Reactions Boiling points

Another possibility to improve selectivity is to reduce the concentration of monoethanolamine in the reactor by using more than one reactor with intermediate separation of the monoethanolamine. Considering the boiling points of the components given in Table 2.3, then separation by distillation is apparently possible. Unfortunately, repeated distillation operations are likely to be very expensive. Also, there is a market to sell both di- and triethanolamine, even though their value is lower than that of monoethanolamine. Thus, in this case, repeated reaction and separation are probably not justified, and the choice is a single plug-flow reactor. 

The normal boiling points of the materials are given in Table 4.6. Synthesize a continuous reaction, separation, and recycle system for the process, bearing in mind that the process will later become batch. 

The problem with the fiowsheet shown in Fig. 10.5 is that the ferric chloride catalyst is carried from the reactor with the product. This is separated by washing. If a reactor design can be found that prevents the ferric chloride leaving the reactor, the effluent problems created by the washing and neutralization are avoided. Because the ferric chloride is nonvolatile, one way to do this would be to allow the heat of reaction to raise the reaction mixture to the boiling point and remove the product as a vapor, leaving the ferric chloride in the reactor. Unfortunately, if the reaction mixture is allowed to boil, there are two problems ... 

The trichloride is obtained as a liquid, boiling point 349 K, when a jet of chlorine burns in phosphorus vapour. Care must be taken to exclude both air and moisture from the apparatus since phosphorus trichloride reacts with oxygen and is vigorously hydrolysed by water, fuming strongly in moist air. The hydrolysis reaction is ... 

Pure hydrogen peroxide is a colourless, viscous liquid, m.p. 272.5 K, density l,4gcm . On heating at atmospheric pressure it decomposes before the boiling point is reached and a sudden increase of temperature may produce explosive decomposition, since the decomposition reaction is strongly exothermic ... 

It is a gas at room temperature with a boiling point of 128 K. It is a strong oxidising agent, some reactions occurring with explosive violence. Water hydrolyses it slowly at room temperature, but the reaction evolving oxygen is rapid in the presence of a base, and explosive with steam ... 

In view of the boiling points of acetone (57°) and isopropanol (82 ), the acetone can be steadily distilled off from the reaction-mixture, and the reduction ultimately becomes virtually complete. 

Chakactkrisation of Unsaturatkd Aliphatic Hydrocarbons Unlike the saturated hydrocarbons, unsaturated aliphatic hydrocarbons are soluble in concentrated sulphuric acid and exhibit characteristic reactions with dUute potassium permanganate solution and with bromine. Nevertheless, no satisfactory derivatives have yet been developed for these hydrocarbons, and their characterisation must therefore be based upon a determination of their physical properties (boiling point, density and refractive index). The physical properties of a number of selected unsaturated hydrocarbons are collected in Table 111,11. 

The alicyclic secondary alcohol, cycZohexanol, may be dehydrated by concentrated sulphuric acid or by 85 per cent, phosphoric acid to cyciohexene. It has a higher boiling point (82-83°) than amylene and therefore possesses some advantage over the latter in.the study of the reactions of unsaturated hydrocarbons. 

This preparation is an example of the use of di-M-butyl ether as a solvent in the Grignard reaction. The advantages are it is comparatively inexpensive, it can be handled without excessive loss due to evaporation, simple distillation gives an ether free from moisture and alcohol, and the vapour does not form explosive mixtures with air. n-Butyl ether cannot, of course, be employed when the boiling point of the neutral reaction product is close to 140°. 

By treatment of the alcohol with a mixture of constant boiling point hydrobromic acid and concentrated sulphuric acid the presence of sulphuric acid results, as a rule, in more rapid reaction and improved 3delds. A typical example is ... 

P -f lOROH -f 5Br, — 2H3PO, -f lORBr -f 2H,0 The reaction is of general application with primary alcohols (n propyl to n hexadecyl) the yields are over 90 per cent, of the theoretical, but with secondary alcohols the yields are 50-80 per cent. in the latter case a small quantity of high boiling point by-product is also formed which can, however, be readily removed by fractional distillation. The reaction is conveniently carried out in a special all glass apparatus. 

Di-n-amyl ether. Use 50 g. (61 5 ml.) of n-amyl alcohol (b.p. 136-137°) and 7 g. (4 ml.) of concentrated sulphuric acid. The calculated volume of water (5 ml.) is collected when the temperature inside the flask rises to 157° (after 90 minutes). Steam distil the reaction mixture, separate the upper layer of the distillate and dry it with anhydrous potassium carbonate. Distil from a 50 ml. Claisen flask and collect the fractions of boiling point (i) 145-175° (13 g.), (ii) 175-185° (8 g.) and (iii) 185-190° (largely 185-185-5°) (13 g.). Combine fractions (i) and (u), reflux for 1 hour in a small flask with 3 g. of sodium, and distil from the sodium amyloxide and excess of sodium this yields 9 5 g. of fairly pure n-amyl ether (iv). The total yield is therefore 22 - 5 g. A perfectly pure product, b.p. 184 185°, is obtained by further distillation from a Little sodium. 

Place 200 g, (250 ml.) of rectified spirit in a 1-litre round-bottomed flask fitted with a reflux condenser. Cool in ice and run in, slowly and with frequent shaking, 200 g. (109 ml.) of concentrated sulphuric acid. Add 83 g. (104 ml.) of -butyl cyanide (Section 111,113) to the mixture and reflux the whole for 10 hours. Allow to cool, pour the reaction mixture into ice water, separate the upper layer of ester and alcohol, and dry over anhydrous magnesium or calcium sulphate. Distil through a fractionating column and collect the ethyl n-valerate at 143-146°. A further amovmt of the pure ester may be obtained by redrying the fraction of low boiling point and redistilling. The yield is 110 g. 

A. Maleic acid. Assemble the apparatus shown in Fig. Ill, 28, 1. Place 45 g. of dry mahc acid in the 200-250 ml. distilling flask and cautiously add 63 g. (57 ml.) of pure acetyl chloride. Warm the flask gently on a water bath to start the reaction, which then proceeds exothermically. Hydrogen chloride is evolved and the malic acid passes into solution. When the evolution of gas subsides, heat the flask on a water bath for 1-2 hours. Rearrange the apparatus and distil. A fraction of low boiling point passes over first and the temperature rises rapidly to 190° at this point run out the water from the condenser. Continue the distillation and collect the maleic anhydride at 195-200°. Recrystallise the crude maleic anhydride from chloroform (compare Section 111,93) 22 g. of pure maleic anhydride, m.p. 54°, are obtained. 

Pour the reaction mixture cautiously into 400 g. of crushed ice and acidify it in the cold by the addition of a solution prepared by adding 55 ml. of concentrated sulphuric acid to 150 ml. of water and then coohng to 0°. Separate the ether layer and extract the aqueous layer twice with 50 ml. portions of ether. Dry the combined ethereal solutions over 50 g. of anhydrous potassium carbonate and distil the filtered solution thror h a Widmer column (Figs. II, 17, 1 and II, 24, 4). Collect separately the fraction boihng up to 103°, and the dimethylethynyl carbinol at 103-107° Discard the high boiling point material. Dry the fraction of low boihng point with anhydrous potassium carbonate and redistil. The total 3 ield is 75 g. 

Sometimes the reaction stops suddenly it is then necessary to add a further 10 ml. of 20 per cent, sodium hydroxide solution and warm to the boiling point this causes the reaction to continue. Occasionally, the reduction becomes very vigorous a wet towel and a bath of ice water should be kept close at hand. 

To the cold acid chloride add 175 ml. of pure carbon disulphide, cool in ice, add 30 g, of powdered anhydrous aluminium chloride in one lot, and immediately attach a reflux condenser. When the evolution of hydrogen chloride ceases (about 5 minutes), slowly warm the mixture to the boiling point on a water bath. Reflux for 10 minutes with frequent shaking the reaction is then complete. Cool the reaction mixture to 0°, and decompose the aluminium complex by the cautious addition, with shaking, of 100 g. of crushed ice. Then add 25 ml. of concentrated hydrochloric acid, transfer to a 2 htre round-bottomed flask and steam distil, preferably in the apparatus, depicted in Fig. II, 41, 3 since the a-tetralone is only moderately volatile in steam. The carbon disulphide passes over first, then there is a definite break in the distillation, after whieh the a-tetralone distils completely in about 2 htres of distillate. 

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