Precipitation Phenolic

At least five procedures for removal of impurities have been described (6) none have been completely successful in removing impurities in an economical way (6). In the best method, active magnesium oxide is mixed rapidly with a solution of the gum heated to almost the boiling temperature (21). The flocculent, brownish precipitate (phenolic compounds and iron salts), which forms almost immediately, is removed quickly by filtration. The almost colorless solution is then drum-dried to produce a white powder that is odorless and has only a slight taste. The... 

Poly(ureas) General Fractional precipitation Phenol-tetrachloroethane 2550... 

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. 

Colorations or coloured precipitates are frequently given by the reaction of ferric chloride solution with.(i) solutions of neutral salts of acids, (ii) phenols and many of their derivatives, (iii) a few amines. If a free acid is under investigation it must first be neutralised as follows Place about 01 g. of the acid in a boiling-tube and add a slight excess of ammonia solution, i,e., until the solution is just alkaline to litmus-paper. Add a piece of unglazed porcelain and boil until the odour of ammonia is completely removed, and then cool. To the solution so obtained add a few drops of the "neutralised ferric chloride solution. Perform this test with the following acids and note the result ... 

Azo-dye formation. Dissolve 2-3 drops of aniline in 1 ml. of cone. HCl and add 3 ml. of water. Shaike to dissolve any hydrochloride which may have separated and cool in ice. Add a few drops of 20% sodium nitrite solution. Add this cold diazonium solution to a cold solution of the phenol in an excess of aqueous NaOH solution. Solutions or precipitates of azo-dyes ranging in colour from orange through scarlet to dark red, according to the phenol used, are obtained. Note in particular that i-naphthol gives a brownish-red, 2-naphthol a scarlet precipitate. Catechol decomposes. 

Action of bromine water. To a concentrated aqueous solution of the phenol or to the phenol itself, add bromine water gradually. At first the bromine is decolorised and then on adding an excess a white or yellowish-white precipitate of a polybromo-derivative is produced with all except catechol, hydroquinone, i- and 2 naphthol. 

Add dil. H2SO4 until the solution is acid to litmus. Cool, and scratch the sides of the vessel with a glass rod a white precipitate indicates an aromatic carboxylic acid or uric acid, or a solid phenol insoluble in water (e.g., i- or 2-naphthol). If a precipitate is obtained, filter off through a Buchner funnel, wash with water, recrystallise if necessary and identify. 

If no solid precipitate is obtained but the solution becomes cloudy, a low-melting or liquid phenol is indicated this will, of course, be revealed also by the characteristic phenolic odour. Transfer to a separating-funnel and extract with an equal volume of ether. Separate and dry with anhydrous sodium sulphate. Distil off the ether and identify the residue. 

Colorations or precipitates given by phenols and many derivatives of phenols by neutral salts of acids by some amines. (The FeCl, solution can be added directly to a small quantity of the phenol or to its aqueous solution free acids must first be neutralised.)... 

The controlled thermal decomposition of dry aromatic diazonium fluoborates to yield an aromatic fluoride, boron trifluoride and nitrogen is known as the Schiemann reaction. Most diazonium fluoborates have definite decomposition temperatures and the rates of decomposition, with few exceptions, are easily controlled. Another procedure for preparing the diazonium fluoborate is to diazotise in the presence of the fluoborate ion. Fluoboric acid may be the only acid present, thus acting as acid and source of fluoborate ion. The insoluble fluoborate separates as it is formed side reactions, such as phenol formation and coupling, are held at a minimum temperature control is not usually critical and the temperature may rise to about 20° without ill effect efficient stirring is, however, necessary since a continuously thickening precipitate is formed as the reaction proceeds. The modified procedure is illustrated by the preparation of -fluoroanisole ... 

Dissolve 0 -5 g. of the phenol in 4-5 ml. of dry p ridine, add 1 - 3 g. of 3 5-dinitrobenzoyl chloride and reflux for 25-30 minutes. Pour the cold reaction mixture into 40 ml. of ca. 2N hydrochloric acid. Decant the supernatant aqueous hquid from the precipitated sohd or oil and stir it vigorously with about 10 ml. of N sodium carbonate solution. Filter off the sohd derivative and wash it with water. RecrystaUise from alcohol, dilute alcohol, benzene - acetone or benzene - light petroleum (b.p. 60-80 ),... 

Dissolve 1 g. (or 0 01 mol) of the phenol in a solution of 0-40 g. of sodium hydroxide in 5 ml. of water. Add the resulting solution to 2-Og. of 2 4-dinitrochlorobenzene dissolved in 30 ml. of 95 per cent, ethanol add more alcohol, if necessary, to effect solution. Heat the solution under reflux on a water bath until the colour (usually red) is discharged and a copious precipitate of sodium chloride appears (30-60 minutes). Dilute the reaction mixture with an equal volume of water, filter off the precipitated 2 4-dinitrophenyl ether, wash with water, and recrystallise from alcohol. 

Add dilute sulphuric acid, with stirring, to the cold alkahne solution until the solution is acid to htmus or Congo red paper and the acid, if a solid, commences to separate as a faint permanent precipitate. Now add dilute sodium carbonate solution until the solution is alkahne (litmus paper) and any precipitate has completely redissolved. Extract the clear solution twice with ether evaporate or distil the ether from the ethereal solution on a water bath CAUTION no flames may be near) and identify the residual phenol as under 1. Remove the dissolved ether from the aqueous solution by boiling, acidify with dilute sulphuric acid and identify the organic acid present (see Sections 111,85 and IV, 175). 

To hydrolyse an ester of a phenol (e.g., phenyl acetate), proceed as above but cool the alkaline reaction mixture and treat it with carbon dioxide until saturated (sohd carbon dioxide may also be used). Whether a solid phenol separates or not, remove it by extraction with ether. Acidify the aqueous bicarbonate solution with dilute sulphuric acid and isolate the acid as detailed for the ester of an alcohol. An alternative method, which is not so time-consuming, may be employed. Cool the alkaline reaction mixture in ice water, and add dilute sulphuric acid with stirring until the solution is acidic to Congo red paper and the acid, if aromatic or otherwise insoluble in the medium, commences to separate as a faint but permanent precipitate. Now add 5 per cent, sodium carbonate solution with vigorous stirring until the solution is alkaline to litmus paper and the precipitate redissolves completely. Remove the phenol by extraction with ether. Acidify the residual aqueous solution and investigate the organic acid as above. 

Dissolve 0 -1 g. of the compound in 10-15 ml. of water and add bromine water until the colour of the latter persists. A white precipitate will form if a phenol is present. 

Treatment of phenol with excess aqueous bromine is actually more complicated than expected A white precipitate forms rapidly which on closer examination is not 2 4 6 tribro mophenol but is instead 2 4 4 6 tetrabromocyclohexadienone Explain the formation of this product... 

Phenolphthalein. Alophen, Ex-Lax, Feen-a-Miat, Modane, and Phenolax are trade names for phenolphthaleia [77-09-8] (3,3-bis(4-hydroxyphen5l)-l-(3ff)-l isobensofuranone) (10). It is a white or faintiy yellowish white crystalline powder, odorless and stable ia air, and practically iasoluble ia water one gram is soluble ia 15 mL alcohol and 100 mL diethyl ether. Phenolphthaleia may be prepared by mixing phenol, phthaHc anhydride, and sulfuric acid, and heating at 120°C for 10—12 h. The product is extracted with boiling water, then the residue dissolved ia dilute sodium hydroxide solution, filtered, and precipitated with acid. 

The solubihty of alkylphenols in water falls off precipitously as the number of carbons attached to the ring increases. They are generally soluble in common organic solvents acetone, alcohols, hydrocarbons, toluene. Solubihty in alcohols or heptane follows the generalization that "like dissolves like." The more polar the alkylphenol, the greater its solubihty in alcohols, but not in ahphatic hydrocarbons likewise with cresols and xylenols. The solubihty of an alkylphenol in a hydrocarbon solvent increases as the number of carbon atoms in the alkyl chain increases. High purity para substituted phenols, through Cg, can be obtained by crystallization from heptane. 

Phenolics. PVP readily complexes phenolics of all types to some degree, the actual extent depending on stmctural features such as number and orientation of hydroxyls and electron density of the associated aromatic system. A model has been proposed (102). Complexation with phenoHcs can result in reduced PVP viscosity and even polymer-complex precipitation (103). 

Phenylphenol was one of the earliest carrier-active compounds used industrially. Originally it was used as its water-soluble sodium salt (4). By lowering the pH of the dyebath, the free phenol was precipitated in fine form and made available to the fiber. However, proprietary Hquid preparations containing the free phenol are available that afford a greater ease of handling. 

By-product processing CO, H2S, methane, ammonia, H2, phenols, hydrogen cyanide, N2, benzene, xylene, etc. Electrostatic precipitator, scrubber, flaring... 

The attractive possibility of dissolving the bis-phenol A in caustic soda solution and bubbling phosgene into it is not practical since the polymer is insoluble in the caustic soda and precipitates out at a low and variable molecular weight. 

Typically in such a process the bis-phenol A is dissolved in about ten times its weight of pyridine and vigorously stirred at 25-35°C. Phosgene is then bubbled into the solution and in a few minutes the pyridine hydrochloride starts to precipitate. As polymer is formed the viscosity of the solution increases and eventually becomes too great for stirring. The polymer is then recovered by the addition of a solvent such as methyl alcohol which dissolves the pyridine hydrochloride but precipitates the polymer. 

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