Fluorescein chloride

Acid amides give a color reaction with fluorescein chloride which has already been described in the discussion on amines (p. 324). The biuret reaction is given by compounds which contain a group in which two carbonamide groups are bound to one carbon or nitrogen atom, as, for example, in malonamide (I), biuret (II), or oxamide (III) in an alkaUne medium these substances give a red-violet complex compound with cupric hydroxide. 

Primary and secondary aliphatic and aromatic amines and tertiary aromatic amines with an N-methyl group give rhodamine dyes on fusion with fluorescein chloride and anhydrous zinc chloride. Different groups of these... 

Reagents HCl, 10% alcoholic HCl, fused ZnCl2, fluorescein chloride [for preparation see (21)]. 

Nitriles also react with fluorescein chloride (p. 324). Another detection scheme for nitriles is based on their pyrolysis with soda lime. The escaping ammonia or alkylamine is detected (59). 

Addition of silver nitrate to a solution of a chloride in dilute nitric acid gives a white precipitate of silver chloride, AgCl, soluble in ammonia solution. This test may be used for gravimetric or volumetric estimation of chloride the silver chloride can be filtered off, dried and weighed, or the chloride titrated with standard silver nitrate using potassium chromate(VI) or fluorescein as indicator. 

Silver nitrate is used volumetrically to estimate chloride, bromide, cyanide and thiocyanate ions. Potassium chromate or fluorescein is used as an indicator. 

Fluorescein is obtained by condensing phthahc anhydride (1 mol) with resorcinol (2 mols) in the presence of anhydrous zinc chloride. The tetra-bromo derivative, readily prepared by the addition of the calculated quantity of bromine, is eosin. 

Acid rhodamines are made by the iatroduction of the sulfonic acid group to the aminoxanthene base. The preferred route is the reaction fluorescein (2) with phosphorous pentachloride to give 3,6-dichlorofluoran (fluorescein dichloride) (23), which is then condensed with a primary aromatic amine in the presence of 2inc chloride and quicklime. This product is then sulfonated. For example, if compound (23) (fluorescein dichloride) is condensed with aniline and the product is sulfonated. Acid Violet 30 Cl45186) (24) is produced. 

Analysis. The abiUty of silver ion to form sparingly soluble precipitates with many anions has been appHed to their quantitative deterrnination. Bromide, chloride, iodide, thiocyanate, and borate are determined by the titration of solutions containing these anions using standardized silver nitrate solutions in the presence of a suitable indicator. These titrations use fluorescein, tartrazine, rhodamine 6-G, and phenosafranine as indicators (50). 

Bromine and bromides can be detected quaUtatively by a number of methods. In higher concentrations bromine forms colored solutions in solvents such as carbon tetrachloride [56-23-5] and carbon disulfide [75-15-0]. Bromine reacts with yeUow disodium fluorescein [518-47-8] to form red disodium tetrabromofluorescein (eosin) [548-26-5] C2QH Br4Na20. As Httle as 0.3 p.g of bromide can be detected and chlorides do not interfere (56). Bromine reacts with platinum sulfate [7446-29-9] Pt(S0 2> solution to form red to brown crystals of potassium hexabromoplatinate [16920-93-7] K PtBr ( )-... 

For the titration of chlorides, fluorescein may be used. This indicator is a very weak acid (Ka = ca lx 10-8) hence even a small amount of other acids reduces the already minute ionisation, thus rendering the detection of the end point (which depends essentially upon the adsorption of the free anion) either impossible or difficult to observe. The optimum pH range is between 7 and 10. Dichlorofluorescein is a stronger acid and may be utilised in slightly acid solutions of pH greater than 4.4 this indicator has the further advantage that it is applicable in more dilute solutions. 

Procedure. Pipette 25 mL of the standard OAM sodium chloride into a 250 mL conical flask. Add 10 drops of either fluorescein or dichlorofluorescein indicator, and titrate with the silver nitrate solution in a diffuse light, while rotating the flask constantly. As the end point is approached, the silver chloride coagulates appreciably, and the local development of a pink colour upon the addition of a drop of the silver nitrate solution becomes more and more pronounced. Continue the addition of the silver nitrate solution until the precipitate suddenly assumes a pronounced pink or red colour. Repeat the titration with two other 25 mL portions of the chloride solution. Individual titrations should agree within 0.1 mL. 

Similar remarks apply to the determination of bromides the Mohr titration can be used, and the most suitable adsorption indicator is eosin which can be used in dilute solutions and even in the presence of 0.1 M nitric acid, but in general, acetic (ethanoic) acid solutions are preferred. Fluorescein may be used but is subject to the same limitations as experienced with chlorides [Section 10.77(b)], With eosin indicator, the silver bromide flocculates approximately 1 per cent before the equivalence point and the local development of a red colour becomes more and more pronounced with the addition of silver nitrate solution at the end point the precipitate assumes a magenta colour. 

Caffeine Xanthine derivatives Purines Purines, pyrimidines Purines Chloraminc-T Iron (111) chloride followed by iodine Silver nitrate followed by sodium dichromate Fluorescein Silver nitrate followed by bromophenol blue... 

Texas Red hydrazide is a derivative of Texas Red sulfonyl chloride made by reaction with hydrazine (Invitrogen). The result is a sulfonyl hydrazine group on the No. 5 carbon position of the lower-ring structure of sulforhodamine 101. The intense Texas Red fluorophore has a QY that is inherently higher than either the tetramethylrhodamine or Lissamine rhodamine B derivatives of the basic rhodamine molecule. Texas Red s luminescence is shifted maximally into the red region of the spectrum, and its emission peak only minimally overlaps with that of fluorescein. This makes derivatives of this fluorescent probe among the best choices of labels for use in double-staining techniques. 

The basis of this method is that when normal seawater is chlorinated at the usual levels of 1 to 10mg/l of chloride, the bromine in seawater (8.1 x 10 4 M, 65 mg/1 at salinity = 35%o) is rapidly and quantitatively oxidised to Br() and HBrO. If 50 mg/1 of bromide is added to distilled or fresh waters containing HCIO plus C1CT, then HBrO plus BrO" are both formed. The HBrO plus BrO" will in turn rapidly brominate fluorecein (9-[o-carboxyphenyl]-6-hydroxy-3-isoxanthenone) to give the pink tetrabromo derivative eosin yellow (2,4,5,7-tetrabromo-9-[o-carboxyphenyl]-6-hydroxy-3-isoxanthenone), provided the molar ratio of bromide to fluorescein is 4 1. The resultant increase in eosin can be measured visually or spectrophotometrically, and the decrease in fluo-roscein measured fluorometrically. If the molar ratio of bromide to fluoroscein is < 4 1, then the mono-, di-, and tri-bromo derivatives are formed repro-ducibly. These derivatives have extinction coefficients close to eosin and are accounted for in the standardisation. 

P.R.90 is derived from the fluorescein structure (147). Fluorescein is a yellow dye with intensely green fluorescence which was discovered by A.v.Bayer in 1871. It is prepared by heating resorcin and phthalic anhydride with zinc chloride or concentrated sulfuric acid ... 

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