Anhydride formal acid

Many oxides of nonmetals form acidic solutions in water and hence are called acid anhydrides. The familiar laboratory acids HN03 and H2S04, for instance, are derived from acidic binary oxides. Even oxides that do not react with water can be regarded as the formal anhydrides of acids. A formal anhydride of an acid is the molecule obtained by striking out the elements of water (H, H, and O) from the molecular formula of the acid. Carbon monoxide, for instance, is the formal anhydride of formic acid, HCOOH, although CO does not react with cold water to form the acid. 

A few oxides are not anhydrides of either acids or bases. For example, CO and N20 do not react directly with water although they are formally the anhydrides of acids. Therefore, we can write the equations... 

The copolymerization between trioxane and suitable comonomers (ethylene oxide, 1,3-dioxolane, diethylene glycol formal, 1,4-butane diol formal in amounts of 2-5% by weight) is performed using cationic initiators. The cationic initiators could be Lewis acids, such as BF3 or its etherate BF3Bu20 which was used, for example by Celanese (the mechanism of this reaction was studied in detail [163,164]) or protic acids such as perchloric acid, perfluoroalkane sulfonic acids and their esters and anhydrides. Heteropoly acids were used and also a series of carbenium, oxocarbenium salts, onium compounds, and metal chelates. To regulate the molecular weight chain-transfer agents, such as methylal and butylal, are added. 

Examples The acids HNO3 and H2SO4 are derived from the oxides N2O5 and SO3, respectively. Oxides that do not react with water are called formal anhydrides of acids. The formal anhydride is obtained by removing the elements of water (H, H, and O) from the molecular... 

The oxidation of alcohols to carbonyl compounds is one of the most fundamental and important processes in the fine chemical industry. The classical methodology is based on the stoichiometric use of heavy metals, notably Cr and Mn (1,2). Alternatively metal-free oxidation, such as the Swern and Pfitzner-Moffat protocols, is based on e.g., dimethylsulfoxide as oxidant in the presence of an activating reagent such as N,N -dicyclohexylcarbodiimide, an acid anhydride or acid halide (3). Although the latter methods avoid the use of heavy metals, they usually involve moisture-sensitive oxidants and environmentally undesirable reaction media, such as chlorinated solvents. The desired oxidation of alcohols only requires the formal transfer of two hydrogen atoms, and therefore the atom economy of these methods is extremely disadvantageous. The current state of the art in alcohol oxidations... 

N2O3 Dinitrogen trioxide Exists as a blue solid at low temperatures, dissociates into NO2 and NO gases at higher temperatures formal acid anhydride of nitrous acid ... 

Liquid crystal polyesters are made by a different route. Because they are phenoHc esters, they cannot be made by direct ester exchange between a diphenol and a lower dialkyl ester due to unfavorable reactivities. The usual method is the so-called reverse ester exchange or acidolysis reaction (96) where the phenoHc hydroxyl groups are acylated with a lower aHphatic acid anhydride, eg, acetic or propionic anhydride, and the acetate or propionate ester is heated with an aromatic dicarboxyHc acid, sometimes in the presence of a catalyst. The phenoHc polyester forms readily as the volatile lower acid distills from the reaction mixture. Many Hquid crystal polymers are derived formally from hydroxyacids (97,98) and thein acetates readily undergo self-condensation in the melt, stoichiometric balance being automatically obtained. 

Studies of the chemical reactivity of N2O3 are complicated by its extensive dissociation into NO and NO2 which are themselves reactive species. With water N2O3 acts as the formal anhydride of nitrous acid and in alkaline solution it is converted essentially quantitatively to nitrite ... 

Condensation of an appropriately substituted phenylacetic acid with phthalic anhydride in the presence of sodium acetate leads to aldol-like reaction of the methylene group on the acid with the carbonyl on the anhydride. Dehydration followed by decarboxylation of the intermediate affords the methylenephthal-ides (12). Treatment of the phthalides with base affords directly the indandiones, probably via an intermediate formally derived from the keto-acid anion (13). The first agent of this class to be introduced was phenindandione (14) this was followed by anisindandione (1S) and chlorindandione (16). ... 

Carbon monoxide, CO, is produced when carbon or organic compounds burn in a limited supply of air, as happens in cigarettes and badly tuned automobile engines. It is produced commercially as synthesis gas by the re-forming reaction (Section 14.3). Carbon monoxide is the formal anhydride of formic acid, HCOOH, and the gas can be produced in the laboratory by the dehydration of formic acid with hot, concentrated sulfuric acid ... 

Give the formula for the formal anhydride of each acid ... 

Give the formula for the acid corresponding to each of the following formal anhydrides (a) N2Os (b) P4O 0 (c) Se03. 

The principles set forth above account reasonably well for the course of bifunctional condensations under ordinary conditions and for the relative difficulty of ring formation with units of less than five or more than seven members. They do not explain the formation of cyclic monomers from five-atom units to the total exclusion of linear polymers. Thus 7-hydroxy acids condense exclusively to lactones such as I, 7-amino acids give the lactams II, succinic acid yields the cyclic anhydride III, and ethylene carbonate and ethylene formal occur only in the cyclic forms IV and V. 

Although they are oxides of nonmetals, CO and N20 do not give acidic solutions when added to water. However, they are formally the anhydrides of formic and hyponitrous acid, respectively. 

Because the oxides of nonmetals are acid anhydrides, CO is formally the anhydride of formic acid. 

Although N20 is formally the anhydride of H2N202, the acid does not result from the reaction of N20 and water. The acid oxidizes in air to produce nitric and nitrous acids. 

Formally related reactions are observed when anthracene [210] or arylole-fines [211-213] are reduced in the presence of carboxylic acid derivatives such as anhydrides, esters, amides, or nitriles. Under these conditions, mono- or diacylated compounds are obtained. It is interesting to note that the yield of acylated products largely depends on the counterion of the reduced hydrocarbon species. It is especially high when lithium is used, which is supposed to prevent hydrodimerization of the carboxylic acid by ion-pair formation. In contrast to alkylation, acylation is assumed to prefer an Sn2 mechanism. However, it is not clear if the radical anion or the dianion are the reactive species. The addition of nitriles is usually followed by hydrolysis of the resulting ketimines [211-213]. 

Two years later, the same group reported a formal synthesis of ellipticine (228) using 6-benzyl-6H-pyrido[4,3-f>]carbazole-5,ll-quinone (6-benzylellipticine quinone) (1241) as intermediate (716). The optimized conditions, reaction of 1.2 equivalents of 3-bromo-4-lithiopyridine (1238) with M-benzylindole-2,3-dicarboxylic anhydride (852) at —96°C, led regioselectively to the 2-acylindole-3-carboxylic acid 1233 in 42% yield. Compound 1233 was converted to the corresponding amide 1239 by treatment with oxalyl chloride, followed by diethylamine. The ketone 1239 was reduced to the corresponding alcohol 1240 by reaction with sodium borohydride. Reaction of the alcohol 1240 with f-butyllithium led to the desired 6-benzylellipticine quinone (1241), along with a debrominated alcohol 1242, in 40% and 19% yield, respectively. 6-Benzylellipticine quinone (1241) was transformed to 6-benzylellipticine (1243) in 38% yield by treatment with methyllithium, then hydroiodic acid, followed... 

A suspension of potassiumperoxodisulfate in a mixture of trifluoroacetic acid and trifluoroacetic acid anhydride at a methane pressure of 20-30 atmospheres methane and 80-100 °C in the presence of catalytic amounts of 18 and 20 leads to the formation of the trifluoroacetic acid methylester. Scheme 23 shows the oxidative character of the reaction which formally can be described as CH4 [CH3]" -1- H -l- 2e". 

A formal asymmetric nucleophilic addition to carbonyl compounds is achieved by Trost and his co-workers in the allylic alkylation of acylals of alkenals. An excellent enantioselectivity is observed in this alkylation. The starting acylals are easily prepared by the Lewis-acid catalyzed addition of acid anhydrides to aldehydes, by use of Trost s ligand 118 (Scheme 13), where various carbon-centered nucleophiles are available (Scheme l4),101,101a-10lc Asymmetric synthesis of some natural products is achieved according to this procedure. 

Carboxylic acids and their derivatives like esters, amides, anhydrides, and acyl halides are formally synthesized from olefins, carbon monoxide, and compounds represented by Nu-H such as H2O, ROH, RNH2, RCOOH (Equations (4) and (5)). Alkynes also react under similar conditions to afford the corresponding unsaturated carboxylic acid derivatives. These reactions have been named hydrocarboxylation, hydroalkoxycarbonylation, and hydroaminocarbonylation. 

Cyclotriboroxanes (RBO)3 (also known as boroxines) are formally anhydrides of the corresponding boronic acids RB(OH)2 only mild heating is required to convert these dibasic acids into a wide range of cyclic trimeric anhydrides [eqn (9.18)]. This dehydration process can be adapted for the synthesis of B3O3 rings with different aryl groups on the boron atoms by using two or more arylboronic acids in the appropriate stoichiometric ratio. 

This is formally the reverse of the BA1,1 cleavage of an ester, and is the only one-stage mechanism for ester formation available for the ionized carboxyl group. Numerous methods are, of course, available which involve initial electrophilic attack on the carboxylate group, followed by a displacement at the carbonyl carbon atom of the intermediate formed, which is often an anhydride. An example134 is the esterification of carboxylic acids in the presence ofp-toluenesulphonyl chloride in pyridine, viz-... 

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