Alcohols decomposition under pressure

In general, acyl azides are too unstable to survive at the temperatures required for addition to acetylenes, although benzoyl azide adds readily to ynamines in toluene. Ethoxycarbonyl azide also gives triazoles in good yield with ynamines. The azide adds to propargylic alcohols in boiling ethanol, and to acetylene at 100° under pressure. Addition to phenylacetylene and to electron-deficient acetylenes has been carried out at 130°. Oxazoles are also formed at this temperature by competing thermal decomposition of the azide, and addition of ethoxycarbonylnitrene to the acetylenes. The triazole obtained from phenylacetylene is 2-ethoxycarbonyl-4-phenyltriazole the two 1-ethoxycarbonyltriazoles can be isolated if the addition is carried out at 50° over several weeks. Since the IH- to -triazole isomerization takes place readily in these systems, a IH-structure cannot be assumed for a triazole formed by addition of these azides. 

Tellurium dipropionylmethane (2 6-Dimethylcyclotelluro-pentanedione) (Formula II), obtained from the dichloride by bisulphite reduction, crystallises from methyl alcohol, benzene or aqueous ethyl alcohol as well-defined golden-yellow needles, M.pt. 151° C. with slight decomposition. Under diminished pressure it sublimes at 110° C. as slender needles, which slowly pass at this temperature into compact prisms. It readily dissolves in organic solvents, except light petroleum in water it is sparingly soluble, the solution giving no enolic reactions. 

If ether was substituted for alcohol the same equilibrium mixtures were obtained at all temperatures up to 450° C., which have been mentioned above, provided, of course, that other conditions are identical. This appears to substantiate Ipatiew s opinion that a condition of equilibrium is maintained in the system. Above 450° C. ether decomposes energetically to give ethylene, this latter reaction being in all probability non-reversible. The statement is made, however, that the addition of water vapor to ether seems to hinder decomposition of the ether since no ethylene is formed under these conditions even at temperatures well above 450° C. it is interesting to note that at higher temperatures diolefins were detected among the products of the decomposition of ether. (Heated in the presence of an iron catalyst at 570° C. under pressure, ether decomposed to give acetaldehyde as the main product of the reaction. 

Metal catalysts, other than iron, which are known to promote aldehyde decomposition at ordinary pressures exhibit in different degrees the same variations that have just been described when the heating of the substance is conducted under pressure. In general, it may be saitl that the equilibrium which is established at any given temperature and pressure is to some extent independent of the substance which is used as tine starting point of the reaction, since when acetaldehyde is substituted for alcohol, the same gaseous decomposition products are formed in the same relative amounts and the liquid products likewise always consist of aldehyde, alcohol, water, saturated and unsaturated hydrocarbons. 

In the presence of reduced nickel, acetone is reduced to isopropyl alcohol at 210° to 220° C. At 200° to 230° C. isopropyl alcohol is dehydrogenated in the presence of nickel and also begins to decompose into saturated hydrocarbons. Under pressure an equilibrium between these two reactions is established. At 250° C. the approach to equilibrium is very slow and is accompanied by decomposition of both acetone and isopropyl alcohol into gaseous hydrocarbons.98 For normal secondary butyl alcohol the corresponding temperatures are somewhat higher, being about 250° to 300° C. in the presence of reduced nickel. The higher... 

The proper choice of catalysts for the vapor phase hydration of olefins under pressure to form alcohols is a very important factor. Apparently, catalysts active in promoting the hydration reaction are likewise active toward promotion of the undesirable polymerization reactions since this latter reaction often proceeds at a more rapid rate than that of alcohol formation as evidenced by the high yields of polymers and low yields of alcohols. The use of catalysts to lower the temperature for the reaction is necessitated by the fact that as the temperature is increased to obtain more favorable rates, the equilibrium conversion to alcohol becomes lower, and the tendency to polymerize is increased. Also, the catalyst must not promote dehydrogenation of the alcohol to form hydrogen and aldehyde since at the temperature of operation the equilibrium is very favorable for this reaction as has been pointed out in a previous chapter. Thus, the reaction, isobutanol = isobutyl aldehyde -f hydrogen has an equilibrium constant corresponding to about 72 per cent decomposition at 450° C even with 100 atmospheres of hydrogen pressure. 

In general, the vapor pressure of carbamates is low, but some may sublimate slowly at room temperature, and this would appear to explain their loss from soil surfaces. As the distribution in air is considered to be minor, the aquatic media is an important transport route for the very soluble carbamates. In this case, the hazard is limited by thefr rapid decomposition under aqueous conditions. Carbamates are hydrolyzed spontaneously yielding, as final products, an amine, carbon dioxide, and an alcohol or phenol ... 

Lobelanine on oxidation with potassium permanganate produces 2 moles of benzoic acid and, therefore, must contain two monosubstituted benzene rings. When lobelanine is heated to 140° with molten benzoic acid or at 125° with excess dilute hydrochloric acid, it gives rise to acetophenone, a product also characteristic of the decomposition of lobeline. Heating with hydrochloric acid also produces methylamine and fluorene whereas heating under pressure with alcoholic potassium hydroxide yields a mixture of methylamine, benzhydrol, and phenylmethylcarbinol. The HCl... 

These reactions can be carried out quantitatively in the case of metal isopropoxides (or ethoxides) by the azeotropic fractionation of the liberated alcohol with a suitable solvent (e.g. benzene), yielding mixed alkoxides or alkoxide-ligand (carboxylate, fi-diketonate, aminoalkoxide) derivatives. Many of these mixed ligand derivatives can be recrystallized and appear to be stable to heat (volatilizing without decomposition under reduced pressure). 

The determination of carbon tetrachloride follows the lines of that for chloroform except that decomposition with alcoholic potash is much more difficult. The use of strong potash (35 g potassium hydroxide in methanol to make 100 ml) and heating under pressure is necessary. 

Equip a 1-litre three-necked flask with a powerful mechanical stirrer, a separatory funnel with stem extending to the bottom of the flask, and a thermometer. Cool the flask in a mixture of ice and salt. Place a solution of 95 g. of A.R. sodium nitrite in 375 ml. of water in the flask and stir. When the temperature has fallen to 0° (or slightly below) introduce slowly from the separatory funnel a mixture of 25 ml. of water, 62 5 g. (34 ml.) of concentrated sulphuric acid and 110 g. (135 ml.) of n-amyl alcohol, which has previously been cooled to 0°. The rate of addition must be controlled so that the temperature is maintained at 1° the addition takes 45-60 minutes. AUow the mixture to stand for 1 5 hours and then filter from the precipitated sodium sulphate (1). Separate the upper yellow n-amyl nitrite layer, wash it with a solution containing 1 g. of sodium bicarbonate and 12 5 g. of sodium chloride in 50 ml. of water, and dry it with 5-7 g. of anhydrous magnesium sulphate. The resulting crude n-amyl nitrite (107 g.) is satisfactory for many purposes (2). Upon distillation, it passes over largely at 104° with negligible decomposition. The b.p. under reduced pressure is 29°/40 mm. 

Properties.—A viscid, colourless liquid, with a sweet taste m.p. 17°, b. p. 290°. It boils, under ordinary pressure. with partial decomposition forming acrolein sp gr. radp at 12° miscible with w ater and alcohol Insoluble in ether and the hydrocarbons. 

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