Decarboxylation, kinetic

Pocker, Y., and Guilbert, L. J. Carbonic anhydrase catalysed hydrolysis and decarboxylation. Kinetic studies of enzyme-catalysed decomposition of mono- and disubstituted derivatives of carbonic acid. Biochemistry 13, 70-78 (1974). 

The formation and decarboxylation kinetics of [Ir(0C02)(NH3)5]+ have been studied as a function of pressure, based on activation volumes for C02 uptake (AF = —4.0 cm3 mol-1) and decarboxylation (AF1 = + 2.5 cm3 mol-1), and partial molar volume measurements. The suggested mechanism for the formation and decarboxylation is given in Scheme 16. Bond formation during C02 uptake and bond breaking during decarboxylation were believed to be ca. 50% completed in the transition state (149) of these processes.342... 

The TLSER methodology has been successfully applied to develop correlation equations for a wide variety of solvent-dependent properties and processes [350, 364-369]. Some examples are the characterization of other solvent polarity, acidity, and basicity scales [364], the acidities of substituted acetic acids in various solvents [365], the basicities of substituted dimethylamines in various solvents [366], the decarboxylation kinetics of 3-carboxybenzisoxazole [367], the C=0 stretching frequencies of substituted pyrrolidin-2-ones [368], and gas-water distribution coefficients [369]. 

Famini, G.R. and Wilson, L.Y. (1994b). Using Theoretical in Quantitative Structure-Property Relationships 3-Carboxy-Benzisoazole Decarboxylation Kinetics. J.Chem.Soc.Perkin Trans.2, 1641-1650. 

In the light of the previous reasoning, describing the solvolysis of tert-butyl chloride or the decarboxylation kinetics of 3-carboxybenzisoxazole in mixed solvents in terms of SPP, SB and SA for the mixtures appeared to be rather difficult owing to the differences between the processes concerned and the solvatochromism upon which the scales were constructed. However, the results are categorical as judged by the following facts ... 

A variety of transition-metal hydroxo complexes, [M(NH3)50H] [M = Co(III), Rh(III), and Ir(III)], react with CO2 to give the corresponding monodentate carbonato complexes [M(NH3)s0C02]. The formation and decarboxylation kinetics of these complexes have now been studied as a function of pressure up to 1000 bar. The volumes of activation for CO2 uptake are -10.1 0.6 (Co(III)), -4.7 0.8 (Rh(III)), and -4.0 1.0 (Ir(III)) cm mor, whereas the corresponding values for decarboxylation are +6.8 0.3, +5.2 0.3, and +2.5 0.4 cm mol , respectively. Combined with partial molar volume measurements, these values enable the construction of overall reaction volume profiles. Bond formation during CO2 uptake and bond breakage during decarboxylation are approximately 50% completed in the transition state of these processes. 

The model results discussed above express only the effects of time and temperature on organic acid generation from kerogen, and the effect of porosity on organic acid concentrations. They do not account for the effects of time and temperature on organic acid decarboxylation since decarboxylation kinetics under natural burial conditions are poorly known. Therefore, the results are best applied to Neogene source rocks where the field data discussed earlier indicate that the effect of thermal decarboxylation or decomposition on total acetate concentration is small, and where temperatures do not exceed approximately 150 °C. 

A significant amount of kinetic data exists for the decarboxylation and oxidation of carboxylic acids. However, a relatively small fraction of these results deals with n-C2 to n-C4 aliphatic mono- and dicarboxylic acids under conditions pertinent to geological interests. For example, the early studies of the decarboxylation kinetics of acetic acid utilized flow-though silica tubes in which the anhydrous gas was exposed to very high temperatures for only seconds (Bamford and Dewar 1949 Blake and Jackson 1968, 1969). Nevertheless, it is useful to consider all of these results because it reveals trends common for structural classes of carboxylic acids. In this background discussion, a brief introduction to the subject of isokinetic relationships is given, as well as an overview of the decarboxylation and oxidation of carboxylic acids in which isokinetic relationships are used to establish trends and gross variations in reaction mechanisms between structural classes of acids. 

Propionic and butyric acids have structures similar to acetic acid and are expected to display much the same chemical and kinetic behavior. Virtually no experimental studies of their decarboxylation kinetics in aqueous solutions have been reported, although it is expected that these reactions are also catalyzed heterogeneously. The rate constant for decarboxylation of a 1.1 mol kg solution of n-butyric acid is 4.20 x 10 s (titanium oxide surface at 359 °C), whereas the comparable value for acetic acid is 3.89 x 10 s (Palmer and Drummond 1986). However, there are no corresponding data on the activation parameters for these acids so that the expected similarity of the linear isokinetic plots for these and acetic acid has not yet been tested. 

Schleusener JL, Drummond SE, Palmer DA, Barnes HL (1987) Effects of common minerals on acetate decarboxylation kinetics. Geol Soc Am Abstr Programs 19 832-833... 

Catalan J, Diaz C, Garcia-Bianco F. Effects of medium on decarboxylation kinetics 3-carboxybenzisoxazoles and their potential use as environmental probes in biochemistry. J Org Chem. 2000 65 3409-3415. 

Famini GR, Wilson LY. Using theoretical descriptors in quantitative structure-property relationships — 3-carboxybenzisoxazole decarboxylation kinetics. J Chem Soc Perkin Trans 2. 1994 1641—1650. 

The kinetics of the sulphuric acid-catalysed decarboxylation of a range of alkyl substituted benzoic acids have been measured by Schubert et a/.634,635. The variation of rate coefficient with temperature for mesitoic acid is given in Table 206 and the value for the methyl ester shows that, at this acid concentration, the... 

The rates of decarboxylation of a range of 3-substituted mesitoic acids in 82.1 wt. % phosphoric and 83.0 wt. % sulphuric acids have been measured636 over a range of temperatures as indicated in Table 209, which gives the first-order rate coefficients together with the log A values and the energies, enthalpies, and entropies of activation calculated at 80 °C for sulphuric acid, and 119 °C for phosphoric acid these kinetic parameters are somewhat different from those... 

The kinetics of the decarboxylation of hydroxybenzoic acids have been studied. Brown et a .639 used resorcinol as an acidic solvent, since it was liquid over a wide range of temperatures and was similar to the reaction products the first-order rate coefficients are given in Table 210. The significant decrease in the log A factor... 

A subsequent kinetic investigation of the effect of added hydrochloric acid upon the rate of decarboxylation of 2,4,6-trihydroxybenzoic acid was analysed in terms of three possible mechanisms640 ... 

The mechanism of decarboxylation of acids containing an amino substituent is further complicated by the possibility of protonation of the substituent and the fact that the species NH2ArCOOH is kinetically equivalent to the zwitterion NHj ArCOO. Both of these species, as well as the anion NH2 ArCOO" and even NH3 ArCOOH must be considered. Willi and Stocker644 investigated by the spectroscopic method the kinetics of the acid-catalysed decarboxylation of 4-aminosalicyclic acid in dilute hydrochloric acid, (ionic strength 0.1, addition of potassium chloride) and also in acetate buffers at 20 °C. The ionisation constants K0 = [HA][H+][H2A+] 1 (for protonation of nitrogen) and Kx = [A"][H+] [HA]-1, were determined at /i = 0.1 and 20 °C. The kinetics followed equation (262)... 

The kinetics of decarboxylation of 4-aminosalicylic acid in some buffer solutions at 50 °C were studied. The first-order rate coefficients increased with increasing buffer concentration, though the pH and ionic strength were held constant (Table 217). This was not a salt effect since the rate change produced by substituting potassium chloride for the buffer salt was shown to be much smaller. It follows from the change in the first-order rate coefficients (kx) with... 

The kinetics of the decarboxylation of anthranilic acid have recently been examined. Earlier, an investigation of the decarboxylation of anthranilic acid in aqueous or acidic solution at 100 °C gave a C12 C13 value of 108.02 after 72 % reaction in 1.0 M sulphuric acid compared with 108.5 from complete decarboxylation, so that there is virtually no kinetic isotope effect for this compound646. First-order rate coefficients are given in Table 218 and from the variation of rate... 

Figure 10.47 Dynamic kinetic resolution ofThrA generated diastereomers by enantioselective decarboxylation (a).

Complementary to the work with aqueous acidic media is the study of the homolytic decompositions of Co(III) carboxylates in carboxylic acid media by Lande and Kochi . For example, Co(III) is reduced in pivalic acid media with first-order kinetics with E = 30.6 kcal.mole , AS = 8 eu and k ko = 1.28+0.10 (69 °C). The main oxidation products were found to be isobutylene and tert-butyl pivalate, which suggests that (CH3)3C- is an intermediate. Oxidative decarboxylation is the probable course in the analogous oxidations of n-butyric and isobutyric acids, in view of the production of propane and CO2 under normal... 

Although Ce(IV) oxidation of carboxylic acids is slow and incomplete under similar reaction conditions , the rate is greatly enhanced on addition of perchloric acid. No kinetics were obtained but product analysis of the oxidations of -butyric, isobutyric, pivalic and acetic acids indicates an identical oxidative decarboxylation to take place. Photochemical decomposition of Ce(IV) carbo-xylates is highly efficient unity) and Cu(ll) diverts the course of reaction in the same way as in the thermal oxidation by Co(IIl). Direct spectroscopic evidence for the intermediate formation of alkyl radicals was obtained by Greatorex and Kemp ° who photoirradiated several Ce(IV) carboxylates in a degassed perchloric acid glass at 77 °K in the cavity of an electron spin resonance spectro-... 

Phosphonoformic acid (85) decarboxylated in acid solution, and it was proposed that the uncatalysed reaction involved a simple decarboxylation of the zwitterion. The acid-catalysed reaction showed some kinetic similarity to that of mesitoic acid and an elimination of carbon dioxide as trihydroxymethylcarbonium ion was preferred. Participation of the trans vicinal phosphonyl group in the solvolysis of the halides (86) and (87) has been deduced from rate measurements. In the norbornene derivatives, the relative rates of loss of chloride from (87a) and (87b) were 5 x 10 1. 

Two types of sulfoximinocarboxylates (analogous to sulfinylcarboxylates 16), namely 5 -aryl-5 -methoxycarbonylmethyl-A(-methyl sulfoximine 36 and -methyl-5 -phenyl-A(-ethoxycarbonyl sulfoximine 37, were subjected to hydrolysis in the presence of PLE in a phosphate buffer. As a result of a kinetic resolution, both the enantiomerically enriched recovered substrates and the products of hydrolysis and subsequent decarboxylation 38 and 39, respectively, were obtained with moderate to good ees (Equations 20 and 21). Interestingly, in each case the enantiomers of the substrates, having opposite spatial arrangement of the analogous substituents, were preferentially hydrolysed. This was explained in terms of the Jones PLE active site model. ... 

The preparation of ketones and ester from (3-dicarbonyl enolates has largely been supplanted by procedures based on selective enolate formation. These procedures permit direct alkylation of ketone and ester enolates and avoid the hydrolysis and decarboxylation of keto ester intermediates. The development of conditions for stoichiometric formation of both kinetically and thermodynamically controlled enolates has permitted the extensive use of enolate alkylation reactions in multistep synthesis of complex molecules. One aspect of the alkylation reaction that is crucial in many cases is the stereoselectivity. The alkylation has a stereoelectronic preference for approach of the electrophile perpendicular to the plane of the enolate, because the tt electrons are involved in bond formation. A major factor in determining the stereoselectivity of ketone enolate alkylations is the difference in steric hindrance on the two faces of the enolate. The electrophile approaches from the less hindered of the two faces and the degree of stereoselectivity depends on the steric differentiation. Numerous examples of such effects have been observed.51 In ketone and ester enolates that are exocyclic to a conformationally biased cyclohexane ring there is a small preference for... 

Table 4-2. Computed and experimental primary 12C/13C and secondary 14N/15N kinetic isotope effects for the decarboxylation of N-methyl picolinate at 25 °C in water...

Thalji NK, Crowe WE, Waldrop GL (2009) Kinetic mechanism and structural requirements of the amine-catalyzed decarboxylation of oxaloacetic acid. J Org Chem 74(1) 144—152... 

The question of the stability of the biomolecules is a vital one. Could they really have survived the tremendous energies which would have been set free (in the form of shock waves and/or heat) on the impact of a meteorite Blank et al. (2000) developed a special technique to try and answer this question. They used an 80-mm cannon to produce the shock waves the shocked solution contained the two amino acids lysine and norvaline, which had been found in the Murchison meteorite. Small amounts of the amino acids survived the bombardment , lysine seeming to be a little more robust. In other experiments, the amino acids aminobutyric acid, proline and phenylalanine were subjected to shock waves the first of the three was most stable, the last the most reactive. The products included amino acid dimers as well as cyclic diketopiperazine. The kinetic behaviour of the amino acids differs pressure seems to have a greater effect on the reaction pathway than temperature. As had been recognized earlier, the effect of pressure would have slowed down certain decomposition reactions, such as pyrolysis and decarboxylation (Blank et al., 2001). 

Kinetic Parameters for the Cycloheptaamylose-Catalyzed Decarboxylation of Phenylcyanoacetic acid anions at pH 8.6 and 60.4° ... 

---