Upper layer

In this accident, the steam was isolated from the reactor containing the unfinished batch and the agitator was switched ofiF. The steam used to heat the reactor was the exhaust from a steam turbine at 190 C but which rose to about 300°C when the plant was shutdown. The reactor walls below the liquid level fell to the same temperature as the liquid, around 160°C. The reactor walls above the liquid level remained hotter because of the high-temperature steam at shutdown (but now isolated). Heat then passed by conduction and radiation from the walls to the top layer of the stagnant liquid, which became hot enough for a runaway reaction to start (see Fig. 9.3). Once started in the upper layer, the reaction then propagated throughout the reactor. If the steam had been cooler, say, 180 C, the runaway could not have occurred. ... 

A counter-propagation network is a method for supervised learning which can be used for prediction, It has a two-layer architecture where each netiron in the upper layer, the Kohonen layer, has a corresponding netiron in the lower layer, the output layer (sec Figure 9-21). A trained counter-propagation network can be used as a look-up tabic a neuron in one layer is used as a pointer to the other layer. 

Counter-propagation network this network also needs the input dimension. It gives the columns that arc used for the upper layer of the network. 

Figure 10.2-9. Application of a counterpropagation neural network as a look-up table for IR spectra sinnulation, The winning neuron which contains the RDF code in the upper layer of the network points to the simulated IR spectrum in the lower layer.

The crude acetonitrile contains as impurity chiefly acetic acid, arising from the action of phosphoric acid on the acetamide. Therefore add to the nitrile about half its volume of water, and then add powdered dry potassium carbonate until the well-shaken mixture is saturated. The potassium carbonate neutralises any acetic acid present, and at the same time salts out the otherwise water-soluble nitrile as a separate upper layer. Allow to stand for 20 minutes with further occasional shaking. Now decant the mixed liquids into a separating-funnel, run off the lower carbonate layer as completely as possible, and then pour off the acetonitrile into a 25 ml, distilling-flask into which about 3-4 g. of phosphorus pentoxide have been placed immediately before. Fit a thermometer and water-condenser to the flask and distil the acetonitrile slowly, collecting the fraction of b.p. 79-82°. Yield 9 5 g. (12 ml.). 

When the sodium has completely dissolved, pour the reaction-mixture into a separating-funnel, run off the strongly alkaline lower layer, and dry the upper layer over sodium sulphate not... 

Cool 1 ml. of amylene in ice and add 1 ml. of cold, dilute sulphuric acid (2 acid 1 water), and shake gently until the mixture is homogeneous. Dilute with 2 ml. of water if an upper layer of the alcohol does not separate immediately, introduce a little sodium chloride into the mixture in order to decrease the solubility of the alcohol. Observe the odour. The unsaturated hydrocarbon is thus largely reconverted into the alcohol from which it may be prepared. 

Reflux a mixture of 68 g. of anhydrous zinc chloride (e.g., sticks), 40 ml. (47 -5 g.) of concentrated hydrochloric acid and 18-5 g. (23 ml.) of sec.-butyl alcohol (b.p. 99-100°) in the apparatus of Fig. 777, 25, 1 for 2 hours. Distil oflF the crude chloride untU the temperature rises to 100°. Separate the upper layer of the distillate, wash it successively with water, 5 per cent, sodium hydroxide solution and water dry with anhydrous calcium chloride. Distil through a short column or from a Claisen flask with fractionating side arm, and collect the fraction of b.p. 67-70° some high boiling point material remains in the flask. Redistil and collect the pure cc. butyl chloride at 67-69°. The yield is 15 g. 

In a 1500 ml. round-bottomed flask, carrying a reflux condenser, place 100 g. of pure cydohexanol, 250 ml. of concentrated hydrochloric acid and 80 g. of anhydrous calcium chloride heat the mixture on a boiling water bath for 10 hours with occasional shaking (1). Some hydrogen chloride is evolved, consequently the preparation should be conducted in the fume cupboard. Separate the upper layer from the cold reaction product, wash it successively with saturated salt solution, saturated sodium bicarbonate solution, saturated salt solution, and dry the crude cycZohexyl chloride with excess of anhydrous calcium chloride for at least 24 hours. Distil from a 150 ml. Claisen flask with fractionating side arm, and collect the pure product at 141-5-142-5°. The yield is 90 g. 

Allyl Chloride. Comparatively poor yields are obtained by the zinc chloride - hydrochloric acid method, but the following procedure, which employs cuprous chloride as a catalyst, gives a yield of over 90 per cent. Place 100 ml. of allyl alcohol (Section 111,140), 150 ml. of concentrated hydrochloric acid and 2 g. of freshly prepared cuprous chloride (Section II,50,i one tenth scale) in a 750 ml. round-bottomed flask equipped with a reflux condenser. Cool the flask in ice and add 50 ml. of concen trated sulphuric acid dropwise through the condenser with frequent shaking of the flask. A little hydrogen chloride may be evolved towards the end of the reaction. Allow the turbid liquid to stand for 30 minutes in order to complete the separation of the allyl chloride. Remove the upper layer, wash it with twice its volume of water, and dry over anhydrous calcium chloride. Distil the allyl chloride passes over at 46-47°. 

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. 

About 0-1 per cent, of hydroquinone should be added as a stabiliser since n-hexaldehyde exhibits a great tendency to polymerise. To obtain perfectly pure n-/iexaldehyde, treat the 21 g. of the product with a solution of 42 g. of sodium bisulphite in 125 ml. of water and shake much bisulphite derivative will separate. Steam distil the suspension of the bisulphite compound until about 50 ml. of distillate have been collected this will remove any non-aldehydic impurities together with a little aldehyde. Cool the residual aldehyde bisulphite solution to 40-50 , and add slowly a solution of 32 g. of sodium bicarbonate in 80 ml. of water, and remove the free aldehyde by steam distillation. Separate the upper layer of n-hexaldehyde, wash it with a little water, dry with anhydrous magnesium sulphate and distil the pure aldehyde passes over at 128-128-5°. 

Place 50 g. of anhydrous calcium chloride and 260 g. (323 ml.) of rectified spirit (95 per cent, ethyl alcohol) in a 1-litre narrow neck bottle, and cool the mixture to 8° or below by immersion in ice water. Introduce slowly 125 g. (155 ml.) of freshly distilled acetaldehyde, b.p. 20-22° (Section 111,65) down the sides of the bottle so that it forms a layer on the alcoholic solution. Close the bottle with a tightly fitting cork and shake vigorously for 3-4 minutes a considerable rise in temperature occurs so that the stopper must be held well down to prevent the volatilisation of the acetaldehyde. Allow the stoppered bottle to stand for 24-30 hours with intermittent shaking. (After 1-2 hours the mixture separates into two layers.) Separate the upper layer ca. 320 g.) and wash it three times with 80 ml. portions of water. Dry for several hours over 6 g. of anhydrous potassium carbonate and fractionate with an efficient column (compare Section 11,17). Collect the fraction, b.p. 101-104°, as pure acetal. The yield is 200 g. 

Pour the reaction mixture into a 1-litre round-bottomed flaak, add 250 ml. of water, fit a still head and a condenser for downward distillation (Fig. II, 13, 3, but without the thermometer). Distil the mixture until about 125 ml. of distillate (two layers) have been collected. Saturate with salt (about 30 g. are required), and separate the upper layer of cj/cZohexanone extract the aqueous layer with 25-30 ml. of ether and combine the ether extract with the cycZohexanone layer. Dry with about 6 g. of anhydrous sodium or magnesium sulphate, filter the solution into a distilling flask of suitable size to which a condenser has previously been attached. Distil oflF the ether from a water bath—a beaker containing warm water is satisfactory. Distil the residual liquid from an air bath or a wire gauze, and collect the cyclohexanone at 153-156°. The yield is 16 g. 

Pinacol (tetramethylethyleneglycol). Pinacol hydrate may be dehydrated in the following manner (compare Section 11,39). Mix 100 g. of pinacol hydrate with 200 ml. of benzene and distil a mixture of water and benzene passes over. Separate the lower layer and return the upper layer... 

Pinacolone. In a 500 ml. round-bottomed flask carrying a dropping funnel and a connection to a condenser set for distillation, place 50 g. of pinacol hydrate and 130 ml. of QN sulphuric acid. Distil the mixture until the upper layer of the distillate no longer increases in volume (15-20 minutes). Separate the pinacolone layer from the water and return the latter to the reaction flask. Then add 12 ml. of concentrated sulphuric acid to the water, followed by a second 50 g. portion of pinacol hydrate. Repeat the distillation. Repeat the process twice more until 200 g. of pinacol hydrate have been used. 

IsoValeric acid. Prepare dilute sulphuric acid by adding 140 ml. of concentrated sulphuric acid cautiously and with stirring to 85 ml. of water cool and add 80 g. (99 ml.) of redistilled woamyl alcohol. Place a solution of 200 g. of crystallised sodium dicliromate in 400 ml. of water in a 1-litre (or 1-5 litre) round-bottomed flask and attach an efficient reflux condenser. Add the sulphuric acid solution of the isoamyl alcohol in amaU portions through the top of the condenser shake the apparatus vigorously after each addition. No heating is required as the heat of the reaction will suffice to keep the mixture hot. It is important to shake the flask well immediately after each addition and not to add a further portion of alcohol until the previous one has reacted if the reaction should become violent, immerse the flask momentarily in ice water. The addition occupies 2-2-5 hours. When all the isoamyl alcohol has been introduced, reflux the mixture gently for 30 minutes, and then allow to cool. Arrange the flask for distillation (compare Fig. II, 13, 3, but with the thermometer omitted) and collect about 350 ml. of distillate. The latter consists of a mixture of water, isovaleric acid and isoamyl isovalerate. Add 30 g. of potassium not sodium) hydroxide pellets to the distillate and shake until dissolved. Transfer to a separatory funnel and remove the upper layer of ester (16 g.). Treat the aqueous layer contained in a beaker with 30 ml. of dilute sulphuric acid (1 1 by volume) and extract the liberated isovaleric acid with two... 

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