Acetaldehyde determination

The Arrhenius activation energy,3 obtained from the temperature dependence of the three-halves-order rate constant, is Ea = 201 kJ mol-1. This is considerably less than the standard enthalpy change for the homolysis of acetaldehyde, determined by the usual thermodynamic methods. That is, reaction (8-5) has AH = 345 kJ mol-1. At first glance, this disparity makes it seem as if dissociation of acetaldehyde could not be a predecessor step. Actually, however, the agreement is excellent when properly interpreted. 

Lactic Acid. Qualitative and even semiquantitative data are obtained by paper chromatography. Quantitative procedures where lactic acid is oxidized to acetaldehyde and the acetaldehyde determined colorimetri-cally are available (4,13, 22, 90). 

Acetaldehyde. In routine winery operation acetaldehyde is seldom measured. However, in the production of sherry, either by the film yeast or submerged culture processes, regular acetaldehyde determination is necessary. 

A. Avramescu, T. Noguer, M. Avramescu and J.L. Marty, Screen-printed biosensors for the control of wine quality based on lactate and acetaldehyde determination, Anal. Chim. Acta, 458 (2002) 203-213. 

Jones et al. (1985) estimated the concentration of acetaldehyde in blood from analysis in breath. The method is based on liquid-air partition coefficients of acetaldehyde determined by GC-FID. Jones et al. (1986) reported a GC-headspace method for its analysis in wine. Habboush et al. (1988) have reported the analysis of acetaldehyde and other low-molecular-weight aldehydes in automobile exhaust gases by GC-FlD. 

From experiments in a constant volume batch reactor at 791K, it is known that the time required for a 50% increase in total pressure is 197 s. The initial pressure is 1 bar. The reaction is known to be second-order in acetaldehyde. Determine the volume of a plug flow reactor necessary to achieve 80% conversion of 120 L/min of pure acetaldehyde gas. The feed pressure is 1 atm. The reaction is essentially irreversible. The pressure drop along the length of the reactor is negligible. 

The formula of acetic acid is often written HC2H3O2 to indicate that one of the hydrogen atoms is acidic (lost easily) while the other three are not (Figure 3.10). Now that you know the formulas of acetic acid and acetaldehyde (determined from the data... 

Reagent A is particularly useful for the treatment of the lower aliphatic aldehydes and ketones which are soluble in water cf. acetaldehyde, p. 342 acetone, p. 346). The Recent is a very dilute solution of the dinitrophenylhydrazine, and therefore is used more to detect the presence of a carbonyl group in a compound than to isolate sufficient of the hydrazone for effective recrystallisation and melting-point determination. 

An internal standard of 1-butanol is used to determine the concentrations of one or more of the following impurities commonly found in whiskey acetaldehyde, methanol, ethyl acetate, 1-propanol, 2-methyl-1-propanol, acetic acid, 2-methyl-1-butanol and 3-methyl-1-butanol. A packed column using 5% Garbowax 20m on 80/120 Garbopak B and an EID detector were used. 

Specifications and Analytical Methods. Vinyl ethers are usually specified as 98% minimum purity, as determined by gas chromatography. The principal impurities are the parent alcohols, limited to 1.0% maximum for methyl vinyl ether and 0.5% maximum for ethyl vinyl ether. Water (by Kad-Fischer titration) ranges from 0.1% maximum for methyl vinyl ether to 0.5% maximum for ethyl vinyl ether. Acetaldehyde ranges from 0.1% maximum in ethyl vinyl ether to 0.5% maximum in butyl vinyl ether. 

Acrolein is produced according to the specifications in Table 3. Acetaldehyde and acetone are the principal carbonyl impurities in freshly distilled acrolein. Acrolein dimer accumulates at 0.50% in 30 days at 25°C. Analysis by two gas chromatographic methods with thermal conductivity detectors can determine all significant impurities in acrolein. The analysis with Porapak Q, 175—300 p.m (50—80 mesh), programmed from 60 to 250°C at 10°C/min, does not separate acetone, propionaldehyde, and propylene oxide from acrolein. These separations are made with 20% Tergitol E-35 on 250—350 p.m (45—60 mesh) Chromosorb W, kept at 40°C until acrolein elutes and then programmed rapidly to 190°C to elute the remaining components. 

The fermentation-derived food-grade product is sold in 50, 80, and 88% concentrations the other grades are available in 50 and 88% concentrations. The food-grade product meets the Vood Chemicals Codex III and the pharmaceutical grade meets the FCC and the United States Pharmacopoeia XK specifications (7). Other lactic acid derivatives such as salts and esters are also available in weU-estabhshed product specifications. Standard analytical methods such as titration and Hquid chromatography can be used to determine lactic acid, and other gravimetric and specific tests are used to detect impurities for the product specifications. A standard titration method neutralizes the acid with sodium hydroxide and then back-titrates the acid. An older standard quantitative method for determination of lactic acid was based on oxidation by potassium permanganate to acetaldehyde, which is absorbed in sodium bisulfite and titrated iodometricaHy. 

Titanium Complexes of Unsaturated Alcohols. TetraaHyl titanate can be prepared by reaction of TYZOR TPT with aHyl alcohol, followed by removal of the by-product isopropyl alcohol. EbuUioscopic molecular weight determinations support its being the dimeric product, octaaHoxydititanium. A vinyloxy titanate derivative can be formed by reaction of TYZOR TPT with vinyl alcohol formed by enolization of acetaldehyde (11) ... 

The most common chromatogram in the distilled spirits industry is the fusel oil content. This consists of / -propyl alcohol, isobutyl alcohol, and isoamyl alcohol. Other common peaks are ethyl acetate, acetaldehyde, and methanol. The gc columns may be steel, copper, or glass packed column or capillary columns. Additional analyses include deterrninations of esters, total acids, fixed acids, volatile acids, soHds or extracts (used to determine... 

In 1883, Bottinger described the reaction of aniline and pyruvic acid to yield a methylquinolinecarboxylic acid. He found that the compound decarboxylated and resulted in a methylquinoline, but made no effort to determine the position of either the carboxylic acid or methyl group. Four years later, Doebner established the first product as 2-methylquinoline-4-carboxylic acid (8) and the second product as 2- methylquinoline (9). Under the reaction conditions (refluxing ethanol), pyruvic acid partially decarboxylates to provide the required acetaldehyde in situ. By adding other aldehydes at the beginning of the reaction, Doebner found he was able to synthesize a variety of 2-substituted quinolines. While the Doebner reaction is most commonly associated with the preparation of 2-aryl quinolines, in this primary communication Doebner reported the successful use of several alkyl aldehydes in the quinoline synthesis. 

Unique methods based on new principles have been developed within the past 10 years. Threonine (27,28,249) is oxidized by lead tetraacetate or periodic acid to acetaldehyde, which is determined by photometric analysis of its p-hydroxydiphenyl complex or iodometric titration of its combined bisulfite. Serine is oxidized similarly to formaldehyde, which is determined gravimetrically (207) as its dimedon (5,5-dimethyldihydro-resorcinol) derivative or photometric analysis (31) of the complex formed with Eegriwe s reagent (l,8-dihydroxynaphthalene-3,5-disulfonic acid). It appears that the data obtained for threonine and serine in various proteins by these oxidation procedures are reasonably accurate. [Block and Bolling (26) have given data on the threonine and serine content of various proteins. ]... 

In practice, one proceeds as follows. The value of bh >s determined for the reaction with a series of acids of similar structure, that is, for carboxylic acids or ammonium ions, etc. Limiting the data to a single catalyst type improves the fit. since the inclusion of data for a second ype of acid catalyst might define a close but not identical line. This means that Ga may be somewhat different for each catalyst type. A plot of log(kBH/p) versus log(A BH(7//i) is then constructed. This procedure most often results in a straight line, within the usual —10-15 percent precision found for LFERs. One straightforward example is provided by the acid-catalyzed dehydration of acetaldehyde hydrate,... 

For acetic acid, CH3COOH, in which the bond from carbon to the OH group has about 35 per cent double-bond character and that to the oxygen atom about 65 per cent double-bond character, as determined from the interatomic distances, we would predict for the potential hump a value about one-third that in acetaldehyde. This prediction is borne out by experiment, the height of the barrier being 0.48 kcal/mole. 

Reactions with molecular species above the arrow e.g. RIO) involve subsequent reactions with these species to produce the indicated products. In most cases the reactants shown to the left of the arrow participate in the slowest or rate-determining step]. The CH3O radical formed in Rll then follows reaction R7. The H02 radical formed in RIO is the other member of the family and is linked with HO in a variety of chain reactions. These radicals are produced following HO attack on hydrocarbons or by photodissociation of oxygenated hydrocarbons such as formaldehyde (RIO) and acetaldehyde ... 

Evaluation of acetaldehyde oxidation reactor especially by determining reaction conversion and selectivity. 

C19-0083. Dichromate ions, C r2 0-j, oxidize acetaldehyde, CH3 CHO, to acetic acid, CH3 CO2 H, and are reduced to Cr . The reaction takes place in acidic solution. Balance the redox reaction and determine how many moles of electrons are required to oxidize 1.00 g of acetaldehyde. What mass of sodium dichromate would be required to deliver this many electrons ... 

Alcohol abuse is a major clinical problem in many countries and has been the subject of investigation for many years by those interested in determining the molecular basis of ethanol-induced liver dam e (see Lieber, 1990). These intensive and extended efforts have revealed much about the metabolism of ethanol in the liver and about the toxicity of its primary oxidative product, acetaldehyde. They have not, however, folly elucidated the molecular mechanisms that lead to the typical features of alcoholic liver injury steatosis, necrosis and eventually cirrhosis. 

Under these conditions the reaction is known to be irreversible with a rate constant of 0.43 m3/ kmole-sec. If 0.1 kg/sec of acetaldehyde is fed to the reactor, determine the reactor volume necessary to achieve 35% decomposition. 

The explosion limits have been determined for liquid systems containing hydrogen peroxide, water and acetaldehyde, acetic acid, acetone, ethanol, formaldehyde, formic acid, methanol, 2-propanol or propionaldehyde, under various types of initiation [1], In general, explosive behaviour is noted where the ratio of hydrogen peroxide to water is >1, and if the overall fuel-peroxide composition is stoicheiometric, the explosive power and sensitivity may be equivalent to those of glyceryl nitrate [2],... 

Both ADH and ALDH use NAD+ as cofactor in the oxidation of ethanol to acetaldehyde. The rate of alcohol metabolism is determined not only by the amount of ADH and ALDH2 enzyme in tissue and by their functional characteristics, but also by the concentrations of the cofactors NAD+ and NADH and of ethanol and acetaldehyde in the cellular compartments (i.e., cytosol and mitochondria). Environmental influences on elimination rate can occur through changes in the redox ratio of NAD+/NADH and through changes in hepatic blood flow. The equilib-... 

In contrast to the above, other reactions have been found to require base assistance by water in the rate-determining step, i.e. the water activity does appear in the rate law. The mechanism formulated for the condensation of acetaldehyde in sulfuric acid is given in equation (63), following on from the enolization of Scheme 7, subsequent dehydration to crotonaldehyde occurring as shown in Scheme 8. The ky k2, k3 and k 3 steps shown were all studied.246... 

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