Ethyl lactate, hydrogenation

Acetaldehyde Cyanohydrin. This cyanohydrin, commonly known as lactonitnle, is soluble in water and alcohol, but insoluble in diethyl ether and carbon disulfide. Lactonitnle is used chiefly to manufacture lactic acid and its derivatives, primarily ethyl lactate. Lactonitnle [78-97-7] is manufactured from equimolar amounts of acetaldehyde and hydrogen cyanide containing 1.5% of 20% NaOH at —10 20 ° C. The product is stabili2ed with sulfuric acid (28). Sulfuric acid hydroly2es the nitrile to give a mixture of lactic acid [598-82-3] and ammonium bisulfate. 

The material balance was calculated for EtPy, ethyl lactates (EtLa) and CD by solving the set of differential equation derived form the reaction scheme Adam s method was used for the solution of the set of differential equations. The rate constants for the hydrogenation reactions are of pseudo first order. Their value depends on the intrinsic rate constant of the catalytic reaction, the hydrogen pressure, and the adsorption equilibrium constants of all components involved in the hydrogenation. It was assumed that the hydrogen pressure is constant during... 

Ethyl hydrogen sebacate, 21, 48 electrolysis of, 21, 48 Ethyl isothiocyanate, 21, 82 Ethyl lactate, 21, 71 Ethyl laurate, 20, 69 Ethyl linoleate, 22, 77 Ethyl linolenate, 22, 83 Ethyl malonate, 23, 16 Ethyl mercaptan, 22, 59 Ethyl 1V-methyl-/3-aminopropionate, 20, 37... 

The concept of using colloids stabilized with chiral ligands was first applied by Bonnemann to hydrogenate ethyl pyruvate to ethyl lactate with Pt colloids. The nanoparticles were stabilized by the addition of dihydrocinchonidine salt (DHCin, HX) and were used in the liquid phase or adsorbed onto activated charcoal and silica [129, 130]. The molar ratio of platinum to dihydrocinchonidine, which ranged from 0.5 to 3.5 during the synthesis, determines the particle size from 1.5 to 4 nm and contributes to a slight decrease in activity (TOF = l s ). In an acetic acid/MeOH mixture and under a hydrogen pressure up to 100 bar, the (R)-ethyl lactate was obtained with optical yields of 75-80% (Scheme 9.11). 

Recently, platinum nanoparticles protected by N,N-dimethyl-N-cetyl-N-(2-hydro-xyethyl)ammonium chloride salt and modified with cinchonidine were investigated in the enantiomeric hydrogenation of ethyl pyruvate in pure biphasic liquid-liquid (water/substrate) media at room temperature [139]. For the first time, the aqueous phase containing Pt(0) nanocatalysts with an average size of 2.5 nm could be reused for successive hydrogenations, and with a total conversion of activity and enantioselectivity in (R)-(+)-ethyl lactate up to 55% (Scheme 9.12). 

Di (l carbethoxyethyl) phosphorofluoridate (XV) was readily produced by the action of sodium fluoride on the corresponding phosphorochloridate obtained from di-(l -carbethoxyethyl) hydrogen phosphite, which in turn was obtained by the action of phosphorus trichloride on ethyl lactate. Although (XV) contained secondary groupings, it was found to be relatively nontoxic and to produce only slight myosis in the pupils of the eyes of rabbits and guinea-pigs. 

Much work [42] has been devoted to cinchona alkaloid modified Pd and Pt catalysts in the enantioselective hydrogenation of a-keto esters such as ethyl pyruvate (Scheme 5.11). Optimal formulation and conditions include supported Pt, the inexpensive (—)-cinchonidine, acetic acid as solvent, 25 °C and 10-70 bar H2. Presently, the highest e.e. is 97.6% [to (R)-ethyl lactate]. 

Enantioselective hydrogenation of a-ketoesters on cinchona alkaloid-modified Pt/Al203 is an interesting system in heterogeneous catalysis [143-146], The key feature is that on cinchonidine-modified platinum, ethyl pyruvate is selectively hydrogenated to R-ethyl lactate, whereas on einchonine-modified platinum, S-ethyl pyruvate is the dominant product (Figure 16) [143]. 

For both Rh and Pt-based systems, the only products obtained were (Rj-ethyl lactate and (Sj-ethyl lactate, and a high hydrogenation rate and a behavior similar to that observed with the respective monometallic catalysts were noted. Figure 6.18... 

Our success in synthesizing silyl ketals containing an aryl halide with (+)-ethyl lactate led us to explore the intramolecular radical translocation reaction (Scheme 29). The term radical translocation is described by Robertson et al. as the intramolecular abstraction of an atom (usually hydrogen) or group by a radical center this results in a repositioning of the site of the unpaired electron which can lead to functionalization at positions normally unreactive towards external reagents or whose selective modification is difficult In the most common cases the abstraction occurs at a site that is five atoms away from the radical 1,6 atom abstraction are less common, and l,n-abstractions where n > 6 are rare. This is because the shortest chain length that can accommodate the trajectory for atom abstraction contains six atoms, as in the case of the 1,5 atom abstraction. Entropic factors usually result in the failure of the process in the cases where n > 6 atoms. 

Minder et al. studied various modifiers containing a nitrogen base for the enantioselective hydrogenation of ethyl pyruvate.223,224 Up to 82% ee with (R)-l-(l-naphthyl)ethylamine and up to 75% ee with (/ )-2-( 1 -pyrrolidinyl)-1 -(1 -naphthyl)-ethanol as modifiers were achieved in the hydrogenation of ethyl pyruvate to (R)-ethyl lactate over Pt-Al203 in acetic acid. 

The Pt-catalyzed enantioselective hydrogenation of ethyl pyruvate to (/ )-ethyl lactate was considerably faster (by a factor of 3-3.5) in supercritical ethane than in the conventional apolar solvent toluene, whereas the enantioselectivity was unaffected. Complete catalyst deactivation was observed in C02, which was shown by FTIR to be due to the reduction of C02 to CO via reverse water gas shift reaction. The catalyst could be regenerated by exposing it to ambient air, while hydrogen treatment was less efficient. This is the first evidence to the limitation of catalytic hydrogenations over Pt metals in supercritical C02. 

ESMS was employed to identify reactive intermediates in the enantioselective hydrogenation of ethyl pyruvate on Pt-alumina, Pt black, and Pt black+alumina catalysts modified by dihydrocinchonidine in acetic acid [56]. The ESMS spectra of the raw product revealed a large number of species which fell into four groups (1) dihydrocinchonidine and its hydrogenated derivatives (2) the adducts of ethyl pyruvate and its oligomers (3) (R)-ethyl lactate, the product of the enantioselective hydrogenation, and its adducts and (4) oxonium compounds formed from alumina. The latter most likely play a decisive role in the development of the chiral environment of the catalyst surface. As suggested by the authors, these oxonium cations could make the so-called electrostatic catalysis [57],based on electrostatic acceleration, possible. 

Derivation (a) By the esterification of lactic acid with ethanol (b) by combining acetaldehyde with hydrogen cyanide to form acetaldehyde cyanohydrin, which is converted into ethyl lactate by treatment with ethanol and an inorganic acid. 

Cinchona promoted Pt or Pd (supported) catalysts are feasible for the hydrogenation of carbonyls or C=C bonds, both at the a-position of another carbonyl group. For example, ethyl pyruvate is hydrogenated on cinchonidine promoted Pt/C, producing ethyl lactate with ca. 95% ee. The product is used in pharmaceuticals, agrochemicals, solvents used in the electronics industry, flavors and fragrances, health care foods, etc. 

During the hydrogenations samples were taken. These samples were analysed with GC on a P-cyclodextrine capillary column (ethyl lactate on 90 C, dihydroisophorone on 110"C). The analysis provided base-line separation of the enantiomers. The chromatograms were recorded and the peak areas were calculated with a CWS (chromatography work station). Enantimoric excess values were calculated fi om the peak areas of the enantiomers with the usual method [R]-[S]/[R]+[S]. 

This paper deals with the asymmetric hydrogenation of ethyl pyruvate to ethyl lactate showing a high enantiomeric excess in favour of the R-enantiomer over (-)cinchonidine modified Pt/carrier catalysts. Due to their regular structures, zeolites in particular have been used as carrier materials. 

The materials were impregnated with 5 wt.-% Pt using an aqueous solution based on H2Pt(OH)6 and HNOj. The precursors were conditioned in a nitrogen stream (16 h at 523 K, flow 10 I h ) and afterwards reduced in a hydrogen stream (3 h at 523 K, flow 8 1 h ). The catalysts were used for the enantioselective hydrogenation of ethyl pyruvate to ethyl lactate immediately after having been reduced. 

Ethyl lactate is produced by reacting acetaldehyde, hydrogen cyanide, and ethyl alcohol. 

Ethyl lactate has been suggested as a relatively nontoxic biodegradable solvent that is inexpensive. It can be made from renewable materials by a new fermentation process.211 Photoresists and organic contaminants can be removed with ozone in water in a process that uses no acids, hydrogen peroxide, or high temperatures while sav-... 

Soaps and detergents are surfactants used in cleaning.260 Soaps are salts of fatty acids (e.g., sodium stearate). Detergents are salts of sulfonic acids, quaternary ammonium salts, tertiary amine oxides, ethylene oxide adducts of alcohols, and phenols.261 Their use in cleaning to replace chlorinated solvents262 was covered in Chap. 3, Sec. VII. (See also the use of hydrogen peroxide,263 ethyl lactate,264 and ultrasound265 to clean process equipment.) Some other environmental aspects of their use will be covered here briefly. 

Figure 6 Concentration-time curve of the catalytic hydrogenation of ethyl pyruvate to ethyl lactate on CIN-modified Pt/Al203 in cyclohexane at 60 bar and 20 °C. 

V. Morawsky, U. Pru 3e, L. Witte, K.-D. Vorlop. Transformation of Cinchonidine during the Enantioselective Hydrogenation of Ethyl Pyruvate to Ethyl Lactate. Catal. Commun. 1 15-20, 2000. 

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