Organic liquids exercises

However, care must be exercised in using molecular sieves for drying organic liquids. Appreciable amounts of impurities were formed when samples of acetone, 1,1,1-trichloroethane and methyl-r-butyl ether were dried in the liquid phase by contact with molecular sieves 4A (Connett Lab.Practice 21 545 1972). Other, less reactive types of sieves may be more suitable but, in general, it seems desirable to make a preliminary test to establish that no unwanted reaction takes place. For the principles of synthesis and identification see R. Szostak Molecular Sieves, Chapman Hall, London 1988, and for structure, synthesis and properties see R.Szostak Handbook of Molecular Sieves, Chapman Hall 1992. 

Many organic liquids have been suspected of exercising more than a solvent action on coal. An indication of chemical interaction is the observation that the total weight of products sometimes exceeds the original weight of coal, although up to about 5% may be the result of strong adsorption of solvents on the residue and extract. With mixed solvents, the potential for interaction may be increased. 

Zinc chloride melts at 275°C, boils at 720°C, and is stable in the vapor phase up to 900 0. It is very hygroscopic, extremely water-soluble, and soluble in organic liquids such as alcohols, esters, ketones, ethers, amides, and nitrides. Hydrates with 1,1.5, 2.5, 3, and 4 molecules of water have been identified and great care must be exercised to avoid hydration of the anhydrous form. Aqueous solutions of zinc chloride are acidic (pH = 1.0 for 6 M) and, when partially neutralized, can form slightly soluble basic chlorides, eg, ZnCl2 4Zn(OH)2 [11073-22-6] and Zn(OH)Cl [14031-59-5]. Many other basic chlorides have been reported (58). 

The purpose of this section is to compare the predictions of the chemo-elasto-plastic model with experimental data showing the chemical effects of organic liquids on clay. For this exercise, the permeation experiments conducted by Fernandez and Quigley (1985,1991) on specimens of Sarnia clay are considered, with the focus on the results obtained for permeation of ethanol. A simplified representation of these experiments can only be considered at this time, as the data available are not... 

Most liquids foUow Trouton s rule (see Exercise 19.95), which states that the molar entropy of vaporization is approximately 88 5 J/mol-K. The normal boiling points and enthalpies of vaporization of several organic liquids are as follows ... 

DIC is a moderately expensive liquid that is employed in solid-phase synthesis to avoid the obstacles presented by the use of DCC. Both the reagent and the corresponding urea are soluble in organic solvents, and hence there is no bulky precipitate to contend with. The urea cannot be removed from an organic solution by aqueous extraction however, it is soluble enough in water that final traces can be removed from a precipitated peptide by washing the latter with a water-ether mixture. Clean up of spills of DIC can cause temporary blindness if utmost care is not exercised. 

Diffusion Coefficient. The method of Reference 237 has been recommended for many low pressure binary gases (238). Other methods use solvent and solute parachors to calculate diffusion coefficients of dissolved organic gases in liquid solvents (239,240). Molar volume and viscosity are also required and may be estimated by the methods previously discussed. Caution should be exercised because errors are multiplicative by these methods. 

The best bases in liquid S02 are sulfites of organic amines, for example, tetramethyl ammonium sulfite, [(CH NhSOg (for most of the inorganic sulfites are quite insoluble in this solvent). As expected, the conductivity of liquid S02 increases when either S03 (an acid) or a soluble sulfite (a base) is dissolved in it, but the conductivity drops if one of these solutions is mixed with the other (neutralization). Thionyl chloride, SOCL, also exhibits acidic reactions when dissolved in S02 but does not, as is sometimes supposed, yield the S02+ ion (Exercise 1). It is interesting that aluminum sulfite, Als(SOs)s, is amphoteric in liquid S02, just as aluminum... 

Monomethylmercury (MMM) is the most toxico-logically prominent of organic mercury compounds due to its environmental ubiquity and high potential for bioconcentration. Although DMM is less frequently encountered, it exhibits a far more toxic profile. Based on the lethality of only a few drops of the substance, DMM has been classified as a supertoxic chemical. Absorption of 100 pi of the colorless liquid is equivalent to a severely toxic dose of 100-200 mg of mercury per 100 ml of whole blood. Its synthesis, transportation, and use should be minimized and exercised with only extreme care. 

Scale will exercise considerable influence on the amount of heat transmitted. Correct data for X are not known in this case, but may be taken the same as boiler scale, which will average about 1.50. The total resistance will be the sum of the resistance of the clean tube and the resistance caused by the scale. Therefore, for a He-in. copper tube coated with a M2 in. lime scale, R = M55 + (1/(384 X 1.50), = Moo Q is 30,600 B.t.u., that is about 50 per cent of the heat transmitted through a clean copper tube. This reduction in heat transmission is somewhat higher than in actual practice, which is probably due to the fact that in most cases scale is not very dense and will permit direct contact between the metallic surface and the boiling liquid. Incrustations of salt and organic matter have a similar influence, and it happens... 

Cautions in Regard to Laboratory Work.—A student uses in laboratory work in organic chemistry inflammable liquids and substances like sodium and phosphorus which have to be handled with great care. Unless care is exercised fires may happen. The laboratory should be provided with buckets of sand and a fire-extinguisher. A heavy woolen blanket should be near at hand to be used in case the clothing catches fire. 

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