Dean and Stark apparatus

Place a mixture of 53 g. of A.R. lactic acid (85-88 per cent, acid), 75 g. (85-5 ml.) of commercial anhydrous isopropyl alcohol, 300 ml. of benzene and 20 g. of Zeo-Karb 225/H (1) in a 700 ml. bolt-head flask, equipped with an automatic water separator (e.g., a large modified Dean and Stark apparatus with a stopcock at the lower end, see Fig. Ill, 126, 1) carrying an efficient reflux condenser at its upper end, and a mercury-sealed stirrer (alternatively, the hquid-sealed stirrer shown in Fig. 11,7,11, c. may be used). Reflux the mixture, with stirring, on a steam bath for 5 hours or until water no longer collects in appreciable amount in the water separator run off the water from time to time. Filter off the resin at the pump and wash it with two 25 ml. portions of benzene. Shake the combined filtrate and washings with about 5 g. of precipit-ated calcium... 

Ethyl bromoacetate (1). Fit a large modified Dean and Stark apparatus provided with a stopcock at the lower end (a convenient size is shown in Fig. Ill, 126, 1) to the 1-htre flask containing the crude bromoacetic acid of the previous preparation and attach a double surface condenser to the upper end. Mix the acid with 155 ml. of absolute ethyl alcohol, 240 ml. of sodium-dried benzene and 1 ml. of concentrated sulphuric acid. Heat the flask on a water bath water, benzene and alcohol will collect in the special apparatus and separate into two layers, the lower layer consisting of approximately 50 per cent, alcohol. Run ofi the lower layer (ca. 75 ml.), which includes all the water formed in the... 

Water Determination. The sample is refluxed with toluene and the resultant toluene—water a2eotrope is distilled iato a gradual water-trap receiver (Dean and Stark apparatus). Here the water and toluene separate iato two distinct layers, permitting the volume of water to be read and its percentage calculated. 

Dried with Linde type 5A molecular sieves, BaO or sodium, and fractionally distd. The distillate (200g) was heated with benzene (500mL) and cone HCl (150mL) in a Dean and Stark apparatus on a water bath until water no longer separated, and the temperature just below the liquid reached 80°. When cold, the supernatant benzene was decanted and the 2,4-lutidine hydrochloride, after washing with a little benzene, was dissolved in water (350mL). After removing any benzene by steam distn, an aqueous soln of NaOH (80g) was added, and the free... 

A 50 mL two-necked round-bottomed flask (dried overnight at 150°C and cooled under vacuum) was equipped with a Dean and Stark apparatus and flushed with nitrogen. 

The Dean and Stark apparatus was removed, replaced by a condenser (the solution was flushed continuously with nitrogen) and the catalyst dissolved in anhydrous toluene (2 mL). Borane-dimethylsulfide (0.5 mL of a 2 M solution in tetrahydrofuran) was added to the mixture, which was heated to 110 °C. 

Fig. 8.1. Modified Dean and Stark apparatus for small silage samples.

Dean and Stark apparatus, modified, 429 n-Decane, 237, 940 Decane-1 10-dicarboxylic acid, 904, 905... 

The two designs of the Dean and Stark apparatus (Fig. 2.31(a) and (b) available from Bibby Science Products) carry a flask on the lower cone and a reflux condenser on the upper socket. They are used for the automatic separation of two immiscible components in a distillate and the subsequent return of the upper layer (a) or the lower layer (b) to the reaction flask. 

Formation and isolation of the enamine are achieved by heating the amine and the diketone in xylene under reflux using a Dean and Stark apparatus until the theoretical amount of water has separated, or alternatively at 100 °C in the presence of anhydrous calcium sulphate. The latter is the most convenient and is the procedure used in Expt 8.42. 

Another test method that can be used, determination of the moisture content of moderately dry coal, can, in fact, be used for all coal samples that can be handled without appreciable loss of moisture. The principle of the method is that the coal is heated with an inert liquid that does not mix with water and which has a boiling point greater than that of water so that, on distillation, the water is carried over with the vapor from the liquid and, on condensation, separates from it in a graduated receiver. The Dean and Stark apparatus (Figure 3.1) or one of its many modifications can be used for this purpose. 

Although this method proved successful for 4-keto-L-proline methyl ester 48, it was decided to investigate the conventional azeotropic dehydration method. Derivative 48 and pyrrolidine (1.2 equiv) were heated under reflux in benzene, collecting the water produced using a Dean and Stark apparatus. A quantitative yield of the corresponding enamine 52 was obtained after only 30 min (Scheme 19). Again, full assignment of NMR spectra was complicated by the apparent presence of rotameric structures. 

Thiazolines 58 One mole each of an aldimine and 2-mercapto-3-pentanone are boiled in benzene (300 ml) under a Dean and Stark apparatus until no more water appears in the separator. Then the solvent is evaporated and the residue is distilled in a vacuum or recrystallized. The 4-thiazolines recorded in the Table below were prepared by this method. 

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