Chlorobenzene solutions, titrations

The catalytic oxidation experiments were carried out in a round bottom flask equipped with condenser and stirrer. Typically, 6 or 12 mmol of substrate, 2 mmol bromobenzene (internal standard), 9 ml solvent (1,2-dichloroethane) and 100 mg zeolite (which contains typically around 2.9 pmol V (0.15wt%), TBHP/V ratio = 2070) were heated to 70°C, after which 6 mmol of TBHP in a 5.3 mmol chlorobenzene solution (which at the same time can function as an internal standard) were added to start the reaction. A sample was taken immediately afterwards. Before and during the reaction the mixture was purged with nitrogen for oxidations with cyclohexene and cyclooctene. Samples were filtrated over cotton wool and/or alumina, and triphenylphosphine was added to remove TBHP. In case of acetone as the solvent at 70°C, reactions were performed in a 50 ml autoclave and the reaction mixture was only purged with nitrogen before heating. After reaction TBHP was determined by iodometric titration. 

Titrations with dibutylamine [111-92-2] can also be used to determine the NCO content of isocyanates and prepolymers. Generally, an excess of amine in a suitable solvent such as chlorobenzene [108-90-7] is added to the sample. The resulting solution is allowed to react and the unreacted amine is back- titrated with dilute hydrochloric acid. For low NCO content levels, a colorimetric method is often used. The isocyanate-containing species is titrated with amine and the unreacted amine is deterrnined using malachite green [569-64-2]. 

The NCO content of diisocyanates can be determined by the reaction with an excess of a standard solution of dibutylamine in chlorobenzene (or dry toluene) and titration of the excess with hydrochloric acid. The dibutylamine is prepared by dissolving 129 g of freshly distilled dibutylamine in 871 g of redistilled chlorobenzene and storing the resultant solution in the dark. The solution is relatively stable, but it is advisable to determine the amine content weekly by titration with 1 N hydrochloric acid in methanol. 

In the determination, 2 g of the diisocyanate should be accurately weighed out into a conical flask and 5 ml of chlorobenzene added. In the case of naphthalene diisocyanate, it is recommended that the mixture be warmed slightly to assist dissolution. To this mixture there is then added 25 ml of the standard dibutylamine solution. The reaction is rapid and takes only a few minutes for completion, when a clear solution is obtained. After adding 2 or 3 drops of a 1% alcoholic solution of bromophenol blue and 100 ml of methanol, the excess dibutylamine can be titrated with 1 N hydrochloric acid. 

The residue from mercaptide stabilizers was dissolved with chlorobenzene, and it was allowed to react with 0.4 ml. of 40% peracetic acid for 10-15 minutes. The reaction product was added with acetone rinsing to a solution of 0.50 gram of sodium sulfite in 100 ml. of water. After adding 5 ml. of concentrated nitric acid the chloride ion was titrated potentiometrically with 0.1N silver nitrate. 

The decompositions were carried out in a 50 ml thermostated glass flask equipped with a condenser and magnetic stirrer. Typically a solution of cyclohexenyl hydroperoxide (2 mmol), n-decane (internal standard) and catalyst (0.02 mmol metal) were stirred (1000 rpm) in 10 ml chlorobenzene at 80 °C for 5 h. The cyclohexenyl hydroperoxide conversion was determined by iodometric titration. Typically, 3.0 g of reaction mixture was diluted with 30 ml acetic acid/chloroform (2 1 v/v), 2.5 ml of saturated aqueous KI solution was added and the solution was allowed to stand for 1 h in fhe dark before adding 50 ml of deionized wafer and titration with a 0.1 M sodium thiosulfate solution. The reaction products were analysed by GC (CP Sil 5 CB column) after destroying remaining cyclohexenyl hydroperoxide by the addition of an excess of triphenylphosphine as a solution in 1,2-dichloroethane (24 g / 1). 

To titrate alkylchlorosilanes such as trimethylsilicon chloride, dimethylsilicon dichloride, methylsilicon trichloride and silicon tetrachloride, titration in methyl cyanide with 0.05 n phenazone or nitron in methyl cyanide, or with a solution of amidopyrine in benzene by visual and potentiometric methods is suggested173. The indicators used are crystal violet, dimethylaminoazobenzene, bromocresol purple, methyl orange, bromo-phenol blue and gallo sea blue (C.I.-Mordant Blue 14) the addition of benzene, toluene, chlorobenzene or carbon tetrachloride does not effect the results. 

The method of defining IFHANGAZ content in a PE film consists in grinding a film sample, extraction of the VCI from the pol3mier using a solvent (chlorobenzene or methylisobutylketone) followed by potentiometric titration of Cl components converted into an organic extract (secondary and tertiary amines) by solution of HCIO4 in a waterless acetic acid [24,153]. 

About 100 mg of anhydrous sodium carbonate, 20 ml of chlorobenzene and 10 ml of glacial acetic acid are taken in an Erlenmeyer flask and magnetically stirred until all the carbonate dissolves. Four drops of 0.1% solution of crystal violet in acetic acid are added. The purple-coloured solution is titrated with hydrogen bromide solution (prepared by diluting about 6 ml of commercial reagent with 250 ml of acetic acid). The titre value is noted at the blue-green end point. About 300 mg of epoxy sample is titrated in a similar way. A blank titration is also carried out without any sample. 

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