Sublimation camphor

Determine the infrared spectium of fhe sublimed camphor and compare it to the spectrum provided in the experiment (use the dry film method in Technique 25, Section 25.4 or other method recommended by your instructor). The spectrum should demonstrate complete oxidation to camphor (absence of OH peak and presence of C=0 peak). There should be sufficienf material for the reduction of camphor to isoborneol. Part B. At the option of fhe instructor, determine the H and NMR spectra of your camphor. Also, at the option of the instructor, determine the melting point (literature mp about 177°C, but it is often lower than this value). Store the camphor in a tightly sealed vial. 

For substances with a moderate triple point pressure e.g., benzoic acid, 6 mm., m.p. 122° naphthalene, 7 mm., m.p. 80° ), the simple process described above for camphor will not give a satisfactory yield of a sublimed product. Thus, for example, if naphthalene is heated it will melt at T (80°), and will boil when the vapour pressure is 760 mm. (218°) ... 

The theory of sublimation, t.e. the direct conversion from the vapour to the sohd state without the intermediate formation of the liquid state, has been discussed in Section 1,19. The number of compounds which can be purified by sublimation under normal pressure is comparatively small (these include naphthalene, anthracene, benzoic acid, hexachloroethane, camphor, and the quinones). The process does, in general, yield products of high purity, but considerable loss of product may occur. 

Camphor Manufacture. Camphor is obtained both naturally and synthetically. Natural camphor is obtained from the wood of the camphor tree, Cinnamormum camphora which grows ia China and Japan. The camphor is isolated by combination of steam distillation, filtration, distillation, and sublimation (169). Natural camphor is the (+)-camphor, whereas synthetic camphor is racemic both products are recognized by the USP. In 1995, the price of synthetic camphor was 7.15/kg (45). In 1992—1993, the total production of synthetic camphor ia India was 3800 t, which is estimated to be about 40% of the world consumption (170). The largest single use (80%) of camphor is for religious purposes ia Asian countries. 

In a 100-ml flask is placed a mixture of 19.5 g (0.18 mole) of freshly sublimed, pulverized selenium dioxide, 15 g (0.10 mole) of df/-camphor and 15 ml of acetic anhydride. The flask is fitted with a magnetic stirrer and a condenser, and the mixture is heated to 135° on an oil bath with stirring for 16 hours. After cooling, the mixture is diluted with ether to precipitate selenium, which is then filtered off, and the volatile materials are removed under reduced pressure. The residue is dissolved in ether (200 ml), washed four times with 50-ml portions of water and then washed several times with saturated sodium bicarbonate solution (until the washes are basic). The ether solution is finally washed several times with water, then dried, and the ether is evaporated. The residue may be purified by sublimation at reduced pressure or recrystallized from aqueous ethanol (with clarification by Norit, if necessary). The product is yellow, mp 197-199°. 

Many solid substances (camphor, iodine, naphthalene, etc.), are known which are appreciably volatile at ordinary temperatures. Others, such as the metals, are apparently quite fixed, but they probably possess a definite, although very small vapour-pressure, even at ordinary temperatures. Thus, if magnesium is heated to 550° for a few hours in a magnesia boat enclosed in a vacuous tube it sublimes in beautiful crystals on the cool part of the tube. The vaporisation of a solid without previous fusion is called sublimation the vapour-pressure (like the vapour-pressure of a liquid), is definite for each temperature, is independent of i the volume of the vapour space, and increases with rise of temperature. 

The growth of large crystals at the expense of small ones occurs, not only in solutions, but also under conditions which resemble even more closely the growth of large drops, i.e., by sublimation. The phenomenon has been observed in the case of sulphur and of sulphur trioxide in an evacuated space, and in the case of camphor crystals condensed from the vapour on a cold glass surface. 

Orange crystals camphor-like odor melts at 172.5°C vaporizes at 249°C sublimes above 100°C thermally stable above 500°C insoluble in water soluble in alcohol, ether and benzene also soluble in dilute nitric acid and concentrated sulfuric acid forming a deep red solution that fluoresces. 

Menthol 0.003-0.015% in suspensions, and syrups Cooling effect Sublimes easily above 25° C and composition of natural oil may vary with source Incompatible with thymol, phenol, camphor, and other excipients Slightly soluble in glycerin very soluble in alcohol... 

Sublimation. Accdu to definition ziven in Perry (Ref 13, p660), it covers the physical changes encountered by a substance in passing from a solid phase to a gas and back to a solid phase. It is characterized by the absence of the liquid phase and is used for purification of volatile substances like iodine, camphor, etc. Detailed description of the process is given in Refs 12, 13, 15 18). 

Durene or Durol (sym-l,2,4,5-Tetramethyl-benzene), C6H2(CH3)4, mw 134.21, colorless crysts with camphor-like odor sp gr 0.838, mp 79—81°, bp 189—191° sublimes and volatilizes with steam sol in ale, eth benz insol in w occurs in coal tar. It can be prepd by heating ortho xylene methyl chloride in presence of A1 chloride ... 

The mclling point of a compound is another property to which symmetry is an important contributor. Symmetrical molecules lend to have higher melting points than their less symmetrical isomers. For example, the melting point of neopentane is - 17 °C, that of n-pentane - 130 °C. If the molecule has very high symmetry, the melting point may be raised until the substance sublimes rather than melts. If you think about some substance that you know sublimes (in addition to SF6 mentioned above), you will note that it has high symmetry. Common examples are I,. CO, and camphor. The extreme example is perhaps dodecahedrane. C H ... 

Among substances that are sublimed under vacuum are anthranilic acid, hydroxyanthraquinone, naphthalene, and fl-naphthoi. Pyrogallol and d-camphor distill from the liquid state but condense as solids. Several metals are purified by sublimation, for instance, magnesium at 600°C and 0.01-0.15 Torr. 

VOLATILE. Having a low boiling or subliming temperature at ordinary pressure in other words, having a high vapor pressure, as ether, camphor, naphthalene, iodine, chloroform, benzene or methyl chloride. 

To 20 gms. (1 mol.) of iso-nitroso-camphor (see p. 307) dissolved in 35 c.ca. of glacial acetic acid, 9 gms. (excess) of sodium nitrite in 20 c.cs. of water are slowly added with mechanical stirring. Initially the temperature must not be allowed to rise above 20°, but when the evolution of gas ceases, the mixture is heated until no more gas is evolved. When cool, the whole is poured into an excess of cold water, and the precipitate filtered off at the pump, well washed with cold water, and dried on a porous plate. It is then sublimed at 60° (see p. 31). 

Stars of the only two compositions which are well approved. Take of powder (gunpowder) four ounces, of saltpeter two ounces, of sulfur two ounces, of camphor half an ounce, of steel filings two treseaux, of white amber half an ounce, of antimony (sulfide) half an ounce, of (corrosive) sublimate half an ounce. For double the efficacy it is necessary to temper all these powders with gum agragante dissolved in brandy over hot cinders. When you see that the gum is well swollen and fully ready, to mix with the said brandy, it is necessary forthwith to mix them in a mortar with the powder, the quicker the better, and then to cut up the resulting paste into pieces. These stars are very beautiful and very flowery. Note that it is necessary to put them to dry in a pastry or baking oven after the bread has been taken off of the hearth. 

The camphor thus obtained is further purified by mixing with soda lime, sand, charcoal and subjected to sublimation... 

By starting with optically active a-pinene, optically active camphor can be synthesised. Commercial camphor is best purified by sublimation. 

Homocamphoric acid is now neutralised with so solution and precipitated with lead acetate tho lo salt of tho acid is collected, dried, and tlion pack into a long combustion tube and heatod gont Camphor sublimes and may bo collected. 

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