Crystallization melting

Method 1. Arrange the flask containing the reaction mixture for steam distillation as in Fig. II, 40, 1. Proceed with the steam distillation until crystals of p-dibromobenzene appear in the condenser. Change the receiver and continue with the distillation until all the p-dibromobenzeiie has passed over from time to time run out the water from the condenser so that the crystals melt and run down into the receiver. Reject the residue in the flask. Transfer the first distillate to a separatory funnel, wash it with a httle water, and dry the lower layer with a little anhydrous magnesium sulphate or anhydrous calcium chloride filter. Distil slowly from a small distilling flask use a wire gauze or an air bath (Fig. II, 5, 3). Collect the fraction which passes over at 150-170° pour the residue (R), while it is still hot, into a small beaker or porcelain basin for the isolation of p-dibromobenzene. Redistil the fraction of b.p. 150-170° and collect the bromobenzene at 154-157° (3). The yield is 60 g. 

Ethyl bis-(2,4-dinitrophenyl) acetate (indicator) the stock solution is prepared by saturating a solution containing equal volumes of alcohol and acetone with the indicator pH range colorless 7.4-9.1 deep blue. This compound is available commercially. The preparation of this compound is described by Fehnel and Amstutz, Ind. Eng. Chem., Anal. Ed. 16 53 (1944), and by von Richter, Ber. 21 2470 (1888), who recommended it for the titration of orange- and red-colored solutions or dark oils in which the endpoint of phenol-phthalein is not easily visible. The indicator is an orange solid which after crystallization from benzene gives pale yellow crystals melting at 150-153.5°C, uncorrected. 

C. Thymoquinone.—The wet aminothymol thus prepared is immediately dissolved in no cc. of concentrated sulfuric acid diluted to 4 1. and contained in a 12-I. flask. To this solution is added 150 g. of sodium nitrite (2.18 moles), in 5-10-g. portions, with shaking after each addition. The resulting mixture is heated to 60° on a steam bath, with occasional shaking, for half an hour (Note 5), and is then distilled in a current of steam, by means of the apparatus described in Org. Syn. 2, 80 (Note 6). All the thymoquinone passes over with the first 3 1. of distillate it solidifies on cooling, and is filtered with suction (Note 7), washed, and dried at room temperature. The yield is 80-87 g. (73-80 per cent of the theoretical amount) of bright yellow crystals, melting at 43-45° (Note 8). 

B. HAUCI4, separates as an oil, but solidifies on standing and may be recrystallised from water containing hydrochloric acid. The crystals melt at 137-9° or below 100° when heated under water. This salt and the picrate, rectangular plates, m.p. 175-6°, are well adapted for the identification of the alkaloid. The methobromide, m.p. 223-5°, and the inethonitrate, m.p. 166-8°, are now both used in medicine. 

The total yield is 134.5 g (66%). Recrystallization from methanol-benzene of material (mp 202-205°) obtained from a pilot preparation gives yellow crystals melting at 208-212° 240 mp (e 11,500), 320-352 m ... 

P,17P-Dihydroxyestr-4-en-3-one 1-acetate. The 6-hydroxy compound is removed from the column with 15-17% acetone. Recrystallization of the crude product (1.92 g) from acetone-hexane gives 1.25 g of crystals melting at 165-166° and 0.13 g melting at 162-164° (12.1% yield). When the analytical sample was prepared from the same solvent mixture, the melting point rose to 192-193° (Lit 166° 189-190°) [a] -59.5° (CHCI3) 2, 236 m/i (fi 14,500). 

An intrinsic surface is built up between both phases in coexistence at a first-order phase transition. For the hard sphere crystal-melt interface [51] density, pressure and stress profiles were calculated, showing that the transition from crystal to fluid occurs over a narrow range of only two to three crystal layers. Crystal growth rate constants of a Lennard-Jones (100) surface [52] were calculated from the fluctuations of interfaces. There is evidence for bcc ordering at the surface of a critical fee nucleus [53]. 

The ferroelectricity usually disappears above a certain transition temperature (often called a Curie temperature) above which the crystal is said to be paraelectric this is because thermal motion has destroyed the ferroelectric order. Occasionally the crystal melts or decomposes before the paraelectric state is reached. There are thus some analogies to ferromagnetic and paramagnetic compounds though it should be noted that there is no iron in ferroelectric compounds. Some typical examples, together with their transition temperatures and spontaneous permanent electric polarization P, are given in the Table. 

Camphene hydrobromide, CjjH],jHBr, forms well-defined crystals melting at 133°, and the hydriodide melts at about 50°. 

Sylvestrene tetrabromide, CjoHjf.Br, is prepared when pure sylvestrene, regenerated from its ihydrochloride and dissolved in acetic acid, is heated with bromine until a permanent yellow colour is produced. Water is added to the reaction product, but not sufficient to precipitate the bromide, and the vessel allowed to stand in a cold place. The bromide separates and can be purihed by recrystallisation from alcohol. It forms mono-symmetric crystals melting at 135° to 136°, and having a specihc rotation -t- 73 7°. 

Humulene nitrosite, C,5H24N203, was obtained in two modifications, one forming blue crystals melting at 120°, and the other colourless melting at 166° to 168°. 

Baker and Smith have isolated an alcohol of the formula C,oH,gO from the cajuput oil, distilled from the leaves of Melaleuca uncinata. The alcohol, which is probably an open-chain compound, forms snow-white crystals, melting at 72 5°, and having a specific rotation + Sfi fifi . 

Ramsay 1 has isolated a crystalline sesquiterpene alcohol from the essential oil distilled from the bark of the juniper tree. It forms optically inactive triclinic crystals, melting at 107°, and having the formula CjjH O. 

Bornyl Acetate.—The acetic acid ester is the most important of the series. It is a constituent of pine-needle and rosemary oils, and has a most fragrant and refreshing odour. It is prepared artificially by the action of acetic anhydride on borneol, in the presence of sodium acetate, or by the condensation of borneol with glacial acetic acid in the presence of a small amount of a mineral acid. It is absolutely necessary in the reproduction of any pine odour. It is a crystalline body, crystallising from peDroleum ether in rhombic hemihedric crystals melting at 29°. The optical activity depends on that of the borneol from which it has been prepared. It has the following characters —... 

It has an odour resembling that of benzyl cinnamate. It forms crystals melting at 44°. It yields a characteristic dibromide, melting at 151°, which serves to characterise this ester. 

It is obtained hy mixing 1 molecule of cyanacetic acid, 1 molecule oh citral, and 2 molecules of caustic soda. The reaction liquid is extracted with ether, in order to remove non-aldehydes, and the clear liquid acidified with acetic acid. The separated acid is dissolved in benzene and precipitated hy petroleum ether when it forms yellow crystals, melting at 122° in the case of a-citral, and at 94° to 95° in the case of -citral. 

When the aldehyde is heated on the water-bath with 25 per cent, hydrochloric acid, it yields a triphenylmethane derivative, nonamethoxy-triphenylmethane, a body consisting of snow-white crystals, melting at 184 5°. The action of concentrated nitric acid upon the solution in glacial acetic acid of this triphenylmethane derivative gives rise to 1, 2, 5-trimethoxy-4-nitrobenzene (melting at 130°). With bromine, nonamethoxytriphenylmethane combines, with separation of a molecule of trimethoxy bromobenzene, into a tribromo additive compound of hexamethoxy diphenylmethane, a deep violet-blue body. The 1, 2, 5-tri-methoxy-4-bromobenzene (melting at 54 5°) may be obtained more readily from asaronic acid. 

It yields a monobromide melting at 41°, a semi-carbazone melting at 220° to 221 °, and an oxime melting at 106°. When reduced with sodium and alcohol it yields a secondary alcohol, which forms large crystals melting at 51°. On oxidation by cold 3 per cent, solution of potassium permanganate it yields geronic acid, a keto-acid of the constitution—... 

If carvacrol be treated, in alcoholic potash solution, with amyl nitrite, nitrosocar acrol, CgH2(CHa)(OH)(C3Hj)(NO), results. This body forms well-defined crystals melting at 153°. 

Cineol forms a number of crystalline derivatives, amongst which may be mentioned the hydrobromide, CjgHjgO. HBr, melting at 56°, and the compound with iodol, CjdHjgO. C I NH, which forms yellowish-green crystals, melting at 112°. It also forms a crystalline compound with resorcinol, which has been used as a basis for its quantitative determination. This compound consists of 2 molecules of cineol with 1 of resorcin, and forms needle-shaped crystals, melting at 80°. 

It is found in civet and in the wood of Celtis reticulosa. It forms crystals melting at 95° and boiling at 265° to 266°. It yields a hydrochloride, 2(C9HgN). HCl, melting at 167° 10 168°, and a picric acid compound melting at 172° to 173°. Skatol yields a blue colour with a solution of dimethyl-aminobenzaldehyde. 

These two acids, of the formula C HgO, are geometrical isomerides. They are both unsaturated, and belong to the aci-ylic acid series. Tiglic acid forms crystals melting at 64 5 and boiling at 198 5 , whilst angelic acid melts at 45° to 46° and boils at 185°. They have the following constitutions —... 

A solution of 50 g of the above ketone-hydrochloride in 30 cc of water was made alkaline by the addition of 30 g of potassium hydroxide. After the alkali was dissolved, 35 g of granular potassium carbonate were added. The free basic ketone was then extracted from the viscous mixture by shaking with 4 portions of hot benzene (300 cc in each portion). The benzene extracts were decanted, filtered over sodium sulfate in order to remove any suspended alkali, and concentrated in vacuo. The residual 1 -ezabicyclo[2.2.2] -3-octanone was purified by sublimation (50°-70 C/0.5 mm Hg) it can also be purified by recrystallization from petroleum ether. It formed feathery crystals melting at 147°-148 C. 

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