Para-hydroxy benzoic acid

Scheme 7 Synthesis of HPOA and its polycondensation with para hydroxy benzoic acid.

The preservatives I select for my formulations is much more limited than the ten listed in the above reference. The products which I develop for a company with natural ingredients image, restricted me to the para hydroxy benzoic acids, benzyl alcohol and phenoxyethanol. I have been allowed to use Myavert C during the last two years due to increase in customer complaints which was assumed to be due to the high levels of phenoxyethanol and benzyl alcohol used hence allergic reaction to the... 

Source Vanillin [wt.%1 Vanillic acid [wt.%1 para-Hydroxy benzaldehyde [wt.%1 para-Hydroxy benzoic acid [wt.%1... 

It is an interesting fact that if potassium phenolate is used in the Kolbe synthesis para-hydroxy benzoic acid is obtained, especially at high temperatures. Potassium phenyl carbonate is first formed, and heated up to 150° yields salicylic acid, but if the temperature be further raised, the para-acidis produced in increasing quantities until at 220° potassium para-hydroxy-benzoic acid is the sole product. 

Anisic Acid.—derivative of para-hydroxy benzoic acid is the COOH (i)... 

Synthesis from meta- or para-Hydroxy Benzoic Acid.—The constitution is proven by its synthesis by sidphonation and then alkali fusion of either meta-hydroxy benzoic acid or para-hydroxy benzoic acid. As this synthesis introduces into each of these acids first a sulphonic acid group and then in place of this a second hydroxyl group the two hydroxyls in the final product, protocatechuic acid, must be in the 3-4 positions as only such positions could be occupied in a product obtained from either the meta or para hydroxy benzoic acid. 

Phenol acids are phenols in which there is also a carboxylic acid group attached to the benzene ring. They include salicylic acid (ortho-hydroxybenzoic acid) and para-hydroxy-benzoic acid (Figure 25.8). Acetylsalicylic acid (aspirin) and sodium salicylate are derivatives of salicylic acid. Like phenol, they have antipyretic and analgesic properties. The methyl, ethyl and propyl esters of para-hydroxybenzoic acid (parabens) are used as preservatives in pharmaceuticals, cosmetics and foodstuffs. 

Jackson and Kuhfuss from Tennessee Eastman demonstrated that liquid crystalline behavior existed in copolymers based on polyfethylene terephthalate) (PET) and para-hydroxy benzoic acid (ABA). However, intricate details pertaining to the polyesterification kinetics have remained imexamined. 

The most common form is the nematic, a bimdle of parallel, long, rodlike molecules. Additional cooling to the primary transition temperature, T leads to solidification into a solid crystalline phase (small crystallites). In the region between Tj and T , a liquid of very low viscosity prevails, in contrast to the high melt viscosity. The aromatic polyesters have high heat distortion temperatures (HDT). Vectra, composed of para-hydroxy-benzoic acid (PHBA) and para-hydroxy-naphtoic acid (PHNA), has an HDT of 180 C-240 C. Xy-dar, composed of PHBA, tera-phthalic acid and biphenol, has an even higher HDT of 260 C-350 C. 

Carbon-carbon bond formation as a consequence of substitution on the phenolic aromatic ring can be effected in a variety of other ways too. For example, if the sodium salt of phenol is heated at high pressure with carbon dioxide to 125-250°C, or//io-substitution occurs (Equation 8.29) at 250-300 C, the para-hydroxy benzoic acid results (Equation 8.30). The carboxylation process is known as the Kolbe-Schmitt reaction. ... 

C.W. Calundann, Polyester of 6-hydroxy-2-naphthoic acid and para-hydroxy benzoic acid capable of readily undergoing melt processing, US Patent 4,161,470, assigned to Celanese Corporation, July 17,1979. 

The para isomer cannol form such a bond because the —OH and —COf groups are too far apart. By stabilizing the product, the internal hydrogen bond is thought to make o-hydroxy-benzoic acid more acidic than p-hydroxybenzoic acid. 

From Sulpho Benzoic Acid.— The most common method of preparing phenols is by the alkali fusion of the sulphonic acids, Sulpho benzoic acids will thus yield hydroxy benzoic acids. In case the sulpho benzoic acid has been made by direct sulphonation of benzoic acid the meta compound will result. If, however, we start with tolmne and sulphonate it we will obtain the ortho and para compounds. 

Orthoform.— Another group of synthetic anesthetics are derivatives of para-amino benzoic acid or of amino hydroxy benzoic acids. Two of these are known as orthoform and new orthoform. 

It should be noted that the relative rates of attack of OH at the ortho-, meta-, and para-positions of benzoic acid cannot be derived from the observed G-values of end products in anoxia. The G-values will be influenced strongly by the redox potentials of the intermediate radicals as well as by steric factors. From our results it appears that the p-hydroxy-benzoic acid radical probably acts as a reducing agent, whereas o-, and m-hydroxybenzoic acid radicals probably are oxidizing entities in dis-mutation reactions taking place in anoxia. 

Solubility of Ortho Hydroxy Benzoic Acid (Salicylic Acid), Meta Hydroxy Benzoic Acid, and Para Hydroxy Benzoic Acm (Anisic Acid) in Water, Benzene, etc. (See also pp. 38 and 274.)... 

The benzoic acid, the acid moiety found in cocaine (98), is also derived from phenylalanine (141). Feeding of [4-3H]phenylalanine to E. coca led to the benzoyl moiety, where 96% of the 3H was located at the para position (138). The intermediacy of cinnamic, 3-hydroxy-3-phenylpropionic, and benzoylacetic acid in the formation of benzoic acid has been suggested (138). 

When substituents can also be involved in the resonance effects, changes in acidity become more marked. Consider hydroxy- and methoxy-benzoic acid derivatives. The pATa values are found to be 3.0, 4.1, and 4.6 for the ortho, meta, and para hydroxy derivatives respectively, and 4.1, 4.1, and 4.5 respectively for the corresponding methoxy derivatives. 

This does not occur in the case of catalyst and reactants here described. With Bronsted-type catalysis, the reaction between the benzoyl cation, Ph-C" =0, and the hydroxy group in phenol is quicker than the electrophilic substitution in the ring. This hypothesis has been also confirmed by running the reaction between anisole and benzoic acid in this case the prevailing products were (4-methoxy)phenylmethanone (the product of para-C-benzoylation) and methylbenzoate (obtained by esterification between anisole and benzoic acid, with the co-production of phenol), with minor amounts of phenylbenzoate, phenol, 2-methylphenol and 4-methylphenol. Therefore, when the 0 atom is not available for the esterification due to the presence of the substituent, the direct C-acylation becomes the more favored reaction. 

Only para coupling was observed during the alkaline ferricyanide oxidation of 4-hydroxy-3-(3-hydroxybenzoyl)benzoic acid. 7-Hydroxy-9-oxoxanthene-2-carboxylic acid (515) was obtained in 21% overall yield from methyl 4-hydroxybenzoate (78JCS(P1)876). The synthesis utilizes a photochemical Fries rearrangement of methyl 4-(3-methoxybenzoyloxy)benzoate to prepare the benzophenone (514 Scheme 189). A similar route was used to prepare 2-hydroxy-2 -methoxybenzophenones, which undergo intramolecular cyclization with loss of methanol on treatment with base. 

Oxidation with alkaline CuO gave large amounts of meta-hydroxy derivatives of benzoic acid and benzene dicarboxylic acids (Hayatsu et al., 1980a). This suggests the presence of phenol ethers in the polymer structure. Interestingly, terrestrial polymers such as lignin, humic acid, and coal yield mainly para-rather than meta-hydroxy derivatives by this method. 

From Amino Benzoic Acid.—Amino acids by the diazo reaction and decomposition with water will yield the corresponding phenol acids. In such cases also if we start with benzoic acid, nitrate directly and reduce this to the amino compound, the final product of the diazo reaction will be the meta hydroxy acid. If we start with toluene and nitrate it and then proceed as in the foregoing and oxidize the amino toluene to amino benzoic acid our product will be the ortho and para hydroxy acids. 

---