Carboxylic acids alkanoic

The name of the parent carboxylic acid (alkanoic) is changed to alkanoa/e and is preceded, as in a separate word, by the name of the ester alkyl group R ... 

Fluorinated carboxylic acids Alkanoic acid fluorides 3M Dai Nippon... 

Silylation of Carboxylic Acids. Alkanoic and aromatic carboxylic acids can be readily silylated with hexamethyldisiloxane. The reaction is carried out under acid catalysis (usually sulfuric acid) and azeotropic removal of water (eq 1). The rate of reaction is strongly influenced by the acidity of the carboxylic acid and increases with increased acidity. This method avoids the use of an amine and thus simplifies isolation of the product because it does not have to be separated from an amine hydrochloride. A limitation is the need for a solvent which allows for azeotropic removal of water. 

TABl.E 11-10. THIAZOt E CARBOXYLIC. THIAZOLE ALKANOIC ACIDS, AND THEIR DERIVATIVES (10)... 

By simply hydrolyzing the easily accessible 2-hydroxy-2-methylalkanenitriles with concentrated acid, 2-hydroxy-2-methylalkanoic acids are obtained without measurable racemization (Table 3). The reaction sequence from the starting ketone to the carboxylic acid can be carried out in one pot without isolation of the cyanohydrin. The enantiomeric excesses of the (/ )-cyanohydrins and the (ft)-2-hydroxyalkanoic acids are determined from the ( + )-(/T)-Mosher ester derivatives and as methyl alkanoates by capillary GC, respectively. The most efficient catalysis by (R)-oxynitrilase is observed for the reaction of hydrocyanic acid with 2-alkanoncs. 3-Alkanoncs are also substrates for (ft)-oxynitrilase, to give the corresponding (/ )-cyanohydrins32. 

Ketones can also be prepared directly from carboxylic acids by activation as mixed anhydrides by dimethyl dicarbonate.236 These conditions were used successfully with alkanoic and alkanedioic acids, was well as aromatic acids. 

Additional BHT-derived 5-LO inhibitors bear heteroatom-linked 4-substituents. Searle s SC-45662 (50) was selective (25 1) for 5-LO over CO in cRBL (3.7 /iM) and in A23187-stimulated RBL-1 cells (7.1 yuM) [146]. Besides NSAID-like activity in RAA (down to 10 mg/kg p.o.), SC-45662 also inhibited GPB (ED30 16.7 mg/kg p.o.), and LTB4 release from ulcerative colitis rectal mucosal biopsy samples was decreased [147]. Several patents have described similar compounds where the alkyl substituent on sulphur is varied quite widely [148 151]. Oxidation of the distal sulphur was consistent with activity, while replacement of this sulphur with oxygen gave reduced potency. Simple alkyl groups, alkylene-linked esters and amides, and disulphide-linked alkanoic esters were also active in cRBL with similar potency free carboxylic acids were somewhat less potent. Oxidation of the sulphur attached to the phenolic ring destroyed the activity. 

Carboxy terminal amino acid or peptide thiols are prepared from various p-amino alcohols by conversion into a thioacetate (R2NHCHR1CH2SAc) via a tosylate followed by saponification.Several methods have been used to prepare N-terminal peptide thiols, the most common procedure is the coupling of (acetylsulfanyl)- or (benzoylsulfanyl)alkanoic acids or add chlorides with a-amino esters or peptide esters, followed by deprotection of the sulfanyl and carboxy groups. 8 16 Other synthetic methods include deprotection of (trit-ylsulfanyl)alkanoyl peptides, 1718 alkaline treatment of the thiolactones from protected a-sulfanyl acids, 19 and preparation of P-sulfanylamides (HSCH2CHR1NHCOR2, retro-thior-phan derivatives) from N-protected amino acids by reaction of P-amine disulfides with carboxylic acid derivatives, followed by reduction. 20,21 In many cases, the amino acid or peptide thiols are synthesized as the disulfides and reduced to the corresponding thiols by the addition of dithiothreitol prior to use. 

Highly stereoselective aldol reactions of lithium ester enolates (LiCR1 R2CC>2R3) with (/0-2-(/ -tolylsulfiny I (cyclohexanone have been attributed to intermediacy of tricoordinate lithium species which involve the enolate and the sulfinyl and carbonyl oxygens of the substrates.43 The O-metallated /<-hydroxyalkanoatcs formed by aldol-type reaction of carbonyl compounds with enolates derived from esters of alkanoic acids undergo spontaneous intramolecular cyclization to /1-lactones if phenyl rather than alkyl esters are used the reaction has also been found to occur with other activated derivatives of carboxylic acids.44... 

Number of C atoms Acyclic primary monoamino alkanoic acids Mono- carboxylic acids Di- carboxylic acids a-Hydroxy- carboxylic acids... 

The IUPAC rules name esters as alkyl alkanoates. That is, the portion of the ester derived from the alcohol is named as an alkyl group. The portion of the ester that is derived from the carboxylic acid is named as the conjugate base of that acid. It is easy to distinguish these parts. The half derived from the carboxylic acid has the carbonyl group. Pentyl ethanoate, or pentyl acetate, is one ester used as artificial banana flavoring. Figure 11.51 shows three ester nomenclature examples. 

Alkanoic acids or their copper salts cannot be decarboxylated under the same conditions as those acids which contain a rr-system (56), although fluorene-9-carboxylic acid appears to be an exception 279). 9-Fluo-renylcopper is the supposed intermediate. Under certain conditions the decarboxylation of alkanoic acids by lead(IV) is catalyzed by copper(II) complexes alkylcopper species have been proposed as intermediates 179). 

Decarboxylation of alkanoic acids means of LTA in benzene as solvent is hindered by die formation of all lbenzenes as by-products. This side reaction is especially pronounced widi radicals derived from primary acids or odier acids from which the radical is not easily oxidized LTA. In some cases, such as that of apocamphane-l-carboxylic acid (equation 54), good yields of alkylbenzene can be obtained. Intramolecular versions of this reaction in which the radical cyclizes onto an aromatic nucleus at the appropriate position in the chain have also been observed. 

Elimination of carbon dioxide from carboxyl, water from alcoholic hydroxyl, carboxylic acid from alkanoate, and hydrogen chloride from chlorine side groups or chain ends are typical thermal decomposition reactions in the temperature range 250-350°C. Hydrogen chloride is an important product of poly(vinyl chloride) because every second carbon atom of the hydrocarbon polymer chain is chlorine substituted. But hydroxyl, alkanoate and free carboxylic acid groups normally occur only at the ends of the macromolecular chains in customary plastics, thus the contribution of their elimination to the volatile pyrolysis products is negligible. 

Most aliphatic acid.s enter the process easily, but more vigorous reaction conditions are necessary for aryl carboxylic acids or for sterically hindered alkanoic acids. Increased pressure can help counteract such problems, e.g. 2,2-dimethylpropanoic acid heated at 112°C in ethanol with o-phenylenediamine dihydrochloride for 24 h at 8kbar pressure gives a 48% yield of 2-l-butylbenzimidazolc 76. Care has to be taken, though, that the ethanol concentration is not too high, as esterification of the carboxylic acid becomes a competing reaction DMSO appears to be a suitable alternative... 

Most alkanoic acids have values near 5, but the exact pK, of a given acid depends on structure. Carboxylic acids substituted by electron-withdrawing groups are more acidic (have a lower p/Cj) because their carbox) -ate ions are stabilized. Carboxylic acids substituted by electron-donating groups are less acidic (have a higher because their carboxylate ions are destabilized. 

Despite the fact that hydrocarboxylation is a one-step synthesis to alkanoic acids and that with specific catalysts and under certain reaction conditions the straight-chain/branched-chain isomer n/i) ratio can be rather high, this route to carboxylic acids is not used commercially today. It will be up to future R D workers to design catalysts that are active and stable enough to replace today s commercial two-step synthesis for the preparation of alkanoic acids from their aldehydes by oxidation. 

Among simple structures that are suitable as key synthetic intermediates, a-branched carboxylic acids are easily prepared and versatile (Figure 2). One would like to obtain such a material from an available chiral pool and proceed, but few a-branched alkanoic acids are available as natural products. (S)-2-Methylbutyric acid, uniquely, can be obtained in 99% enantiomeric excess (ee) by Jones oxidation of the commercially available alcohol (3). ... 

Alkanoic acid. A carboxylic acid derived from an alkane. 

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