Acetaldehyde, complex with

This monomer polymerizes faster ia 50% water than it does ia bulk (35), an abnormaHty iaconsistent with general polymerization kinetics. This may be due to a complex with water that activates the monomer it may also be related to the impurities ia the monomer (eg, acetaldehyde, 1-methyl pyrroHdone, and 2-pyrroHdone) that are difficult to remove and that would be diluted and partitioned ia a 50% aqueous media (see Vinyl polymers, A/-VINYLAMIDE POLYPffiRS). 

The acidity dependences are not simple. V(V) is thought to form a complex with the enol which undergoes slow oxidative breakdown. Propionaldehyde and n-butyraldehyde are, however, oxidised by Mn(III) pyrophosphate with a zero-order dependence on oxidant concentration but first-order dependences on substrate and HjO " concentrations. Here oxidation immediately follows enol formation. Ce(IV) sulphate oxidises acetaldehyde at a rate much faster than enolisation . 

In 1994 we published the first chiral dendrimers built from chiral cores and achiral branches [ 1,89], see for instance dendrimer 57 with a core from hydroxy-butanoic acid and diphenyl-acetaldehyde and with twelve nitro-groups at the periphery (Fig. 21). As had already been observed with starburst dendrimers, compound 57 formed stable clathrates with many polar solvent molecules, and it could actually only be isolated and characterized as a complex [2 (57- EtO-Ac (8 H20))]. Because no enantioselective guest-host complex formation could be found, and since compounds of type 57 were poorly soluble, and could thus not be easily handled, we have moved on and developed other systems to investigate how the chirality of the core might be influencing the structure of achiral dendritic elongation units. 

The carbon dioxide anion-radical was used for one-electron reductions of nitrobenzene diazo-nium cations, nitrobenzene itself, quinones, aliphatic nitro compounds, acetaldehyde, acetone and other carbonyl compounds, maleimide, riboflavin, and certain dyes (Morkovnik and Okhlobystin 1979). The double bonds in maleate and fumarate are reduced by CO2. The reduced products, on being protonated, give rise to succinate (Schutz and Meyerstein 2006). The carbon dioxide anion-radical reduces organic complexes of Co and Ru into appropriate complexes of the metals(II) (Morkovnik and Okhlobystin 1979). In particular, after the electron transfer from this anion radical to the pentammino-p-nitrobenzoato-cobalt(III) complex, the Co(III) complex with thep-nitrophenyl anion-radical fragment is initially formed. The intermediate complex transforms into the final Co(II) complex with the p-nitrobenzoate ligand. 

The details of the organic chemistry of the reaction of ethylene with PdCl2 (equation (1) above) are also known and are shown in Fig. 9.2. The palladium ion complexes with ethylene and water molecules and the water adds across the bond while still complexed to palladium. The palladium then serves as a hydrogen acceptor while the double bond reforms. Keto-enol tautomerism takes place, followed by release of an acetaldehyde molecule from the palladium. 

Methyl acetate probably originates from the reaction of methanol with the intermediate cobalt-acyl complex. The reaction leading to the formation of acetaldehyde is not well understood. In Equation 8, is shown as the reducing agent however, metal carbonyl hydrides are known to react with metal acyl complexes (20-22). For example, Marko et al. has recently reported on the reaction of ri-butyryl- and isobutyrylcobalt tetracarbonyl complexes with HCo(CO) and ( ). They found that at 25 °C rate constants for the reactions with HCo(CO) are about 30 times larger than those with however, they observed that under hydroformylation conditions, reaction with H is the predominant pathway because of the greater concentration of H and the stronger temperature dependence of its rate constant. The same considerations apply in the case of reductive carbonylation. Additionally, we have found that CH C(0)Co(C0) L (L r PBu, ... 

Because of this hydration, the total solubility, i.e., effective Henry s law constant, is larger than expected based on physical solubility alone. The data in Table 8.3 show that most aldehydes have quite large effective Henry s law constants (// ), the exceptions being acetaldehyde and benzaldehyde. As a result of these high solubilities, significant concentrations can occur in fogs and clouds and hence be available to complex with S(IV). 

A group at the Academy of Sciences in Moscow 197) has synthesized chiral threonine. Derivatives of cyclic imino acids form copper complexes with glacine and carbonyl compounds. Hydroxyethylation with acetaldehyde and decomposition of the resulting complexes produced threonine with an optical purity of up to 97-100% and with threo/allo ratios of up to 19 1 197). The chiral reagents could be recovered and re-used without loss of stereoselectivity. The mechanism of this asymmetric synthesis of amino acids via glacine Schiff base/metal complexes was also discussed 197). 

Structures of aliphatic and aromatic aldehyde complexes are concluded to be identical in principle with that of the acetaldehyde complex from the comparison of their IR and H-NMR spectra. 

In the case of copper(II) complexes, the reaction with acetaldehyde is believed to proceed by the steps shown in Scheme 38. The bis(oxazolidine)copper(II) complex (148 R = Me) has been characterized by X-ray analysis.486 Treatment of this complex with H2S in acid solution gives threonine. Synthetic procedures have been developed giving threonine in 95% yields.483... 

Two types of inhibitors, pyrazoles and imidazoles (with E-NAD+) and iso-butyramide (with E-NADH), form tight ternary complexes with E-coenzyme, allowing single turnover to be observed (through photometry at 290 nm or fluorescence caused by NADH) and thus titration of the active sites (see Section 9.2.3.). Pyrazole and isobutyramide are kinetically competitive with ethanol and acetaldehyde, respectively. If the reaction E + NADH + aldehyde is run in the presence of a high concentration of pyrazole, the complex E-NAD+ formed by dissociation of alcohol immediately binds pyrazole for a single turnover only. Under favorable conditions, a single NADH oxidation can be observed by stopped-flow techniques to find a kcat of about 150 s 1 and a deuterium isotope effect kD 4 as expected (see Section 9.2.5). 

The chiral hosts 8a and 9a were found to be useful for the resolution of cyanohydrins which cannot be resolved with 4. For examples, 61g and 61m were resolved by complexation with 9a and 8a, respectively, to give (-)-61g of 72.5% ee (70%) and (+)-61m of 100% ee (47.6%), respectively, in the yield indicated. The most simple chiral cyanohydrin derived from acetaldehyde (62g) was resolved by complexation with 8a and optically pure (+)-62g was obtained in 52.6% yield.23... 

The electrophilic activation of a C—C multiple bond as a result of coordination to an electron-deficient metal ion is fundamental to much of organometallic chemistry, both conceptually and in synthetic applications (11). The Wacker process, a classic example of an efficient catalytic oxidation, is an important industrial reaction, used for the conversion of ethylene into acetaldehyde. The catalytic reaction begins with the coordination of ethylene to a Pd(ll) center, leading to activation of the ethylene moiety. The key step is the reaction of the metal-olefin complex with a nucleophile to give substituted metal-alkyl species (12). The integration of this reaction into a productive catalytic cycle requires the eventual cleavage of the newly generated M—C bond. 

Thc highest conversion rates and acetaldehyde/ethanol yields could be obtained with the diiododiligand cobalt compound. Complexes with an increased phosphine and decreased iodine content were clearly less efficient. Interestingly,... 

The oxidative addition of methyl iodide to an unsaturated cobalt carbonyl according to Equation (27) was proposed by Wender, CO insertion gives an acetyl species (28) which is thought to be hydrogenated by cobalt carbonyl hydride or H to yield acetaldehyde [4]. Numerous examples of the oxidative addition of methyl iodide to transition metal complexes with a electron configuration (e.g. Rh Ir ) ate known from the literature [66, 67]. For the carbonytaiion of methanol, the rate has been found to be the oxidative addition of methyl iodide to rhodium(l) [68]. 

Thioaldehydes have been used as ligands in metal complexes with osmium (76CC1044 77CC901 83JA5939) and rhenium (83JA1056). The first metal complexes with thio- (and seleno)-acetaldehyde as ligands were... 

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