Phenolic acids groups

Typical organic acids contain the --C(0)0H group, but many other acid groupings, e.g. the sulphonic -S(0)20H give acidic properties to organic compounds. Phenols have acidic properties and are classified with enols as pseudo-acids. 

When the phenol contains a carboxylic acid group, e.g., m- or p-hydroxy-benzoic acid, the acetylated derivative will of course remain in solution as the sodium salt, but is precipitated when the solution is subsequently acidified. Salicylic acid, however, cannot be acetylated under these conditions. 

Sodium carbonate solution [cf. Section 5, p. 330). Note that phenols (except those containing acidic groups, e.., nitrophenols) give no reaction with sodium carbonate solution. 

Picric acid, the 2 4 6-trinitro derivative of phenol, cannot be prepared in good yield by the action of nitric acid upon phenol since much of the latter is destroyed by oxidation and resinous products are also formed. It is more convenient to heat the phenol with concentrated sulphuric acid whereby a mixture of o- and p-phenolsulphonic acids is obtained upon treatment of the mixture with concentrated nitric acid, nitration occurs at the two positicsis mela to the —SOjH group in each compound, and finally, since sulphonation is reversible, the acid groups are replaced by a third iiitro group yielding picric acid in both cases ... 

RCH(OH)=CHCOR or -keto esters RCH(OH)=CHCOOR ) dissolve in dilute sodium hydroxide solution, i.e., contain an acidic group of sufficient strength to react with the alkah. Carboxyhc acids and sulphonic acids are soluble in dilute solutions of sodium bicarbonate some negatively-substituted phenols, for example, picric acid, 2 4 6-tribromo-phenol and 2 4-dinitrophenol, are strongly acidic and also dissolve in dilute sodium bicarbonate solution. 

The best known aryl ester is O acetylsalicylic acid better known as aspirin It is pre pared by acetylation of the phenolic hydroxyl group of salicylic acid... 

Substitution Reactions on Side Chains. Because the benzyl carbon is the most reactive site on the propanoid side chain, many substitution reactions occur at this position. Typically, substitution reactions occur by attack of a nucleophilic reagent on a benzyl carbon present in the form of a carbonium ion or a methine group in a quinonemethide stmeture. In a reversal of the ether cleavage reactions described, benzyl alcohols and ethers may be transformed to alkyl or aryl ethers by acid-catalyzed etherifications or transetherifications with alcohol or phenol. The conversion of a benzyl alcohol or ether to a sulfonic acid group is among the most important side chain modification reactions because it is essential to the solubilization of lignin in the sulfite pulping process (17). 

Dyes, Dye Intermediates, and Naphthalene. Several thousand different synthetic dyes are known, having a total worldwide consumption of 298 million kg/yr (see Dyes AND dye intermediates). Many dyes contain some form of sulfonate as —SO H, —SO Na, or —SO2NH2. Acid dyes, solvent dyes, basic dyes, disperse dyes, fiber-reactive dyes, and vat dyes can have one or more sulfonic acid groups incorporated into their molecular stmcture. The raw materials used for the manufacture of dyes are mainly aromatic hydrocarbons (67—74) and include ben2ene, toluene, naphthalene, anthracene, pyrene, phenol (qv), pyridine, and carba2ole. Anthraquinone sulfonic acid is an important dye intermediate and is prepared by sulfonation of anthraquinone using sulfur trioxide and sulfuric acid. 

Ca.rhoxyla.tlon, This is the process of iatroduciag a carboxyUc acid group iato a phenol or naphthol by reaction with carbon dioxide under appropriate conditions of heat and pressure. Important examples are the carboxylation of phenol and 2-naphthol to give sahcyhc acid and 2-hydroxy-3-naphthoic acid, respectively. 

An isopropyl ether was developed as a phenol protective group that would be more stable to Lewis acids than an aryl benzyl ether. The isopropyl group has also been... 

In the H NMR spectrum five protons can be exchanged by deuterium. Here the molecular formula permits only OH groups. The shift values above 7.9) identify four phenolic OH groups and one less acidic alcoholic OH function = 4.0, overlapping). 

In general, this method is a one-step procedure for the oxidation of a cresol type of molecule to the corresponding phenolic acid. The vigorous reaction conditions clearly limit the type of functional groups that may be present in the molecule. There is no evidence that the reaction has been applied to polynuclear or heterocyclic alkylphenols. 

Ion exchange, in which cation and/or anion resins are used to replace undesirable anionic species in liquid solutions with nonhazardous ions. For example, cation-exchange resins may contain nonhazardous, mobile, positive ions (e g., sodium, hydrogen) which are attached to immobile acid groups (e.g., sulfonic or carboxylic). Similarly, anion-exchange resins may include nonhazardous, mobile, negative ions (e.g., hydroxyl or chloride) attached to immobile basic ions (e.g., amine). These resins can be used to eliminate various species from wastewater, such as dissolved metals, sulfides, cyanides, amines, phenols, and halides. 

Primary and secondary amines, amino acids and phenols react In the case of long-wavelength UV light (A = 365 nm) the DANS amides fluoresce yellow-green, while amines that have reacted at a phenolic OH group have an intense yellow to yellow-orange fluorescence The detection hmit for DANS amides is ca 10 mol [86]... 

From this discussion, the limitations of the force field should have become clear. There is no such thing as a universal force field which describes every system in every condition. The force field is a function with few adjustable parameters and can, therefore, not be expected to reproduce all properties of all chemical species under all circumstances. This means, for example, that an OH group in an aliphatic alcohol will have to be treated differently from a phenolic OH or from the OH of a carboxylic acid group. Similarly, the density and temperature window of a force field is often limited [22]. 

Comforth has reviewed literature reports and independently studied the special cases of reaction of 1 with salicylaldehyde and with 2-acetoxybenzaldehyde. Coumarins (10) are afforded in the condensation of 1 with salicylaldehyde or its imine, whereas when 2-acetoxybenzaldehyde is used, acetoxy oxazolone 12 is the major product. The initial aldol condensation product between the oxazolone and 2-acetoxybenzaldehyde is the 4-(a-hydroxybenzyl)oxazolone 11, in which base-catalyzed intramolecular transacetylation is envisioned. The product 9 (R = Ac) can either be acetylated on the phenolic hydroxy group, before or after loss of acetic acid, to yield the oxazolone 12, or it can rearrange, by a second intramolecular process catalyzed by base and acid, to the hydrocoumarin, which loses acetic acid to yield 10. When salicylaldehyde is the starting material, aldol intermediate 9 (R = H) can rearrange directly to a hydrocoumarin. Comforth also accessed pure 4-(2 -hydroxyphenylmethylene)-2-phenyloxazol-5(4//)-one (13) through hydrolysis of 12 with 88% sulfuric acid. 

The respective amide was prepared from 7-substituted 5-oxo-2,3-dihydro-5//-pyrido[l,2,3-de]-l,4-benzoxazine-6-carboxylic acids via acid chlorides with different benzylamines (00M1P3). 6-Carboxamides were N-benzylated, and a side-chain phenolic hydroxy group was O-alkylated. 7-Aryl-5-oxo-2,3-dihydro-5//-pyrido[l, 2,3-r/e]-1,4-benzoxazine-6-carboxylic acid was obtained from the ethyl ester by alkalic hydrolysis. 

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