76-60-8Relevant articles and documents
Detection and identification of side reactions of halogenated hydrocarbon solvents with amines of pharmaceutical interest by secondary processes to the neutralizations of sulphonphthaleinic dyes with these amines
Gainza,Konyeaso,Asenjo
, p. 226 - 232 (2007/10/02)
The neutralization reactions between amines and diprotic acid dyes in organic solvents generate {dye-, amineH+} and {dye2-, (amineH+)2} ion associates that show two absorption bands in the visible spectrum. An unidentified third absorption band; which appears with a high amine concentration, proves that halogenated hydrocarbon solvents (dichloromethane, chloroform, 1,2-dichloroethane, and carbon tetrachloride) give side reactions with amines (atropine, tropine, quinine, ephedrine, and ajmaline) that generate a quaternary ammonium salt, N-halogenalkylammonium halide ({N+- RX,X-}). The molecular weight of the quaternary ammonium salt is the sum of the amine and that of the solvent. The {N+-RX,X-} ion associated reacts with {dye2-, (amineH+)2} by substitution reactions, forming {dye2-, amineH+, N+-RX} and {dye2-, (N+-RX)2} ion associates that justify the third absorption band. The amine-solvent side reactions are of first order with respect to the amine, being very slow processes with rate constant values from 399.4 h-1 (tropine-dichloromethane reaction) to 15.8 h-1 (atropine-1,2-dichloroethane reaction). Rate constants increase with the basicity of the amine measured in the halogenated hydrocarbons employed. Rate constants also increase with a reduction in the number of the halogen atoms present in the halogenated solvent. The new visible absorption band that appears in the amine-dye neutralization gives a quick colorimetric test to bring to light this kind of side reaction in these solvents.
Substitution reactions of benzethonium chloride with ion associates of bromocresol green - quinine and bromophenol blue - quinine in dichlormethane
Gainza, Alberto Hernandez,Konyeaso, Roy Ikemefula
, p. 937 - 944 (2007/10/02)
An excess concentration of base quinine (Q) reacts with a sulphonphthalein diacidic dye XH2, (bromocresol green, BCGH2, or bromophenol blue, BPBH2) in dichlormethane solution to form an ion associate (X(2-)(QH21+)2) of stoichiometry 1:2 (dye:amine).Benzethonium chloride (CIB) reacts with the 1:2 ion associate to form an ion associate (QH1+,X2-,B1+) and quinine hydrochloride ClQH(1+).This substitution reaction is a chemical equilibrium with formation constants of 1.50+/-0.67, 1.64+/-0.54, 1.07+/-0.29, 1.04+/-0.20, and 0.84+/-0.26 for BCG and 1.86+/-0.59, 1.47+/-0.23, 1.40+/-0.65, 1.13+/-0.37, and 1.11+/-0.27 for BPB at 283.16, 288.16, 293.16, 298.16, and 303.16 K respectively.The thermodynamic parameters determined by van't Hoff's equation are ΔH0 = -21.766+/-7.482 kJmol-1, ΔS0 = -73+/-51 Jmol-1K-1, and ΔG0 = -1.134+/-0.972 kJmol-1 for BCG and ΔH0 = -18.678+/-7.482 kJmol-1, ΔS0 = -61+/-26 Jmol-1K-1, ΔG0 = -0.916+/-0.401 kJmol-1 for BPB (ΔG0 at 293.16K; and ΔH0 and ΔS0 determined in the range 283-303K). Key words: bromocresol green-quinine-benzetonium, ion associate mixture, bromophenol blue-quinine-benzethonium, equilibrium constants, thermodynamic parameters.
Antiglaucoma agents
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, (2008/06/13)
Pharmaceutical compositions and a method for reducing intraocular pressure by topically applying a carboxyalkyl dipeptide are disclosed.