Decarboxylation of acetic acid

A large variety of organic oxidations, reductions, and rearrangements show photocatalysis at interfaces, usually of a semiconductor. The subject has been reviewed [326,327] some specific examples are the photo-Kolbe reaction (decarboxylation of acetic acid) using Pt supported on anatase [328], the pho-... 

Kharaka, Y.K., Carothers, W.W., and Rosenbauer, R.J., Thermal decarboxylation of acetic acid implications for origin of natural gas, Geochimica et Cosmochimica Acta, 47, 397-402, 1983. 

Simple carboxylic acids suffer photo-Kolbe decarboxylation under the usual photoelectrochemical conditions. In fact, this reaction type was one of the first characterized examples of oxidative cleavage of an organic molecule induced by long w avelength irradiation of a semiconductor. In the decarboxylation of acetic acid at... 

Fig. 41. Proposed mechanism for the retentive decarboxylation of acetic acid side chain during haem biosynthesis.

The use of manganese catalysts maintains a low concentration of Co(III), which is important since the latter promotes extensive decarboxylation of acetic acid at T >130°C. A somewhat similar process which operates under biphasic conditions rather than in acetic acid also gives high conversions and selectivities [133]. 

Table II. Experimental Decarboxylation of Acetic Acid and Acetate. Data from Kharaka et al. (2Q and Palmer and Drummond (26)...

Halting and Maass (1980), and Giggenbach (1982). Rates of decarboxylation of acetic acid in stainless steel from Kharaka et al. (1983), in silica tubes (Palmer and Drammond 1986), and in the presence of Ca-montmorillonite (Bell et al. 1994). Figme modified from Giggenbach (1997). 

Kharaka YK, Carothers WW, Rosenbauer RJ (1983) Thermal decarboxylation of acetic acid Implications for origin of natural gas. Geoehim Cosmoehim Acta 47 397-402 Kilner JA (1986) New techniques for studying mass transport in oxides. In Freer R, Dennis PF (eds) Mater SciForam 7 205-222... 

Acrylic acid is more stable than acetic acid and HCHO is much more stable than acetic acid over the V-P oxide catalysts. It is therefore concluded that CO2 observed in the reaction of HCHO with acetic acid is mainly formed by the decomposition of acetic acid but not by that of HCHO. It is also found that the decarboxylation of acetic acid over the V-P oxide catalysts is suppressed markedly by the presence of water and HCHO. ... 

Oxidative decarboxylation of acetic acid at 75 °C by (NH4)2S20g and silver ions as catalyst in 10% H2SO4 containing 3-methyl-IbP 41 led to the formation of a mixture of variously C-methylated IbPs. Gradually increasing the excess of the generated methyl radicals with respect to the substrate first gave a mixture of di- and trimethyl-IPs 295 and 296 (in 71% overall yield), and then 2,3,5,7-tetramethyl-IbP 297 in 6% yield. 

The attempts to methylate 1-methyl-IbP 228 by means of oxidative decarboxylation of acetic acid silver salts failed because this base bound the silver ions into an insoluble complex. However, the catalytic decomposition of mrt-butylhydroperoxide in 70% H2SO4 first provided 1,2-dimethyl-IbP 298, later converted into a mixture of 1,2,5- and 1,2,7-trimethyl-IbP 299 and 300 isomers that were hard to separate. The final compound is 1,2,5,7-tetramethyl-IbP 301 (78MI3). 

Reactions in which a substance decomposes by losing CO2 are called decarboxylation reactions. The decarboxylation of acetic acid proceeds as follows ... 

Scheme 6.3 Gas-phase catalytic cycles for the metal-mediated decarboxylation of acetic acid [64],...

Aparallel reaction that also occurs is the uranyl ion photosensitized decarboxylation of acetic acid to methane ... 

Chapter P, by Bell and Palmer, reviews experimental studies concerned with the decomposition of organic acids and their anions. In the absence of an effective catalytic surface, acetic acid may be expected to survive indefinitely. However, there are many potential catalysts. Laboratory determined activation energies for the decarboxylation of acetic acid varies from 34 to 170kJmol for stainless steel and titanium oxide, respectively. Reaction rates for the decarboxylation of dicarboxylic acids are extremely fast and uncomplexed acids are not likely to survive geologically significant lengths of time. However, the observed occurrence of dicarboxylic acids in some subsurface brines suggests the acids have been stabilized by complexation... 

CH3COOH + 2O2 2CO2 + 2H2O, whereas decarboxylation of acetic acid is represented by CH3COOH CH4 + CO2. 

The decarboxylation of acetic acid was first studied as a side reaction in the high temperature (400 to 600 C) dehydration reaction to acetone or ketene (Nef 1901 Hurd and Martin 1929 Mitchell and Reid 1931). When heated, acetic acid decomposes according to several competing pathways, one of which is decarboxylation ... 

Fig. 2. Activity diagram for the decarboxylation of acetic acid, as given in Eq. (4), at 100 °C and 300 bar (Shock 1988), showing log(/co2) versus Iog(flcH3CooH)- The solid lines are contours for log(/cH4)- (With permission by E.L. Shock and The Geological Society of America)...

The large variations in rate constant observed for decarboxylation of acetic acid and acetate, the very low activation energies observed by Kharaka et al. (1983) in their pioneering work on this reaction in stainless steel vessels, the observation of first- and zero-order kinetics with respect to acetic acid concentration depending on surface type (Palmer and Drummond 1986), and the reversal in the trend in the values for AH for acetic acid and acetate over a number of different surfaces attest to the surface playing a vital role in controlling the stability of acetic acid (and probably other... 

The existence of the n-C2 to n-C4 mono- and dicarboxylic acids in hydro-thermal sedimentary environments depends upon the rates of their production and the rates of decomposition and/or oxidation. These two classes of acids exhibit very different rates and mechanisms of decarboxylation. Decarboxylation of acetic acid, and probably of other aliphatic monocar-boxylic acids, proceeds by a heterogeneous catalytic mechanism apparently very different from the homogeneous mechanism for decarboxylation of the dicarboxylic acids. Due to the limited amount of experimental information regarding the kinetics of oxidation or condensation for both classes of acids, no definitive mechanistic trends can be postulated for this process. Nevertheless, it is possible to place constraints on the kinetics and mechanism for the oxidation reaction(s) if this process were assumed to control the ultimate decomposition of acetic acid. Results from studies of mono- and dicarboxylic acid decarboxylation are summarized below. 

Adinarayana M, Saiprakash PK, Sethuram B, Navaneeth Rao T (1976) Kinetics of Ag" catalysed oxidative decarboxylation of acetic acid by in H2SO4 medium. J Indian Chem Soc LIII 255-257... 

Drummond SE, Palmer DA (1986) Thermal decarboxylation of acetic acid. Part II. Boundary conditions for the role of acetate in the primary migration of natural gas and the transportation of metals in hydrothermal systems. Geochim Cosmochim Acta 50 825-833... 

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