Use Of Acetaldehyde Research Articles

Thermodynamically Spontaneous Reactions and Use of Acetaldehyde as Fuel in Direct Ethanol Fuel Cells

A set of fuel cells was fabricated using a cation exchange membrane (CEM), and ethanol and acetaldehyde were used as fuels for the cells. Spontaneous reactions in the fuel cells were studied under various conditions such as excess oxygen at the cathode and at higher temperatures without application of an external voltage and without forcing an external current. When acetaldehyde was used as a fuel, the current in the circuit and the concentration of acetic acid (product of the fuel cells) were not influenced by the experimental conditions. On the other hand, when ethanol was used as a fuel, the current in the circuit and the concentration of acetic acid were influenced by the experimental conditions. It was thus concluded that ethanol is oxidized directly to acetic acid without oxidation to acetaldehyde and then to acetic acid. The calculated ΔG for possible half reactions in direct ethanol fuel cells (DEFCs) with CEM and AEM (anion exchange membrane) suggests that a reliable AEM should be developed for the further development of DEFCs.

Acetaldehyde as a Food Flavoring Substance: Aspects of Risk Assessment.

The Senate Commission on Food Safety (SKLM) of the German Research Foundation (DFG) has reviewed the currently available data in order to assess the health risks associated with the use of acetaldehyde as a flavoring substance in foods. Acetaldehyde is genotoxic in vitro. Following oral intake of ethanol or inhalation exposure to acetaldehyde, systemic genotoxic effects of acetaldehyde in vivo cannot be ruled out (induction of DNA adducts and micronuclei). At present, the key question of whether acetaldehyde is genotoxic and mutagenic in vivo after oral exposure cannot be answered conclusively. There is also insufficient data on human exposure. Consequently, it is currently not possible to reliably assess the health risk associated with the use of acetaldehyde as a flavoring substance. However, considering the genotoxic potential of acetaldehyde as well as numerous data gaps that need to be filled to allow a comprehensive risk assessment, the SKLM considers that the use of acetaldehyde as a flavoring may pose a safety concern. For reasons of precautionary consumer protection, the SKLM recommends that the scientific base for approval of the intentional addition of acetaldehyde to foods as a flavoring substance should be reassessed.

Comparative analysis of the qualitative characteristics of formaldehyde and acetaldehyde resins based on styrene-modified oil shale alkylresorcinols

Reducing the amount of volatile compounds in alkylresorcinol-aldehyde resins, reducing the impact of their components on the environment, and improving their performance can be achieved by replacing formaldehyde with acetaldehyde and by preliminary aralkylation of the resorcinol components of the raw material. To prove this, a comparative analysis of the properties of resins synthesized based on oil shale alkylresorcinols pre-treated with styrene, formaldehyde, or acetaldehyde was carried out. The effects of the molar ratio of feedstock/aldehyde and the amount of catalyst on the yield and characteristics of the resins were considered. Both individual alkylresorcinols (R, 5-MR, 2.5-DMR) and industrial fractions (REZOL, HONEYOL) were used as the raw materials. The following indicators were used to compare the obtained resins: softening point, ash content, coke number, moisture content, volatile substances, and solubility in organic solvents. The thermal properties of the resins were studied by TG/DTG/DTA in inert and oxidative atmosphere. Qualitative and quantitative analyses of resins and distillates for the content of unreacted resorcinol, individual alkylresorcinols, and styrene were carried out using iodometry, thin-layer chromatography (TLC), and gas chromatography (GC). It has been shown that the use of acetaldehyde makes it possible to obtain resins with the stated characteristics. The formaldehyde (SF) and acetaldehyde (SAc) resins obtained consist of oligomers with different chain lengths. Synthesized SAc resins are solids with a softening point of 51 °C–103 °C. Resins are soluble in acetone, EtOH, acetonitrile, and THF, and insoluble in benzene. SAc resins contain 3–4 times less unreacted original resorcinol components compared to SF resins. The conversion of styrene in the synthesis of Rez100SF resins was 42 wt%, Rez100SAc and Hon100SAc are 98 and 97 wt%, respectively. A comparative analysis of resins synthesized using acetaldehyde instead of formaldehyde helped identify both the advantages and disadvantages of the proposed synthesis variation.

Stellungnahme zu Acetaldehyd als Aromastoff: Aspekte der Risikobewertung

ZusammenfassungAcetaldehyd kommt natürlicherweise in zahlreichen Lebensmitteln vor und wird aufgrund seines fruchtigen Aromas auch als Aromastoff eingesetzt. Die Internationale Agentur für Krebsforschung (IARC) stufte Acetaldehyd als möglicherweise krebserregend sowie in Verbindung mit der oralen Aufnahme über alkoholhaltige Getränke als humanes Kanzerogen ein. Vor diesem Hintergrund stellt sich die Frage, ob die Verwendung von Acetaldehyd als Aromastoff weiterhin vertretbar ist. Die Senatskommission zur gesundheitlichen Bewertung von Lebensmitteln (SKLM) der Deutschen Forschungsgemeinschaft (DFG) hat die aktuelle Datenlage zur Bewertung des gesundheitlichen Risikos der Verwendung von Acetaldehyd als Aromastoff geprüft und hierzu eine Stellungnahme verabschiedet. Demnach kann die Frage, ob Acetaldehyd nach oraler Exposition in vivo gentoxisch und mutagen wirkt, derzeit nicht abschließend beantwortet werden. Weiterhin ist auch unklar, welchen Beitrag die Verwendung von Acetaldehyd als Aromastoff zur Gesamtexposition des Verbrauchers gegenüber Acetaldehyd leistet. Eine wissenschaftliche Bewertung des gesundheitlichen Risikos der Verwendung von Acetaldehyd als Aromastoff ist daher weiterhin nicht möglich. Die SKLM weist darauf hin, dass aufgrund des gentoxischen Gefährdungspotenzials sowie zahlreicher Datenlücken, die für eine vollständige Risikobewertung geschlossen werden müssen, Zweifel an der Sicherheit von Acetaldehyd als Aromastoff bestehen. Nach Ansicht der SKLM sollte der gezielte Zusatz von Acetaldehyd als Aromastoff aus Gründen des vorsorgenden Verbraucherschutzes neu beurteilt werden.

Organocatalytic Stereoselective Addition of Aldehydes to Acylquinolinium Ions

A direct and simple activation of quinolines, without isolating unstable intermediates, or using isolated N,O‐acetals in the presence of Lewis or Brønsted acids, is described. The procedure is quite straightforward and allows the addition in a stereoselective manner of different aldehydes to various differently substituted quinolines. The desired products were obtained in 28–76 % yields, with dr values up to 83:17 in favor of the syn isomer, and up to 99 % ee. Studies towards the use of acetaldehyde were also performed with different catalysts and the addition was promoted affording the desired product in 62 % yield with 46 % ee. Finally, deprotection and chemical transformations of the enantioenriched adducts were performed.

ChemInform Abstract: Acetaldehyde: A Small Organic Molecule with Big Impact on Organocatalytic Reactions

AbstractReview: [61 refs.

Acetaldehyde: A Small Organic Molecule with Big Impact on Organocatalytic Reactions.

Stereocontrolled formation of carbon-carbon and carbon-heteroatom bonds through asymmetric organocatalysis is a formidable challenge for modern synthetic chemistry. Among the most significant contributions to this field are the transformations involving the use of acetaldehyde or α-heteroatom-substituted acetaldehydes for constructing valuable synthons (e.g., amino acid derivatives and hydroxycarbonyl). In this Minireview, versatile (enantioselective) organocatalytic transformations are discussed.

P-78D-PENICILLAMINE PREVENTS THE ALCOHOL DEPRIVATION EFFECT IN THE OPERANT SELF-AMINISTRATION PARADIGM

Although pharmacological treatments for relapse prevention have experienced some progress, their general effectiveness can be considered low and the problem could not be considered solved. In recent years, our group has explored the use of acetaldehyde (ACD) sequestering agents as a new and very promising strategy. These agents, such as …

ChemInform Abstract: Acetaldehyde in Asymmetric Organocatalytic Transformations

AbstractReview: [recent developments in the use of acetaldehyde as substrate in various organo‐catalyzed organic transformations and its application in the synthesis of bioactive molecules; 67 refs.

Acetaldehyde in asymmetric organocatalytic transformations

This review summarize both the recent developments in the organocatalysed use of acetaldehyde as a substrate in various organic transformations and its application in the synthesis of bioactive molecules.

Efficacy of d-penicillamine, a sequestering acetaldehyde agent, in the prevention of alcohol relapse-like drinking in rats

Nowadays, very few approved anti-relapse treatments for alcoholism exist, and their overall efficacy can be considered moderate. An exciting rationale drug development opportunity for the treatment of chronic alcoholism is the use of acetaldehyde sequestering agents. Although these compounds are able to attenuate or prevent most of the behavioral and neurochemical effects of ethanol, the efficacy of acetaldehyde sequestration, by using agents such as D-penicillamine (DP), in relapse prevention has not been studied yet. The aim of this study was to analyze the effects of DP treatment on the alcohol deprivation effect (ADE) in long-term ethanol-experienced rats as a model of relapse behavior and measure drug plasma and brain levels during treatment. Rats were subcutaneously implanted with mini-osmotic pumps delivering 0, 0.25, or 1mg/h of DP during 1 week. The efficacy to prevent ADE was determined. DP plasma and brain levels achieved during its subcutaneous administration were measured. In a second experiment, animals received bilateral infusions of 0 or 1.5μg/h of DP directly into pVTA, and the appearance of ADE was evaluated. One milligram per hour, but not 0.25mg/h, DP infusion prevented ADE and reduced the total ethanol preference in animals. DP plasma concentrations associated with ADE suppression were around 3-4μg/ml, and brain DP levels in these conditions were about 2-3% of those found in plasma. Intra-pVTA DP administration also suppressed ADE. DP is able to prevent alcohol-relapse-like drinking in rats suggesting that this drug may be a useful new tool in the management of relapse in alcohol-dependent patients.

Biooxidation of Primary Alcohols to Aldehydes through Hydrogen Transfer Employing Janibacter terrae

AbstractChemoselective oxidations still represent a challenge for chemists. Lyophilized cells of Janibacter terrae were employed for the chemoselective oxidation of primary alcohols to the corresponding aldehydes by hydrogen transfer with the use of acetaldehyde as the hydrogen acceptor. Secondary alcohol moieties were transformed at a much slower rate. The substrate spectrum encompasses substituted benzyl alcohols, whereby substrates with a substituent in the meta position were well tolerated, whereas only very small substituents were tolerated in the ortho position. Furthermore, n‐alkanols and allylic alcohols were transformed with good conversions. The biocatalyst was compatible with DMSO as a water miscible organic solvent up to 30 % v/v.

The use of acetaldehyde to control carnation flower longevity

Acetaldehyde is the causal agent of ethanol-induced longevity increases in carnation cut flowers. It increases the vase life of cut carnation flowers by at least 50%. The capacity of acetaldehyde to regulate carnation flower senescence was therefore investigated. Ethylene formation was reduced or inhibited as a result of acetaldehyde application. There was, however, no prevention of ethylene action. The morphological development of the ovary was also inhibited, thus eliminating the movement of metabolites from the petals. The potential use of acetaldehyde as a post-harvest treatment is however impractical, due to the inefficiency of pulse treatments and ineffectiveness in preventing the action of exogenous ethylene.

Inactivation of Cu,Zn-superoxide dismutase by free radicals derived from ethanol metabolism: A γ radiolysis study

The reactions of free radicals derived from ethanol metabolism with Cu,Zn SOD were studied. 1-Hydroxyethyl radicals were generated by γ radiolysis of a N 2O-saturated ethanolic solution (10 -2 M) in phosphate buffer (10 -3 M, pH 7.4). To generate acetyl radicals by γ radiolysis, we used ethylene glycol (10 -2 M) in phosphate buffer (10 -3 M, pH 7.4). This allows us to avoid the use of acetaldehyde, which may be toxic toward various cellular constituents. We have previously reported that HO radicals reacting with either acetaldehyde or ethylene glycol produce the same free radicals (Santiard et al., 1991, J. Chim. Phys. 88, 967–976). The rate constant of reaction of 1-hydroxyethyl free radicals with Cu,Zn-SOD was measured separately by competition kinetics with the spin trapping agent α-(4-pyridyl 1-oxide) N-terbutylnitrone (4-POBN), after having measured the rate constant of scavenging of 1-hydroxyethyl free radicals by 4-POBN in the absence of SOD. We found k 1 (4-POBN + 1-hydroxyethyl radical) = 4.2 10 5 M −1 s −1 and k R (SOD + 1-hydroxyethyl radical) = 6.8 10 5 M −1 −1). 1Hydroxyethyl or acetyl radicals produced dose-dependent Cu,Zn-SOD inactivation. The inactivation rate constant of Cu,Zn-SOD by 1-hydroxyethyl radicals is k 1 = 1.13 10 4 M −1 s −1 Free radicals derived from ethanol metabolism can thus react SOD leading to enzyme inactivation, besides the fact that the reactivities of 1-hydroxyethyl radicals with 4-POBN and with proteins such as Cu,Zn SOD are of the same order of magnitude could explain the difficulties to trap in vivo these radicals.

Induction of diamine oxidase activity in rat kidney during compensatory hypertrophy

Diamine oxidase (EC 1.4.3.6) activity, measured as [ 14C]Δ 1-pyrroline formation from [ 14C] putrescine, was studied in homogenates of rat kidney during compensatory hypertrophy after unilateral nephrectomy. Acetaldehyde and to a lesser degree phenobarbital, at concentrations which did not modify the activity of a preparation of hog kidney diamine oxidase, increased Δ 1-pyrroline formation in kidney homogenate, which suggests that aldehyde-metabolizing enzymes present in this tissue may interfere with yield of Δ 1-pyrroline and that the use of acetaldehyde may give better information on kidney diamine oxidase activity. Other inhibitors of aldehyde-metabolizing enzymes such as chloral hydrate, disulfiram, and pyrazole cannot be used for diamine oxidase determination since they stimulated or depressed this enzyme activity. In rat kidney undergoing compensatory hypertrophy the levels of putrescine, spermidine, and spermine increased rapidly and were followed by an increase in diamine oxidase activity that presented a first peak on day 2 and a second peak on day 6. The administration of cycloheximide or actinomycin D to nephrectomized rats prevented the increase in diamine oxidase activity. The study of the turnover rate of diamine oxidase with cycloheximide demonstrated that the half-life of this enzyme was about 14 h in normal and hypertrophic kidney. These results suggest that the increase in diamine oxidase activity in renal hypertrophy was due to the synthesis of new enzyme rather than to a slowing of its degradation.

An experimental simulation of los angeles reactive pollutant program (LARPP) operation 33—part I. experimental simulation in an outdoor smog chamber

The reactions occurring along LARPP operation 33 were simulated in the UNC outdoor smog chamber. Variable rates of dilution and computer-controlled precursor injections were determined from analysis of the mixed region along the operation's trajectory. Also, the production of ozone equivalent to LARPP by static systems (initial injection only) and the effect of the products of the previous day's reactions were investigated. The difference between simulation and LARPP O 3 concentrations for one run was within the limits of measurement error at the end of the experiment, although simulation O 3 production lagged behind that of LARPP earlier. The other simulation produced 6pphm less O 3 than LARPP. The inability to simulate the effects of day-old materials and the use of acetaldehyde to represent all aldehydes were judged to reduce O 3 production in the chamber relative to the atmosphere. In static experiments, one-half to two-thirds of the LARPP morning nonmethane hydrocarbons were found to have roughly equal O 3 production potential to LARPP. Both simulation and static runs support the hypothesis that, under similar meteorological condition, the ozone produced is more closely related to the total precursor input divided by the total volume of air into which it is mixed than to initial concentrations.

The mechanism of the acetaldehyde pyrolysis

Previous work on the acetaldehyde pyrolysis is shown to be vitiated by the presence, in the acetaldehyde, of impurities, mainly ethanol and crotonaldehyde. The reaction has been reinvestigated with the use of acetaldehyde, prepared from paraldehyde, which is free from these and other impurities. On the basis of a study of the kinetics of formation of the major products (methane and carbon monoxide) and of a number of minor products (hydrogen, acetone, propionaldehyde, ethane and ethylene) a reaction mechanism is proposed. This includes all of the reactions in the original Rice-Herzfeld scheme, together with a number of other elementary processes, in particular CH 3 + CH 3 CHO → CH 4 + CH 2 CHO. The decomposition of the radical CH 2 CHO into CH 2 CO and H provides an additional source of hydrogen, the rate of production of which is therefore not a measure of the rate of the initiation process. Acetone is believed to arise mainly by the reaction CH 3 + CH 3 CHO → CH 3 COCH 3 + H, and only to a negligible extent by the combination of CH 3 and CH 3 CO. The main chain-ending step is concluded to be CH 3 + CH 3 → C 2 H 6 , with a small contribution from CH 3 + CH 2 CHO → CH 3 CH 2 CHO. The work provides further evidence for the falling off, at low pressures, of the second order coefficient for the combination of methyl radicals. Rate constants for various elementary processes are deduced from the rates of formation of the various products, and are shown to be consistent with values obtained directly.

Ignition of acetaldehyde‐air and acetaldehyde‐oxygen mixtures

AbstractIn view of the dangers said to attend the use of acetaldehyde in industrial processes, the sensitiveness to ignition of acetaldehyde vapour in admixture with air or oxygen was investigated. In the first series of experiments, case of ignition was measured by the minimum temperature at which spontaneous ignition occurred on admitting the gas mixture into a glass or metal‐lined tube kept at a specific temperature. This being a common method of determining ignition temperatures, the results could be compared with published data on other inflmmable gases and vapours. The experiment was carried out with mixtures of acetaldehyde and air or oxygen distributed over the range of maximum sensitiveness in each case. The most sensitive mixtures of acetaldehyde with air were those containing 30–60% of acetaldehyde, the lowest ignition temperature recorded being 176deg; c. in an aluminium tube; the most sensitive mixtures with oxygen contained 60–80°, of acetaldehyde, the minimum ignition temperature being 105° c. in glass or aluminium tubes. The results thus show that acetaldehyde is among the most dangerous of industrial solvents in respect of ignition by hot surfaces.In the second series of experiments, case of ignition was measured by the minimum current in the primary circuit of an induction coil which, on interruption, would produce between standard electrodes sparks which were capable of igniting the gas mixture. This being an arbitrary test, comparative tests with other explosive gases and vapours were also included. The most sensitive mixture of acetaldehyde and air in this test contained approximately 8%, of acetaldehyde. Compared with other inflammable gases and vapours, acetaldehyde did not appear unduly sensitive to ignition by a transient source of heat of this nature.These experiments indicate that the liability of acetaldehyde mixtures to accidental explosion in industrial operations is more likely to be due to a low ignition temperature than to exceptional sensitiveness to fugitive sources of heat such as electrical or frictional sparks. The formation of peracetic acid during the pre‐ignition oxidation of acetaldehyde could account for a number of the phenomena observed, and the explosive decomposition of peracetic acid round 110° c. may be responsible for the exceptionally low ignition temperatures of certain acetaldehyde—oxygen mixtures.

The use of acetaldehyde for the detection of chain reactions

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On the induced oxidation of iodobenzene during the oxidation of acetaldehyde in an atmosphere of oxygen

AbstractThe use of acetaldehyde and oxygen instead of peracetic acid as an oxidising agent. A simple preparation of iodoxybenzene.