Acetic acid hydroxybenzoic acids

Advances in analytical procedures resulted in several reports on anthocyanins acy-lated with hydroxycinnamic acids (p-coumaric, caffeic, ferulic, sinapic, and 3,5-dihydroxycinnamic acids), hydroxybenzoic acids (p-hydroxybenzoic and gallic acids), and aliphatic acids (malonic, acetic, malic, oxalic, succinic and tartaric acids). However, not all of them were found in anthocyanins isolated from foods. Among the 44 fruits listed in Table 4.3.1, 15 presented acylated anthocyanins as did 12 of 13 vegetables shown in Table 4.3.3 and 2 of the 9 grains cited in Table 4.3.4. On the other hand, acylated anthocyanins were found in all grapes from Vitis species, although at different abundance levels, as can be seen in Table 4.3.2. A higher... 

Figure 2. Linear regression plot of root growth inhibition of tomato and radish seedlings by o and -hydroxyphenyl) acids. o-Hydroxycinnamic acid, (o-hydroxyphenyl) acetic acid ( ) melilotic acid, 2-(o-hydroxyphenyl) butanoic acid ( ) o-hydroxy-benzoic acid, ( -hydroxypheny 1 )acetic acid (0) -hydroxycinnamic acid, =hydroxybenzoic acid, 3-( -hydroxyphenyl) propanoic acid (X) o-coumaryl glucoside, water control (----) (1 ). ...

The main drawback of the acid hydrolysis processes is the formation of undesirable by-products. This not only lowers the yield of sugars, but several of the by-products severely inhibit the formation of ethanol in the fermentation process. Potential inhibitors are furfural, 5-hydro ethylfiirfural (HMF), levulinic acid, acetic acid, formic acid, uronic acid, 4-hydroxybenzoic acid, vanillic acid, vanillin, phenol, cinnamaldehyde, formaldehyde, etc. (I, 36). Some inhibitors, such as terpene compounds, are initially present in the wood, but apparently most of the inhibitors are formed in the hydrolysis process. 

Acetate ion Acetic acid Benzoic Acid Benzoic Acid Benzoic Acid Benzoic Acid Ethyl 4-hydroxybenzoate Ethyl salicylate Humic acid... 

First,/)-hydroxybenzoic acid (HBA) and 6-hydroxy-2-naphthoic acid (HNA) are acetylated to produce the low melting acetate esters which are molten at 200°C. In an inert gas, the two monomers are melted together at 200°C. The temperature is raised to 250—280°C and acetic acid is coUected for 0.5 to 3 h. The temperature is raised to 280—340°C and additional acetic acid is removed in vacuum for a period of 10 to 60 min. The opalescent polymer melt produced is extmded through a spinning jet, foUowed by melt drawdown. The use of the paraUel offset monomer, acetylated HNA, results in the formation of a series of random copolyesters of different compositions, many of which faU within the commercially acceptable melting range of... 

The ansa-chain of the ansamycins streptovaricins (4), rifamycins (263), geldanamycin (4), and herbimycin (32) has been shown to be polyketide in origin, being made up of propionate and acetate units with the 0-methyl groups coming from methionine. The remaining aromatic C N portion of the ansamacroHdes is derived from 3-amino-5-hydroxybenzoic acid (264—266) which is formed via shikimate precursors. Based on the precursors of the rifamycins and streptovaricins isolated from mutant bacteria strains, a detailed scheme for the biosynthesis of most of the ansamacroHdes has been proposed (95,263). 

Conversion of Acid Anhydrides into Esters Acetic anhydride is often used to prepare acetate esters from alcohols. For example, aspirin (acetylsalicylic acid) is prepared commercially by the acetylation of o-hydroxybenzoic acid (salicylic acid) with acetic anhydride. 

This is prepared from 4-hydroxybenzoic acid and acetic anhydride following a procedure for 2-acetoxybenzoic acid.2 The crude product is conveniently purified by stirring with chloroform (about 15 ml. per gram of acid) and removing any insoluble residue by filtration. Evaporation of the chloroform gives material melting at 186-188° (lit.3 189-190°). 

Only the bromodecarboxylation reaction has been subjected to kinetic studies733, the reaction of bromine in 70-80 wt. % aqueous acetic acid with 3,5-dibromo-2(or 4)-hydroxybenzoic acids at 20 °C giving the titrimetically determined rate coefficients in Table 258. These results demonstrated that the reaction is first-order in aromatic and bromine, and that reaction rates are decreased by a decreasing water content of the solvent, by added acids, and by added bromide ion which is... 

C21H25O4 23637-81-2) see Gestrinone ethyl 4-hydroxybenzoic acid (QjHiqOj 120-47-8) see Gabexate ethyl (2-hydroxybenzylamino)acetate (C H,5N03 57938-78-0) -see Caroxazone... 

The effect of incorporating p-hydroxybenzoic acid (I) into the structures of various unsaturated polyesters synthesised from polyethylene terephthalate (PET) waste depolymerised by glycolysis at three different diethylene glycol (DEG) ratios with Mn acetate as transesterification catalyst, was studied. Copolyesters of PET modified using various I mole ratios showed excellent mechanical and chemical properties because of their liquid crystalline behaviour. The oligoesters obtained from the twelve modified unsaturated polyesters (MUP) were reacted with I and maleic anhydride, with variation of the I ratio with a view to determining the effect on mechanical... 

Another MOF constructed from Cu paddlewheel SBUs and with 5-nitro-1,3-benzenedicarboxylate as the ligand can be used for the acetylation of methyl 4-hydroxybenzoate with acetic acid anhydride. The framework did not remain intact upon exposure to acetic acid, one of the reaction products [53]. 

In Fig. 4.6, the titration of p-hydroxybenzoic acid in pyridine shows that the COOH and OH groups can be clearly determined. However, in acetonitrile there is half-way the titration of the COOH group an additional potential jump this can be explained by a phenomenon which was already known for acetic acid23, viz., in the inert solvent acetonitrile intermolecular hydrogen-bridge... 

The reference intermolecular reaction for the aliphatic compounds is the formation of ethyl acetate from ethanol and acetic acid measured under the same conditions (20% ethanol-water, ionic strength 0.4 M) by Storm and Koshland (1972a). The esterification of benzoic acid in methanol at 25° is 290 times slower than that of acetic acid (Kirby, 1972), so this factor is used to correct the EM s, calculated otherwise in the same way, for the hydroxybenzoic acids. For the phenolic acids see notes m and n b Rate constants are in units of dm3 mol-1 s-1 c Storm and Koshland, 1972a d Storm and Koshland, 1972b Bunnett and Hauser, 1965... 

A method was proposed for the preparation of p-hydroxybenzoic acid by oxidation of p-cresol with atmospheric oxygen in an acetic acid-acetic anhydride mixture under catalysis of cobalt acetate, manganese(II) acetate, and sodium bromide (Litvintsev et al. 1994). This procedure ensures 60% yield of p-acetoxybenzoic acid and 100% conversion of the initial p-cresol. 

Kj, or the ratios of solution-phase solute concentration and adsorbed-phase concentration were calculated to estimate the relative affinity of the soils for phenolic acids. The Kj values for p-hydroxybenzoic acid, p-coumaric, vanillic, ferulic, and syringic icids were 67, 75, 69, 92 and 376, respectively for a 48-hr equilibration of 0.1 nmol mL phenolic acid solution with a sample of an alfisol preextracted in boiling water. The sorption capacity was greatly reduced by pretreatment of soil samples with sodium acetate-hydrogen peroxide to remove organic matter and metal sesquioxides. 

FIGURE 10.7 Numbers of anthocyanins containing the various acyl moieties identified in anthocyanins. The upper dark part of each bar represents the anthocyanins reported later than 1992. cou, p-coumaric acid caf, caffeic acid fer, ferulic acid sin, sinapic acid cin, 3,5-dihydroxycinnamic acid hba, p-hydroxybenzoic acid gao, gallic acid mal, malonic acid ace, acetic acid mli, malic acid sue, succinic acid tar, tartaric acid oxa, oxalic acid sul, sulfate. 

Nitration of ///-hydroxybenzoic acid with filming nitric acid in the presence of sulfuric acid and acetic anhydride gives a mixture of the 2-nitro [602-00-6] and 4-nitro [619-14-7] substitution products. Bromination and iodination yield the 4-halogenated derivatives (4-bromo [14348-38-0] and 4-iodo [58123-77-6]). When ///-hydroxybenzoic acid is treated with formalin in the presence of hydrochloric acid, 4-hydroxyphthalide [13161 -32-5] is obtained as shown in equation (10). 

Figure 11-10 Titration ot a mixture of acids with tetrabutylammonium hydroxide in methyl isobutyl ketone solvent shows that the order of acid strength is HCI04 > HCI > 2-hydroxybenzoic acid > acetic acid > hydroxybenzene. Measurements were made with a glass electrode and a platinum reference electrode. The ordinate is proportional to pH. with increasing pH as the potential becomes more positive. [D. B. Brass and G. E. A. Wyld. Methyl Isobutyt Ketone as a Wide-Range Solvent for Titration of Acid Mixtures and Nitrogen Bases," Anal Chem. 1957, 29.232.]...

Reverse-phase chromatography has been used extensively for the determination of saccharin. Smyly et al. (30) and Eng et al. (39) used /rBondapak Cl 8 and 5% acetic acid for the determination of saccharin. Based on this work, an Association of Official Analytical Chemists (AOAC) collaborative study was conducted, and the method using a mobile phase buffered to pH 3 with sodium acetate and modified with 3% isopropanol was adopted. Webb and Beckman (61) used this method successfully for the separation of saccharin from aspartame, caffeine, sodium benzoate, and artificial colors and flavors. Veerabhadrarao et al. (27) added methanol to the mobile phase (methanol acetic acid water, 4 1 1, v/v) for improved separation of saccharin from caffeine, benzoic and p-hydroxybenzoic acids, vanillin, aspartame, acesulfame-K, and dulcin. Saccharin was also determined using LiChrosorb Cl8 and 4 6 v/v methanol phosphate buffer,... 

This part of the chapter describes HPLC techniques for the separation and determination of preservatives, as follows S02, postharvest preservatives (PPs), benzoic acid (BA), sorbic acid (SA), and the ethyl, methyl, propyl esters of 4-hydroxybenzoic acid (EsHBA) and 5-nitrofury-lacrylic acid (5-NFA). The propionic, lactic, acetic acids are discussed in the chapter on organic acids. 

Flak and Schaber (5,62) used reverse-phase HPLC for the quantitative and simultaneous determination of benzoic acid and sorbic acid, as well as 4-hydroxybenzoic acid, salicylic, 5-nitrofurylacrylic, and p-chlorobenzoic acid and the EsHBA (methyl, ethyl, propyl) in wines and beverages. The first five compounds can be determined by isocratic elution from a Clg column using 0.12 M acetate, pH 3.8 acetonitrile (85 15), and all may be separated with gradient elution (increasing acetonitrile from 10 to 60%, with a simultaneous decrease of the pH of the acetate buffer from 3.9 initially to 3.3). 

Veerabhadrarao et al. (76) used reverse-phase HPLC for the determination of some food additives (acesulfame, saccharine, BA, p-hydroxybenzoic acid). The samples (beverages, tomato sauce) were diluted and then separated on a /rBondapak CJg column with methanol/acetic acid/water (20 5 75) or (35 5 60) as mobile phases. The determination was done at 254 nm. Recoveries varied from 98 to 106% for direct analysis and from 91.6 to 101.8% for extraction of samples (76). 

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