Acids and anhydrides

Acids present in coffee can be divided into two classes  

For this functional group we will mention the non-volatile members, nevertheless excluding the chloro-genic acids (Section 2.1.4) and the phenolic compounds resulting from their degradation during roasting (Section 5.H). 

Using partition chromatography on a silicic acid column, Mabrouk and Deatherage (1956) determined the organic acids in five coffee extracts. Such a column does not normally separate the volatile acids, nevertheless, acetic acid was found to represent 0.59% of the total acid content, far away from the predominant non-volatile acid, chlorogenic acid, which represents 66.7% of the total organic acids. Also present in higher proportions than acetic acid were the non-volatile citric acid (E.57), 7.7 %, malic acid (E.53), 7.2%, and tartaric acid (E.55), 6.2%. Oxalic acid (E.42) and pyruvic acid (E.38) were quantified. 

Analytical work on the acid content of raw and roasted coffees was published by von Werner and Kohley (1965a,b,c), but mainly on the chlorogenic acids. 

By NMR and GC, Kung et al. (1967) determined the volatile acids (Ci to Cio) in coffee beverages. They examined the difference in acid concentration between medium- and dark-roasted coffees (Columbian, Santos, robusta) and observed that, in general, the dark roasts were lower in volatile acids than were the medium roasts, and robusta coffee had the highest volatile acid content. They confirmed the predominance of the non-volatile acids. 

Ab initio calculations have been carried out on the decomposition of mandelic acid (70) at the MP2/6-31G level.62 Three competitive pathways have been characterized. Two are stepwise processes with the formation of an a-lactone intermediate and ring 

The kinetics and mechanism of the reaction of carboxylic acids with phosgene COCI2 in DMF in benzene were zero-order in substrate and proceeded via rapid formation of 

Solvent effects on the dissociation of 11 2,6-disubstituted benzoic acids have been analysed by chemometric analysis.66 The acid-base behaviour of the three zwitterionic pyridinecarboxylic acids (picolinic, nicotinic, and isonicotinic acid) has been studied. The cationic form of picolinic acid converts partially into the corresponding zwitterion within a borderline acidity range (pH/acidity function). The various p/y, values were determined for the three isomers by spectrophotometric and potentiometric methods and reasonable agreement was found.67 

Kinetic data for the reactions of diazodiphenylmethane in 10 different alcohols with 2-(4-phenyl substituted)cyclohex-l-enylcarboxylic acids (75) were correlated using the extended Hammett equation.68 Reaction of the species (76)-(78) with the light radioactive H isotope, the muonium atom, has been studied.69 The largest primary kinetic isotope effects ever reported (ca 850) are seen in this work for the addition of muonium to one of the C=0 groups. 

The kinetics of the reaction of acrylic acid with aqueous ammonia giving /1-alanine have been investigated.73 

Mechanistic studies are reported of the esterification of carboxylic acids with dimethylformamide dimethyl acetal and other amide acetals. The reaction between phenylacetic acid (36), acetic anhydride, and o-hydroxybenzophenone (38) catalysed by EtsN yielded 3,4-diphenylcoumarin (40) in 78% yield.The mechanism presumably involves the initial formation of the mixed anhydride of acetic acid and phenylacetic acid (37), which then acylates the o-hydroxybenzophenone (38) to yield o-phenacyloxybenzophenone (39), cyclization of which, via the carbanion, produces the coumarin (40). Kinetic studies have been reported of the hydrothermal oxidation and hydrolysis of lactic acid at 300-400 °C and a nominal pressure of 27.6 MPa.  

A quantum-chemical study of the mechanism of the condensation reaction between propanoic acid and aniline has been made. The mechanism of proton-transfer reactions of 3,5-dinitrosalicylic acid (41) has been the subject of a review (50 references). A successful correlation has been obtained between dissociation of a variety of acids in different solvents and quantum self-similarity measures of the CO2H fragment. The substituent effects of the isopropyl group in 2- (42), 3- (43), and 4-isopropylbenzoic acid (44) have been evaluated from their enthalpies of formation, gas-phase acidities, acidities in MeOH and in DMSO, and their IR spectra in tetrachloromethane. Particular attention was given to the influence of variable conformation on the observed steric effect. In contrast to 2-r-butylbenzoic acid and similarly to 2-methylbenzoic acid, 2-isopropylbenzoic acid exists in two planar conformations (42a,b) in equilibrium. Owing to this conformational freedom, the 

A kinetic study of the isotope-exchange reactions of malonic acid and several of its monoalkyl derivatives in various acidic D2O media using H NMR spectroscopy has revealed the order of reactivity of RCH(C02H)2 to be R = Ph H Me Et, Bu.  

A parallel study of the isotope-exchange reactions of malonate ion in Na0D-D20 has shown that the rate of exchange of malonate in D2O decreases to a minimum and then increases with increased [NaOD]. The oxidation of y,5-unsaturated acids to lactones with H2O2 is catalysed by methyltrioxorhenium a concerted mechanism is proposed. The activation of carboxylic acids by carbonates has been reviewed (79 references). Among the topics discussed is the esterification of A-protected amino acids (46) using di-f-butyl carbonate (47) the putative active intermediate is the mixed anhydride (48). The reaction between maleic anhydride and f-butyl 

Smdies of the thermal degradation of several aromatic acids have been reported. Phthalic acid (80), but not isophthalic acid (81) or terephthalic acid (82), decomposes via dehydration to its anhydride at 140-160 °C. However, (81) and (82) and benzoic acid are thermally stable below 200 °C. Dissociation constants of all 19 isomers of methyl-substimted benzoic acids (83) have been measured in methanol and DMSO. From the pA a values, the substiment effects of the methyl groups were calculated and tentatively divided into polar and steric effects. Also, in the case 

Kinetics of the reaction of diazodiphenylmethane (92) in a wide range of alcohols with pyridine and pyridine-A -oxide 3- and 4-carboxylic acids (84)-(87), 4-substituted benzoic acids (88), cw -substituted cinnamic acids (89), 2-(4-phenyl-substituted)cyclohex-l-enyl carboxylic acids (90), and 4 -substituted-biphenyl-2-carboxylic acids (91) have been reported. Comparison of the new results for 4-substituted benzoic acids with the published results of data for 3-substituted benzoic acids was made, and it was concluded that the most important solvent property influencing the rate of reaction appears to be the polarity of the alkyl group expressed as Taft s polar constant a. Transmission coefficients in the cinnamic acids (89) were compared with those in the bicyclic acids (90) and 

A new water-soluble calix[4]arene-triacid-monoquinone (99) has been synthesized and its ion-binding properties in aqueous solution were investigated by means of voltammetry and UV-visible spectrophotometry. The electrochemical behaviour of (99) is dependent on the concentration of Ca + ion rather than that of other alkaline 

2-Chloro-4,6-dimethoxy-l,3,5-triazine (100) reacts with iV-methylmorpholine at 20 °C to yield an isolable quaternary triazinylammonium salt (101 R = Me, R, R = C4H8O). This salt can then be reacted with a carboxylic acid to yield a 2-acyloxy-4,6-dimethoxy-l,3,5-triazine (102), which, in turn, can be reacted with an amine to yield an amide (103). This sequence of reactions provides an explanation for the activation (formation of reactive ester) of the carboxylic acid function by 2-chloro-4,6-disubstituted-l,3,5-triazines (100) in the presence of hindered amines. Several other hindered amines may replace iV-methylmorpholine in the process, but unhindered amines such as triethylamine and tributylamine were inactive.  

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Acetaldehyde oxidation generates peroxyacetic acid which then reacts with more acetaldehyde to yield acetaldehyde monoperoxyacetate [7416-48-0], the Loesch ester (26). Subsequently, parallel reactions lead to formation of acetic acid and anhydride plus water. 

Acetic Acid and Anhydride. Synthesis of acetic acid by carbonylation of methanol is another important homogeneous catalytic reaction. The Monsanto acetic acid process developed in the late 1960s is the best known variant of the process. 

Chemical Properties. A combination of excellent chemical and mechanical properties at elevated temperatures result in high performance service in the chemical processing industry. Teflon PEA resins have been exposed to a variety of organic and inorganic compounds commonly encountered in chemical service (26). They are not attacked by inorganic acids, bases, halogens, metal salt solutions, organic acids, and anhydrides. Aromatic and ahphatic hydrocarbons, alcohols, aldehydes, ketones, ethers, amines, esters, chlorinated compounds, and other polymer solvents have Httle effect. However, like other perfluorinated polymers,they react with alkah metals and elemental fluorine. 

S. D. Cooley andj. D. Powers, "Maleic Acid and Anhydride," iu Enyclopedia of Chemical Processing and Design, Vol. 29, Marcel Dekker, Inc., New York, 1988,... 

This article discusses the benzenepolycarboxyhc acids, their anhydrides, and their esters. Table 1 includes lUPAC nomenclature, common names, and CAS Registry Numbers for the benzenepolycarboxyhc acids. These acids and anhydrides are highly stable. The carboxyUc acid groups provide from two to six sites for reaction for a wide variety of products, mostly polymers and plasticizers. 

HemimeUitic acid is not manufactured commercially but is available as a laboratory chemical in a hydrate form (99). Like ttimesic acid, it is formed when coal-like materials are oxidized, but can be synthesized in a purer form by oxidizing hemimeUitene [562-73-8] (1,2,3-trimethylbenzene) or hemimeUitol [526-85-2]. HemimeUitic anhydride can be produced by thermal dehydration of the acid in trichiorohenzene at 261°C (147). Synthesis of hemimellitic acid and anhydride have been described (148). There are no reported uses which ate unique to hemimellitic acid. 

Commodity Phthalate Esters. The family of phthalate esters are by far the most abundandy produced woddwide. Both orthophthaUc and terephthahc acid and anhydrides are manufactured. The plasticizer esters are produced from these materials by reaction with an appropriate alcohol (eq. 1) terephthalate esterification for plasticizers is performed more abundandy in the United States. Phthalate esters are manufactured from methanol (C ) up to Qyj alcohols, although phthalate use as PVC plasticizers is generally in the range to The lower molecular weight phthalates find use in nitrocellulose the higher phthalates as synthetic lubricants for the automotive industries. 

Polybasic Acids and Anhydrides. The principal polybasic acids used ki alkyd preparation are Hsted ki Table 2. 

Retarders. The purpose of vulcanization retarders is to delay the initial onset of cure in order to guarantee sufficient time to process the unvulcanized mbber. Three main classes of materials are used commercially, including organic acids and anhydrides, cyclohexylthiophthalimide (Santogard PVI or CTP), and a sulfenamide material (Vulkalent E). 

Succinic acid and anhydride undergo most of the reactions characteristic of dicarboxyhc acids and cycHc acid anhydrides, respectively. Other interesting reactions take place at the active methylene groups. 

In many appHcations succinic acid and anhydride are esterified with polyhydric compounds, ie, polyols (57—59), cellulose (60), or starch (61—64). 

Succinic acid and anhydride should be handled with mbber or plastic gloves safety goggles and a dust filter are recommended when handling the products in powder form. A full-face gas mask with a type A (brown) filter cartridge should be worn when handling molten products. 

The reactions of carboxyUc acids and anhydrides with epoxy resins have been extensively studied in a variety of investigations, particularly References 27—31. The general reaction of epoxide resins and anhydrides is... 

Palmitic acid anhydride (hexadecanoic anhydride) [623-65-4] M 494.9, m 63-64 , 64 , d 0.838, n 1.436. It is moisture sensitive and hydrolyses in water. Purified by refluxing with acetic anhydride for Ihr, evaporating and freeing the residue of acetic acid and anhydride by drying the residue at high vac and crystallising from pet ether at low temperature. 

Organic acids and anhydrides, sulfur dioxide, carbon monoxide, particulate matter... 

Epoxy plastics Group of plastics composed of resins produced by reactions of epoxides or oxiranes with compounds such as amines, phenols, alcohols, carboxylic acids, and anhydrides, and unsaturated compounds. 

During electrochemical fluorination retention of important functional groups or atoms in molecules is essential. Acyl fluorides and chlorides, but not carboxylic acids and anhydrides (which decarboxylate), survive perfluorination to the perfluorinated acid fluorides, albeit with some cyclization in longer chain (>C4) species [73]. Electrochemical fluorination of acetyl fluoride produces perfluoro-acetyl fluoride in 36-45% yields [85]. Electrochemical fluorination of octanoyl chloride results in perfluorinated cyclic ethers as well as perfluorinated octanoyl fluonde. Cyclization decreases as initial substrate concentration increases and has been linked to hydrogen-bonded onium polycations [73]. Cyclization is a common phenomenon involving longer (>C4) and branched chains. a-Alkyl-substituted carboxylic acid chlorides, fluorides, and methyl esters produce both the perfluorinated cyclic five- and six-membered ring ethers as well as the perfluorinated acid... 

Copper chromite 14) and barium-promoted copper chromite (75,/7) have been used for acid reductions but very high temperatures (300 C) are required. The necessary temperature is sufficiently higher than that required foresters to permit selective reduction of half-acid esters to the hydroxy acid 23). The reverse selectivity can be achieved by reduction over H Ru4 CO)a PBu3)4 at I00-200 C and 1500-3000 psig. This homogeneous catalyst will reduce acids and anhydrides, but not esters (2). 

This chapter covers not only nuclear and extranuclear quinoxahnecarboxylic acids (and anhydrides) but also the carboxylic esters, acyl halides, carboxamides, carbohydrazides, carbonitriles, carbaldehydes, and (ketonic) acyl derivatives of quinoxaline a few related speceis are also included. To avoid repetition, the interconversions of these quinoxaline derivatives are discussed only at the first opportunity thus the esterification of quinoxalinecarboxylic acids in covered as a reaction of carboxylic acids rather than as a preparative route to carboxylic esters, simply because the section on carboxylic acids precedes that on carboxylic esters. To minimize any confusion, appropriate cross-references have been inserted. 

There is an extensive recent literature on quinoxalinecarboxylic acids and anhydrides, much of it in connection with their role as intermediates for derivatives such as carbohydrazides. 

Quinoxalinecarboxylic Acids and Anhydrides By Hydrolysis of Quinoxaline Nitriles... 

Reaction between amino acids and anhydrides (Daidn-West)... 

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