Acids dehydrogenation

Hydropyridinyl radicals ESR, 2, 145 Hydroquinoline synthesis, 1, 441 Hydroquinones synthesis, 1, 417 of-Hydroxy acids dehydrogenation by flavins, 1, 253... 

These conditions do not obtain in cassanic acid (p. 728) although this acid dehydrogenates to 1 7 8-trimethylphenanthrene. 

The onward metabohsm of succinate, leading to the regeneration of oxaloacetate, is the same sequence of chemical reactions as occurs in the P-oxidation of fatty acids dehydrogenation to form a carbon-carbon double bond, addition of water to form a hydroxyl group, and a hirther dehydrogenation to yield the oxo- group of oxaloacetate. 

This is the reason why, for example, the zero order formic acid dehydrogenation may easily be measured on bulk metal catalysts at 200-300°C. whereas the approximately first order ethanol dehydrogenation requires highly activated porous metals of large specific surface in order to become measurable under the same conditions. The same has been shown for the decomposition of formaldehyde, acetic acid, and hydrazine hydrate. In these cases, the fractional surface coverage is simply 1000 times lower than in the case of a zero order reaction. 

Menthone can be obtained by distillation of dementholized cornmint oil or by oxidation of (—)-menthol (e.g., with chromic acid). Dehydrogenation of (—)- menthol (e.g., with copper chromite) yields a mixture of (—)-menthone and (+)-isomenthone. 

TPP functions as a coenzyme which participates in decarboxylation of or-keto acids. Dehydrogenation and decarboxylation must precede the formation of active acetate in the initial reaction of the TCA cycle (citric acid cycle) ... 

Activiation Energies of Model Catalysis and Alloys for Formic Acid Dehydrogenation... 

The results with magnesia led us to a planned series of experiments with doped aluminas. Nickel was evaporated in vacuo onto the surface of grains of undoped or doped alumina or, alternatively, onto compact nickel. These preparations were then used as catalysts for the donor model reaction of formic acid dehydrogenation as above. Table II shows the results. 

Encouraged by these results, we used the donor test (or model) reaction of formic acid dehydrogenation for the study of the well-known ammonia... 

Flo. 2. Activation energy of formic acid dehydrogenation over silver on doped silicon carhide (19). (Copyright by the Universite de Liege. Reprinted with permission.)... 

Recently, Potts and Liljegren (97) have synthesized J15> 20-yohimbene (XXXV) by condensation of 3-chloroacetylindole with 5,6,7,8-tetra-hydroisoquinoline, and reduction of the tetracyclic quaternary chloride (XXXIV) so obtained with lithium aluminum hydride in tetrahydro-furan (THF) solution. Since A15> 20-yohimbene (XXXV) has previously been converted by palladium-maleic acid dehydrogenation into 5,6-dihydrosempervirine (XXXIII) (98) and sempervirine (99), this constitutes a third formal synthesis of sempervirine. 

Lederer, F, 1997, The mechanism of flavoprotein-catalyzed a-hydroxy acid dehydrogenation, in Flavins and Flavoproteins 1996 (K. J. Stevenson, V. Massey, and C. H. Williams, eds.). University of Calgary Press, Calgary, Alberta, pp. 545n554. 

Figure 2 Volcano plots illustrating how catalytic activities depend on the nature of the metal used as catalyst, (a) Correlation between catal)hic activity for formic acid dehydrogenation and enthalpy of formation of metal formates. (Ref 10. Reproduced by permission of John Wiley Sons, Inc.) (b) Correlation between catal)hic activity for ammonia synthesis and degree of d-band fiUing in the metal used as catalyst. (Ref 12. Reproduced by permission of John Wiley Sons, Inc.) ...

A number of anthraquinones have been synthesized by adding dienes to aroylacrylic acids, dehydrogenating the adducts in the form of the esters, and cyclizing as before. ... 

C02 + CH4- CH3-C=0-0H acetic acid dehydrogenation of propane CO2 + C3H8 - C3H6 + H2 + CO reforming... 

The already-numerous examples of enzyme-catalyzed organic reactions were supplemented by adding biological Baeyer-Villiger oxidations and fumaric acid dehydrogenation. 

An acetoacetate side-chain provides the four carbon atoms required to form a pyridine ring by this base-induced cyclization [2034,2081] a better yield (90%) was later obtained by heating the acetoacetate (74.3) in xylene [2356]. DMSO has also been used as solvent [3252]. A pyridin-2-one ring is formed by heating the ester (74.4) with first ammonia and then 4-toluenesulphonic acid. Dehydrogenation with DDQ gives an aromatized ring [3545]. 

A shorter and neater synthesis of (+ )-dihydrogambirtannine involved the multiple-phase reduction of the isoquinolinium salt 78 with sodium borohydride in a methanol-ether—water system in the presence of a high concentration of cyanide ion. The intermediate, presumably the cyanide (79) formed by trapping of the initially generated dihydroisoquinoline derivative by nucleophilic cyanide ion, was not isolated but was converted directly into ( )-dihydrogambirtannine (67) by heating in dilute hydrochloric acid. Dehydrogenation of the stable hydrochloride of 67 by means of iodine and sodium acetate afforded an improved route... 

Chromic acid dehydrogenates primary alcohols between 0° and 100° yields of aldehyde lie between 40% and 60%, by-products being mainly carboxylic acids and their esters. A proven oxidation mixture consists of l.mole of dichromate, 2.5 moles of sulfuric acid, and 300 g of water (Beckmann mixture), into which the alcohol is dropped C02 or N2 is led through the mixture so as to prevent the aldehyde s being further oxidized and, if possible, cooling is arranged so that only the alcohol is condensed. The aldehyde that distils off is best collected in cooled receivers. It is best to use an excess of chromic acid calculated according to the equation ... 

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