Disproportionation Of Aldehydes Research Articles

Exploring the Core Formose Cycle: Catalysis and Competition.

The core autocatalytic cycle of the formose reaction may be enhanced or eroded by the presence of simple molecules at life's origin. Utilizing quantum chemistry, we calculate the thermodynamics and kinetics of reactions both within the core cycle and those that deplete the reactants and intermediates, such as the Cannizzaro reaction. We find that via disproportionation of aldehydes into carboxylic acids and alcohols, the Cannizzaro reaction furnishes simple catalysts for a variety of reactions. We also find that ammonia can catalyze both in-cycle and Cannizzaro reactions while hydrogen sulfide does not; both, however, play a role in sequestering reactants and intermediates in the web of potential reactions.

Uncover aldehydes in biomass hydrolyzates: disproportionation of aldehydes in alkaline solution and subsequent measurement using an automated HPAEC-PAD method.

High-performance anion exchange chromatography coupled to pulsed amperometric detection (HPAEC-PAD) was used for developing a method for identifying and quantifying aldehydes in biomass hydrolyzates. This method was optimized to the requirements of HPAEC-PAD in order to allow for a simultaneous determination of aldehydes by respective Cannizzaro alcohols. To this end, sodium hydroxide concentration (0.1 to 5.0mol/L), temperature (30 to 40°C), and reaction time (0 to 24h) were investigated for sufficient and reproducible disproportionation of the biomass-derived aldehydes. The optimized method for aldehyde disproportionation and subsequent measurement are 1mol/L sodium hydroxide, 40°C, and 1h reaction time. The detection limits resulting from this method are lower than 68.55mg/L and the sensitivity above 0.024 (nCmin)/(mg/L) for 3,4-dimethoxybenzaldehyde. Linearity for aldehyde calibration always exceeded 0.98. Thus, HPAEC-PAD analysis allows for the quantification of biomass-derived compounds from all natural polymers and, therefore, it has exemplarily been used to quantify aldehyde concentration of beech wood, orange peel, and algae biomass hydrolyzates. Graphical abstract.

Oxide supported metal catalysts for the aldehyde water shift reaction: Elucidating roles of the admetal, support, and synergies

There is significant interest in the use of H2O as a reactant for production of commodity chemicals and fuels, in particular from water-laden biomass-derived feedstocks. In this paper, we describe results for the aldehyde water shift (AWS), a reaction where aldehydes are partially oxidized by water to produce the corresponding carboxylic acid and H2, over a series of CeO2-, Al2O3-, and SiO2-supported Cu, Pt, and Au catalysts. The effects of support were further investigated by evaluating the performances of a Cu-Zn-Al water gas shift catalyst and bulk Cu nanoparticles. The supported Cu catalysts were more active than the supported Pt and Au catalysts, and the reducible oxide (CeO2) supported Cu catalyst had the highest AWS activity. The high activity of the Cu/CeO2 catalyst is believed to derive from coupling H2O dissociation and aldehyde oxidation. The two major side reactions, aldol condensation and aldehyde disproportionation, appeared to be catalyzed by acid and Cu sites, respectively. The results indicate that both the admetal and support play critical roles in catalyzing the AWS reaction and provide guidance for the design of highly active AWS catalysts.

Biocatalytic Parallel Interconnected Dynamic Asymmetric Disproportionation of α-Substituted Aldehydes: Atom-Efficient Access to Enantiopure (S)-Profens and Profenols.

The biocatalytic asymmetric disproportionation of aldehydes catalyzed by horse liver alcohol dehydrogenase (HLADH) was assessed in detail on a series of racemic 2‐arylpropanals. Statistical optimization by means of design of experiments (DoE) allowed the identification of critical interdependencies between several reaction parameters and revealed a specific experimental window for reaching an ′optimal compromise′ in the reaction outcome. The biocatalytic system could be applied to a variety of 2‐arylpropanals and granted access in a redox‐neutral manner to enantioenriched (S)‐profens and profenols following a parallel interconnected dynamic asymmetric transformation (PIDAT). The reaction can be performed in aqueous buffer at ambient conditions, does not rely on a sacrificial co‐substrate, and requires only catalytic amounts of cofactor and a single enzyme. The high atom‐efficiency was exemplified by the conversion of 75 mM of rac‐2‐phenylpropanal with 0.03 mol% of HLADH in the presence of ∼0.013 eq. of oxidized nicotinamide adenine dinucleotide (NAD+), yielding 28.1 mM of (S)‐2‐phenylpropanol in 96% ee and 26.5 mM of (S)‐2‐phenylpropionic acid in 89% ee, in 73% overall conversion. Isolated yield of 62% was obtained on 100 mg‐scale, with intact enantiopurities.

Revised Mechanisms for Aldehyde Disproportionation and the Related Reactions of the Shvo Catalyst

It is widely believed that the Shvo catalyst (1) dissociates to form two active species in solution: the 18-electron hydride RuH(CO)2[η5-C5(OH)Ph4] (2) and the naked 16-electron complex Ru(CO)2[η4-C5(═O)Ph4] (3). This combined experimental/computational study demonstrates that a sustained presence of 3 is not viable in the reactions of alcohols and organic carbonyls; thus, 3 is better treated as nonexistent under the typical catalytic conditions. We propose a modified view where the key catalytic species are the hydride 2 and the 18-electron metal alkoxide intermediate Ru(OR)(CO)2[η5-C5(OH)Ph4] existing in equilibrium with the corresponding alcohol complex. An X-ray crystallographic study of 2 revealed an interesting dihydrogen-bonded dimer structure in the solid state. The mechanistic ideas of this paper explain the highly efficient Tishchenko-like aldehyde disproportionation reaction with the Shvo catalyst. Additionally, our observations explain why 1 is inefficient for hydrogenation of ethyl acetate an...

The Importance of Cannizzaro-Type Reactions during Electrocatalytic Reduction of Carbon Dioxide.

A seemingly catalytically inactive electrode, boron-doped diamond (BDD), is found to be active for CO2 and CO reduction to formaldehyde and even methane. At very cathodic potentials, formic acid and methanol are formed as well. However, these products are the result of base-catalyzed Cannizzaro-type disproportionation reactions. A local alkaline environment near the electrode surface, caused by the hydrogen evolution reaction, initiates aldehyde disproportionation promoted by hydroxide ions, which leads to the formation of the corresponding carboxylic acid and alcohol. This phenomenon is strongly influenced by the electrolyte pH and buffer capacity and not limited to BDD or formaldehyde, but can be generalized to different electrode materials and to C2 and C3 aldehydes as well. The importance of these reactions is emphasized as the formation of acids and alcohols is often ascribed to direct CO2 reduction products. The results obtained here may explain the concomitant formation of acids and alcohols often observed during CO2 reduction.

High Catalytic Efficiency Combined with High Selectivity for the Aldehyde–Water Shift Reaction using (para-cymene)Ruthenium Precatalysts

A family of (para-cymene)RuII complexes are shown to be competent precatalysts for the oxidation of aldehydes to carboxylic acids using water as the oxidant. This reaction, known as the “aldehyde–water shift” (AWS), has been previously demonstrated to be in competition with aldehyde disproportionation. For the few reported mononuclear catalysts for this reaction, either high selectivity for AWS and low conversion or low AWS selectivity and high conversion is observed. A homogeneous precatalyst which is both highly selective for the desired AWS and is highly efficient for conversion of the aldehyde to products is reported herein. In addition, catalyst activity is found to be general to a variety of sterically unencumbered aliphatic aldehydes producing the corresponding carboxylic acid and hydrogen gas.

Iridium, Rhodium, and Ruthenium Catalysts for the “Aldehyde–Water Shift” Reaction

A series of half-sandwich complexes of iridium, rhodium, and ruthenium are shown to be active catalysts for the conversion of aldehydes and water to carboxylic acids. Depending on the catalyst, H2 is either released (the “aldehyde–water shift”) or transferred to a second equivalent of aldehyde (aldehyde disproportionation). Mechanistic studies suggest hydride transfer to be the selectivity-determining step along the reaction pathway. Using [(p-cymene)Ru(bpy)OH2][OTf]2 as precatalyst, we demonstrate a novel example of a highly selective aldehyde–water shift in the absence of a hydrogen acceptor or base.

Alkali Metal tert‐Butoxides, Hydrides and Bis(trimethylsilyl)amides as Efficient Homogeneous Catalysts for Claisen–Tishchenko Reaction

AbstractShelf‐available alkali metal tert‐butoxides, hydrides and bis(trimethylsilyl)amides were shown to be highly efficient homogeneous precatalysts for the disproportionation of aldehydes to the corresponding carboxylic esters. Potassium compounds in combination with 18‐crown‐6 ether could drastically increase the rate of reaction in a few cases. Alternatively, efficient aldol condensations were found for aldehydes possessing an enolizable methylene group at the α‐position to the aldehyde functionality. The active species involved in this esterification using any of these alkali metal catalysts is expected to be the metal alkoxide. Potassium compounds were found to be much more efficient when compared to analogous sodium compounds and kinetic studies revealed the rate‐determining step to be a second order concerted hydride transfer from a potassium hemiacetal species to another molecule of aldehyde.

ChemInform Abstract: Selenide Ions as Catalysts for Homo‐ and Crossed‐Tishchenko Reactions of Expanded Scope.

AbstractSelenide ions are superior to previously reported thiolate analogues and promote the disproportionation of aldehydes with increased reaction rates and broader scope at lower loadings and temperature.

Selenide Ions as Catalysts for Homo- and Crossed-Tishchenko Reactions of Expanded Scope

Selenide ions have been shown to catalyze the Tishchenko reaction for the first time. These catalysts are superior to previously reported thiolate analogues and promote the disproportionation of aldehydes with increased reaction rates and broader scope at lower catalyst loadings and temperatures. Significantly improved catalyst performance was also observed in the aryl selenide mediated crossed intermolecular Tishchenko reaction.

Catalytic Intramolecular Ketone Hydroacylation: Enantioselective Synthesis of Phthalides

The development of a new transition-metal-catalyzed transformation can often allow a traditional reaction, perhaps one that employs stoichiometric amounts of reagents and harsh reaction conditions, to be replaced by a selective, atom economic process which proceeds under mild reaction conditions. This is certainly the case with the recent report from Dong and co-workers of a catalytic enantioselective synthesis of phthalide compounds. The disproportionation of aldehydes has traditionally been achieved under basic conditions and is known as the Cannizzaro reaction. A Lewis acid promoted variant—the Tishchenko reaction—is a related transformation that converts two carbonyl units into the corresponding ester. Both processes suffer from the formation of side products and have not been readily adapted to catalytic asymmetric reactions. As an alternative to these processes the Dong research group has developed catalytic enantioselective intramolecular ketone hydroacylation reactions. Transition-metal-catalyzed hydroacylation reactions usually proceed through initial formation of an acyl metal hydride species, and subsequent addition of this species across a multiple bond. Hydroacylation reactions of alkenes and alkynes are now well-studied processes, with a number of enantioselective variants already reported. However, the corresponding processes requiring addition of the acyl metal species across a ketone or an aldehyde—carbonyl hydroacylation—are much less studied. The key intermediates for both types of reaction, the acyl metal hydride species, are formed by the oxidative addition of the metal catalyst to the aldehyde C H bond; a process that can be considered as a type of C H activation. In common with a number of reactions that are based on C H functionalization, hydroacylation reactions offer advantages in terms of step and atom economy. Dong and co-workers originally developed a catalytic enantioselective intramolecular ketone hydroacylation reaction as a route to enantiomerically enriched seven-membered lactones (Scheme 1). To achieve efficient reactions the substrates employed in these transformations were required to feature a chelating ether group. Developing a ketone hydroacylation route to phthalide compounds presented a greater challenge, as the substrates needed to target the phthalide architecture would no longer allow the presence of a coordinating ether group. The reaction shown in Scheme 2 illustrates the basic process used to access enantiomerically enriched phthalide compounds. Ketobenzaldehydes such as 1 were the key substrates for the process, and delivered five-membered lactones 2, phthalides, through the proposed ketone hydroScheme 1. Synthesis of seven-membered lactone derivatives based on enantioselective ketone hydroacylation.

Hydrothermal reactions of formaldehyde and formic acid: Free-energy analysis of equilibrium

The chemical equilibria concerning formaldehyde and formic acid are computationally investigated in water over a wide range of thermodynamic conditions. The free energy is evaluated in the method of energy representation for the solvent effect on the decomposition processes of these two compounds. The solvation is found to suppress the production of nonpolar species from a polar. In the two competitive decomposition reactions of formic acid, the solvent strongly inhibits the decarboxylation (HCOOH-->CO2+H2) and its effect is relatively weak for the decarbonylation (HCOOH-->CO+H2O). The equilibrium weights for the two decomposition pathways of formic acid are determined by the equilibrium constant of the water-gas-shift reaction (CO+H2O-->CO2+H2), which is an essential and useful process in fuel technology. The reaction control by the solvent is then examined for the water-gas-shift reaction. Through the comparison of the equilibrium constants in the absence and presence of solvent, even the favorable side of the reaction is shown to be tuned by the solvent density and temperature. The reaction equilibrium is further treated for aldehyde disproportionation reactions involving formaldehyde and formic acid. The disproportionation reactions are found to be subject to relatively weak solvent effects and to be dominated by the electronic contribution.

(.eta.3-Oxaallyl)rhodium(I) Complexes as Catalyst Precursors for the Disproportionation of Aldehydes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXT(.eta.3-Oxaallyl)rhodium(I) Complexes as Catalyst Precursors for the Disproportionation of AldehydesGreg A. Slough, John R. Ashbaugh, and Luke A. ZannoniCite this: Organometallics 1994, 13, 9, 3587–3593Publication Date (Print):September 1, 1994Publication History Published online1 May 2002Published inissue 1 September 1994https://doi.org/10.1021/om00021a035RIGHTS & PERMISSIONSArticle Views191Altmetric-Citations23LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (871 KB) Get e-Alerts Get e-Alerts

Catalytic disproportionation of aldehydes with ruthenium complexes

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTCatalytic disproportionation of aldehydes with ruthenium complexesNaim Menashe and Youval ShvoCite this: Organometallics 1991, 10, 11, 3885–3891Publication Date (Print):November 1, 1991Publication History Published online1 May 2002Published inissue 1 November 1991https://doi.org/10.1021/om00057a019RIGHTS & PERMISSIONSArticle Views1220Altmetric-Citations172LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (866 KB) Get e-Alerts Get e-Alerts

Interferences from aldehydes and peroxyacetyl nitrate when sampling urban air organic acids on alkaline traps

The authors have investigated the possible conversion of formaldehyde to formate and of acetaldehyde and peroxyacetyl nitrate (PAN) to acetate when sampling organic acids in urban air using alkaline traps. Tests were carried out with cartridges (C{sub 18} and alumina) and with filters (25 and 47 mm, glass or paper) coated with KOH and carbonate, aldehydes concentrations of 8-240 ppb, PAN concentrations of 50-160 ppb, sampling flow rates of 0.4-15 L/min, and sampling times of 1-24 h, in both purified and particle-free ambient air. Disproportionation of aldehydes to acids was negligible, accounting for 1-3% of the aldehyde concentration irrespective of trap type, aldehyde concentration, sampling flow rate, and test duration. Conversion of PAN to acetate on alkaline traps heterogeneous alkaline hydrolysis was 11-17% for carbonate and KOH filters, 16-27% for carbonate cartridges, and 100% for KOH cartridges. Laboratory tests and analysis of ambient data for three recent southern California field studies both indicate negligible contribution of formaldehyde and acetaldehyde to the formic acid and acetic acid, respectively, measured in alkaline filter and cartridge samples.

Surface properties of zno-based catalysts and related mechanistic features of the higher alcohol synthesis by FT-IR spectroscopy and TPSR

Aspects of the mechanism involved in the synthesis of methanol and higher alcohols from syngas have been investigated by combined FT-IR spectroscopy and Temperature Programmed Surface Reaction (TPSR) techniques. Results concerning the interaction of C 4 linear oxygenated molecules with ZnO-based catalysts have been interpreted on the basis of a mechanistic scheme demonstrating a number of catalytic functions. Some of the related reactions are characteristic of base-catalyzed organic chemistry in solution: aldolic-type condensation, aldehyde disproportionation, ketonization, decarboxylation and dehydrogenation. By comparison with catalytic activity data under actual reaction conditions, it is found that the same functions also play an important role in determining the spectrum of products of the synthesis, although the relative relevance of the associated chemical reactions is altered by the different operating conditions as well as by thermodynamic constraints.

Asymmetric synthesis by chiral ruthenium complexes

Abstract Disproportionation of aldehydes with formation of the corresponding acid and alcohol is catalyzed by phosphine-substituted cluster ruthenium carbonyls. The reaction takes place in the presence of water. An enantiomeric selection is shown by H4Ru4(CO)8[(−)-DIOP]2 in the disproportionation reaction of (R)(S)-2-methylbutanal; (−)(S)-2-methylbutanoic acid of 1.7% optical purity is obtained.