Phenolic acid solutions

2 Plant-Plant AUelopathic Interactions. Phase 1 The Laboratory 

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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. 

Cucumber seeds and seedlings have associated with them substantial microbial populations that are difficult to eliminate because microbes are not only found on and in the cutinized surface of the seed coat but can also be found internally within the seed (Leben 1961 Mundt and Hinkle 1976). Depletion of phenolic acids from nutrient solutions thus represent uptake by roots and microbial utilization. By replacing the nutrient solution (control) and nutrient-phenolic acid solutions (treatments) every other day, microbial populations were kept in check and phenolic acid concentrations were brought back to the original treatment concentrations. However, since phenolic acid treatments changed microbial populations on the rhizoplane (Fig. 2.9)... 

Fig. 3.10 Effects of a 7-phenolic acid solution modeled after phenolic acids found in wheat stub-ble/soybean (no-till) soil extracts (pH 5) on radicle and hypocotyl lengths of crimson clover as modified by solute potential of PEG (polyethylene glycol a r = 0.61) and Hoagland s solution (b r = 0.37) based on freezing point depression (mOsm, mUliosmoles) of solutions. The 7-phenohc acid mixture was composed of 10% caffeic acid, 9% ferulic acid, 35% p-coumaric acid, 15% p-hydroxybenzoic acid, 4% sinapic acid, 10% syringic acid, and 17% vanillic acid. Figures based on regressions from Blum et al. (1992). Plenum Publishing Corporation, regressions used with permission of Springer Science and Business Media...

The mixed bases are dissolved in dilute hydrochloric acid and sodium nitrite solution added. The aniline is thus diazotised and, if the mixture is subsequently boiled, converted into phenol. The solution is then made alkaline and steam-distilled, the quinoline passing over, while the phenol remains behind in the alkaline solution. 

The Reaction has the following limitations (i) a compound that can liberate nitrous acid in acid solution is required (e.g., a metallic nitrite or a nitroso-amine, p. 204). (2) Nitrophenols and />-substituted phenols do not give the test. (3) Among the dihydroxyphenols. only resorcinol gives a satisfactory positive test. 

Benzylthiouronium salts. Add 0 5 g. of sulphanilic acid to 10 ml. of water and 5 ml. of 10% NaOH solution, zndgently warm the shaken mixture until a clear solution is obtained. Cool, add 1 drop of phenol-phthalein solution, and then add dilute HCl dropwise with shaking until the pink colour is just discharged. Now add very dilute NaOH solution until the pink colour yt/rZ returns. Cool and add with shaking a solution of 0-5 g. of benzylthiouronium chloride in 5 ml. of water. The thiouronium salt rapidly separates filter at the pump, wash with water, drain and recrystallise from ethanol. Colourless crystals, m.p. 185°. (M.ps., p. 548.)... 

To a mixture of 10 g. of the compound and 3-5 ml. of 33 per cent, sodium hydroxide solution in a test-tube, add 2-5 ml. of 50 per cent, chloroacetic acid solution. If necessary, add a little water to dissolve the sodium salt of the phenol. Stopper the test-tube loosely and heat on agently-boiling water bath for an hour. After cooling, dilute with 10 ml. of water, acidify to Congo red with dilute hydrochloric acid, and extract with 30 ml. of ether. Wash the ethereal extract with 10 ml, of water, and extract the aryloxyacetic acid b shaking with 25 ml. of 5 per cent, sodium carbonate solution. Acidify the sodium carbonate extract (to Congo red) with dilute hydrochloric acid, collect the aryloxyacetic acid which separates, and recrystallise it from hot water. 

The mixed aliphatic - aromatic ethers are somewhat more reactive in addition to cleavage by strong hydriodio acid and also by constant b.p. hydrobromio acid in acetic acid solution into phenols and alkyl halides, they may be bromi-nated, nitrated and converted into sulphonamides (Section IV,106,2). 

This IS the most general method for preparing phenols It is easily performed the aque ous acidic solution m which the diazonium salt is prepared is heated and gives the phe nol directly An aryl cation is probably generated which is then captured by water acting as a nucleophile... 

Preparation of phenols Heating its aqueous acidic solution converts a diazonium salt to a phenol This IS the most general method for the synthesis of phenols... 

Minerals, particularly Bentonite, ate used to remove proteins that tend to cause haze in white wines. The natural tannin of ted wines usually removes unstable proteins from them. Excess tannin and related phenols can be removed and haze from them prevented by addition of proteins or adsorbents such as polyvinylpyttohdone. Addition of protein such as gelatin along with tannic acid can even be used to remove other proteins from white wines. Egg whites or albumen ate often used to fine ted wines. Casein can be used for either process, because it becomes insoluble in acidic solutions like wines. 

The pH is measured colorimetricaHy with phenol red indicator. High FAC causes lower pH rea dings due to bleaching of the indicator and resultant HCl formation. The pH of pool water is readily controlled with inexpensive chemicals. Hydrochloric acid solution or sodium bisulfate lower it, whereas sodium carbonate raises it. Since acid addition neutralizes a portion of the alkalinity, this must be replenished if the alkalinity drops below the minimum. By contrast, pH adjustment with carbon dioxide does not affect alkalinity. 

Donation of a proton to the reactant often forms a carbenium ion or an oxonium ion, which then reacts ia the catalytic cycle. For example, a catalytic cycle suggested for the conversion of phenol and acetone iato bisphenol A, which is an important monomer used to manufacture epoxy resias and polycarbonates, ia an aqueous mineral acid solution is shown ia Figure 1 (10). 

Hydroxythiophene also exists mainly in ketonic forms. Electrophilic reagents react either at oxygen or at C-5. O-Methyl and O-acetyl derivatives are obtained in alkaline solution, probably through intermediacy of the anion. In acidic solution, coupling with benzenediazonium ion, a characteristic phenolic reaction, is found to take place (Scheme 72). 

Dissociation extraction is the process of using chemical reac tion to force a solute to transfer from one liquid phase to another. One example is the use of a sodium hydroxide solution to extract phenolics, acids, or mercaptans from a hydrocarbon stream. The opposite transfer can be forced by adding an acid to a sodium phenate stream to spring the phenolic back to a free phenol that can be extrac ted into an organic solvent. Similarly, primary, secondary, and tertiary amines can be protonated with a strong acid to transfer the amine into a water solution, for example, as an amine hydrochloride salt. Conversely, a strong base can be added to convert the amine salt back to free base, which can be extracted into a solvent. This procedure is quite common in pharmaceutical production. 

A comparison of phenol acidity in DMSO versus the gas phase also shows an attenuation of substituent effects, but not nearly as much as in water. Whereas the effect of ubstituents on AG for deprotonation in aqueous solution is about one-sixth that in the gas phase, the ratio for DMSO is about one-third. This result points to hydrogen bonding of the phenolate anion by water as the major difference in the solvating properties of water and DMSO. ... 

Adolph Baeyer is credited with the first recognition of the general nature of the reaction between phenols and aldehydes in 1872 ([2,5-7] [18], Table 5.1). He reported formation of colorless resins when acidic solutions of pyrogallic acid or resorcinol were mixed with oil of bitter almonds, which consists primarily benzaldehyde. Baeyer also saw resin formation with acidic and basic solutions of phenol and acetaldehyde or chloral. Michael and Comey furthered Baeyer s work with additional studies on the behavior of benzaldehyde and phenols [2,19]. They studied a variety of acidic and basic catalysts and noted that reaction vigor followed the acid or base strength of the catalyst. Michael et al. also reported rapid oxidation and darkening of phenolic resins when catalyzed by alkaline materials. 

Nitro-pJienols and Nitro-acids dissolve in ctiustic alkahs as a rule with a deep yellow or orange colour. On reduction with st. innous chloride or zinc dust, as described above, they yield the amino-derivatives. In the case of the amino-phenol, the solution is made alkaline with caustic soda, satuiated with CO.j, salt added and extracted w ith ether. In the case of the amino-acid, the method used is that desciibed under Prep. 91 (p. 201). 

Carbol. carbolic, carbolized, carbolated. kalk, n. carbolated lime. >dl( n. carbolated oil. salbe,/. Pharm.) ointment of phenol. carbolic acid, phenol. ldsung, /. carbolic acid solution. seife, /. carbolic acid soap. 

Phenol red is an indicator with a pffa of 7.4. It is yellow in acid solution and red in alkaline. 

Discussion. A number of phenols can be substituted rapidly and quantitatively with bromine produced from bromate and bromide23 in acid solution (Section 10.131). The determination involves treating phenol (Note 1) with an... 

A. 2,i,l,()-Tetrabromo-2,5-cyclohexadien-l-one. A mixture of 66.2 g. (0.2 mole) of 2,4,6-tribromophenol (Note 1), 27.2 g. (0.2 mole) of sodium acetate trihydrate, and 400 ml. of glacial acetic acid is placed in a 1-1. Erlenmeyer flask and warmed until a clear solution is obtained. The temperature of the solution is approximately 70°. The solution is magnetically stirred and cooled to room temperature to produce a finely divided suspension of the phenol. A solution of 32 g. (0.2 mole) of bromine in 200 ml. of glacial acetic acid is added dropwise over 1 hour (Note 2). The resulting mixture is kept at room temperature for 30 minutes and is then poured onto 2 kg. of crushed ice. The yellow solid which separates is removed by suction filtration after the ice has melted, and the damp crystals are dissolved in the minimum quantity of warm chloroform (Note 3). The upper aqueous layer is removed by means of a pipet fitted with a suction bulb. The dienone crystallizes from the... 

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