Acid, carboxylic

Aliphatic acids yields low-abundance molecular ions. A prominent signal at m/z 60 [CH2C(0H)2 ], formed by the McLafferty rearrangement. 

The molecular ion of aromatic acids is more stable and hence more abundant. The sequential losses of the OH and CO moieties are observed from that ion. In the presence of an ortho group with a labile hydrogen, a prominent loss of H2O can also occur [reaction (6.34)], followed by the loss of CO. 

Carboxylic acids are generally attached to polymeric supports as esters or amides. Depending on the type of linker and on the cleavage conditions used, cleavage can lead either to the regeneration of a carboxylic acid, or to the formation of a new product, such as an ester, amide, ketone, or alcohol. This section covers only linkers which lead, upon cleavage, to the release of carboxylic acids. 

Carboxylic acids do not react with phosgene easily, and the reactions require promotion with catalysts in order to avoid the need to use excessively high temperatures. The situation may be compared to the reactions of the highly acidic (for example fluorinated) alcohols. 

The action of phosgene on a carboxylic acid in the absence of other reactive functional groups is to form the corresponding acid chloride, consistent with Equation (10.22)  

Although acid chlorides can be produced in a similar way from the reactions of sulfinyl chloride (SOClj) or phosphorus(V) chloride with RC(0)0H, the by-products obtained from the phosgene reaction are less troublesome and are more amenable to disposal. 

Phosgene does not react with ethanoic acid at normal temperatures, but ethanoyl chloride is produced according to Equation (10.22) when the reactants are combined in a Carius tube at 120 C [1080]. Long-chain acids, such as CH 3(CH j) ,COOH (n = 10, 14 or 16) have been treated in the molten state at 150 C, and the unsaturated material, CH3(CHj) CH=CH(CHj)jCOOH, behaves similarly i.e. according to Equation (10.22) [1658]. 

Anhydrous (COOH)j is claimed to react with phosgene in the presence of NEt Ph, at room temperature and atmospheric pressure, to give ethanedioyl dichloride [1919]. The 

Carboxylic acids hydrogen bond strongly to water—they can act as both H-bond donors and acceptors (4.46), and the lower acids are miscible with water. In nonpolar solvents, such as benzene, they self-associate through hydrogen bonding to give dimers (4.47). 

Give systematic names for each of the following molecules  

The longest chain here is fairly obvious and has six carbon atoms, so this is a hexanoic acid. Add the substituents, thus 3,4-dimethylhexanoic acid. The commonest error in problems of this type is not to start the numbering scheme on the carboxylic acid carbon atom. Despite the presence of a ketone, this will be named as a carboxylic acid, so the chain is numbered from the -COOH group. 

This will be named as a benzoic acid, 4-hydroxybenzoic acid, as the carboxyl group takes precedence over the -OH. 

The aromatic acids do not have a well-defined pattern of odors all are faintly balsamic with various spicy, floral, or even fruity overtones. Benzoic and cinnamic acids, and the higher members of the series are odorless, although compounds based on a saturated cyclic sttncture (e.g., hexahydrobenzoic acid) have an unpleasant rancid character. 

As a group, the organic acids impart a sharp, sour taste to a product. The di-and tri-carboxyhc acids are of particular value in this respect as they occur naturally in many fruits. These compounds are odorless and are not used directly in flavoring formulations, but citric, malic, and tartaric acids are often used in end products to improve and even enhance added fruit flavorings which would otherwise be atypical of the natural finit 

Alcohols and glycols may react with the carbonyl group of aldehydes in the presence of an anhydrous acid to form mixed ethers called acetals. It is suggested that, in alcoholic solution, aldehydes really exist in equilibrium with compounds called hemiacetals but that these are too unstable to be isolated. In the presence of acids, the hemiacetals act as an alcohol and react to form the acetal. The reaction is reversible, and in the presence of water, acetals are readily hydrolyzed back to the parent aldehyde and alcohol. 

The acetals are liquids having a wide range of odors but are not extensively used in flavorings. Two are of particular interest (a) acetaldehyde diethyl acetal — pleasantly nutty and (b) cinnamaldehyde ethylene glycol — warm, sweetly spicy. The product of glycol with hydrotropic aldehyde (l-oxo-2-phenyl-2-methylethane) has a strong odor reminiscent of mushrooms. The formation of acetals in finished 

In the aromatic series where the hydroxyl group (-OH) is substituted directly on the benzene nucleus, the compounds are known as phenols. These differ significantly from the alcohols and are considered separately. The alcohols as a group are important flavoring materials and are extensively found throughout nature. All contain a hydroxyl group, which largely determines their characteristics. 

5 Carboxylic Acids Carboxylic acids exist as stable hydrogen-bonded dimers in nonpolar solvents even at high dilution. The carboxylic proton therefore absorbs in a characteristic range 8 — 13.2-S —10.0 and is affected only slightly by concentration. Polar solvents partially disrupt the dimer and shift the peak accordingly. 

Another large group of acids is illustrated by acetic acid, a weak acid (Kfl = 1.8 X 10 )  

What group of atoms is present in aii carboxylic acids  

As we will discuss in greater detail in Chapter 24, amino acids are the building blocks of proteins. The general structure of amino acids is 

Amine group Carboxyl group (basic) (acidic) 

Amino acids contain a carboxyl group and can therefore serve as acids. They also contain an NH2 group, characteristic of amines 

Several carboxylic acids are manufactured by fermentation (Table 6.8). The production of acetic and lactic acids underlies the important traditional processes of vinegar and of milk fermentation, but, of these two, only lactic acid is commercially manufactured in this way. From time to time other carboxylic acids which are used in large amounts, notably adipic acid (Table 6.8), are proposed as suitable candidates for a fermentative process. However, where suitable and more economic chemical routes are available from petrochemical feedstocks, there is no real incentive for change. 

1 Lactic acid. Lactic acid was the first of the organic acids to be manufactured by fermentation. The process was first used in 1880, but even by 

1920 the nature of the organism was not well defined. Today several species of lactobacilli are used, and presumably they were responsible for the earlier fermentations which were inoculated with small amounts of decomposing meat or cheese. 

2 Citric acid. Citric acid is largely responsible for the acidic properties of lemon juice, and Scheele crystallized it from this source in 1784. For many 

The levels of the trace metals in the medium all have a crucial effect on the yield of citric acid, and the concentrations of copper, manganese, magnesium, iron, zinc and molybdenum all need to be controlled. For this reason the fermenter pans are constructed of aluminium or stainless steel to prevent the corrosive solution of citric acid leaching metals into solution. The metals are also removed from the molasses. They are either adsorbed onto ion- 

Organic acids, known as carboxylic acids, are characterized by the functional group called a carboxyl group. The carboxyl group is represented in the following ways  

CH3COOH ethanoic acid CH3CH2COOH propanoic acid 

Open-chain carboxylic acids form a homologous series. The carboxyl group is always at the beginning of a carbon chain, and the carbon atom in this group is understood to be C-1 in naming the compound. 

To name a carboxylic acid by the lUPAC system, first identify the longest carbon chain, including the carboxyl group. Then form the acid name by dropping the -e from the corresponding parent hydrocarbon name and adding -oic acid. Thus, the names corresponding to the C-1, C-2, and C-3 acids are methanoic acid, ethanoic acid, and propanoic acid. These names are, of course, derived from methane, ethane, and propane  

TABLE 19.7 Formulas and Names of Saturated Carboxylic Acids 

2 Reactions of Carboxylic Acids 3.16.2.1 Acidity Salt Formation 

Hydrogenation of Carboxylic Acids, Esters, and Related Compounds 

In general, carboxylic acids are hydrogenated with difficulty under mild conditions over usual metallic catalysts. However, it has been recognized that acetic acid may be reduced over platinum oxide under very mild conditions in the presence of perchloric acid.1 Kaplan observed that acetic acid was reduced rapidly over rhodium catalysts at room temperature and pressure, but the reduction stopped abruptly after a very small conversion.2 The occurrence of these reductions may lead to appreciable errors in the amounts of absorbed hydrogen when hydrogenations are carried out in acetic acid as solvent, although the reductions usually proceed only to limited extents, probably due to formation of some poisonous products. These undesired reductions of acetic acid solvent may be depressed in the presence of a substrate that may be adsorbed more strongly than acetic acid. 

Williams, Synthesis of Optically Active a-Amino acids. Organic Chemistry Series Vol. 7, Pergamon, Oxford (1989). 

Jacobus, M. Raban, K. Mislow, J. Org. Chem. 33 (1968) 1142. (R)-2-Cyclohexyl-2-hydroxyacetic acid 

7-Trimethyl-3-oxo-2-oxa-bicyclo[2.2.1]heptane-l-carboxylic acid [(-)-1 -(1 S,4R)-camphanic acid] 

Becher, R. Albrecht, K. Bernhard, H. G. W. Leuenberger, H. Mayer, R. K. Muller, W. Schuep, H. P. Wagner, Helv. Chim. Acta 64 (1981) 2419. 

Compared to aliphatic monocarboxylic acids, aliphatic dicarboxylic acids exhibit a slightly higher affinity toward carbonate-selective stationary phases. The retention behavior of aliphatic dicarboxylic acids such as succinic acid, malonic acid, and oxalic acid is very similar to that of nitrate and sulfate. In contrast to monocarboxylic acids, the retention of aliphatic dicarboxylic acids 

This finding is explained by the charge-stabilizing effect exerted by the +1-effect of the methylene groups that decreases from succinic acid to oxalic acid  

The presence of additional hydroxide groups in dicarboxylic acids such as malic acid, tartaric acid, and tartronic acid increases the acidic character and thus the retention (Table 3.25). A corresponding chromatogram is shown in 

Aliphatic tricarboxylic acids such as citric acid, isocitric acid, tricarballylic acid, and aconitic acid exhibit a remarkably high affinity toward the stationary phase of carbonate-selective anion exchangers. Hence, low-ionic strength car-bonate/bicarbonate buffer solutions are not particularly suitable as eluents. However, when a sodium hydroxide solution at a comparatively high concentration (c 0.08 mol/L) is used, tricarboxylic acids may be eluted. When the detection of these compounds is carried out via electrical conductivity, a high-capacity suppressor system such as micromembrane (MMS) or self-regenerating suppressors must be used to reduce background conductivity. 

Compared to aliphatic monocarboxylic acids, aromatic monocarboxylic acids exhibit a higher affinity toward the stationary phase. The simplest congener. 

The electrophilic addition of carboxylic acids to olefins can be drastically enhanced by the presence of a Lewis acid. Indeed, for the weakest acids such as acetic acid itself, the addition does not take place in the absence of a catalyst (strong Br nsted acid or Lews acid) capable of increasing the protonatir power of tiie medium, unle very basic olefins are used The rde of Lewis acids in these esterification reactions must be 

SnCl4 (CH3C00H)2 + CH3COOH - SnCl4 H(CH3COO)2 CH3COOH2. 

Guenzet and Camps proposed that the above interaction actually proceeds further and the real acidic species possesses the stmcture  

Latremouille and Eastham had already studied a similar esterification process. They found that the reaction of butene-2 with acetic acid-boron fluoride catalytic mixtures in ethylene chloride at 20 °C gave a quantitative yield of the corresponding acetate if the molar ratio [CH3COOH]/[Bp3] was higher than unity. The kinetics of this esterification followed the empirical law  

In the above studies the use of an excess carboxylic acid over the Lewis acid determined the specific situation whereby the catalytic species is an adduct between the two acidic components, virtually no free Lervis acid being present. Such situations seems most adequate for maximising esterification and minimising polymerisation. 

Also in the cathodic reduction of carboxylic acids, electrolysis is in competition with catalytic methods. However, catalytic hydrogenations in this area do not always proceed so smoothly that electrochemical processes are without any prospects from the outset. 

Aromatic carboxylic acids, e.g., benzoic acid, can be electrochemically reduced to benzyl alcohols  

Ratio of alcohol to aldehyde, about 5 1 Total current efficiency 53V. 

Benzyl alcohol, on the other hand, is produced industrially from benzaldehyde or benzyl chloride, which are available economically in large amounts. 

Better results are obtained in the reduction of o- and m-hydroxybenzoic acid  

The XH NMR spectrum for fumaric acid contains two lines, assigned to the olefinic and carboxylic acid protons, the latter of which is characterised by the same O- -O distance and has the same Siso value as the intermolecular hydrogen bond in maleic acid. 

A single crystal XH NMR study of potassium hydrogen maleate has established the chemical shift tensors of all magnetically inequivalent XH nuclei in the unit cell [131]. 

COOH HOOC Maleic Acid Fumaric Acid 

The orientation of the H chemical shift tensor for the carboxylic acid group was found to be consistent with the position of the hydrogen atoms at the midpoints between the two oxygen atoms in the hydrogen bond. 

For these complexes, the isotropic and 15N chemical shifts and the 15N chemical shift tensor elements were measured as a function of the hydrogen bond geometry. Lineshape simulations of the static powder 15N NMR spectra revealed the dipolar 2H-15N couplings and hence the corresponding distances. The results revealed several correlations between hydrogen bond geometry and NMR parameters which were analysed in terms of the valence bond order model. It was shown that the isotropic 15N chemical shifts of collidine and other pyridines depend in a characteristic way on the N-H distance. A correlation of the and 15N 

Compounds that contain the carboxyl group, —c—O—H carboxylic acids. Their general formula is R 

Unless otheiwise noted, all content on this page is Cengage Learning. 

Organic acids occur widely in natural products, and many have been known since ancient times. Their common (trivial) names are often derived from a Greek or Latin word that indicates the original source (see Table 23-11). 

The names of modified carboxylic acids are often derived from the trivial names of the acids. Positions of substituents are sometimes indicated by lowercase Greek letters, beginning with the carbon adjacent to the carboxyl carbon, rather than by numbering the carbon chain. 

The molecular packing characteristics of crystalline carboxylic acids have been analyzed both qualitatively [39, 135, 136] and quantitatively by atom-atom potentials [24, 26, 98). Here we review some of their principal packing characteristics. 

The carboxyl group adopts either the synplanar 24a (0=C-0-H ) or an-tiplanar 24b (0=C-0-H ) conformation, the former being by far the more prevalent [39] and stable [137, 138]. The 0=C-0-H conformation 24b occurs almost exclusively when the O-H bond participates in an intramolecular O - H... O bond, as for example in 1,2-disubstituted carboxylic acids 25. There are rare examples of molecules which form intermolecular O-H... O hydrogen bonds via an antiplanar 0=C-0-Ha conformation [139]. In their synplanar conformation, carboxylic acids generally form the cyclic dimer 26 Only a handful of carboxylic acid molecules RCO2H appear in a catemer motif C(4). 

Fermentation processes are the sources of a number of carboxylic acids, of which the largest bulk products are citric (S) and the amino acids 

Route Methanol Ethanol Propan-2-ol Butan-l-ol Acetone 

L-glutamate (6) and L-lysine (7). The annual world production of citric acid is now well over 0.5 million tonnes. Indeed, this figure probably underestimates the output in the Far East, particularly in countries such as China. Some estimates place the world production as high as 0.9 million tonnes, representing a sustained annual growth of over 8.5% for the past 60 years (Table 6.3). 

Several amino acids are manufactured in large quantities (Table 6.4). They are mostly used as food ingredients, for example to supplement 

Amino acid Method of manufacture Annual tonnage (1987) 

Amines and amides are organic compounds that contain nitrogen. Many nitrogen-containing compounds are important to life as components of amino acids, proteins, and nucleic acids (DNA and RNA). Many amines that exhibit strong physiological activity are used in medicine as decongestants, anesthetics, and sedatives. Examples include dopamine, histamine, epinephrine, and amphetamine. 

Alkaloids such as caffeine, nicotine, cocaine, and digitalis, which have powerful physiological activity, are naturally occurring amines obtained from plants. In an amide, the functional group consists of a carbonyl group attached to an amine. Amides, which are derived from carboxylic acids, are important in biology in proteins. In biochemistry, the amide bond that links amino acids in a protein is called a peptide bond. Some medically important amides include acetaminophen (Tylenol) used to reduce fever phenobarbital, a sedative and anticonvulsant medication and penicillin, an antibiotic. 

In a carboxylic acid, the carbon atom of a carbonyl group is attached to a hydroxyl group that forms a carboxyl group. The carboxyl functional group may be attached to an alkyl group or an aromatic group. 

Give the lUPAC and common names for carboxylic acids draw their condensed structural formulas or skeletal formulas. 

The lUPAC names of carboxylic acids replace the e of the corresponding alkane name with oic acid. If there is a substitnent, the carbon chain is numbered beginning with the carboxyl carbon. 

So far our discussion has focused on inorganic acids. A particularly important group of organic acids is the carboxylic acids, whose Lewis stractures can be represented by 

The conjugate base of a carboxylic acid, called a carboxylate anion, RCOO , can be represented by more than one resonance stracture  

In terms of molecular orbital theory [ M Section 9.6], we attribute the stability of the anion to its ability to spread out or delocalize the electron density over several atoms. The greater the extent of electron delocalization, the more stable the anion and the greater the tendency for the acid to undergo ionization— that is, the stronger the acid. 

The strength of carbojgrlic acids depends on the nature of the R group. Consider, for example, acetic acid and chloroacetic acid  

The presence of the electronegative Cl atom in chloroacetic acid shifts the electron density toward the R group, thereby making the O—H bond more polar. Consequently, there is a greater tendency for chloroacetic acid to ionize  

Various workers have used ion chromatography to determine low molecular weight carboxylic acids in wastewater [3] and rainwater [4,5]. Detection limits in the three methods were less than Ipg mL 

FIGURE 14.29 A flow chart emphasizing the carboxylic acid classification and giving the condensed structures and lUPAC names (left) and common names (right) of two simple carboxylic acids. 

The high oxidation state of carhon in which there are three bonds to electronegative atoms is the characteristic of carboxylic acids and the related acid chlorides, anhydrides, esters, ortho esters, amides, and nitriles. The transformations may involve oxidation from hydrocarbons or other partially oxidized substrates or exchange among various electronegative atoms on the carbon. 

Carbons that are already partially oxidized such as alkenes, primary alcohols, aldehydes, and methyl ketones are more readily oxidized to the carboxylic acid. Appropriately substituted alkenes may be cleaved using ozone followed by treatment with hydrogen peroxide to give carboxyUc acids. A convenient alternative is the combination of sodium periodate and a catalytic amount of permanganate (Eq. 6.2) [4]. The permanganate 

Primary alcohols are oxidized by the easily prepared pyridinium dichromate [6] (PDC) in DMF (Eq. 6.3) [7] or by Jones reagent in acetone (Eq. 6.4) [8]. Secondary alcohols are also easily oxidized to ketones under these conditions. Potassium permanganate in aqueous NaOH will oxidize primary alcohols but is not selective, attacking alkene sites as well. 

Aldehydes are more readily oxidized than alcohols and thus react with the reagents given above. Nonconjugated aldehydes give acids in good yield with PDC in DME. Where selectivity is needed, very mild reagents such as freshly precipitated silver oxide [9] or sodium chlorite (Eq. 6.5) [10] serve well. 

Within the same oxidation level, any of the acid derivatives may be hydrolyzed with aqueous acid or base, leading ultimately to the acid or the salt thereof. Nitrile hydrolysis is particularly difficult, requiring prolonged heating in water-ethylene glycol (Eq. 6.6) [11]. 

You learned in Chapter 4 [ W Section 4.1 ] that carboxylic acid formulas are often written with the ionizable H atom last, in order to keep the functional group together. You should recognize the formulas for organic acids written either way. For example, acetic add imy be written as HC2H3O2 or as CH3COOH. 

The abnormally strong hydrogen bonding in these acids is an advantage in one way, as the O—H stretching vibrations are so distorted from the normal as to be characteristic, sO that observations in this region give a valuable indication of the presence of carboxylic acids. 

There are also a number of other regions of the spectra from which some data may be obtained, although with less certainty than from those mentioned above. There are the regions near 1400 cm, 1250 cm and 920 cm The first two arise from strongly 

The study of all of these regions will generally provide a reasonably rehable identification of carboxylic acids, especially if account is taken of the intensity of the carbonyl absorption in relation to that of known acids. In addition, a hmited amount of data on the immediate environment of the COOH group may sometimes be obtained from a study of the C=0 frequency. 

Confirmation of the identification of a carboxylic acid can be readily obtained by the examination of a salt, or of a solution of the acid in water in which ionisation has occurred. Ionisation of the acid results in equilibration of the two oxygen atoms attached to the carbon with the disappearance of the carbonyl absorption, and the appearance of two new bands near 1550 cm and 1400 cm arising from the symmetrical and anti-symmetrical vibrations of the COO- grouping. The addition of mineral acids to ionised aqueous solutions reduces the ionisation, and the carbonyl absorption reappears. 

The identification of carboxylic acids by infra-red methods is therefore usually possible with reasonable certainty and, as will be seen, it is sometimes possible to obtain some additional data on the environment of the carboxyl group. 

Because the reaction of an amine with an acyl chloride is much faster than the hydrolysis of the acyl chloride, the reaction can usually be carried out in an aqueous alkah solution. This is well known as the Schotten-Baumann procedure. Eor example, a number of A-acyl taxol analogs have been prepared under Schotten-Baumann conditions by the reaction of A-debenzoyltaxol with various acid chlorides (Eq. 9.4). Highly purified A-long-chain-acyl neutral amino acids such as potassium A-lauroyTy-aminobutyrate, useful as surfactants for detergent 

1-methylpyiidinium chloride, prepared in situ from benzoyl chloride and l-methyl-2(lH)-pyridinethione, afforded the corresponding benzoyl deiivervatives in good yields. Thiocarbamates were prepared by adding RNHCOCl or RNCO to an aqueous alkaline solution (or emulsion) of thiophenols in high yields.The trifiuoroacetylation of amino 

Alternatively, esterification of carboxylic acid can be carried out in aqueous media by reacting carboxylic acid salts with alkyl halides through nucleophilic substitutions (Eq. 9.10). ° The reaction rate of alkyl halides with alkali metal salts of carboxylic acids to give esters increases with the increasing concentration of catalyst, halide, and solvent polarity and is reduced by water. Various thymyl ethers and esters can be synthesized by the reactions of thymol with alkyl halides and acid chlorides, respectively, in aqueous medium under microwave irradiation (Eq. 9.11). Such an esterification reaction of poly(methacrylic acid) can be performed readily with alkyl halides using DBU in aqueous solutions, although the rate of the reaction decreases with increasing 

Direct amide formation in aqueous solution between carboxylic acids and amines can occur and the rates are first order in the anion of the acid and the basic form of the amine (Eq. 9.12). The second-order rate constant is independent of the acidity of the medium. The condensation reaction of glycine to form di- and triglycine occurs in aqueous solution 

Kirk-Othmer Encyclopedia of Chemical Technology (4th Edition) 

The temperature at which decarboxylation occurs is of particular interest in manufacturing processes based on polymerisation in the molten state where reaction temperatures may be near the point at which decomposition of the diacid occurs. Decarboxylation temperatures are tabulated in Table 2 along with molar heats of combustion. The diacids become more heat stable at carbon number four with even-numbered acids always more stable. Thermal decomposition is strongly influenced by trace constituents, surface effects, and other environmental factors actual stabiUties in reaction systems may therefore be lower. 

Dicarboxyhc acid Decarboxylation temp, °C Molar heat of combustion, kJ /mol 

Order of thermal stabiUty as determined by differential thermal analysis is sebacic (330°C) a2elaic = pimelic (320°C) suberic = adipic = glutaric (290°C) succinic (255°C) oxahc (200°C) malonic (185°C) (19). This order is somewhat different than that in Table 2, and is the result of differences in test conditions. The energy of activation for decarboxylation has been estimated to be 251 kj/mol (60 kcal/mol) for higher members of the series and 126 kJ/mol (30 kcal/mol) for malonic acid (1). 

In a subsequent study using a resting cell system of N. diaphanozonaria JCM3208, deracemization of 4-substituted-2-thiopropanoic adds (34) were 

Only Co(IlI) has sufficient reactivity to oxidise RCO2H at an appreciable rate however, all these oxidants attack the atypical formic acid which can function like a secondary alcohol. 

The kinetics of oxidation of propionic acid in aqueous perchloric acid by Co(III) perchlorate are  

Similar kinetics are given by phenylacetic acid, but with isobutyric and pivalic acids the rates are given by the simple expression k2[Co(IIl)][RC02H]/[H ]. The oxidation of C6H5CD2CO2H proceeds at 80% of the rate of the protio compound. The relative rates of oxidation of a series of acids of formula RCO2H at 10 C° are 

Detailed product analyses indicate the major route of oxidation to be one of oxidative decarboxylation. The detailed mechanism is 

The synchronous departure of R- (as opposed to a two-step process) is supported by (i) the considerable effect on the rate of varying R and ( ) the isotope effect. R- can also be scavenged by bromoform giving RBr . As with nearly all oxidations by Co(III), these are characterised by large E values (19 to 23 kcal. mole ) and large A values (10 -10 l.mole . sec ). 

The value 2.70 A for the O—H- O distance in this substance is smaller than that in ice, 2.76 A, as expected for this stronger bond. From the enthalpy of dimerization, 14.12 kcal/mole, the O—H O bond energy is found to have the value 7.06 kcal/mole. The value 7.6 kcal/mole is similarly found for the hydrogen-bond energy in acetic acid. 4 These values are about 50 percent greater than those for ice. 

The distance from each hydrogen atom to the nearer of the two adjacent oxygen atoms in the dimer of acetic acid has been reported to be 1.075 0.015 A this is considerably greater than the value 1.01 A for ice, as is to be expected in consequence of the increased strength of the hydrogen bond. 

The increased strength of this hydrogen bond can be accounted for in the following way. The resonance of the molecule to the structure 

Benzoic acid and other carboxylic acids have been shown to be associated with double molecules in solution in certain solvents, such as benzene, chloroform, carbon tetrachloride, and carbon disulfide.88 The value 4.2 kcal/mole for the hydrogen-bond energy has been found in this way for benzoic acid and o-toluic acid, and 4.7 kcal/mole for ftZr-toluic acid. 

Benzoic acid exists in the monomeric form in solution in acetone, acetic acid, ethyl ether, ethyl alcohol, ethyl acetate, and phenol in these solutions the single molecules are stabilized by hydrogen-bond formation with the solvent. 

1- The anhydride in the stmling compound suffers a basic hydrolysis, producing a p-keto acid. 

2- One of the liberated alcohols attacks the protonated carbonyl of the methyl ester, producing the elimination of methanol and formation of a 6-lactone. 

1- The catalytic hydrogenation produces the reductive breakage of the N-O bond, liberating an amine and an alcohol. 

2- The amine attacks one of the esters, displacing, via an addition-elimination mechanism, an ethoxide, and generating a lactam. 

1- The methyllithium attacks the lactam carbonyl and causes the expulsion of an amide. 

The hydride anion (H ) behaves as a nucleophile in the reduction of a carbonyl group and binds to the positively charged carbon atom. The remaining AIH3 is a Lewis acid which, as an electron acceptor, attacks the oxygen. After hydrolysis and release of aluminum hydroxide, the reaction ends with the formation of an alcohol, in this case propanol (see the following scheme). 

The reduction of a ketone follows the same mechanism. In the following example, acetone is reduced to propane-2-ol. 

Justus von Liebig and Bernhard Tollens have discovered that milder agents such as silver oxide, Ag20 oxidize aldehydes to carboxylic acids. This reaction, which is characteristic for aldehydes, serves as a specific qualitative test for this 

An alternative method for the preparation of carboxylic acids is the reaction of nitriles with sulfuric acid. This reaction is important in organic synthesis because it can be used to extend the hydrocarbon chain by one carbon atom. Nitriles can be obtained from the corresponding alkyl halides in the reaction with HCN by nucleophilic substitution. Nitrile can easily be oxidized to carboxylic acid. 

Many essential natural products that are ubiquitous in living organisms are carboxylic acids. The simplest (parent) carboxylic acid is formic acid acidum for-micum) which is named methanoic acid in the lUPAC nomenclature. This acid is the main component of the poison of ants. 

Isotope effects have been used to examine the HCr04 cooxidation of 2-hydroxy-2-methylbutyric acid and propan-2-ol. The reaction involves the proposed intermediate 3, which decomposes to give EtCOMe, Mc2CO, 

Oxidation of aliphatic acids by Ag shows a slight dependence on [Ag ] but the rate-determining step is electron transfer to Ag or AgOH. The rate constants increase from 5.59 s to 8.55 x 10 s for 

Decarboxylation of a-amino-a-isopropyl malonate, chelated to a cobalt(III) N4-chelate, where N4 is a chiral tetradentate amine ligand, in acidic media gives valine with considerable asymmetric induction. With N4 = l,7-bis(2(S)-pyrrolidyl)-2,6-diazaheptane, the ratio of S R isomers is 2 98 and it is thought that attack by is obstructed in this case by the in-plane pyrridoline ring and the bulky isopropyl substituent on the malonate. Other substituents show lesser asymmetric induction. The reaction kinetics are pH dependent with a pK 0. 

The rates of oxidative decarboxylation of amino acids by the cop-per(III) complex [Cu(I06)2] increase with increasing pKb of the substrate. Periodate inhibition in the rate law suggests formation of a complex between the amino acid and [CuflOe)] , which decomposes in 

The effects of H20-dioxane mixtures have been examined on the Mg, Mn , and Zn -catalyzed decarboxylation of oxaloacetate. The mechanism involves metal-oxaloacetate complex formation and though the rates are considerably enhanced, complications from the formation of enolate complexes are detected. The results of these studies are compared with metal ion catalysis in the presence of pyruvatekinase and it is concluded that bonding is aided by the presence of the metal ion but that other enzyme functional groups promote decarboxylation. 

It must be mentioned that to understand the stereochemical outcome of the reaction a detailed mechanistic analysis turns out to be critical, not only to determine the binding mode in the active site and the stereochemistry of the addition, but also to identify which of the EWGs acts as the activating one. In different instances, it has been done by either deuterium labeling experiments [122,123] or computational docking studies [37]. 

A surprisingly broad substrate specificity has been found for the enoate reductases from Clostridium tyrohutyritMm and Clostridium kluyveri [126], however, up to now, no preparative-scale bioreduction of a,p-unsaturated carboxylic acids using these enzymes in their purified form has been reported, most likely due to the technical difficulties in handling these sensitive biocatalysts. 

On the other hand, double bonds activated by two carboxylic acid groups are seldom accepted also by ene reductases, though they are considered borderline substrates [25,121]. For instance, citraconic add was shown to afford (iJ)-2-meth-ylsucdnic add with a few OYEs, while mesaconic acid has been reduced only by EBPl yielding the (S)-enantiomer vdth less than 50% ee [28]. Anyway, the reaction is much less efficient compared to the corresponding diesters. 

MS Molecular ion Aliphatic moderate, strong for long chains, tendency to protonate Aromatic strong 

Saturated acids a,(5-Unsaturated acids Aromatic adds 

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Equation (12), applicable at low or moderate pressures, is used in this monograph for typical vapor mixtures. However, when the vapor phase contains a strongly dimerizing component such as carboxylic acid. Equation (7) is not applicable and... 

This chapter presents a general method for estimating nonidealities in a vapor mixture containing any number of components this method is based on the virial equation of state for ordinary substances and on the chemical theory for strongly associating species such as carboxylic acids. The method is limited to moderate pressures, as commonly encountered in typical chemical engineering equipment, and should only be used for conditions remote from the critical of the mixture. 

Numerous empirical equations of state have been proposed but the theoretically based virial equation (Mason and Spurling, 1969) is most useful for our purposes. We use this equation for systems which do not contain carboxylic acids. 

Equation (10b) is used in this work whenever the vapor mixture does not contain one or more carboxylic acids. 

Chemical" Theory of Vapor Nonideality for Strongly Interacting Substances (Mixtures Containing Carboxylic Acids)... 

The virial equation is appropriate for describing deviations from ideality in those systems where moderate attractive forces yield fugacity coefficients not far removed from unity. The systems shown in Figures 2, 3, and 4 are of this type. However, in systems containing carboxylic acids, there prevails an entirely different physical situation since two acid molecules tend to form a pair of stable hydrogen bonds, large negative... 

Figure 3-6. Fugacity coefficients for saturated mixtures containing two carboxylic acids formic acid (1) and acetic...

While vapor-phase corrections may be small for nonpolar molecules at low pressure, such corrections are usually not negligible for mixtures containing polar molecules. Vapor-phase corrections are extremely important for mixtures containing one or more carboxylic acids. 

As discussed in Chapter 3, at moderate pressures, vapor-phase nonideality is usually small in comparison to liquid-phase nonideality. However, when associating carboxylic acids are present, vapor-phase nonideality may dominate. These acids dimerize appreciably in the vapor phase even at low pressures fugacity coefficients are well removed from unity. To illustrate. Figures 8 and 9 show observed and calculated vapor-liquid equilibria for two systems containing an associating component. 

However, when carboxylic acids are present in a mixture, fugacity coefficients must be calculated using the chemical theory. Chemical theory leads to a fugacity coefficient dependent on true equilibrium concentrations, as shown by Equation (3-13). ... 

It is an important dyestuffs intermediate. It condenses with chloroethanoic acid to give phenylglycine-o-carboxylic acid for the synthesis of indigo. It can be diazotized and used as a first component in azo-dyes it condenses also with chloroanthraquinones to give intermediates for anthraquinone dyes. 

Arndt-Eistert synthesis A procedure for converting a carboxylic acid to its next higher homologue, or to a derivative of a homologous acid, e.g. ester or amide. 

Colourless solid m.p. 79 - C. Forms a quinone, duroquinone, a phenol, durenol and a carboxylic acid, durylic acid. Oxidized to pyro-mellitic dianhydride. 

Kolbe reaction The pre >aration of saturated or unsaturated hydrocarbons by the electrolysis of solutions of the alkali salts of aliphatic carboxylic acids. Thus, ethanoic acid gives ethane,... 

However, the term saturated is often applied to compounds containing double or triple bonds which do not easily undergo addition reactions. Thus ethanoic acid is termed a saturated carboxylic acid and acetonitrile a saturated nitrile, whereas a Schiff base is considered to be unsaturated. 

Crude oils contain carboxylic acids. These are analyzed by titration with potassium hydroxide and the result of the analysis is expressed in mg of KOH/g crude. 

Fig. IV-20. Film pressure-area plots for cerebronic acid (a long-chain a-hydroxy carboxylic acid) and cholesterol (see insert) and for an equimolar mixture. At low pressures the r-a plot is close to that of the average (dashed line), an unanticipated kink then appears, and finally, the horizontal portion probably represents ejection of the cholesterol. (From Ref. 239.)...

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