by a number of reactions where one of the pyridine rings is built up from simpler components. Thus 4-(aminomethyl)pyridine with acetylene or acetaldehyde at 450"C affords 2,4 -bipyridine and 4-cyanopyridine reacts with acetylene at 120 C under pressure in the presence of a cobalt catalyst to give 2,4 -bipyridine in over 90% yield. 4-Acetylpyridine with acrolein and ammonia in the presence of dehydrating and dehydrogenating catalysts also gives 2,4 -bipyridine. A number of minor routes to 2,4 -bipyridine are worthy of... 

SABATIER, PAUL (1854-1941). A French chemist who received the Nobel prize in Chemistry in 1912 along with Victor Grignard. His work involved the behavior of oxides as oxidizing catalysts and as agents for dehydrating and dehydrogenating. He received his PhD. In Nimes, France, and went on to become lecturer and faculty member in Toulouse, France. 

Krupay and Ross (272b), in a study of the decomposition of formic acid on manganese (II) oxide, demonstrate that manganese (II) formate is produced during reaction and discuss the probable role of this participant in the catalytic process. The reported Arrhenius parameters (log A, E) for the dehydration and dehydrogenation reactions were (28.7, 132) and (24.9, 87), respectively both points were close to the compensation line (Table V, K) characteristic of the breakdown of formic acid on oxides. 

Grignard Reaction. By addition of an arylmagnesium halide to a cyclic ketone, a carbinol is formed which can be dehydrated and dehydrogenated to a biaryl compound.89 4 > 41> 42 43 480 For example, m-tolyl-magnesium bromide and cydohexanol yield 1-m-tolylcyclohexanol, which on dehydration and dehydrogenation gives 3-methylbiphenyl. 

T. A., Aliev, L. A. Dehydration and Dehydrogenation of Alcohols, Catalyzed by Ferrocene Polymers. Dokl. Akad. Nauk. SSSR 186, 108 (1969). 

Janot et al. [90] described the increased hydrogen adsorption of ball-milled Mg2Ni alloys and interpreted their findings with the removal of oxide layers. A Pd-Mg catalyst precursor used for the synthesis of methyl isobutyl ketone was prepared by milling PdO with Mg [91]. Dehydration and dehydrogenation reactions of 4-methylpentan-2-ol over ball-mined catalysts such as CuM (M = Ti, Zr, Hf) have also been investigated [92]. 

MODELING OF DEHYDRATION AND DEHYDROGENATION IN ZIRCONIA WITH ANION IMPURITY... 

Spectra of AgHf2(PC>4)3 during dehydration and dehydrogenation of butan-2-ol were recorded by Brik et al. (2001), who used the Harrick accessory to determine the state of silver. The authors reported slightly lower conversions in the cell than in a U-shaped microreactor. The catalytic data corresponding to the spectra are not shown in the paper. 

Butadiene (bpi.oi3= —4.413 C, 44 =0.6211) has become a major petrochemical product thanks to the development of its copolymers with styrene and acrylonitrDe. The earliest processes for manufacturing butadim started with acetylene and formaldehyde (Germany, the Reppe process), or produced it by the alUnited States Unwn Carbide). 

Dehydration and dehydrogenation lead to 2-phenyl- and 2,6-diphenylphenol. Oxidation of the latter with an oxidant e.g. chromiumtrioxide give rise to 2,6-diphenyl-quinone and 2,2, 6,6 -tetraphenyl-diphenoquinone80) ... 

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