Absolute ethanol, preparation

Preparation of Diethyl Allyl (1-Methyl-2-Pentynyl) Malonate A solution of 12.1 g of sodium in 182 ml of absolute ethanol was prepared, and thereto were added 126.6 g of diethyl (1-methyl-2-pentynyl) malonate. Most of the ethanol was then distilled off under reduced pressure, and the residue was cooled and 63.5 g of allyl bromide were slowly added thereto. After completion of the addition, the mixture was refluxed for about 1 hour. 

It is important to maintain strictly anhydrous conditions throughout this reaction. The equipment should be carefully predried and the absolute ethanol freshly prepared (preferably by the magnesium ethoxide method2) and distilled directly into the reaction flask. If the volume of ethanol is less than 2.5 1. the sodium ethoxide may not remain in solution. It is convenient to employ a three-necked flask carrying two condensers for this operation and to add the sodium through the third neck, which is otherwise kept stoppered. 

A solution of sodium ethoxide in ethanol is prepared by adding 23 g. (1 gram atom) of freshly cut sodium metal, as J -in. cubes, in portions of 3-4 g., to 300 ml. of absolute ethanol, contained in a 1-1. three-necked flask, fitted with a thermometer and an upright, water-cooled condenser, the open end of which is capped with a drying tube filled with a mixture of Drierite and coarse lime (Note 1). The sodium is added through the third neck of the flask, which is otherwise kept stoppered. 

It is necessary to maintain strictly anhydrous conditions in this reaction. The apparatus should be carefully predried and the absolute ethanol freshly prepared either by the diethyl phtha-late method 2 or by the magnesium ethoxide method.3... 

A solution of 90 g. of potassium hydroxide in 150 cc. of absolute ethanol is prepared in a 500-cc. round-bottomed flask fitted with a reflux condenser (Note 1). The solution is cooled somewhat, and the stilbene dibromide is added in several portions (Note 2). The mixture is then refluxed for twenty-four hours in an oil bath (Note 3). The hot mixture is poured into 750 cc. of cold water, and the product is removed by filtration and washed with 50 cc. of water. The crude diphenylacetylene is dried over calcium chloride in a vacuum desiccator for eighteen hours at room temperature. The chunky, pale yellow crystals melt at 58-60° and weigh 33.7-37.8 g. By recrystallization of this product from 50 cc. of 95 per cent ethanol there is obtained 29.2-30.5 g. (66-69 per cent of the theoretical amount based on the stilbene)... 

Solution in ethanol. For preparation of 6-10% solutions of the ethoxide in absolute ethanol, investigators conventionally add sodium to the alcohol in lumps or slices, with or without mechanical stirring, with or without a nitrogen atmosphere, and cool or heat as required until the metal is dissolved. Commercial anhydrous ethanol now available is satisfactory. A glycerol-sealed stirrer has been used, also a magnetic stirrer. The hydrogen liberated should be vented into a hood. Two inverse procedures are described below the second is shorter. 

Gold substrates were dipped in a solution of 8.4 mmol/L hexadecanethiol in ethanol for 1 min, rinsed with ethanol, and cleaned by a hydrogen plasma. A 1 mM solution of each of 1-11 in absolute THF as well as absolute ethanol, was prepared under a stream of nitrogen. Substrates were stored in these solutions for 24 h in the absence of light, rinsed with ethanol, blown dry under a stream of nitrogen and stored in the dark until further use. 

A solution of 5.0 g. of shiny K in 72 ml. of carefully dehydrated ethanol is prepared in a round-bottom flask equipped with a reflux condenser and a drying tube. After the evolution of Hg ends, exactly half the solution is decanted and is saturated with HgS (in the absence of atmospheric moisture) in the manner described for NaHS. Excess HgS is removed by brief boilii in a stream of Ng or Hg. The two portions of the solution are then recombined in the original reaction flask. This K S solution is then mixed with 4.1 g. of pure S and boiled for 30 minutes orar e-yellow KgSg crystals separate. These are quickly suction-filtered in a fast Hg or Ng stream, washed with absolute ethanol, and freed of adhering solvent in a vacuum desiccator over PgOg. 

The 1.5 M solution of dimethylamine in ethanol was prepared as follows Aqueous 40% dimethylamine is heated at 65°C under a flow of argon. The gas is passed through potassium hydroxide pellets and blown across a known quantity (100 mL) of absolute ethanol (analytical grade used without purification), then cooled to 0°C in an ice bath, with continuous stirring, for 3 hr. The ethanolic solution is weighed and diluted to 150 ml with absolute alcohol. The ethanolic dimethylamine solution (ca. 1.5... 

Ethanol absolute and graded solutions of 95, 80,70, and 50% v/v, prepared with DEPC-treated water... 

Absolute Preparation obtained by extracting a concrete with ethanol and... 

Ethanol is a monohydric primary alcohol. It melts at -117.3°C and boils at 78.5°C. It is miscible (i.e., mixes without separation) with water in all proportions and is separated from water only with difficulty ethanol that is completely free of water is called absolute ethanol. Ethanol forms a constant-boiling mixture, or azeotrope, with water that contains 95% ethanol and 5% water and that boils at 78.15°C since the boiling point of this binary azeotrope is below that of pure ethanol, absolute ethanol caimot be obtained by simple distillation. However, if benzene is added to 95% ethanol, a ternary azeotrope of benzene, ethanol, and water, with boiling point 64.9°C, can form since the proportion of water to ethanol in this azeotrope is greater than that in 95% ethanol, the water can be removed from 95% ethanol by adding benzene and distilling off this azeotrope. Because small amounts of benzene may remain, absolute ethanol prepared by this process is poisonous. 

The preparation of absolute ethanol in moderate quantity for classes may be carried out as follows. Pour 3 Winchester bottles (i.e., 7-8 litres) of rectified spirit into a 3-gallon (14-15 litre) can C (Fig. 58), add about 600 g. of the... 

Ammonium cyanate, because of its instability in solution, is usually prepared (NHJaSO, + 2KCNO 2NH4CNO + KjSO by mixing aqueous solutions of ammonium sulphate and potassium cyanate. Complete evaporation then gives a mixture of potassium sulphate and urea, from which the urea may be extracted w ith hot absolute ethanol, in which potassium sulphate is insoluble. 

The independent preparation of potassium phthabmide (from a solution of phthalimide in absolute ethanol and potassium hydroxide in 75 per cent, ethanol) may be avoided in many cases by boiling phthalimide with the halide in the presence of anhydrous potassium carbonate. The N-substituted phthalimide (I) is frequently cleav with difficulty this is often facilitated by reaction with hydrazine hydrate to give an intermediate product, which is easily decomposed by hydrochloric acid to 3deld the insoluble hydrazide of phthaUc acid (II) and the primary amine (III) ... 

The diethyl fumarate is readily prepared as follows. Reflux a mixture of 146 g. of fumaric acid (Section 111,143), 185 g. (236 ml.) of absolute ethanol, 450 ml. of boizene and 20 g. of concentrated sulphuric acid for 12 hours. Pour into a large volume of water, separate the benzene layer, wash successively with water, saturated lodium bicarbonate solution and water, dry with anhydrous magnesium sulphate, and remove the solvent on a steam bath. Distil the residue and collect the diethyl fumarate at 213-215° the yield is 150 g. 

Girard s reagent P , C5H5NCH2C0NHNH2 C1. In a 1-htre threenecked flask, equipped as in the previous preparation, place 200 ml. of absolute ethyl alcohol, 63 g. (64 -5 ml.) of pure anhydrous pyridine and 98 - 5 g. (84 5 ml.) of ethyl chloroacetate. Heat the mixture under reflux for 2-3 hours until the formation of the quaternary salt is complete acidify a small test-portion with dilute sulphuric acid it should dissolve completely and no odour of ethyl chloroacetate should be apparent. Cool the mixture in ice and salt. Replace the thermometer by a dropping funnel, and add a solution of 40 g. of 100 per cent, hydrazine hydrate in 60 ml. of absolute ethanol all at once. A vigorous exothermic reaction soon develops and is accompanied by vigorous effervescence. The pro duct separates almost immediately. When cold, filter with suction, wash... 

Purification of the Methylamine HCI is in order now, so transfer all of the crude product to a 500mL flask and add either 250mL of absolute Ethanol (see end of FAQ for preparing this) or, ideally, n-Butyl Alcohol (see Footnote 4). Heat at reflux with a Calcium Chloride guard tube for 30 minutes. Allow the undissolved solids to settle (Ammonium Chloride) then decant the clear solution and cool quickly to precipitate out Methylamine HCI. Filter rapidly on the vacuum Buchner funnel and transfer crystals to a dessicator (see Footnote 3). Repeat the reflux-settle-cool-filter process four... 

Hydrolysis of the ester is achieved by refluxing in aqueous N or 2N NaOH solution until the insoluble ester dissolves. The solution is then cooled, and the alcohol is extracted into a suitable solvent, e.g. ether, toluene or alcohol-free chloroform. The extract is dried (CaS04, MgS04) and distilled, then fractionally distilled if liquid or recrystallised if solid. (The p-nitrobenzoic acid can be recovered by acidification of the aqueous layer.) In most cases where the alcohol to be purified can be readily extracted fi-om ethanol, the hydrolysis of the ester is best achieved with N or 2N ethanolic NaOH or 85% aqueous ethanolic N NaOH. The former is prepared by dissolving the necessary alkali in a minimum volume of water and diluting with absolute alcohol. The ethanolic solution is refluxed for one to two hours and hydrolysis is complete when an aliquot gives a clear solution on dilution with four or five times its volume of water. The bulk of the ethanol is distilled off and the residue is... 

Although the first all-sulfur macrocycles were prepared many years ago " the first systematic study of such compounds was initiated by Busch and his coworkers , who were interested in the cation binding properties of such ligands. A sequential synthesis was utilized to produce 1,4,8,11-tetrathiacyclotetradecane [tetrathia-14-crown-4 (70)] . In the first step, 1,3-propanedithiol is metallated using sodium and alkylated with 2-chloroethanol. The diol was then treated with thiourea to form the dimercapto-dithioether compound 9. The latter was once again metallated with sodium and allowed to react with 1,3-dibromopropane. The yield of 70 in the ring closure step, conducted at high dilution in absolute ethanol, was 7.5% after recrystallization. The entire sequence is illustrated in Eq. (6.8) . ... 

To an ethanolic solution of sodium ethoxide prepared by addition of 0.46 g (0.02 mole) of freshly cut sodium metal in 100 mL of absolute ethanol was slowly added 5.10 g (0.02 mole) of ethyl 4-nitrobenzylthioacetate 28 with stirring at 5°C. The mixture was refluxed for about 4 to 6 hours until the reaction was complete (monitored by tic). The resultant mixture was allowed to cool to room temperature and then added into an ice-water mixture. The solution was neutralized with slow addition of dilute aqueous hydrochloric acid (10%). The precipitated solid was removed by filtration, washed with water, and recrystallized from a dimethylformamide-ethanol (T.l) mixture yielding 2.10 g (76 %) of 29 as a light brown crystalline solid, mp 227°C ir (nujol) (neat (1710 cm ms m/z Til (NT). Anal. Calcd. For C13H11NO4S C, 56.31 H, 3.97 N, 5.05 S, 11.55. Found C, 56.36 H, 3.95 N, 5.01 S, 11.49. 

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