Aldol Condensation Products Research Articles

Electrochemical characteristics of a new electric double layer capacitor with acidic polymer hydrogel electrolyte

The article presents the results of a study on activated carbon fiber cloth (AC) and a hydrophobic microporous polypropylene (PP) membrane, both chemically modified with acidic acetone aldol condensation products, and on testing their use as an electrode material and separator in electric double layer capacitors (EDLCs). Polymer hydrogel used was based on poly(acrylamide) (PAAM), H2SO4 and water. Electrochemical characteristics of EDLCs were investigated by cyclic voltammetry and galvanostatic charge–discharge cycle tests and also by impedance spectroscopy. As a result, the capacitor with polymer hydrogel was found to exhibit similar capacitance as that with the H2SO4 aqueous solution and an excellent high-rate dischargeability. At the 4000th cycle of potential cycling (0.5Ag−1) the specific capacitance of 132Fg−1 was obtained with a energy density of 3.45Whkg−1 at a power density of 56Wkg−1. The above results provide valuable information to explore the novel composition of EDLCs.

Stereochemistry of products of aldol condensation of 2-(3-oxo-1,3-diphenylpropyl)cyclohexanone with aromatic aldehydes

The aldol condensation of various aromatic aldehydes with 2-(3-oxo-1,3-diphenylpropyl)cyclohexanone in CH2Cl2 in the presence of TiCl4-Et3N at 0°C afforded perhydrochromens with two equatorial and one axial substituents whereas the aldol reaction under base catalysis gave perhydrochromens with equatorial substituents.

On the reactivity of isoindolo[2,1-a]quinazoline-5-ones

Base- and acid-catalyzed nucleophilic addition of 11 H -isoindolo[2,1- a ]quinazoline-5-one to aromatic aldehydes and maleimides was investigated. The aldol adducts and condensation products were obtained stereoselectively. Main diastereomers of the Michael adducts were isolated in 74–89% yield, and converted by N -methylation to new stable α-substituted isoindole derivatives, for which 6-methylisoindolo[2,1- a ]]quinazoline-5-one stands as the unsubstituted reference. The stability of the latter was monitored in moist aerated CDCl 3 solution, and one of the oxidative hydrolysis product was characterized by X-ray diffraction analysis as the corresponding N -arylphthalimide. The reactivity of the unsubstituted 6-methylisoindolo[2,1- a ]]quinazoline-5-one was also investigated with acetylenic Michael acceptors. Fully conjugated isoindole derivatives possessing an original pull–push–pull structure were obtained. The conformations and molecular orbitals of the dibenzoylacetylene adduct were studied at the DFT level of theory. Its static quadratic hyperpolarizabilty β 0 was also calculated at the ZINDO level.

Aldol condensation products during photocatalytic oxidation of ethanol in a photoelectrochemical cell

Electric current was produced in a photoelectrochemical cell during photocatalytic oxidation of ethanol, which was used as a representative organic compound present in wastewater from biomass processing industries. Thus, the cell behaved as a PhotoFuelCell that consumed waste material to produce electricity. The cell consisted of two compartments separated by a silica frit. The anode electrode was a Fluorine-doped Tin Oxide transparent electrode bearing nanocrystalline titania Degussa P25, applied as a paste and calcined at 550°C. The cathode electrode was a carbon-cloth bearing Pt/Carbon-Black catalyst. The electrolyte was 1.0M NaOH. When 20%v. ethanol was added in the anode compartment, the cell gave 0.75mA/cm2 short-circuit current density (calculated over 12cm2 electrode area) and 1.1V open-circuit voltage. The anode compartment of the cell was operated under three different conditions: (1) under continuous air flow, i.e. oxygen-rich conditions; (2) under Ar flow, i.e. anaerobic conditions; and (3) exposed to ambient air but without any gas flow through the cell, i.e. oxygen-deficient, mass transfer-limited conditions. In the latter two cases, the oxidation of ethanol and its photo-oxidation products was incomplete and resulted in aldol condensation reactions that produced various aldehydes, some of them of high molecular weight and insoluble. It was concluded that in order to avoid such reactions, which impede mineralization process, measures should be taken for continuous oxygen supply and for optimal combination of the quantity of the photocatalyst and the concentration of the photodegradable substance. Thus only 1%v. ethanol can give 75% of the maximum current obtained in the presence of large ethanol concentration.

Investigation into the mast cell stabilizing activity of nature-identical and synthetic indanones

As part of an ongoing search for novel molecules with therapeutic potential we examined the mediator release inhibition activity of a number of indanones and their derivatives. The aldol condensation product 18 was approximately twice as potent as disodium cromoglycate as an inhibitor of compound 48/80-stimulated histamine release from rat peritoneal mast cells. The activity of this class of dimeric indanone compound is significantly higher than controls and may represent a new class of mast cell stabilizing agents. Compound 18 has been selected for further biological evaluation of its mast cell stabilization profile.

Secondary organic material formed by methylglyoxal in aqueous aerosol mimics

Abstract. We show that methylglyoxal forms light-absorbing secondary organic material in aqueous ammonium sulfate and ammonium nitrate solutions mimicking tropospheric aerosol particles. The kinetics were characterized using UV-Vis spectrophotometry. The results suggest that the bimolecular reaction of methylglyoxal with an ammonium or hydronium ion is the rate-limiting step for the formation of light-absorbing species, with kNH4+II=5×10−6 M−1 min−1 and kH3O+II≤10−3 M−1 min−1. Evidence of aldol condensation products and oligomeric species up to 759 amu was found using chemical ionization mass spectrometry with a volatilization flow tube inlet (Aerosol-CIMS). Tentative identifications of carbon-nitrogen species and a sulfur-containing compound were also made using Aerosol-CIMS. Aqueous solutions of methylglyoxal, with and without inorganic salts, exhibit significant surface tension depression. These observations add to the growing body of evidence that dicarbonyl compounds may form secondary organic material in the aerosol aqueous phase, and that secondary organic aerosol formation via heterogeneous processes may affect seed aerosol properties.

Síntese de fotoprotetores e sua imobilização em poli(metacrilato de metilo): um projeto integrado de química orgânica, química de polímeros e fotoquímica

Dibenzalacetone and other aldol condensation products are known sunscreens commonly used in cosmetics. This type of compounds can easily be prepared in an Organic Chemistry Lab by reaction of aldehydes with ketones in basic medium. These compounds can be incorporated in poly(methyl methacrylate) and used as UV light absorbers, for example in sunglasses. This project has the advantage of using inexpensive reagents which are readily available in Chemistry Laboratories. This experiment can also be a base starting point for discussions of organic, polymer and photochemistry topics.

Production of linear alkane via hydrogenative ring opening of a furfural-derived compound in supercritical carbon dioxide

A simple method has been described to accomplish the formation of linear alkane with >99% selectivity in supercritical carbon dioxide under very mild conditions using Pd/Al-MCM-41 catalyst. The linear alakne was formed through the hydrogenation and dehydration/hydrogenation of 4-5-(5-(hydroxymethyl)furan-2-yl)but-3-en-2-one, which is an aldol condensation product of 5-hydroxymethyl furfural and acetone.

Electric double layer capacitors with polymer hydrogel electrolyte based on poly(acrylamide) and modified electrode and separator materials

Activated carbon fiber cloths (AC) and hydrophobic microporous polypropylene (PP) membrane, both modified by acetone aldol condensation products, and filled with polymer hydrogel were used as electrodes, separator and electrolyte in electric double layer capacitors (EDLCs). Polymer hydrogel used was based on poly(acrylamide) (PAAM), KOH and water. Electrochemical characteristics of EDLCs were investigated by cyclic voltammetry and galvanostatic charge–discharge cycle tests and also by impedance spectroscopy, compared with a case of the capacitor with only a KOH aqueous solution used as an electrolyte. As a result, the capacitor with polymer hydrogel was found to exhibit higher capacitance than that with the KOH aqueous solution and an excellent high-rate dischargeability. The above results provide valuable information to explore novel composition of EDLCs.

Keggin-Type Heteropolyacids-Catalyzed One Pot Oxidation-Trimerization of Alcohols into 2,4,6-Trisubstituted-1,3,5-Trioxanes

The catalytic air oxidation-trimerization of alcohols was carried out with hetropolyacids. In the presence of hetropolyacid formation of cyclotrimers of alcohols and aldol condensation products was observed. The 1,3,5-trioxanes were major and aldol condensation compounds were minor products.

Features of reaction of aromatic nitro-substituted aldehydes with ketones on the matrix of 2(1H)-pyridone

Condensation of nitrobenzaldehydes with 3-acetyl-4,6-dimethyl-2(1H)-pyridone gives rise to chalcones with high yield. Condensation of the close analogs of 3-acetyl-4,6-dimethyl-2(1H)-pyridone containing ethyl and benzyl radical was established to give stable products of aldol condensation, the corresponding alcohols, under the same conditions.

Direct asymmetric aldol reaction of hydroxyacetone promoted by chiral tertiary amines

The tertiary amine-catalyzed direct asymmetric aldol reaction of hydroxyacetone with a variety of aromatic aldehydes is developed. Using 5–10 mol % of quinidine as catalyst, the direct aldol condensation products were obtained in reasonable yields and with asymmetric induction (up to 47% ee). The present approach is extended to asymmetric organocatalytic strategies for the preparation of 1,2-diols.

Biomimetic Chemoselectivity Control of Aldol Reactions

The synthesis and utilization of polymeric catalyst 1 bearing proline moieties as active sites is reported. This catalyst aggregate was applied successfully in aldol reactions of aldehydes and ketones in aqueous media. In a self-­aldol process of butanal, mainly reversibly formed β-hydroxyaldehyde 2 was obtained, whereas the formation of aldol condensation product 3 could be suppressed. These results were transferred to more complex dynamic catalytic cross-aldol reactions, giving rise to α,β-unsaturated ketones 4, favored over formation of self-condensation product 5. The likewise expected ketones 6 were not observed.

Hydride Migration from Silicon to an Adjacent Unsaturated Imino Carbon: Intramolecular Hydrosilylation

1,3-Hydride shift from silicon to an adjacent imino carbon (“intramolecular hydrosilylation”) is observed in the reaction of MeSiHCl2 with O-trimethylsilyl-N-(alkylidenimino)imidates [RC(OSiMe3)═NN═CR1R2; R = Me, Ph, CH2Ph, t-Bu; R1, R2 = Me (1), (CH2)n (9), Ph, H (14)], leading to pentacoordinate silicon complexes. The reaction proceeds further to rearrange to the tricyclic pentacoordinate complexes, observed previously as products of intramolecular aldol condensation of imine moieties residing on two chelate rings in the reactions of XSiCl3 (X = alkyl, aryl) and 1.

Accretion Reactions of Octanal Catalyzed by Sulfuric Acid: Product Identification, Reaction Pathways, and Atmospheric Implications

Atmospheric accretion reactions of octanal with sulfuric acid as a catalyst were investigated in bulk liquid-liquid experiments and gas-particle experiments. In bulk studies, trioxane, alpha,beta-unsaturated aldehyde, and trialkyl benzene were identified by gas chromatography-mass spectrometry as major reaction products with increasing sulfuric acid concentrations (0-86 wt%). Cyclotrimerization and one or multiple steps of aldol condensation are proposed as possible accretion reaction pathways. High molecular weight (up to 700 Da) oligomers were also observed by electrospray ionization-mass spectrometry in reactions under extremely high acid concentration conditions (86 wt%). Gas-particle experiments using a reaction cell were carried out using both high (approximately 20 ppmv) and low (approximately 900 ppbv) gas-phase octanal concentrations under a wide range of relative humidity (RH, from < 1% to 50%, corresponding to > 80 wt% to 43 wt% H2SO4) and long reaction durations (24 h). One or multiple steps of aldol condensation occurred under low RH (< 1% and 10%, > 80 wt% and 64 wt% H2SO4, respectively) and high octanal concentration (approximately 20 ppmv) conditions. No cyclotrimerization was observed in the gas-particle experiments even under RH conditions corresponding to similar sulfuric acid concentration conditions that favor cyclotrimerization in bulk studies. No accretion reaction product was found in the low octanal concentration (approximately 900 ppbv) experiments, which indicates that the accretion reactions are not significant as expected when the gas-phase octanal concentration is low. A kinetic analysis of the first-step aldol condensation product was performed to understand the discrepancies between the bulk and gas-particle experiments and between the high and low octanal concentrations in the gas-particle experiments. The comparisons between experimental results and kinetic estimations suggest that caution should be exercised in the extrapolation of laboratory experiment results to ambient conditions.

Convenient synthesis and unusual reactivity of 2-oxo-2 H,5 H-pyrano[3,2- c]chromenes

The reaction of 4-oxo-4 H-chromen-3-carbaldehydes with coumarin-4-acetic acids under the Perkin conditions follows an interesting pathway that involves aldol reaction and subsequent intramolecular lactonization to afford 2-oxo-2 H,5 H-pyrano[3,2- c]chromene skeleton. In contrast to chromone-3-carbaldehydes, the same reaction with chromone-2-carbaldehydes yielded only the aldol condensation product. The reaction was performed under thermal and microwave conditions. The reactivity of 2-oxo-2 H,5 H-pyrano[3,2- c]chromenes in water, alcohol and acetic acid was described.

Formation of Pyrazines and a Novel Pyrrole in Maillard Model Systems of 1,3-Dihydroxyacetone and 2-Oxopropanal

Alkylpyrazines are a very important class of Maillard flavor compounds, but their mechanism of formation is complex and consists of different pathways. The model reaction of 20 different amino acids with 1,3-dihydroxyacetone, as a precursor of 2-oxopropanal, was studied by means of SPME-GC-MS to investigate the involvement of the amino acid side chain in the substitution pattern of the resulting pyrazines. 2,5-Dimethylpyrazine was quantitatively the most important pyrazine formed from all of the amino acids. The amino acid side chain is not involved in its formation. The substituents of other less abundant pyrazines resulted mainly from the incorporation of the Strecker aldehyde or aldol condensation products in the intermediate dihydropyrazine. The importance of different reaction mechanisms was evaluated, taking into account the pattern of pyrazines identified. In the solvent extracts of aqueous model reactions of 2-oxopropanal with amino acids, the main reaction product was not a pyrazine but a novel pyrrole. This pyrrole was identified as 2,5-diacetyl-3-methyl-1 H-pyrrole by means of spectral analysis, secured by chemical synthesis. A reaction mechanism for its formation was proposed and evaluated. The influence of various reaction conditions on the formation of 2,5-diacetyl-3-methyl-1 H-pyrrole and 2,5-dimethylpyrazine in the model reaction of alanine with 2-oxopropanal was studied. These results underscore the importance of the ratio of the different reagents and the presence of water in the resulting flavor formation in the Maillard reaction.

Stereoselective synthesis of highly enantioenriched 3-methyl-2-cyclohexen-1-ones possessing an asymmetric quaternary carbon as C-4 or C-6: a sugar template approach

The 1,4-addition of the enolate generated from α-methylated acetoacetate incorporated at C-4 of methyl 6-deoxy-2,3-di- O-( tert-butyldimethylsilyl)-α- d-glucopyranoside to methyl vinyl ketone, followed by aldol condensation of the resulting 1,4-addition product under two base-mediated conditions, provided 4-O-functionalized d-glucose derivatives with high diastereoselectivity. These products install a 3-methyl-2-cyclohexen-1-one-4- (or -6-) carboxylic acid as the O-4 ester, in which C-4 or C-6 is an asymmetric quaternary carbon. Removal of the sugar template from those aldol condensation products provided synthetically useful 3,6-dimethyl-2-cyclohexen-1-one-6-carboxylic acid and 3,4-dimethyl-2-cyclohexen-1-one-4-carboxylic acid derivatives both in high enantioenriched forms.

Synthesis and Characterization of Aldol Condensation Products from Unknown Aldehydes and Ketones

An experiment for the undergraduate chemistry laboratory in which students perform the aldol condensation on an unknown aldehyde and an unknown ketone is described. The experiment involves the use of techniques such as TLC, column chromatography, and recrystallization, and compounds are characterized by 1H NMR, GC–MS, and FTIR. This experiment provides the students with a thorough exercise in the practical aspects of organic chemistry. It requires students to think like researchers and allows them the opportunity to independently apply previously learned techniques in the laboratory.

Methoxycarbonylation of ketones with dimethyl carbonate over solid base

The methoxycarbonylation of various ketones with dimethyl carbonate was carried out in the presence of solid base catalysts. The results showed that the reaction scope seemed to be limited to the ketones with Hα and the main by-products were methylation and aldol condensation products. The reactivity of aliphatic and aromatic ketones for the methoxycarbonylation was closely related to their acidities. Basic catalysts were supposed to activate ketones via the abstraction of Hα by base sites. As a result, solid base with moderate strength such as MgO facilitated the reaction.