Methyl alcohols

Methyl alcohol (methanol) is the first member of the aliphatic alcohol family. It ranks among the top twenty organic chemicals consumed in the U.S. The current world demand for methanol is approximately 25.5 million tons/year (1998) and is expected to reach 30 million tons by the year 2002. The 1994 U.S. production was 10.8 billion pounds. 

Methanol was originally produced by the destructive distillation of wood (wood alcohol) for charcoal production. Currently, it is mainly produced from synthesis gas. 

Old processes use a zinc-chromium oxide catalyst at a high-pressure range of approximately 270-420 atmospheres for methanol production. 

Methanol synthesis over the heterogeneous catalyst is thought to occur by a successive hydrogenation of chemisorbed carbon monoxide. 

Other mechanisms have been also proposed. Uses of Methanol 

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Sodium fluoroacetate, which is not volatile and not irritating to the skin, is used as a rodenticide. It is made from CH2ClC02Et and KF, which react to give ethyl fluoroacetate, which is then hydrolysed with NaOH in methyl alcohol. 

A method of estimating small amounts of water in organic liquids (and also in some inorganic salts) is that of Karl Fischer. The substance is titrated with a mixture of iodine, sulphur dioxide and pyridine dissolved in methyl alcohol. The essential reaction is ... 

Other pairs of liquids which exhibit an upper consolute temperature are methyl alcohol - cyclohexane (C.S.T. 49 -1° critical composition 29 per cent, by weight of methyl alcohol) isopentane - phenol (63 5° 51 per cent, of isopentane) and carbon disulphide - methyl alcohol (40-5° 80 per cent, of carbon disulphide). 

An important application of the critical solution temperature is to the determination of the water content in such substances as methyl and ethyl alcohols. Here the system is usually the alcohol and a hydro carbon, such as -hexane or dicyclohexyl the water is, of course, insoluble in the hydrocarbon. Thus, the methyl alcohol - cyclohexane system has a C.S.T. of 45 -5° and even 0 01 per cent, of water produces a rise of 0-15° in the C.S.T. The experimental details are given below. 

For methyl alcohol, two volumes of synthetic n-hexane, b.p. 68-6-69 0° (uncorr.), and one volume of the alcohol to be tested are mixed and the homogeneous mixture is cooled in ice until the appearance of a cloudiness. A thermometer is placed in the solution, which is allowed to warm gradually to the temperature at which the second phase disappears. The... 

The developer is generally a solvent in which the components of the mixture are not too soluble and is usually a solvent of low molecular weight. The adsorbent is selected so that the solvent is adsorbed somewhat but not too strongly if the solvent is adsorbed to some extent, it helps to ensure that the components of the mixture to be adsorbed will not be too firmly bound. Usually an adsorbate adheres to any one adsorbent more firmly in a less polar solvent, consequently when, as frequently occurs, a single dense adsorption zone is obtained with light petroleum and develops only slowly when washed with this solvent, the development may be accelerated by passing to a more polar solvent. Numerous adsorbat are broken up by methyl alcohol, ethyl alcohol or acetone. It is not generally necessary to employ the pure alcohol the addition from 0 5 to 2 per cent, to the solvent actually used suffices in most cases. 

Absolute methyl alcohol. The synthetic methanol now available is suitable for most purposes without purification indeed, some manufacturers claim a purity of 99 85 per cent, with not more than 0 1 per cent, by weight of water and not more than 0 02 per cent, by weight of acetone. Frequently, however, the acetone content may be as high as 0 1 per cent, and the water content 0-5-1 per cent. 

If the small proportion of acetone present in synthetic methyl alcohol is objectionable, it may be removed when present in quantities up to... 

Other mixtures which may be employed are carbon tetrachloride (b.p. 77°) and toluene (b.p. 110-111°) chloroform (b.p. 61°) and toluene methyl alcohol (b.p. 65°) and water (b.p. 100°). The last example is of interest because almost pure methyl alcohol may be isolated no constant boiling point mixture (or azeotropic mixture) is formed (compare ethyl alcohol and water, Sections 1,4 and 1,5). Attention is directed to the poisonous character of methyl alcohol the vapour should therefore not be inhaled. 

Alternative experiments (a) RecrystaUisation of crude benzoic acid (5-0 g.) from methyl alcohol (30 ml.) the wash liquid should be 50 per cent, methyl alcohol. (6) RecrystaUisation of acetaniUde (5 g.) from toluene (100 ml.) filter through a preheated funnel. 

Shake 1 ml. of anhydrous methyl alcohol with 1 ml. of paraffin oil. Repeat the experiment with 1 ml. of n butyl alcohol. From your results state which is the better solvent for paraffin oil (a mixture of higher hydrocarbons) and thus explain why n-butanol and higher alcohols are incorporated in pyroxylin lacquers in preference to methyl and ethyl alcohols. 

Methyl Iodide. Use 38 g. (48 ml.) of methyl alcohol, 8-27 g. of purified red phosphorus and 127 g. of io ne. Cover the iodine completely with the hot methyl alcohol before running the alcoholic solution into the boiling alcohol - phosphorus mixture. B.p. 42-42-5°. 

The 0 -S.V alcoholic potassium hydroxide solution Is prepared by dissolving 16g. of potassium hydroxide pellets in 500 ml. of alcohol (or industrial spirit) contained in a bottle closed by a cork. After standing for 24 hours, the clear solution is decanted or filtered from the residue of potassium carbonate. It is said that a solution in methyl alcohol has better keeping qualities than that in ethyl alcohol. 

Formaldehyde is a gas, b.p. — 21°, and is usually prepared by the dehydrogenation of methyl alcohol m the presence of heated copper or silver. By admitting air with the methyl alcohol vapour, part of the hydrogen is oxidised to give the heat necessary for the reaction ... 

Formaldehyde is a gas, b.p. — 21°, and cannot obviously be stored as such moreover, it polymerises readily in the liquid and the gaseous state. The commercial preparation, formalin, is an aqueous solution containing 35-40 per cent, of formaldehyde and some methyl alcohol. The preparation of a solution of formaldehyde may be demonstrated by the following experiment. 

Prepare a coil of copper wire by winding several turns around a glass tube. Heat the coil in the oxidising flame of a Bunsen burner for 1-2 minutes and plunge the spiral, whilst still red hot, into a test-tube containing a solution of 1 ml. of methyl alcohol and 5 ml. of water. Stopper the test-tube loosely, cool, remove the wire, and repeat the process two or three times. Observe the odour of the solution and use it (or formalin diluted with water) to carry out the following tests. 

To obtain a maximum yield of the acid it is necessary to hydrolyse the by-product, iaoamyl iaovalerate this is most economically effected with methyl alcoholic sodium hydroxide. Place a mixture of 20 g. of sodium hydroxide pellets, 25 ml. of water and 225 ml. of methyl alcohol in a 500 ml. round-bottomed flask fitted with a reflux (double surface) condenser, warm until the sodium hydroxide dissolves, add the ester layer and reflux the mixture for a period of 15 minutes. Rearrange the flask for distillation (Fig. II, 13, 3) and distil off the methyl alcohol until the residue becomes pasty. Then add about 200 ml. of water and continue the distfllation until the temperature reaches 98-100°. Pour the residue in the flask, consisting of an aqueous solution of sodium iaovalerate, into a 600 ml. beaker and add sufficient water to dissolve any solid which separates. Add slowly, with stirring, a solution of 15 ml. of concentrated sulphuric acid in 50 ml. of water, and extract the hberated acid with 25 ml. of carbon tetrachloride. Combine this extract with extract (A), dry with a httle anhydrous magnesium or calcium sulphate, and distil off the carbon tetrachloride (Fig. II, 13, 4 150 ml. distiUing or Claisen flask), and then distil the residue. Collect the wovaleric acid 172-176°. The yield is 56 g. 

The acetamide often contains a minute amount of impurity having an odour resembling mice excrement this can be removed by washing with a small volume of a 10 per cent, solution of ethyl alcohol in ether or by recrystallLsation. Dissolve 5 g. of impure acetamide in a mixture of 5 ml. of benzene and 1 5 ml. of dry ethyl acetate warm on a water bath until all is dissolved and cool rapidly in ice or cold water. Filter oflF the crystals, press between Alter paper and dry in a desiccator. The unpleasant odour is absent and the pure acetamide melts at 81°. Beautiful large crystals may be obtained by dissolving the acetamide (5 g.) in warm methyl alcohol (4 ml.), adding ether (40 ml.) and allowing to stand. 

Into a 1500 ml. round-bottomed flask place 97-5 g. of finely-powdered sodium cyanide (1), 125 ml. of water, and a few chips of porous porcelain. Attach a reflux condenser and warm on a water bath until all the sodium cyanide dissolves. Introduce a solution of 250 g. (196 ml.) of n-butyl bromide (Sections 111,35 and 111,37) in 290 ml. of pure methyl alcohol, and reflux gently on a water bath for 28-30 hours. Cool to room temperature and remove the sodium bromide which has separated by filtration through a sintered glass funnel at the pump wash the crystals with about 100 ml. of methyl alcohol. Transfer the filtrate and washings to From n caproamide by SOClj method. 

Place 425 ml. of concentrated ammonia solution (sp. gr. 0-88) in a 500 ml. round-bottomed flask and add slowly 75 g. of a-bromocaproic acid (Section 111,126). Stopper the flask tightly and allow it to stand in a warm place (50-55°) for 30 hours. Filter the amino acid at the pump and keep the filtrate A) separately. Wash the amino acid (ca. 26 g.) well with methyl alcohol to remove the ammonium bromide present. Evaporate the aqueous filtrate (A) almost to dryness on a steam bath. 

Conversion of (3- into a-glucose penta-acetate. Add 0-5 g. of anhydrous zinc chloride rapidly to 25 ml. of acetic anhydride in a 200 ml. round-bottomed flask, attach a reflux condenser, and heat on a boiling water bath for 5-10 minutes to dissolve the solid. Then add 5 g. of the pure P glucose penta-acetate, and heat on a water bath for 30 minutes. Pour the hot solution into 250 ml. of ice water, and stir vigorously in order to induce crystaUisation of the oily drops. Filter the solid at the pump, wash with cold water, and recrystaUise from methylated spirit or from methyl alcohol. Pure a-glucose penta-acetate, m.p. 110-111°, will be obtained. Confirm its identity by a mixed m.p. determination. 

The aluminium amalgam is prepared as described in Section 11,50,72. After washing with water, it slioidd lir.st be washed with methyl alcohol and Anally with a little dry benzene. 

Place 18 g. (12 ml.) of fuming nitric acid, sp. gr. 1 5, and 30 g. (16-5 ml.) of concentrated sulphuric acid and a few fragments of broken glass in a 250 or 500 ml. round-bottomed flask. Add gradually, in small portions, 14 g. of p-nitrotoluene do not allow the temperature to rise above 50 and cool the flask, if necessary, by immersion in cold water. Place a small funnel in the mouth of the flask and heat on a water bath at 90-95° for 30 minutes. Allow to cool almost to the laboratory temperature and pour the reaction mixture slowly into about 500 ml. of ice water containing a few small pieces of ice. Filter the crude dinitrotoluene through a Buchner funnel at the pump, wash it thoroughly with cold water, and drain as completely as possible. RecrystalUse from the minimum volume of hot methyl alcohol (flask, reflux condenser, and water bath experimental details as in Section IV,12). The yield of pure 2 4-dinitrotoluene, m.p. 71°, is 12 -5 g. 

The formaldehyde may be replaced by methylal CHjlOCH,), or by chloro-methyl ether CHjOCHjCl, produced from paraformaldehyde, hydrogen chloride and methyl alcohol ... 

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