Hydroxylation aliphatic carboxylic acids

Hydroxylation of short chain aliphatic carboxylic acids can be accomplished by a number of micro-organisms (see also Scheme 3) including Endomyces reessii, Trichosporum fermentans, Torulopsis Candida and Micrococcusflavus. Longer chain carboxylic acids can also be satisfactorily hytfaoxylat ... 

The platinum(II) ion, in the presence of a Pt(IV) complex, catalyzes the hydroxylation of unactivated C-H bonds of aliphatic carboxylic acids in water [23b]. The following order of reactivity has been evaluated ... 

Castor oil is a clear [almost colorless), or pale yellow-colored viscous oil, where 90% of the content corresponds to rlclnolelc acid. It presents aliphatic carboxylic acid with an 18-carbon chain, having a double bond between carbon 9 and 10 and a hydroxyl group on the carbon 12, which is exclusive to castor oil. This renewable resource also has high water resistance and, when... 

Alkyl halides in the presence of silver oxide will convert any non-hindered carboxylic acid (or its salt) to the corresponding alkyl ester in minutes, and phenolic or thiol groups will also be alkylated rapidly [436]. Hydroxyl groups are alkylated slowly an ot always to completion. The alkyl halides most frequently uJQp are the lower molecular weight aliphatic... 

You can use analogies to put adipic acid in its right place. Acetic acid is the most important aliphatic monocarboxylic acid adipic is the most important aliphatic dicarboxylic acid. (You remember, of course, that carboxylic is the contraction for carbonyl and hydroxyl, -C-O and -OH, or together, -COOH. Right ) Also, adipic acid is to Nylon 66 what cumene is to phenol. About 95% of the adipic acid ends up as Nylon 66, which is used for tire cord, fibers, and engineering plastics. 

This simple, selective and efficient method was applied to a wide range of aliphatic/ aromatic carboxylic acid derivatives that contain hydroxyl-, halo-, ester and other base-sensitive groups as substituents. 

Composition. Shellac is primarily a mixture of aliphatic polyhydroxy acids in the form of lactones and esters. It has an acid number of ca 70, a saponification number of ca 230, a hydroxyl number of ca 260, and an iodine number of ca 15. Its average molecular weight is ca 1000. Shellac is a complex mixture, but some of its constituents have been identified. Aleuritic acid, an optically inactive 9,10,16-trihydroxypalmitic acid, has been isolated by saponification. Related carboxylic acids such as 16-hydroxy- and 9,10-dihydroxypalmitic acids, also have been identified after saponification. These acids may not be primary products of hydrolysis, but may have been produced by the treatment. Studies show that shellac contains carboxylic acids with long methylene chains, unsaturated esters, probably an aliphatic aldehyde, a saturated aliphatic ester, a primary alcohol, and isolated or unconjugated double bonds. 

Changes in aliphatic side chains are mainly initiated by the abstraction of a hydrogen atom from a C-H bond. This produces a free radical which in the absence of O2 can combine with similar free radicals to give dimerization products or with CO2 [probably the CO2 ion. (40)] to give monoamino-dicarboxylic acids. In oxygen these are replaced by oxidative reactions which produce carbonyl, hydroxyl, and carboxyl groups through hydro-peroxy intermediates ... 

Phenolic compounds are, in general, weak acids. Compared to the hydroxyl group of unsubstituted aliphatic alcohols, however, the phenolic OH-group is more acidic. The reason for this is that the anion formed after abstracting the proton from the hydroxyl group is relatively stable because of the existence of several mesomeric structures. The anion is referred to as the phenolate anion. Hence, phenol (2.5) is a weak acid, with a pKa value of 10. This places phenol in between carboxylic acids (pKa = 4-5) and aliphatic alcohols (pKa = 16-19). 

Benzylic and allylic positions are hydroxylated by CPO in halide-dependent catalytic transformations. Toluene and p-xylene are oxidized to the respective aldehydes and carboxylic acids [247, 248]. Ethylbenzene and other substrates with longer alkyl chains form the respective benzylic/allylic alcohols with high enantio-selectivity. Straight-chain aliphatic and cyclic (Z)-alkenes are hydroxylated, favoring small unsubstituted substrates in which the double bond is not more than two carbon atoms from the terminus. Steric control is observed for benzylic hydroxylations. 

Peroxyacetic acid oxidation is similar to the peroxytrifluoroacetic acid (Deno) oxidation (28). These peroxide systems are reported to selectively oxidize the aromatic portions of molecules while leaving aliphatic portions intact (29). Peroxyacetic acid will oxidize aromatic units to phenolic units via hydroxylation. These phenolic moieties will oxidize rapidly to ortho and para quinones, the latter of which are unstable are undergo ring fission to form diene carboxylic acids (30). 

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