Phenolphthalein compound

Tanaka, H. Kobayashi, M. Ohara, H. Nakayama, T. Positive-working photoresist compositions comprising novolak resin, quinonediazido compound, and phenolphthalein compound. Jpn. Kokai Tokkyo Kobo JP 04130322, 1992 Chem. Abstr. 1992, 117, 160945. 

A 0.2521-g sample of an unknown weak acid is titrated with a 0.1005 M solution of NaOH, requiring 42.68 mL to reach the phenolphthalein end point. Determine the compound s equivalent weight. Which of the following compounds is most likely to be the unknown weak acid ... 

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. 

The apparent acid strength of boric acid is increased both by strong electrolytes that modify the stmcture and activity of the solvent water and by reagents that form complexes with B(OH) 4 and/or polyborate anions. More than one mechanism may be operative when salts of metal ions are involved. In the presence of excess calcium chloride the strength of boric acid becomes comparable to that of carboxyUc acids, and such solutions maybe titrated using strong base to a sharp phenolphthalein end point. Normally titrations of boric acid are carried out following addition of mannitol or sorbitol, which form stable chelate complexes with B(OH) 4 in a manner typical of polyhydroxy compounds. EquiUbria of the type ... 

It was found already by Cattelain that the 3-thioxo derivatives behave as monobasic acids that can be titrated on phenolphthalein and he considered them as more acid than the analogous 3,5-dioxo-triazines. This assumption was recently confirmed by determining the dissociation constants. Just as with 6-azauracil, it was possible to demonstrate, by comparing the dissociation constants of the V-methyl derivatives of all the thioxo analogs, that with the 3-thioxo compounds too, dissociation proceeds first at the NH group in position 3 122... 

Alkalinity measurement is also required for the determination of active matter by difference and equivalent weight calculations. It can be determined as two of the following compounds sodium bicarbonate, sodium carbonate, or sodium hydroxide. The sample is titrated to a phenolphthalein endpoint to determine the sodium hydroxide/sodium carbonate content. An added measure of acid converts any bicarbonate to carbon dioxide, which is subsequently removed from the solution. Back-titration of the excess acid gives a measure of the amount of bicarbonate and/or carbonate present. 

Fluoran compound used as leuco dye needs to have substituent(s) on the xanthene moiety to develop color, though fluoran 1 itself is prepared as a by-product in the synthesis of phenolphthalein from phenol and phthalic anhydride. 

Phenolphthalein, like anthraquinones and other irritant phenolic compounds, is a stimulant laxative Colonic peristalsis is increased by stimulation of sensory nerve endings in the mucosa of the intestine. Phenolphthalein also enhances entrance of water and salts into the bowel... 

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). 

Experiment.—Dissolve 1 c.c. of nitromethane in water and test the solution with litmus paper. Then add some phenolphthalein and, drop by drop from a burette, OliV-sodium hydroxide solution. Before a permanent pink colour develops about 2 c.c. of the alkali will be added—a sign that an acid, aci-nitromethane, H2C NOOH, has been formed from the neutral nitromethane. A small sample of this solution gives with ferric chloride a blood-red colour, characteristic of aci-nitro-compounds. The salts of the oci-compound undergo extensive hydrolysis. This is shown by further addition of 0-1 N-alkali which produces a deep red colour. If 10 c.c. of alkali were added and 5 c.c. of 0-1 JV-hydrochloric acid are now run in the solution is decolorised because the liberated oci-compound restricts the hydrolysis of its salt. But the conversion of H2C N02H into H3C.N02 proceeds so rapidly that the red colour reappears in a few moments. 

Each of the above liquid residues was tritrated against standard sodium hydroxide, using phenolphthalein as indicator. Identical titer values were obtained the same titer value was also given by the original solid residue of unreacted TBTA (0-1). Such an observation of identical titer Values should be expected if the conversion of TBTA, by reaction with sodium chloride, is solj.ly to TBTCl. However, any side reaction leading to TBT hydroxide or TBTO will result in lower titer values since these tin compounds, unlike TBTA or TBTCl cannot be titrated like weak acids. Clearly, the side reactions are not noticeable in these experiments. Hydrolysis is not competitive under the conditions of this study, probably because chloride concentration never drops below 10-1 whereas hydroxide concentration is always below 10 s. (It was noticed that the pH of the aqueous layer in each case had risen from 6.5 to 9.0.)... 

Uses Antiseptic and disinfectant pharmaceuticals dyes indicators slimicide phenolic resins epoxy resins (bisphenol-A) nylon-6 (caprolactum) 2,4-D solvent for refining lubricating oils preparation of adipic acid, salicylic acid, phenolphthalein, pentachlorophenol, acetophenetidin, picric acid, anisole, phenoxyacetic acid, phenyl benzoate, 2-phenolsulfonic acid, 4-phenolsulfonic acid, 2-nitrophenol, 4-nitrophenol, 2,4,6-tribromophenol, 4-bromophenol, 4-/ert-butylphenol, salicylaldehyde, and many other organic compounds germicidal paints laboratory reagent. 

Ammonium chloride is analyzed by treatment with formaldehyde (neutralized with NaOH) and the product HCl formed is analyzed by titration using an acid-base color indicator such as phenolphthalein. Alternatively, it may be mixed with caustic soda solution and distdled. The distillate may be analyzed for NH3 by titration with H2SO4 or by colorimetric Nesslerization or with an ammonia-selective electrode (APHA, AWWA, WEF. 1995. Standard Methods for the Examination of Water and Wastewater. 19th ed. Washington, DC, American Pubhc Health Association). The presence of ammonia or any other ammonium compound would interfere in the test. The moisture content in NH4CI may be determined by Karl—Fischer method. 

A less accurate way to measure pH is to use indicators. An indiccitor is a compound, such as phenolphthalein or methyl orange, that changes color reversibly at different pH values. For example, phenolphthalein is a colorless substance in any solution with a pH value smaller than 8.3. It turns red-violet in solutions with a pH value greater than 8.3. 

Wise et al. investigated a number of crystalline organic compounds polynuclear aromatics, polyphenols, diacids, phthalein salts and phenolphthalein etc. as a substitute for charcoal in pyrotechnic formulations. Charcoal in black powder was substituted by these compounds in order to probe the chemical functionality of charcoal required for combustion. The data indicate that polynuclear aromatics which do not contain any oxygen do not sustain... 

Color Plate 15 Absorption Spectra (Demonstration 18-1) (a) Projected visible spectra of (from top to bottom) white light, potassium dichromate, bromophenol blue, and phenolphthalein. (b) Visible absorption spectra of the same compounds recorded with a spectrophotometer. 

Reaction XXIX. (a) Condensation of a Phenol with Phthalic Anhydride to form a Phthalein. (A., 183, 1 202, 68.)—The phthaleins result from the condensation of phthalic anhydride (1 mol.) with phenols (2 mols.) on heating with dehydrating agents—sulphuric acid, fused zinc chloride (to 120°) or anhydrous oxalic acid (to 115°). These compounds are particularly important some are dyes of great technical value. The simplest representative of the class is phenolphthalein. 

The free phthaleins are usually colourless crystalline compounds dissolving with intense colorations in alkalis, but being reprecipitated by acids, even by C02. In very concentrated alkali they give colourless solutions. A quinone structure is assumed for the coloured salts, e.g., for phenolphthalein in alkali solution. 

Appleyard (64) noted that addition of ethanol to incubation mixtures of sodium phenolphthalein diphosphate with prostatic extract increased the rate of free phenolphthalein formation. Phosphate ion failed to show a comparable increase, and this discrepancy was attributed to transphosphorylation. Phosphoryl transfer may be effected by prostatic phosphatase to acceptors other than solvent (65-67). Nigam and Fishman (25) studied phosphoryl transfer under conditions of 60-80% transfer to an acceptor. In the case of 1,4-butanediol, the optimal concentration was 0.8 M. In this experiment, water molecules outnumbered acceptor molecules by 55/0.8 or 70-fold. In spite of this, transfer far exceeded hydrolysis. Phosphoryl transfer to aliphatic alcohols can be easily measured when phosphates are used as donor compounds. The difference between alcohol formation from the substrate and phosphate ion production is a measure of the transfer reaction. Table IX (25) shows that four different substrates can transfer phosphoryl to butanediol with high efficiency. Table X (25) shows that aliphatic alcohols are good acceptors... 

---