Hydroxide transfer

Amino-5-methylthiazole. Suspend 76 g. of thiourea in 200 ml. of water in a 500 ml. three-necked flask equipped as in the preceding pre paration. Stir and add 92 -5 g. (80 ml.) of monochloroacetone (1) over a period of 30 minutes. The thiourea dissolves as the reaction proceeds and the temperature rises. Reflux the yellow solution for 2 hours. To the cold solution immersed in an ice bath add, with stirring, 200 g. of solid sodium hydroxide. Transfer to a separatory funnel, add a little ice water, separate the upper oil layer and extract the aqueous layer with three 100 ml. portions of ether. Dry the combined oil and ether extracts with anhydrous magnesium sulphate, remove the ether by distillation from a steam bath, and distil the residual oil under diminished pressure. Collect the 2-amino-5-methylthiazole at 130-133°/18 mm. it solidifies on coohng in ice to a solid, m.p. 44-45°. The yield is 84 g. 

Alizarin. Dissolve successively in 75 ml. of water 6 g. of potassium chlorate, 20 g. of sodium anthraquinone- p-sulphonate and 75 g. of sodium hydroxide. Transfer the mixture to a 500 ml. autoclave (compare Section VI,4) and heat for 20 hours at 170°. After coohng, scrape out... 

C. 7-Aminotheophylline. The reaction flask of a steam distillation apparatus is charged with 19.6 g (0.069 mol) of 7-benzylideneam1notheophyll1ne and 100 mL (0.1 mol) of 1 N hydrochloric acid. The suspension is steam distilled until no more benzaldehyde is detected 1n the distillate (Note 7), The resulting clear solution in the reaction flask 1s concentrated by rotary evaporation to a volume of 30 mL, adjusted to pH 10 with concentrated ammonium hydroxide, transferred to a separatory funnel and extracted with five 60-mL portions of chloroform. The combined chloroform extracts are dried with anhydrous sodium sulfate, filtered and concentrated to dryness by rotary evaporation. The residue is recrystal 11 zed from 75 mL of water to afford 11.3 g (84%) of 7-aminotheophylline, mp 222°C.3... 

Cognate preparation. Alizarin. Dissolve successively in 75 ml of water 6g (0.049 mol) of potassium chlorate, 20 g (0.065 mol) of sodium anthraquinone-2-sulphonate (Expt 6.39) and 75 g of sodium hydroxide. Transfer the mixture to a 500-ml autoclave (compare Section 2.17.2, p. 97) and heat for 20 hours at 170°C. After cooling, scrape out the violet-coloured mass and extract it three or four times with 100 ml portions of boiling water. Acidify the filtered extract with hydrochloric acid. When cold, filter the orange precipitate of alizarin at the pump, wash it thoroughly with cold water and dry at 100 °C. The yield of alizarin is 14 g (90%). It may be purified by recrystallisation... 

N EDTA/0.2 N TRIS Solution Transfer 18.6 g of disodium ethylenediaminetetraacetate (EDTA) and 6.05 g of tris (hydroxymethyl)aminomethane (TRIS), both accurately weighed, into a 250-mL beaker. Add 200 mL of hot, deionized water, and stir until dissolved. Adjust the pH to 7.5 to 7.6 by adding 5 N sodium hydroxide. Cool the solution, and adjust the pH to 8.0 with 5 N sodium hydroxide. Transfer the solution into a 250-mL volumetric flask, and dilute to volume with deionized water. Mix well, and store in a plastic container. 

Cyanide Standard Solution Dissolve 0.25 g of potassium cyanide in 100 mL of 0.1 A sodium hydroxide. Transfer a 1-mL aliquot into a 100-mL volumetric flask, dilute to volume with 0.1 A sodium hydroxide, and mix. Each milliliter of this solution contains 10 pig of cyanide (CN). 

Place the wet crude salt in a beaker, cool by means of running water, and add (using the hood) sufficient solution of 30 per cent sodium hydroxide to decompose the salt and cause the base to rise as an oil to the top. Avoid breathing the fumes given off by phenylhydrazine, as they are very toxic. Cool, and transfer to a separatory funnel, washing the beaker with 20 ml of ether. Extract twice with 50-ml portion of ether, and dry the ethereal solution of the base with solid sodium hydroxide. Transfer the ether solution into a 250-ml Claisen flask and distill off the ether by means of a water bath. Remove the bath, and arrange for distillation under reduced... 

Cool the solution and, using a pH meter, adjust the pH to 6.9-7.1 with 1 M sulfuric acid or 1 M sodium hydroxide. Transfer the solution to a volumetric flask and make it up to 1 litre with water. 

With the growth of PTC, various new technologies have been developed where PTC has been combined with other methods of rate enhancement. In some cases, rate enhancements much greater than the sum of the individual effects are observed. Primary systems studied involving the use of PTC with other rate enhancement techniques include the use of metal co-catalysts, sonochemistry, microwaves, electrochemistry, microphases, photochemistry, PTC in single electron transfer (SET) reactions and free radical reactions, and PTC reactions carried out in a supercritical fluid. Applications involving the use of a co-catalyst include co-catalysis by surfactants (Dolling, 1986), alcohols and other weak acids in hydroxide transfer reactions (Dehmlow et al., 1985,1988), use of iodide (traditionally considered a catalyst poison, Hwu et... 

Decomposition of a quaternary salt increases with agitation rate up to a point and then levels off, which is consistent with the slow hydroxide transfer rate limited process at low agitation rates, but slow intrinsic reaction rate limited process at high agitation rates. 

In principle, hydroxide anion is very difficult to transfer from aqueous to organic phases, yet it is one of the most valuable and most commonly used anions in the PTC systems. Addition of small amounts of alcohols to PTC systems requiring hydroxide transfer causes a dramatic increase in rates. Therefore, addition of alcohol enhances the PTC reaction as the cocatalytic effect. For example formation of alkoxide anions, RO, which are more readily transferred than the highly hydrated hydroxide anion, and which can serve as a strong base just as well as OH", and solvation of the hydroxide with alcohol rather than with water, making the hydroxide anion more organophilic and more easily transferred. ... 

Using a pipette transfer 2, 3, 10, 20 and 25 ml of cyanide reference solution into five 230 ml measuring flasks and top each one up to the 230 ml mark with 0.4 m sodium hydroxide. Transfer 10 ml from each flask to five 23 ml measuring flasks. To each of these add 1 m hydrochloric acid, buffer solution, chloramine T solution and barbituric acid-pyridine reagent, as described under "Measurement". Then carry out photometric analysis, in which the measured values must lie on a straight line. Check the calibration curve from time to time. 

Weigh a 5 g sample in a beaker, dissolve in 50 ml neutral ethanol and titrate to phenolphthalein with 0.1 M sodium hydroxide. Transfer to a separating funnel, using 50 ml water. 

M sodium acetate buffer pH 5.5. Add 58 mL of glacial acetic acid to a 500 mL beaker containing approximately 300 mL of deionized water. Adjust pH to 5.5 with 50% aqueous sodium hydroxide. Transfer to a 1 L volumetric flask and dilute to volume with deionized water. 

Cyclohexanone ethylene ketal treated at room temp, with trityl fluoroborate in methylene chloride cyclohexanone. Y 80%. - Similarly during 4 hrs. 0,0-Isopropylidenecholestane-2j, 3j -diol 3j -hydroxydiolestan-2-one. Y 79%. F. e. s. D. H. R. Barton et al., Chem. Commun. 1971, 861 removal of protective groups by hydroxide transfer under mild and neutral conditions s. a. Chem. Commun. 1971, 1109 Soc. Perkin I 1972, 542. 

This is followed by a fast reaction with the allyl alcohol. The ratedetermining step is a subsequent - or allyl process with concomitant hydroxide transfer in an allyl-hydroxo-intermediate." Reactivity trends in solution and in the solid state have been compared for the conversion of [Pd(en)(enH)X] + in the presence of X to [Pd(en)X2]. ... 

For tablets Finely powder twenty tablets and weigh accurately an amount of powder expected to contain about 10 mg of aneurine into a 100-ml conical flask. Add exactly 5 ml of dilute hydrochloric acid and 10 ml of water, heat to boiling and boil gently for four minutes. Cooh add (x — 1) ml of N sodium hydroxide, transfer to a 100-ml graduated flask and dilute to 100 ml with water. (The value of x is the number of ml of N sodium hydroxide required to neutralise the hydrochloric acid in a control determination, after cooling.) Use 5 ml of this solution for a determination as described for simple solutions. 

To extract the aneurine, weigh accurately about 5 g of the sample, suspend it in 50 ml of 01N sulphuric acid in a covered conical flask, heat in a water-bath for thirty minutes, cool and add 2-5M sodium acetate until the pH value lies between 4 5 and 5 0 (using an external indicator). Then add about 01 g of Mylase P (a mixed enzyme preparation) followed by a few drops of toluene and incubate.at 37° for twenty-four hours. Steam for fifteen minutes, adjust the pH value to 6 5 with 2N sodium hydroxide, transfer to a 100-ml graduated flask and make up to volume with water. For test purposes, filter an aliquot of this solution and dilute with water so that the solution contains an estimated aneurine concentration of about 0 02 g per ml. 

A major problem in cellulose cyanoethylation is control of the concommitant anionic polymerization of acrylonitrile. At base concentrations greater than 12%, exothermic polymerization occurs rapidly if the temperature is raised to 40 . In the presence of TMAC, the polymerization is suppressed, until a significant increase in the extent of substitution as evidenced by gelation occurs. However, at this point hydroxide ions must be released and a rapid polymerization ensues. Derivatives with apparent M.S. of 6.5 are isolated, but it is difficult to separate homopolyacrylonitrile from cyanoethyl cellulose to confirm if grafting has occurred. However, the initial suppression of base catalysed polymerization is a convincing demonstration of hydroxide transfer and binding in the cellulose phase. 

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