Unusual reaction of chloramine-T with araldoximes

Reaction of araldoximes with 4 equiv of chloramine-T in refluxing methanol produces N-(p-tolyl)-N-(p-tosyl)benzamides via addition of 2 equiv of chloramine-T to the intermediate nitrile oxide followed by extrusion of sulfur dioxide.     

A modified method for no carrier added radioiodination of L-tyrosine via chloramine-T as an oxidizing agent

A modified method for the preparation of L-[^131/123I] iodotyrosine as a brain imaging agent is described. The method is based on direct electrophilic radioiodination of L-tyrosine with NaI [^131/123I] using chloramine-T (CAT) and 0.001 g KI as a carrier at pH 7.0. The product was purified by reverse phase high performance liquid chromatography (HPLC). A high radiochemical yield up to 85% of L-[^131/123I] iodotyrosine has been achieved with radiochemical purity of greater than 97%. The relation between the pKa of L-tyrosine and pH of the reaction medium was calculated in order to correlate the radiochemical yield of L-[^131/123I] iodotyrosine and the state of the three ionizable groups of L-tyrosine. Also, the influence of the reaction conditions on the radiochemical yield of L-[^131/123I] iodotyrosine was investigated.     

N-substituted phenothiazines as indicators in titrations with chloramine-T

Trifluoperazine dihydrochloride, butaperazine dimaleate, promethazine hydrochloride, diethazine hydrochloride, prochlorperazine maleate and chlorpromazine hydrochloride have been studied as redox indicators in titrations of hydroquinone, metol and ascorbic acid with chloramine-T. The end-points obtained are sharper than with conventional indicators. The molar absorptivities of the oxidized indicators are reported. Simple but accurate methods for the determination of hydroquinone and metol are described.     

Titrimetric study of the reaction of chloramine-T with ammonia

A titrimetric study of the reaction between chloramine-T (CAT) and ammonia is described. The effects of the presence of bromide, the ratio of CAT to ammonia concentrations, the time for reaction and the pH of the reaction media are all significant in the quantitativeness of the reaction that occurs.     

N-Bromosuccinimide-mediated reaction of cyclic styrenes with chloramine-T

A facile route toward substituted allylic sulfonamides 3 is developed from the N-bromosuccinimide (NBS)-mediated allylic amination of cyclic styrenes 2 with chloramine-T (1a). Skeleton 2 is prepared by Grignard addition of cyclic ketones with different arylmagnesium bromides in THF followed by dehydration of the resulting tertiary alcohols with BF₃·OEt₂ in CH₂Cl₂. The synthetic route obtained moderate yields from the one-step operation and the key structures of skeleton 3 were confirmed by X-ray crystallographic analysis.     

Steric effects in the reaction of alkyl-phenyl and dialkyl-sulphides with chloramine-T

The rate of the reaction of dialkyl- and alkyl-phenyl-sulphides with TsNHCl increases with the increasing +I effect of the S-substituents, while the steric effect is only of minor importance. Rate constants of the reaction of dialkyl sulphides can be correlated with the Taft equation (?^* = ?1.96, δ = 0.285). The effect of ring size of cyclic sulphides on the reaction is discussed. The change of the rate constants with varying S-alkyl substituents is in agreement with a sterically unhindered electrophilic addition of Cl⁺ on bivalent sulphur, leading to chlorosulphonium ion. Sulphimides and sulphoxides are formed from the chlorosulphonium intermediates in the subsequent S_N-type reactions with different steric control.     

N-substituted phenothiazines as redox indicators in titrations with chloramine-T and chloramine-B

Profenamine hydrochloride, fluphenazine dihydrochloride, trifluopromazine hydrochloride, cyamepromazine maleate, perphenazine dihydrochloride and mepazine hydrochloride are proposed as redox indicators in the titration of hydroquinone, metol and ascorbic acid with chloramine-T and chloramine-B in sulphuric, hydrochloric and acetic acid media. They give a sharp reversible colour change at the equivalence point. A simple but accurate method for the determination of hydroquinone, metol and ascorbic acid is described. The conditional potentials and molar absorptivities of the indicators and redox potential of chloramine-B are reported.     

Redox indicators in titrations with chloramine-T

Naphthidine, 3,3'-dimethylnaphthidine disulphonic acid, o-dianisidine, di-phenylbenzidine, quinoline yellow, amaranth, methyl red, methyl orange, rhodamine-B and erioglaucine-A are examined as indicators in macro-and micro-titrations of arsenic(III), antimony(III), ascorbic acid, hydroquinone, metol, hydrazinium sulphate, isonicotinic acid hydrazide, semicarbazide hydrochloride and phenylhydrazine hydrochloride with chloramine-T. The indicators give sharp colour changes under optimal conditions. Transition potentials are reported.     

Spectrophotometric determination of verapamil hydrochloride in drug formulations with chloramine-T as oxidant

A new spectrophotometric method is described for the determination of verapamil hydrochloride, based on its oxidation with chloramine-T in hydrochloric acid medium. It produces a yellow colored compound with maximum absorbance at 425 nm. Beer's law was obeyed in the concentration range 0-340 micro g mL(-1) with molar absorptivity 2 x 10(3) L mol(-1) cm(-1) and RSD 0.3-0.82%. All variables were studied to optimize the reaction conditions. No interferences were observed from the common excipients present in the formulations. The method has been applied successfully to the determination of the drug in pharmaceutical preparations. Statistical comparison of the results with those from the reference method reveals excellent agreement and confirms that accuracy and precision are not significantly different.     

Formation of diethylene glycol as a side reaction during production of polyethylene terephthalate

Polymers of poly(ethylene terephthalate) (PET) always contain a certain amount of incorporated diethylene glycol (DEG), substituting the incorporated glycol. DEG is formed in a side reaction during the ester interchange of dimethyl terephthalate (DMT) with ethylene glycol or during direct esterification of terephthalic acid with ethylene glycol, and to a smaller extent during the polycondensation of the low-molecular material. DEG is formed via an unusual type of reaction: ester + alcohol → ether + acid. Some evidence of this type of reaction is given by the formation of dioxane in low molecular PET and of methyl Cellosolve and methyl carbitol during the ester interchange of DMT with ethylene glycol and diethylene glycol, respectively. The strongest support for this type of reaction, however, was obtained from kinetic data. Polyesters of low molecular weight with OH group contents ranging from 3 to 0.5 mole/kg were heated at 270°C in sealed tubes for 1–7 hr. The kinetic equation for the proposed reaction is: d[DEG]/dt = k[OH] [ester]. With the aid of one rate constant the formation of DEG in all esters could be described.     

Determination of iodide with chloramine-T

A method is described for the estimation of iodide, based on its oxidation to iodate by the addition of excess of chloramine-T, destruction of the excess of chloraniine-T with dimethyl sulphoxide and determination of the iodate iodometrically. In addition, the dimethyl sulphoxide eliminates any interference from bromide or bromate.     

Estimation of xylenes with chloramine-T

The reaction between xylenes and chloramine-T has been found to proceed quantitatively over a wide range of experimental conditions. A back-titration procedure in which xylenes are reacted with excess of chloramine-T in 1M perchloric acid-0.03M sodium chloride medium has been developed. Inorganic ions other than chloride do not interfere. The method can be used for estimating xylenes in the presence of some other petrochemicals.     

Nucleophilic radioiodination of 6-bromocholesterol via non-isotopic exchange reaction in molten state

A synthetic method for preparing radioiodinated 6-[125 I]iodocholesterol[CL-6-125 I] for adrenal evaluation is described. The radioiodine atom wasincorporated onto the cholesterol molecule via non-isotopic exchange between6-bromocholesterol [CL-6-Br] and radioiodine as iodide ion [ 125 I –]in a molten state. The different parameters affecting the yield of exchange were investigated using 125 I (T 1/2 .60 d) to centralize the different physical and chemical reaction conditions and purification of the final product as pure as 6-[125 I]iodocholesterol. The method was suitable to either 131 I (T 1/2 .8 d) nucleophilic radioiodination which facilitates the scanning of the adrenal for a few days after administration or the use of 124 I (T 1/2 .4.16 d) nucleophilic radioiodination for PET evaluation of the adrenal. TLC as well as HPLC chromatographic analysis is used to determine the efficiency of the exchange reactions under different chemical reaction conditions and to monitor the stability of the final product as pure as CL-6-125 I with radiochemical purity of .99%. This no-carrier-added method improved the speed of the reaction and affords high radiochemical yield of 90 % and suitable specific activity due to the use of CL-6-Br rather than CL-6-I as substrate. Kinetic studies revealed second order iodine-bromine exchange reaction. The activation energy for the exchange reaction in ammonium acetate (m.p. 114 °C) was calculated to be 4.576 kcal/mole.     

Estimation of thiosemicarbazide with chloramine-T

A rapid and accurate method for the estimation of thiosemicarbazide in aqueous solution has been developed based on its oxidation with chloramine-T at room temperature and pH 4. The effect of such variables as pH, mode of addition of reagents and concentration of chloride ion on the extent of oxidation has been studied.     

Estimation of dimethylsulphoxide with chloramine-T

A rapid and accurate method for the estimation of dimethyl-sulphoxide has been developed based on its oxidation to dimethyl-sulphone at room temperature by chloramine-T at pH 4-4.5. The effect of variables such as the pH, the mode of addition of reagents and the concentration of chloride ion on the extent and nature of oxidation has been studied and optimal conditons for analytical determination of dimethylsulphoxide derived.     

Oxidation of polythionates with chloramine-T

Summary Chloramine-T has been found to bring about the rupture of S-S link in polythionates in acid medium and oxidise all the sulphur present in the chain into sulphuric acid. Quantitative estimation of a polythionate may be made on the basis of this oxidation reaction.Our thanks are due to Prof. M. R. A. Rao for his interest in the work.     

Assay of p-aminobenzenesulphonamides with chloramine-T

New spectrophotometric and titrimetric methods for the assay of p-aminobenzenesulphonamides with chloramine-T have been developed. They are simple, reproducible and accurate within the limits described (+/-3%) and are useful at high concentration levels. These methods are also applicable to the assay of p-aminobenzenesulphonamides in rat urine.     

Unexpected formation of aryl dialkyl carbinol as a side product from the reaction of methoxyarylaldehydes with Grignard reagents

In the attempted formation of secondary aryl alkyl carbinols from the reaction of methoxyarylaldehydes with Grignard reagents, aryl dialkyl carbinols were formed as unexpected side products. A mechanism for their formation is proposed.     

Titrimetric determination of mercaptans with chloramine-T

Propyl mercaptan, allyl mercaptan, 2-mercaptoethanol, cysteamine hydrochloride, thio-p-cresol, 2-aminobenzenethiol, 2-mercaptopropionic acid and thioglycollic acid react with chloramine-T in 2:1 molar ratio in the presence of iodide, forming the corresponding disulphides. Mercaptans having a free beta-carbonyl group do not react quantitatively. The oxidation of the mercaptans is a function of time, and the corresponding sulphonic acids are formed on allowing them to stand with excess of chloramine-T. The oxidation to sulphonic acid is, however, instantaneous in the presence of iodine cyanide which acts as a catalyst and preoxidizer. This method is simple, accurate and rapid, and as little as 0.5 mg of the mercaptan can be determined with +/- 0.25% error.