Reagent solution , preparation

An oven-dried, 1-L, round-bottomed flask is equipped with a magnetic stirring bar and a rubber septum. The flask is charged with 25.61 g of copper bromide-dimethyl sulfide complex (124 mmol) and 250 mL of dry diethyl ether, and the resulting slurry is cooled to -78°C with a dry ice-acetone bath. The Grignard reagent solution prepared above is added to the copper bromide-dimethyl sulfide slurry via cannula... 

Relaxation Reagent Solution prepared from ferric acetylacetonate (Fe(acac)j - MW = 353.16, reagent grade)— Prepare a fresh 0.02 M Fe(acac)3 solution by dissolving 1.77 g of Fe(acac)3 in 250 mL TCE. If any of the ferric acetylacetonate remains undissolved, filter the solution and use the filtrate in subsequent steps. 

This sodium bisulphite reagent Is prepared by treating a saturated aqueous solution of sodium bisulphite with 70 per cent, of its volume (if rectified (or methylated) spirit, and then adding just sufiScient water to produce a clear solution. 

The carbon disulphide reagent is prepared by adding to a solution of 0-5 g. of crystallised nickel chloride in 100 ml. of water enough carbon disulphide so that after shaking a globule of carbon disulphide is left at the bottom of the bottle. The reagent is stable for long periods in a well-stoppered bottle. If all the carbon disulphide evaporates, more must be added. 

Barfoed s reagent Is prepared by dissolving 13-3 g. of crystallised neutral copper acetate in 200 ml. of 1 per cent, acetic acid solution. The reagent does not keep well. 

For many reductions it is not necessary to distil the reagent. Dilute the dark solution, prepared as above to the point marked with an asterisk, to 1 htre with dry isopropyl alcohol this gives an approximately one molar solution. Alternatively, prepare the quantity necessary for the reduction, using the appropriate proportions of the reagents. 

Certain features of the addition of acetyl nitrate to olefins in acetic anhydride may be relevant to the mechanism of aromatic nitration by this reagent. The rapid reaction results in predominantly cw-addition to yield a mixture of the y -nitro-acetate and y5-nitro-nitrate. The reaction was facilitated by the addition of sulphuric acid, in which case the 3rield of / -nitro-nitrate was reduced, whereas the addition of sodium nitrate favoured the formation of this compound over that of the acetate. As already mentioned ( 5.3. i), a solution of nitric acid (c. i 6 mol 1 ) in acetic anhydride prepared at — 10 °C would yield 95-97 % of the nitric acid by precipitation with urea, whereas from a similar solution prepared at 20-25 °C and cooled rapidly to —10 °C only 30% of the acid could be recovered. The difference between these values was attributed to the formation of acetyl nitrate. A solution prepared at room... 

Raagent. The yellow CrOa-pyndine reagent is prepared by adding rad CrOa at 15-20° to 10 parts of pyridine in portions with stimng. The complex is moderately soluble in pyridine and used as a suspension to whx h a 10% solution of the alcohol in pyridine is added Note if pyndine is added to CrOa the mixture usually inflamed... 

The chromatogram is freed from mobile phase and immersed for 1 s in the freshly prepared reagent solution and then heated to 105 to 110 °C for 5 to 10 min. Green, blue or purple fluorescence appears on a dark background under long-wavelength UV light (2 = 365 nm). 

Dipping solution Mix 2 ml antimony(V) chloride with 8 ml carbon tetrachloride. Storage The reagent solution should always be freshly prepared. 

The reagent solution may be kept for several days in the refrigerator. However, it should always be freshly prepared for quantitative analyses. 

Snatzke has found that a solution prepared from chromium trioxide and dimethylformamide with a small amount of sulfuric acid has similar chemical properties as the Sarett reagent. It is useful with acid sensitive compounds and oxidation occurs at such a moderate rate that selective oxidations are often possible. Although the position allylic to a A -double bond is not attacked, the 3-hydroxy-A -system cannot be oxidized satisfactorily to the cor-... 

Much better known are the fluonnatedphosphoranes, which have been widely used m the Wittig reaction for the preparation of fluoroolefms Difluoromethylena tion reactions have been effected by using a variety of conditions Treatment of dibromodifluoromethane with two equivalents of tns(dimethylammo)phosphine m carefully dried tnglyme yields a solution of bromodifluoromethylphosphonium broomide, which very effectively converts ketones to difluoromethylene derivatives A more sensitive reagent is prepared by the addihon of two equivalents of the phosphine to the reaction mixture of fluorohalomethane and a carbonyl compound [39, 40] (equation 40) (Table 14)... 

The chromic acid oxidizing reagent is prepared by dissolving 13.4 g of chromium trioxide in 25 ml of water. To this solution is added 12 ml of concentrated sulfuric acid. An additional minimum quantity of water is added if necessary to dissolve any precipitated salts. 

Reactions in liquid ammonia (cf. Chapter 3, Section III) require a certain amount of care, since the solvent is low boiling (—33 ) and its fumes are noxious. Nevertheless, with reasonable caution, the preparation of an ammonia solution of sodium acetylide can be carried out as described. The reagent so prepared can then be directly used for displacements on alkyl halides or for additions to suitable carbonyl compounds. Examples of both reactions are given. 

Notes. (1) The dimethylglyoxime reagent is prepared by dissolving 0.50 g of dimethylglyoxime in 250 mL of ammonia solution and diluting to 500 mL with water. 

Notes. (1) The reagent solution should be freshly prepared using analytical-grade dithizone and 1,10-phenanthroline, preferably taken from new or recently opened reagent bottles. 

Procedure. Prepare the CDTA solution (0.02M) by dissolving 6.880 g of the solid reagent in 50 mL of sodium hydroxide solution (1M) and making up to 1 L with de-ionised water the solution may be standardised against a standard calcium solution prepared from 2.00 g of calcium carbonate (see Section 10.61). The indicator is prepared by dissolving 0.5 g of the solid in 100 mL of water. 

Hydroxyquinaldine (2-methyloxine) is a pale yellow, crystalline solid, m.p. 72 °C it is insoluble in water, but readily soluble in hot ethanol, benzene, and diethyl ether. The reagent is prepared by dissolving 5 g of 8-hydroxyquinaldine in 12 g of glacial acetic acid and diluting to 100 mL with water the solution is stable for about a week. 

The reagent is prepared by mixing equal volumes of Solutions A and B and filtering after standing overnight. 

Lead (ca 100mg in 25 mL solution). Add 10 mL of freshly prepared reagent solution, dilute to 50 mL and add 12.5 mL of concentrated ammonia solution. 

Reagents. Standard nickel and cobalt ion solutions. Prepare solutions of nickel and cobalt ion (ca 10 mgmL"1) from pure ammonium nickel sulphate and pure ammonium cobalt sulphate respectively. 

Reagents required. Prepare a ca 0.001 M sodium thiosulphate solution and also a standard 0.005 M iodine solution. 

When plotting the standard curve it is customary to assign a transmission of 100 per cent to the blank solution (reagent solution plus water) this represents zero concentration of the constituent. It may be mentioned that some coloured solutions have an appreciable temperature coefficient of transmission, and the temperature of the determination should not differ appreciably from that at which the calibration curve was prepared. 

Reagents. Buffer solution (pH = 10.1). This consists of a 0.75 per cent w/v solution of ammonium chloride in dilute ammonia solution, prepared by mixing 5 volumes of concentrated ammonia solution (sp. gr. 0.88) and 95 volumes of water. 

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