Water with calcium hydride

Drawert at al. [38] employed chemical reactions in the chromatographic determination of water in alcohol solutions and of ethanol in blood. To determine water in alcohol solutions they used a reactor filled with a mixture of Sterchamol and calcium hydride (1 1). The hydrogen formed as a result of the reaction of water with calcium hydride was easily separated from all alcohols on a chromatographic column and detected as a narrow peak. 

A method for the determination of water in hquids, based on GC analysis of the hydrogen evolved during the reaction of water with calcium hydride, was described by Starshovet al. [83],... 

The presence of water results in very rapid saponification of ethyl benzoate. Dimethyl sulfoxide (Crown Zellerbach Corp.) may be dried by stirring with calcium hydride for 4-8 hours, followed by distillation under reduced pressure at 80-90° without filtration. Commercial 2-butyl alcohol and ethyl benzoate are conveniently dried by stirring for 2-4 hours with calcium hydride followed by filtration. 

With Calcium Hydride. —If calcium hydride is aght into contact with water, hydrogen is evolved... 

The procedures described below require rigorous exclusion of water and oxygen. All solvents should be distilled and stored under an inert atmosphere. Tetra-hydrofuran (THF) and diethyl ether are initially dried with calcium hydride or 4A molecular sieves, bubbled with nitrogen, and then heated to reflux with sodium wire plus 0.1 g of benzophenone per 500 mL of ether. After a deep blue color develops the solvent is distilled from the sodium benzophenone ketyl. 

A mixrnre of [RuCl2( -p-cymene)]2 (306 mg, 0.5 mmol), TsDPEN (366 mg, 1.0 mmol) and KOH (400 mg, 7.1 mmol) in 7 mL dichloromethane was stirred at room temperature for 5 min. On addition of water (7 mL) to the reaction mixmre, the colour changed from orange to deep purple. The purple organic layer was washed with 5 mL of water, dried with calcium hydride and concentrated to dryness to give the deep purple complex Ru(p-cymene)(TsDPEN) (455 mg, 75.8 % yield). 

HMPT is now thought to be a potent carcinogen. It should be handled with extreme care inhalation of the vapour and contact with the skin should be avoided. This solvent is miscible both with water and with many polar and non-polar organic solvents with the exception of saturated aliphatic hydrocarbons. It forms a complex with chlorinated solvents by which means it may be removed from aqueous solutions. The solvent may be dried by shaking with calcium hydride or barium oxide followed by distillation under reduced pressure and... 

Methanol containing no acetone is fractionally distilled through an efficient column, dehydrated with calcium hydride, and the distillation and drying are repeated three times. This process will yield about 50% of the starting material. One distillation of methanol over sodium reduces the water content to 0.003% after the second distillation it is 0.00005%. 

Materials. Sulfolane (99%purity) (Aldrich) was treated with calcium hydride and distilled under reduced pressure. The freshly prepared solvent had a specific conductivity of 1.0 X 10 7 O"1 cm"1 and a residual water content of 8 X 10"3M as determined by Karl Fisher titration. Conductivity water and reagent grade ether (Baker) were used. Glacial acetic acid (CIL), trifluoroacetic acid (Baker), and trifluoro-methanesulfonic acid (3M) were used as received. All these acids had a minimum purity of 99.5% as determined by titration with standard sodium hydroxide. Methanesulfonic acid (Eastman), distilled under reduced pressure, had a purity of 99.6%. Sulfolane solutions of these acids were prepared by weight, and the acid concentrations were checked by acidimetry after the samples were flooded with water. The solutions... 

Hydrogen can also be made by the reaction of a metallic hydride (a com pound of a metal and hydrogen) with water. Thus calcium hydride, CaHg, produces hydrogen according to the following reaction ... 

Purification and drying of dimethyl sulfoxide Dimethyl sulfoxide (11) containing 0.5% of water is stirred for a day with calcium hydride (20 g), then decanted and fractionated in a vacuum, if necessary under nitrogen. It boils at 72.5°/12 mm. 

In a variation of this procedure, the monomer is extracted twice with dilute aqueous sodium hydroxide, twice with water, then dried over calcium chloride, refluxed with calcium hydride, and distilled from this drying agent [32]. 

Acetonitrile is hygroscopic and also prone to hydrolytic decomposition. Hence, in addition to water, it virtually always contains acetamide, ammonia and possibly ammonium acetate as impurities. It cannot be dried with potassium hydroxide, since this would catalyze the hydrolysis. A molecular sieve with a pore size of 0.4 nm has proved effective for the drying of acetonitrile. Following treatment with this, the solvent is subjected to fractional distillation. Application of the molecular sieve makes unnecessary the previously employed treatment with calcium hydride and phosphorus pentoxide. 

In our experience, in addition to moisture, commercial methanol may also contain of organic impurities such as acetone, formaldehyde, ethanol, methyl formate and even acetaldehyde. The water content can be reduced to less than 0.01% by fractional distillation. Further drying may be effected with calcium hydride or calcium sulphate, but most efficiently with metallic sodium. Experiments in this laboratory showed that treatment with sodium, twice repeated, decreased the water content to S x 10 %. If a larger amount of acetone is present as an impurity, it can be precipitated first in the form of iodoform, by treatment with iodine and sodium hydroxide. Methanol is then distilled off from the precipitate, and the dehydration process is performed afterwards. 

Note Z. Dried by stirring the commercial product during some hours with calcium hydride at 40-50 C and subsequently distilling in a water-pump vacuum. HMPT as a cosolvent gives similar results, but the reaction times are much longer. 

Calcium hydride is highly ionic and is insoluble in all common inert solvents. It can be handled in dry air at low temperatures without difficulty. When heated to about 500°C, it reacts with air to form both calcium oxide and nitride. Calcium hydride reacts vigorously with water in either Hquid or vapor states at room temperature. The reaction with water provides 1.06 Hters of hydrogen per gram CaH2. 

The purification of diethyl ether (see Chapter 4) is typical of liquid ethers. The most common contaminants are the alcohols or hydroxy compounds from which the ethers are prepared, their oxidation products (e.g. aldehydes), peroxides and water. Peroxides, aldehydes and alcohols can be removed by shaking with alkaline potassium permanganate solution for several hours, followed by washing with water, concentrated sulfuric acid [CARE], then water. After drying with calcium chloride, the ether is distilled. It is then dried with sodium or with lithium aluminium hydride, redistilled and given a final fractional distillation. The drying process should be repeated if necessary. 

In a dry, 250 ml, three-necked flask equipped with a dropping funnel and magnetic stirrer are placed 40 ml of dry /-butyl alcohol (distilled from calcium hydride) and 4.0 g (0.036 mole) of potassium /-butoxide. The solution is cooled in ice and 40 g (49 ml, 0.49 mole) of dry cyclohexene is added. Bromoform (10 g, 3.5 ml, 0.039 mole) is added to the cooled, stirred reaction vessel dropwise over about hour, and the vessel is stirred an additional hour with the ice bath removed. The reaction mixture is poured into water (approx. 150 ml), and the layers are separated. The aqueous layer is extracted with 25 mi of pentane, and the extract is combined with the organic layer. The combined layers are dried (sodium sulfate), and the solvent is removed. The product is purified by distillation, bp 10078 mm. 

Reaction of calcium hydride (CaHJ with water. 

To inflate a life raft with hydrogen to a volume of 25.0 L at 25°C and 1.10 atm, what mass of calcium hydride must react with water ... 

A 300 ml three-neck flask equipped with condenser, stirrer, dropping funnel, dry nitrogen inlet tube, and containing 5.5 g (0.145 mol) lithium aluminum hydride LAH suspension in 100 ml anhydrous diethyl ether, was placed in an ice bath. Over a period of 25 min 30 ml (0.123 mol) 1 was added dropwise into the stirred suspension. The mixture was stirred for an additional hour at 0 °C, then poured over a mixture of 50 ml ether, 100 g crushed ice, and 50 ml ice water with stirring. When necessary more crushed ice was added to cool the mixture. The layers were separated, and the organic layer was concentrated first by distillation over calcium hydride, then by vacuum distillation over calcium hydride. The yield of 4 was 22.5 g (86%). Bp. 78-9 °C, 0.4 mm. The product was stored in a freezer. The structure of 4 was confirmed by its H NMR spectrum as shown in Fig. 4. 

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