Phenol phthalein

It condenses with resorcinol and amino-phenols to give phthalein and rhodamine dyestuffs respectively. Esters are used in the formation of polyimides. ... 

NOTE. It is not expected that a student xvill attempt to memorise all the colour tests given in Part III. He might for example be expected to know the Phthalein Reaction for phenol itself (p. 339). Details of the divergence from the standard result are recorded primarily for reference, so that a student will not be diverted from his line of investigation if he observes that a suspected phenol does not respond exactly to the standard colour changes. 

Phthalein reaction. Place in a dry test-tube about 0 2 g. of the phenol and an equal quantity of phthalic anhydride (or acid), moisten with 2 drops (not more) of cone. H2SO4 and gently fuse together for about 1 minute. Allow to cool somewhat, and then add 10% NaOH solution in excess. 

C) Phenacyl and p-Bromophenacyl esters. Ammonium salts in aqueous-ethanolic solution do not however usually condense satisfactorily with phenacyl and />-bromophenacyl bromide. The aqueous solution of the ammonium salt should therefore be boiled with a slight excess of sodium hydroxide to remove ammonia, and the solution then cooled, treated with hydrochloric acid until just alkaline to phenol-phthalein, and then evaporated to dryness. The sodium salt is then treated as described (p. 349) to give the ester. Filter the ester, and wash with water to remove senium halide before recrystallisation. 

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.)... 

The method is based on the conversion of urea to amnionium carbonate and the estimation of the latter by titration with standard acid. For this purpose, two equal quantities of urea (or urine) are measured out into two flasks A and B. A is treated with 10 ml. of a strong urease preparation and some phenol-phthalein, warm water is added and the mixture is adjusted by the addition of V/io HCl from a burette A until the red colour is just discharged. This brings the mixture to about pH 8 (the optimum for urease) and also prevents loss of ammonia. 

The above simple experiments illustrate the more important properties of aliphatic acid chlorides. For characterisation, the general procedure is to hydrolyse the acid chloride by warming with dilute alkali solution, neutralise the resulting solution with dilute hydrochloric acid (phenol-phthalein), and evaporate to dryness on a water bath. The mixture of the sodium salt of the acid and sodium chloride thus obtained may be employed for the preparation of solid esters as detailed under Aliphatic Acids, Section 111,85. The anilide or p-toluidide may be prepared directly from the acid chloride (see (iii) above and Section III,85,i). 

Ethyl bis-(2,4-dinitrophenyl) acetate (indicator) the stock solution is prepared by saturating a solution containing equal volumes of alcohol and acetone with the indicator pH range colorless 7.4-9.1 deep blue. This compound is available commercially. The preparation of this compound is described by Fehnel and Amstutz, Ind. Eng. Chem., Anal. Ed. 16 53 (1944), and by von Richter, Ber. 21 2470 (1888), who recommended it for the titration of orange- and red-colored solutions or dark oils in which the endpoint of phenol-phthalein is not easily visible. The indicator is an orange solid which after crystallization from benzene gives pale yellow crystals melting at 150-153.5°C, uncorrected. 

Phthaleins. Dyes of this class are usually considered to be triaryhnethane derivatives. Phenolphthalein [77-09-8] (23, R = CO) and phenol red [143-74-8] (23, R = SO2) are used extensively as indicators in colorimetric and titrimetric determinations (see Hydrogen-ION activity). These compounds are prepared by the condensation of phenol with phthaUc anhydride or i9-sulfoben2oic anhydride, respectively, in the presence of a dehydrating agent. 

Remove 10 ml of this solution and add a few (three to five) drops of phenol phthalein and shake. 

To the same solution add a few drops of phenol phthalein, and titrate it against N/10 NaOH until a pink colour appears, which will indicate the total acidity of the bath. This is approximately 35 to 37 for a concentration of 5% for a hot process and 60 to 64 for a concentration of 10% for a cold process. Obtain the standard total acidity of the hot or cold process chemicals from the manufacturer. 

One 1-ml aliquot is added to 1.0 ml of freshly-distilled 1,2-dibromo-ethane (bp 132°C) in an oven-dried flask which contains a static atmosphere of nitrogen or argon. After the resulting solution has been allowed to stand at 25°C for 5 min, it Is diluted with 10 rat of water and titrated for base content (residual base) to a phenolphthalein endpoint with standard 0.100 M hydrochloric acid. The second 1-mL aliquot is added cautiously to 10 ml of water and then titrated for base content (total base) to a phenol phthalein endpoint with standard aqueous 0.100 M hydrochloric acid. The methyllithium concentration is the difference between the total base and residual base concentrations.2 Alternatively, the methynithiura concentration may be determined by titration with a standard solution of sec-butyl alcohol employing 2,2 -bipyridyl as an indicator. 

Dissolve a sample containing 0.5 meq anion-active material with a ether carboxylic acid group in alcohol and neutralize with 0.5 N NaOH on phenol-phthalein. Transfer this solution to a 250-ml graduated flask with a stopper and make up to the mark with distilled water. Introduce into a 100-ml graduated cylinder with a stopper ... 

Irreversible reaction of [18] iodine with acetylsalicylic acid, aethaverine, amidopyrine, ascorbic acid, benzo-caine, quinine, dihydrocodeine, fluorescein, glycine, hydrocortisone acetate, isoni-azid, metamizole, papaverine, paracetamol, phenacetin, phenol-phthalein, piperazine, resorcinol, salicylic acid, salicylamide, sulfaguanidine, thymol, triethanolamine, tris buffer detection by reaction chromatography... 

The answer is c. (Hardman, p 924.) Dioctyl sodium sulfosuccinate (docusate) is a detergent that, when given orally, softens the stool and prevents straining. Mineral oil also softens the stool, but it tends to inhibit the absorption of fat-soluble vitamins and other nutrients. Castor oil, phenol-phthalein, and cascara sagrada are strong laxatives and cause watery stools... 

Table 5.1 summarizes the details of some useful acid-base indicators. Exact agreement with the pH range expressed by equation (5.5) is by no means always observed. This is because some colour changes are easier to see than others and so the general approximation made in deriving equation (5.5) is not uniformly close. Structurally, the indicators form three groups phthaleins (e g. phenolphthalein) sulphonephthaleins (e.g. phenol red) and azo compounds (e.g. methyl orange). 

B. The Phthaleins.—If two molecules of a phenol and one molecule of phthalic anhydride are caused to interact under the conditions which prevail during the Friedel-Crafts synthesis (Chap. IX. p. 342), the tendency of the ketone first formed to combine with a second molecule of the phenol outweighs condensation to the anthraquinone derivative in this way are formed the phthaleins, discovered by Baeyer in 1871. This process may be discussed by taking phenolphthalein as an example. 

Indicator dyes for pH having the phthalide structure fall into two types, the phthaleins, shown in the lactone form of general structure (1.66) and the sulfoph-thaleins (1.67). The synthetic pathways to these products are very similar. The phthaleins (1.66) are made by reacting phenol with phthalic anhydride in the presence of Lewis acid catalyst, e.g. ZnCl, whilst (1.67) are obtained by using 2-sul-fobenzoic anhydride (Figure 1.20). 

The process is reversible and therefore provides an easily visible method for measuring pH change in the range of 8.5-9.0. The ionisation reactions of sulfophthaleins follow a similar pathway. Substitution in the phenolic rings of the phthaleins and sulfophthaleins provides a variety of coloured dianions, which change colour over different ranges of pH (see section 1.4.2.1). 

A few drops of 1.0% alcoholic solution of phenol-phthalein indicator shall be added and the sample titrated with standard 0.1N ale KOH to the first pink end point permanent for 15 secs. 

Completion of the run, after 30-40 hours, is indicated when a few drops of the solution show an alkaline reaction to phenol-phthalein. No harm is done if the electrolysis is carried a few hours beyond this point however, after excessively long periods, formation of polymeric material lowers the yield and renders purification of the product rather troublesome. 

A. Lithium triethylcarboxide (Solution 1). A thoroughly dried, 1-1., three-necked, round-bottomed flask is fitted with a septum inlet with serum cap, a reflux condenser, and a magnetic stirrer. The flask is purged with and maintained under an atmosphere of dry nitrogen. A solution of 300 ml. of 1.66 M butyllithium (0.50 mole) in hexane (Note 1) is introduced into the flask by syringe (Note 2) and cooled to 0° in an ice bath. Then 58 g. (0.50 mole) of 3-ethyl-3-pentanol (Note 3) is added slowly but constantly by syringe (Note 4). At the end of addition the yellow tint of the butyllithium solution disappears. The alkoxide solution is standardized by hydrolysis of aliquots in water and by titration of the resulting lithium hydroxide with standard acid to a phenol-phthalein end point (Note 5). 

The samples shall be added dropwise and the flasks swirled to prevent local overheating. Stopper each flask immediately and, after 3 to 5 mins of standing,wash down the contents of 1st flask with 100 ml w (neutral to phenol-phthalein) and titrate with N/2 HC1 to phpht end point. Cool 2nd flask, wash down the contents with 100 ml of aq methanol (75 25) (neutral to phpht) and titrate with N/2 carbonate-free NaOH to a phpht end point. Titrate a blank so In consisting of 100 ml of aq methanol and 20 ml aniline using 0.1N carbonate-free NaOH... 

CHjC0.NH C6H N02 +CH,COOH After allowing to stand for 1 hr, add distd w through the condenser in an amt sufficient to hydrolyze surplus anhydride to acetic acid. Transfer to a 1 1 vol flask and dilute to the mark. Pipette an aliquot into a beaker and titrate with N/10 NaOH soln in presence of an indicator, such as phenol-phthalein. Take the burette reading (Rj). Run a blanc by titrating with N/10 NaOH the same quantity of acetic anhydride... 

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