Acetic acid equivalents

The retrosynthetic summary emphasises that diethyl malonate may be regarded as an acetic acid equivalent, and may be used when a disconnection gives rise to the synthons0CH2,CO2H or 20CH-CO2H. The use of diethyl malonate in the preparation of carboxylic acids is illustrated in the sections below. 

Reaction temperature Acetic acid equivalent in AO Molecular weight of acetic acid Heat capacity of reacting mixture Heat of reaction Conversion Average feed rate AO Density... 

Titratable acidity is expressed in tartaric acid equivalents, volatile acidity is expressed in acetic acid equivalents... 

In this chapter, we will discuss the evolution of processes for the production of the acetyl chemicals - acetic acid (AcOH), acetic anhydride (AC2O), acetaldehyde (AcH), and vinyl acetate (VA). These four materials coevolved in a series of synergistic relationships which ultimately led to the modem acetyl stream which now exceeds 6 X 10 kg/yr of acetyl (as acetic acid equivalents) per year and will be discussed in evolutionary context with each other. Opportunities and resultant innovations in the chemical industry are normally created when lower cost raw materials become available or existing products fail... 

Acidic Hydrolysis. Hot concentrated caustic alkalis first hydrolyse off the ethyl group, and then split the molecule to give one equivalent of acetic acid and one equivalent of the mono- or di-substituted acetic acid (as their alkali salts). 

It follows therefore that ethyl malonate can be used (just as ethyl aceto- acetate) to prepare any mono or di-substituted acetic acid the limitations are identical, namely the substituents must necessarily be alkyl groups (or aryl-alkyl groups such as CjHjCHj), and tri-substituted acetic acids cannot be prepared. Ethyl malonate undergoes no reaction equivalent to the ketonic hydrolysis of ethyl acetoacetate, and the concentration of the alkali used for the hydrolysis is therefore not important. 

The excess of unchanged acetic anhydride is then hydrolysed by the addition of water, and the total free acetic acid estimated by titration with standard NaOH solution. Simultaneously a control experiment is performed identical with the above except that the alcohol is omitted. The difference in the volumes of NaOH solution required in the two experiments is equivalent to the difference in the amount of acetic add formed, i.e., to the acetic acid used in the actual acetylation. If the molecular weight of the alcohol is known, the number of hydroxyl groups can then be calculated. 

The monoarylurea may be prepared directly from the amine by heating it in aqueous solution with an equivalent quantity of alkali cyanate and excess of acetic acid, for example ... 

Alternatively, dissolve approximately equivalent amounts of the aldehyde (or ketone) and the solid reagent in the minimum volume of cold glacial acetic acid, and reflux for 15 minutes. The p-nitrophenyl-hydrazone separates on cooling or upon careful dilution with water. 

Method A. Cool a solution of the nitrate-free dichloride, prepared from or equivalent to 5 0 g. of palladium or platinum, in 50 ml. of water and 5 ml. of concentrated hydrochloric acid in a freezing mixture, and treat it with 50 ml. of formahn (40 per cent, formaldehyde) and 11 g. of the carrier (charcoal or asbestos). Stir the mixture mechanically and add a solution of 50 g. of potassium hydroxide in 50 ml. of water, keeping the temperature below 5°. When the addition is complete, raise the temperature to 60° for 15 minutes. Wash the catalyst thoroughly by decantation with water and finally with dilute acetic acid, collect on a suction filter, and wash with hot water until free from chloride or alkali. Dry at 100° and store in a desiccator. 

Pyrano[3,4-b]indol-3-ones are the most useful equivalents of the indol-2,3-quinodimethane synthon which are currently available for synthetic application. These compounds can be synthesized readily from indole-3-acetic acids and carboxylic anhydrides[5,6]. On heating with electrophilic alkenes or alkynes, adducts are formed which undergo decarboxylation to 1,2-dihydro-carbazoles or carbazoles, respectively. 

Electron delocalization in carboxylate ions is nicely illustrated with the aid of elec trostatic potential maps As Figure 19 4 shows the electrostatic potential is different for the two different oxygens of acetic acid but is the same for the two equivalent oxygens of acetate ion... 

Reaction with ammonia and amines (Section 20 14) Acid an hydrides react with ammonia and amines to form amides Two molar equivalents of amine are required In the example shown only one acyl group of acetic anhydride becomes incor porated into the amide the other becomes the acyl group of the amine salt of acetic acid... 

Titrating a Weak Acid with a Strong Base For this example let s consider the titration of 50.0 mL of 0.100 M acetic acid, CH3COOH, with 0.100 M NaOH. Again, we start by calculating the volume of NaOH needed to reach the equivalence point thus... 

The equilibrium constant for reaction 9.2 is large K = KJK = 1.75 X 10 ), so we can treat the reaction as one that goes to completion. Before the equivalence point, the concentration of unreacted acetic acid is... 

At the equivalence point, the moles of acetic acid initially present and the moles of NaOH added are identical. Since their reaction effectively proceeds to completion, the predominate ion in solution is CH3COO-, which is a weak base. To calculate the pH we first determine the concentration of CH3COO-. 

Howardt describes a model system used to test the molecular weight distribution of a condensation polymer The polymer sample was an acetic acid-stabilized equilibrium nylon-6,6. Analysis showed it to have the following end group composition (in equivalents per 10 g) acetyl = 28.9,... 

Although acetic acid and water are not beheved to form an azeotrope, acetic acid is hard to separate from aqueous mixtures. Because a number of common hydrocarbons such as heptane or isooctane form azeotropes with formic acid, one of these hydrocarbons can be added to the reactor oxidate permitting separation of formic acid. Water is decanted in a separator from the condensate. Much greater quantities of formic acid are produced from naphtha than from butane, hence formic acid recovery is more extensive in such plants. Through judicious recycling of the less desirable oxygenates, nearly all major impurities can be oxidized to acetic acid. Final acetic acid purification follows much the same treatments as are used in acetaldehyde oxidation. Acid quahty equivalent to the best analytical grade can be produced in tank car quantities without difficulties. 

Trityl Ethers. Treatment of sucrose with four molar equivalents of chlorotriphenylmethyl chloride (trityl chloride) in pyridine gives, after acetylation and chromatography, 6,1, 6 -tri-O-tritylsucrose [35674-14-7] and 6,6 -di-O-tritylsucrose [35674-15-8] in 50 and 30% yield, respectively (16). Conventional acetylation of 6,1, 6 -tri-O-tritylsucrose, followed by detritylation and concomitant C-4 to C-6 acetyl migration using aqueous acetic acid, yields a pentaacetate, which on chlorination using thionyl chloride in pyridine and deacetylation produces 4,l, 6 -trichloro-4,l, 6 -trideoxygalactosucrose [56038-13-2] (sucralose), alow calorie sweetener (17). 

This was first demonstrated ia 1862 by Berthelot and Saint-Gibes (32), who found that when equivalent quantities of ethyl alcohol and acetic acid were abowed to react, the esterification stopped when two-thirds of the acid had reacted. Sinularly, when equal molar proportions of ethyl acetate and water were heated together, hydrolysis of the ester stopped when about one-third of the ester was hydroly2ed. By varyiag the molar ratios of alcohol to acid, yields of ester >66% were obtained by displacement of the equbibrium. The results of these tests were ia accordance with the mass action law shown ia equation 5. 

A wide variety of /3-lactams are available by these routes because of the range of substituents possible in either the ketene or its equivalent substituted acetic acid derivative. Considerable diversity in imine structure is also possible. In addition to simple Schiff bases, imino esters and thioethers, amidines, cyclic imines and conjugated imines such as cinnamy-lidineaniline have found wide application in the synthesis of functionalized /3-lactams. A-Acylhydrazones can be used, but phenylhydrazones and O-alkyloximes do not give /3-lactams. These /3-lactam forming reactions give both cis and /raMS-azetidin-2-ones some control over stereochemistry can, however, be exercised by choice of reactants and conditions. 

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