Novel photopolymerizations initiated by alkyl radicals generated from photocatalyzed decarboxylation of carboxylic acids over oxide semiconductor nanoparticles: Extended photo-Kolbe reactions

Polymerizations of vinyl acetate are photocatalyzed by TiO₂ nanoparticles in presence of carboxylic acids including propionic acid, n-butyric acid and pivalic acid. Nuclear magnetic resonance (NMR) analysis using ¹³C-labeled n-butyric acid as the probing molecule demonstrates that the polymerization of vinyl acetate is initiated by alkyl radicals generated from photocatalytic decarboxylation of the carboxylic acid. A universal mechanism is established with extending the photo-Kolbe reaction from acetic acid to the carboxylic acids with longer chains. Kinetics studies find that n-butyric acid has higher initiation rate than acetic acid, indicating more efficient decarboxylation for butyric acid than acetic acid in their aqueous solutions. It is proved that carboxylates participate in the decarboxylation. Attenuated total reflection Fourier-transform infrared (ATR-FTIR) spectra are obtained with aqueous solutions of the carboxylic acids in contact with a layer of the TiO₂ nanoparticles, and the observations are discussed with respect to the interaction between the TiO₂ and carboxylic acids.     

Improved liquid chromatography/mass spectrometric analysis of low molecular weight carboxylic acids by ion exclusion separation with electrospray ionization

An improved, simple and sensitive analytical method for low molecular weight organic acids has been developed. A mixture of acetic, propionic, butyric, glycolic, lactic, 2-hydroxybutyric, malonic, succinic, glutaric, tartaric and citric acids was separated on a semi-rigid styrene-divinylbenzene copolymer-based H-type cation-exchange resin (ULTRON PS-80H) based on an ion exclusion chromatographic (IEC) mechanism, with detection using electrospray ionization mass spectrometry (ESI-MS). Formic or acetic acid was used as a mobile phase to separate the carboxylic acids within 15 min. For liquid chromatography/mass spectrometry (LC/MS), the ESI interface was used in both positive and negative ionization mode. ESI produced reasonable signals from positive ions, [M+NH(4)](+), of acetic, propionic and butyric acids and from negative ions, [M-H](-), of glycolic, lactic, 2-hydroxybutyric, malonic, succinic, glutaric, tartaric and citric acids. The effects of ionization parameters, source temperature, capillary voltage and cone voltage, on sensitivity and linearity were examined. Linear plots of peak area versus concentration were obtained over the range 0.1-20 ppm for MS detection. The detection limits of the target carboxylic acids calculated at signal-to-noise (S/N) ratio of 3 ranged from 9 to 59 ppb. The reproducibility of retention times and peak areas were 0.55-1.25 and 0.85-2.45%, respectively.     

The Effect of Iodide Ion in Phase-Transfer Catalytic Syntheses of Benzyl Esters

In order to examine the effect of iodide ions on reaction catalyzed by phase-transfer technique, we made kinetic studies, under the influence of added Na1, on the synthesis of benzyl esters from benzyl chloride and sodium carboxylate. These carboxylates include sodium acetate, sodium benzoate, sodium salicylate and sodium formate; the catalyst was a quaternary ammonium salt. The results reveal that iodide ions at a suitable concentration accelerate the reaction, whereas iodide ions in excess poison the catalyst. The optimum concentration varies with the reaction system. This critical concentration depends upon the distribution coefficient of the intermediates formed in the reactions.     

Transport and separation of carboxylic acids through bulk liquid membranes containing tributylamine

In this study, transport and separation of carboxylic acids (formic, acetic, propionic, and butyric acids) from their aqueous solutions through bulk liquid membrane (BLM) containing tributylamine (TBA) and the parameters affecting the transport were investigated. The influence of the parameters on the separation process such as the stirring of membrane phase, the stripping phase type and concentration, the feed phase type, and the feed:membrane:stripping phase ratio (F/M/S phase ratio) were examined. In the experiments, 10% (w/w) acid solutions (formic, acetic, propionic, and butyric acids) were used as the feed phase, different concentrations of NaOH solutions within the range of 0–2?N were used as the stripping phase, and 0.5?mol/lt TBA, dissolved in oleyl alcohol, was used as the membrane phase. It was determined that the stirring of the membrane phase increases the transport of acids. In the case of 2 N NaOH solution in the stripping phase and F/M/S phase ratio 1:2:1 gave the best recovery (96.75%) for butyric acid. It was observed that BLM was an effective technique for the separation of carboxylic acids from aqueous solutions.     

Complexation of carboxylic acids and anions by alpha and beta cyclodextrins

A pH potentiometric method is used to measure complex formation constants of aqueous alpha- and/or beta-cyclodextrin with several carboxylic acids and carboxylate anions: butyric acid/butyrate; valeric acid/valerate; hexanoic acid/hexanoate; octanoic acid/octanoate; decanoic acid/decanoate; cyclohexanecarboxylic acid/cyclohexanecarboxylate and benzoic acid/benzoate. Standard enthalpies and entropies of complex formation are calculated from the temperature dependencies of the equilibrium constants. These thermodynamic parameters of the alpha-cyclodextrin complexes largely conform to a correlation based on complexes with other substrate species previously reported. Both standard enthalpies and entropies of formation of beta-cyclodextrin complexes are found to be more positive than the corresponding complexes of alpha-cyclodextrin with the same substrates. These observations lead to insights into the bonding mechanism of cyclodextrin complexation.     

Extraction of copper(II) carboxylates with chloroform under substoichiometric conditions

The features are considered of binding carboxylic acids (HR) as dimeric solvated copper(II) complexes at the copper(II) extraction with chloroform under substoichiometric conditions, with excess of the metal ion in the aqueous phase. The fundamental difference in the optimization of the quantitative extraction of copper(II) in the form of any carboxylate with a maximum ratio of Cu:R and the total binding with carboxylic acids to form the copper complex of the minimum stoichiometry was noted. It was found that quantitative binding of HR occurred at the extraction of mixed-ligand acetate-carboxylate copper(II) complexes without control over the aqueous phase acidity when acetic acid medium or copper(II) acetate was used, but not copper chloride, nitrate, perchlorate, or sulfate. The possibility of determination by extraction-photometric method by the color of the Cu(II) complex was shown that was suitable only to those carboxylic acids, whose logarithm of the partition coefficient in the water-chloroform mixture was higher than three.     

One-step, nonenzymatic synthesis of O-acetyl-ADP-ribose and analogues from NAD and carboxylates

O-Acetyl-ADP-ribose (OAADPR) is a metabolite produced from nicotinamide adenine dinucleotide (NAD) as a product of sirtuin-mediated protein deacetylation. We present here a simple, one-step, nonenzymatic synthesis of OAADPR from NAD and sodium acetate in acetic acid. We extended the reaction to other carboxylic acids, demonstrating that the reaction between NAD and nonaqueous carboxylate buffers produces mixtures of the corresponding 2'- and 3'-carboxylic esters.     

Über Kupfer(I)-carboxylate und Chlorocuprate(I)

In mixtures of 7 vol. acetonitrile and 3 vol. acetic acid, solutions or suspensions of copper(II) acetate can be reduced with hydrazine hydrate to solutions of copper(I) acetate. In this way, purely white copper(I) acetate can be isolated. Other copper(I) carboxylates can be prepared by reduction of copper(II) carboxylates or by reaction of solid carboxylic acids with copper(I) acetate. By adding acetyl chloride to solutions of copper(I) acetate in acetonitrile/acetic acid mixtures, solutions of chlorocuprates(I) are formed. From these, highly pure copper(I) chloride can be obtained. By adding alkali acetate or tetramethyl ammonium chloride to solutions of chlorocuprates(I), the pure compounds Cs₃[Cu₂Cl₅], Rb₂[CuCl₃] and NMe₄[Cu₂Cl₃] were obtained.     

Adsorption of gaseous formaldehyde and carboxylic acids by ammonium-ion-exchanged alpha-zirconium phosphate

Ammonium-ion-exchanged alpha-Zr(HPO(4))(2)H(2)O (alpha-ZrP) was obtained as a single phase with the interlayer distance of 9.4 A by the ion-exchange of proton with ammonium ion. The ammonium ion-exchanged alpha-ZrP could adsorb ill-smelling gases, such as formaldehyde and carboxylic acids (formic acid, acetic acid, propionic acid, and butyric acid). The adsorption amounts of carboxylic acids increased in the order, butyric acid相似文献   

The Effect of Acid Strength on the Mitsunobu Esterification Reaction: Carboxyl vs Hydroxyl Reactivity

In the presence of carboxylic acids, the adduct formed between triphenylphosphine and diisopropyl azodicarboxylate reacts to form mono- and bis-acylated hydrazides and the carboxylic acid anhydrides. These products are formed via attack of the carboxylate on the triphenylphosphonium group of the adduct, with weaker acids reacting much faster than stronger acids. This provides an explanation for the observation in the literature that acids stronger than acetic acid, such as 4-nitrobenzoic acid and chloroacetic acid, provide better yields in esterification reactions, since reaction of the alcohol with the phosphonium group of the adduct is more rapid than the competing reaction of the carboxylate for the phosphonium group.     

PHOTOCHEMICAL REACTIONS OF THYMINE WITH CARBOXYLIC ACIDS. A MODEL FOR NUCLEIC ACID-PROTEIN PHOTOCROSSLINKING

When nucleic acid bases are UV-irradiated in the presence of carboxylic acids or carboxylate anions new photoproducts are formed as compared to the bases irradiated in the absence of carboxylic acids. The behavior of thymine and thymidine has been examined in detail. At least four photoproducts are formed in the presence of propionic acid and three in the presence of butyric acid. None of them appears to be a cyclobutyl dimer. From the concentration dependence of the rate of photoproduct formation it is concluded that the reactive excited species is the first excited singlet state of thymine. When ¹⁴C-labelled thymine is irradiated in the presence of polyglutamic acid an important part of the radioactive material is covalently linked to the polymer. Photochemical reaction of thymine with glutamic (or aspartic) acid could thus induce crosslinks between proteins and nucleic acids. It is also shown that these photoproducts are stable under usual conditions of acidic hydrolysis of UV-irradiated DNA.     

硫酸氢钠催化合成羧酸苄酯

讨论了一水硫酸氢钠催化合成乙酸苄酯的条件。羧酸、苄醇和硫酸氢钠的质量比为 3∶2∶0 .1 45 ,以环己烷为溶剂 ,进行回流分水 ,合成了甲酸苄酯、乙酸苄酯、丙酸苄酯和丁酸苄酯 ,其收率为 68.5 %～ 84.1 %     

The influence of concentration and anion nature on the support effect

The kinetic of decomposition of copper formate, acetate, propionate and butyrate under non-isothermal conditions was studied. The support materials were carborundum and silica and the concentrations of the supported compounds were 15, 20, 25 and 30 mass%. In order to avoid the effects of thermal gradients and dilution, a series of parallel samples of carboxylate/support mixtures with the same concentration were studied. The support effect was estimated by the difference between the isokinetic temperature of the supported, respectively mixted carboxylate series, and is discussed in connection with the precursor concentration and the nature of the carboxylate anion. The suggestion of considering the thermodynamic activation function instead of the Arrhenius parameters for discussion on compensation effect was argued. This revised version was published online in July 2006 with corrections to the Cover Date.     

Determination of sulfophenyl carboxylic acids in agricultural groundwater samples by CE with ultraviolet absorption detection

An analytical method for the determination of six sulfophenyl carboxylic acids, namely (p-sulfophenyl)acetic, 2-(p-sulfophenyl)propionic, 2-(p-sulfophenyl)butyric, 3-(p-sulfophenyl)butyric, 4-(p-sulfophenyl)butyric, and 5-(p-sulfophenyl)valerianic acid, in agricultural irrigation water samples was developed. It involves an SPE procedure, an on-line preconcentration normal stacking mode and subsequent separation and determination using CE with UV detection (CE-UV). p-Sulfobenzoic acid was used as internal standard. The compounds were separated with an uncoated capillary and a 25 mM ammonium acetate/acetic acid buffer solution (pH 5.5) with 2-propanol (30% v/v) and 0.75 mM CTAB. Analyses were run at -25 kV, 25 degrees C, and 100 s of hydrodynamic injection with UV detection at 225 nm. Quantification limits found ranged between 4 and 6 ng/mL. The proposed method was validated using a recovery assay. It was satisfactorily used for the determination of these compounds in groundwater samples to track down the biodegradation of linear alkylbenzene sulfonates in an agricultural soil from the fertile plain of Granada (Spain).     

Untersuchungen zur Trennung der Seltenerdmetalle durch Ionenaustausch, 5. Mitt.: Über die Trennung von Dysprosium und Yttrium

Zusammenfassung Die Abhängigkeit der effektiven Höhe eines theoret. Bodens von der Strömungsgeschwindigkeit wurde für die Trennung von Dy und Y durch Elution von Dowex 50W-Kationenaustauscher mit Acetat-Puffern untersucht.Der beobachtete Einfluß des Vernetzungsgrades des Austauschers wird in Beziehung zur Harzselektivität und dem Komplexgleichgewicht in Lösung gedeutet.Die Elutionswirksamkeit von Ameisen-, Essig-, Propion-, Butter- und Isobuttersäure wurde bei gleicher molarer Konzentration und Pufferzusammensetzung verglichen. Die Reihenfolge des Elutionsvermögens ist: Acetat Propionat > Isobutyrat > Butyrat > Formiat für Dy, und: Propionat > Acetat > Isobutyrat > Butyrat > Formiat für Y.

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The dependence of the effective height of a theoretical plate from the flow rate was studied for the separation of Dy and Y by elution with acetate buffers from Dowex 50 W cation-exchange resins.The observed influence of the degree of cross-linking of the resin is discussed in relation to resin selectivity and complex equilibria in solution.The elution efficiency of formic, acetic, propionic, butyric, and isobutyric acid was compared at identical molar concentration and buffer composition. The order of elution power is: acetate propionate > isobutyrate > butyrate > formate for Dy, and: propionate > acetate > isobutyrate > butyrate > formate in case of Y.

     

Die Oxydation von Alkoholen mit Bleitetraacylaten; Einfluss der Acylreste bei der thermischen Reaktion

The competitive thermal oxidation of a 6β-hydroxy steroid (to a 6β, 19-ether) and the thermal oxidative decarboxylation of various carboxylic acids by lead⁴⁺ was investigated. The alcohol oxidation is faster than acetate and benzoate oxidation, about as fast as the oxidative decarboxylation of higher primary carboxylic acids (propionic, butyric acid), and much slower than the oxidative decarboxylation of secondary and tertiary carboxylic acids.     

The Solid-state Structures of a Non-hydrated Yttrium Carboxylate and a Yttrium Carboxylate Hemihydrate Obtained by Reaction of Yttrium Alkoxides with Carboxylic Acids

The yttrium carboxylates Y(methacrylate)₃ and Y(acetate)₃·0.5 H₂O were prepared by reaction of Y(OCH₂CH₂OMe)₃ with methacrylic or acetic acid and characterized by X-ray structure analyses. Both carboxylates have chain structures with both bridging and chelating-bridging carboxylate ligands. In Y(acetate)₃·0.5 H₂O, every second yttrium atom is nine-coordinate due to the additional coordination of a water molecule.     

Enantio- and chemoselective differentiation of protected α-amino acids and β-homoamino acids with a single copper(II) host

The association between an achiral copper(II)-containing host 1 and chiral carboxylates has been expanded beyond previous studies to new chiral carboxylate guests, both α-amino acids and β-homoamino acids. The observed exciton-coupled circular dichroism (ECCD) signals for the enantiomers of each carboxylate were equal and opposite, and these signals differed in size and shape between the individual amino acids. Linear discriminant analysis (LDA) was applied as a statistical analysis technique to differentiate the amino acids, both enantioselectively and chemoselectively, giving the absolute configuration and identity of the amino acid. The identity of each of the α-amino acids and β-homoamino acids were determined independently by LDA, and then the two were considered together. Each of these analyses showed good differentiation of the amino acid guests with the use of only one host molecule.     

Carbodeoxygenation of Biomass: The Carbonylation of Glycerol and Higher Polyols to Monocarboxylic Acids

Glycerol is converted to a mixture of butyric and isobutyric acid by rhodium‐ or iridium‐catalysed carbonylation using HI as the co‐catalyst. The initial reaction of glycerol with HI results in several intermediates that lead to isopropyl iodide, which upon carbonylation forms butyric and isobutyric acid. At low HI concentration, the intermediate allyl iodide undergoes carbonylation to give vinyl acetic acid and crotonic acid. Higher polyols C_nH_n+2(OH)_n are carbonylated to the corresponding C_n+1 mono‐carboxylic acids.     

Effect of solute hydrophobicity on phase behaviour in solutions of thermoseparating polymers

 Two-phase systems consisting of a polymer rich phase and polymer depleted phase, where the polymer is either ethyl(hydroxy ethyl)cellulose (EHEC) or Ucon (a random copolymer of ethylene oxide and propylene oxide), have been studied. Both of these polymers can be separated from an aqueous solution by either temperature increase or addition of cosolutes. The polymers are thermoseparating and phase separate in water solutions at the cloud point temperature. Two types of EHEC have been studied: one with a cloud point at 60 °C and the other at 37 °C. The Ucon polymer used in this study has a cloud point at 50 °C. Ternary phase diagrams of polymer/water/cosolute systems have been investigated. When a strongly hydrophilic or hydrophobic cosolute is added to an EHEC- or Ucon–water solution, a phase separation occurs already at, or below, room temperature. As cosolutes, hydrophobic molecules like phenol, butyric and propionic acid, and hydrophilic molecules like glycine, ammonium acetate, sodium carboxylates (acetate to valerate), were studied. The polymer rich phase formed when mixing polymer, water and cosolute was strongly enriched or depleted with hydrophobic or hydrophilic cosolutes, respectively. The two phase region increased for propionic acid, butyric acid and phenol as a result of increased cosolute hydrophobicity. The opposite occurred in the series sodium acetate, sodium butyrate and sodium valerate. The effect of temperature on the phase behaviour has also been investigated. Model calculations based on Flory–Huggins theory of polymer solutions are presented, in form of a phase diagram, which semiquantitatively reproduce some experimental results. Received: 5 July 1996 Accepted: 4 November 1996