Theoretical crystal yield

An experimental study of barbituric acid found one new polymorph where molecules in the asymmetric unit adopted two different conformations [10]. The conformational aspect was investigated through the use of ab initio calculations, which permitted the deduction that the new form found would have a lower lattice energy than would the known form. It was also found that many hypothetical structures characterized by a variety of hydrogen-bonding structures were possible, and so the combined theoretical and experimental studies indicated that a search for additional polymorphs might yield new crystal structures. 

What is the theoretical yield of crystals which may be obtained by cooling a solution containing 1000 kg of sodium sulphate (molecular mass = 142 kg/kmol) in 5000 kg water to 283 K The solubility of sodium sulphate at 283 K is 9 kg anhydrous salt/100 kg water and the deposited crystals will consist of the deca-hydrate (molecular mass = 322 kg/kmol). It may be assumed that 2 per cent of the water will be lost by evaporation during cooling. 

Yield.—Theoretical (16 gms.). White crystals almost insoluble in cold water, ether, and ligroin fairly soluble in hot water easily soluble in alcohol M.P. 127°. (B 16, 2597.)... 

Yield.—Theoretical (27 gms.). Colourless glistening crystals soluble in hot water, in alcohol and in ether decomposes at 200° with formation of hydrobromic acid and bromo-maleic acid. (A., 117, 120 A. Spl., 1, 351 Bl 18, 168.)... 

Yield.—Theoretical. White rhombohedral crystals with greenish tinge infusible almost insoluble in water, solution being decomposed on boiling with evolution of hydrocyanic acid insoluble in alcohol or in ether. Many other aromatic organic bases yield similar compounds. (J. C. S., 121,1293.)... 

A slurry of sodium bicarbonate comprising 39.8 g sodium bicarbonate and 254 ml water was placed in an autoclave. 96.3 g hexadecyl bromide and 635 ml acetone were then added. The autoclave was sealed and while stirring (590 r.p.m.) it was heated to a temperature of 218°C over a period of 1 hour 15 min. The temperature was maintained at 218-220°C for an additional hour. At the end of the reaction the autoclave was cooled to about 50°C, that is, to a temperature at which the alcohol remains molten. The autoclave was then rinsed with acetone and 1 N hydrochloric acid add to neutralize the sodium bicarbonate. The reaction mixture was diluted with an equivalent volume of water and then extracted with n-pentane. (Other suitable water insoluble solvents such as benzene, carbon tetrachloride, chloroform, petroleum ether and the like can be used for extraction). The pentane extract was washed with water and then dried over magnesium sulfate. The dried solution was filtered and evaporated. The residue was melted and a vacuum applied to remove the last traces of pentane. On distillation a yield of 94.8% of the theoretical yield white crystals of hexadecanol was recovered M.P. 49°C, B.P. 344°C, nD79 = 1.4283. 

Calculate (a) the quantity of heat to be removed and (b) the theoretical crystal yield when 50001b of a 30 per cent solution of MgS04 by mass at 110°F is cooled to 70 °F. Evaporation and radiation losses may be neglected. 

The theoretical crystal yield for simple cooling or evaporating crystallization can be estimated from the solubility characteristics of the solution. For aqueous solutions, the following general equation applies (section 3.5) ... 

For polymer chains in a crystal lattice, however, acoustic vibrations of polymer chains are subject to interchain interactions, yielding the crystal vibrations of the acoustic and optical branches. Accordingly, for vibrational analyses of neutron-scattering spedra in the low-frequency region, it is required to treat the normal vibrations of the crystal, on the basis of the interchain force field as well as the intrachain force field. Treatments of crystal vibrations are also necessary for the theoretical study of specific heat, zero-point energy and temperature factor of x-ray diffraction. 

Naphthyl Acetate. CHgCOOCi H,. Dissolve 1 g. of pure 2-naphtnol in 5 ml. (r8 mols.) of 10% sodium hydroxide solution as before, add 10 g. of crushed ice, and i-i ml. (1-14 g., 1 5 mols.) of acetic anhydride. Shake the mixture vigorously for about 10-15 minutes the 2-naphthyl acetate separates as colourless crystals. Filter at the pump, wash with water, drain, and dry thoroughly. Yield of crude material, 1-4 g. (theoretical). Recrystallise from petroleum (b.p. 60-80 ), from which, on cooling and scratching, the 2-naphthyl acetate separates as colourless crystals, m.p, 71 yield, 10 g. 

Place I g. of benzamide and 15 ml. of 10% aqueous sodium hydroxide solution in a 100 ml. conical flask fitted with a reflux water-condenser, and boil the mixture gently for 30 minutes, during which period ammonia is freely evolved. Now cool the solution in ice-water, and add concentrated hydrochloric acid until the mixture is strongly acid. Benzoic acid immediately separates. Allow the mixture to stand in the ice-water for a few minutes, and then filter off the benzoic add at the pump, wash with cold water, and drain. Recrystallise from hot water. The benzoic acid is obtained as colourless crystals, m.p. 121°, almost insoluble in cold water yield, o 8 g. (almost theoretical). Confirm the identity of the benzoic acid by the tests given on p. 347. 

Assemble in a fume-cupboard the apparatus shown in Fig. 67(A). Place 15 g. of 3,5-dinitrobenzoic acid and 17 g. of phosphorus pentachloride in the flask C, and heat the mixture in an oil-bath for hours. Then reverse the condenser as shown in Fig. 67(B), but replace the calcium chloride tube by a tube leading to a water-pump, the neck of the reaction-flask C being closed with a rubber stopper. Now distil off the phosphorus oxychloride under reduced pressure by heating the flask C in an oil-bath initially at 25-30, increasing this temperature ultimately to 110°. Then cool the flask, when the crude 3,5-dinitro-benzoyl chloride will solidify to a brown crystalline mass. Yield, 16 g., i.e,y almost theoretical. Recrystallise from caibon tetrachloride. The chloride is obtained as colourless crystals, m.p. 66-68°, Yield, 13 g Further recrystallisation of small quantities can be performed using petrol (b.p. 40-60°). The chloride is stable almost indefinitely if kept in a calcium chloride desiccator. 

For the HCI salt Do exactly as above except use 6N Hydrochloric Acid. 6N HCI may be produced by diluting 60.4mL of "Muriatic Acid" to lOOmL with distilled water. Evaporate the bubbler solution to dryness then add 15ml of water, lOmL 10% NaOH soln. and heat gently to a boil with constant motion until dense white fumes appear. This will remove the Ammonium Chloride. Remove from heat while stirring as it cools down. Pulverize the dry residue, then reflux with absolute Ethanol for several minutes. Filter the refluxed soln. on a heated Buchner or Hirsch funnel, then distill the alcohol off the filtrate until crystals just begin to form. Allow the soln. to cool naturally to room temperature, then cool further in an ice bath. Filter the solution on a chilled Buchner funnel with suction. The yield of Meth iamine Hydrochloride should be around 55% of the theoretical. 

At equihbrium, the specific composition of a concentrated phosphoric acid is a function of its P2 s content. Phosphoric acid solutions up to a concentration equivalent of about 94% H PO (68% P2O5) contain H PO as the only phosphoric acid species present. At higher concentrations, the orthophosphoric acid undergoes condensation (polymerization by dehydration) to yield a mixture of phosphoric acid species (Table 5), often referred to genericaHy as polyphosphoric or superphosphoric acid, H20/P20 = - 3, or ultraphosphoric acid, H20/P20 = - 1. At the theoretical P2O5 concentration for orthophosphoric acid of 72.4%, the solution is actually a mixture containing 13% pyrophosphoric acid and about 1% free water. Because the pyrophosphoric acid present is the result of an equihbrium state dependent on the P2 5 content of the solution, pure orthophosphoric acid can be obtained because of a shift in equihbrium back to H PO upon crystallization. 

If the material is not partly dried before hydrolysis, the yield of the hydrochloride is diminished because of its solubility. If pure 3-bromo-4-acetaminotoluene is desired, the crude material may be crystallized from 50 per cent alcohol with the addition of decolorizing carbon (Norite) as almost colorless needles, m.p. 116-117°, The yield is 360 g, (79 per cent of the theoretical amount). This purification has no advantage when the acetam-ino compound is to be hydrolyzed to the amine. 

The flask is immersed in an oil bath heated to 120° and dry steam is then passed through the reaction mixture. The first few cubic centimeters of distillate contain the excess of thiophos-gene and are discarded. The isothiocyanate passes over with the water as an oil that solidifies on cooling. The steam distillation requires about four hours. The crude material is crystallized from two parts of ethyl alcohol at 50°, from which it separates as white needles melting at 44-45°. The yield is 245-275 g. (72-81 per cent of the theoretical amount) (Note 3). 

The yield is 147-160 g. (68-74 per cent of the theoretical amount). It sinters at 190-191° and melts at 199-200° (corr.). A sample twice recrystallized from glacial acetic acid melted at 200-202° (corr.) (Note 3). The crystal form of this product compares very favorably with that of quinizarin of the highest purity, as observed under the microscope. 

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