System carbon tetrachloride-iodine

Let us illustrate the meaning of partition coefficients with the simple extraction system carbon tetrachloride/water. Using ammonia or iodine as the solute, the partition coefficient Kp at 25°C is 0.0042 and 55, respectively [62]. With polar ammonia as the solute, this would move primarily to the water phase on extraction, hence the low Kp. With nonpolar iodine, the higher concentration would accumulate in the nonpolar carbon tetrachloride phase. 

G. N. Lewis proposed the term escaping tendency to give a strong kinetic-molecular flavor to the concept of the chemical potential. Let us consider two solutions of iodine, in water and carbon tetrachloride, which have reached equilibrium with each other at a flxed pressure and temperature (Fig. 9.2). In this system at equilibrium, let us carry out a transfer of an inflnitesimal quantity of iodine from the water phase to the carbon tetrachloride phase. On the basis of Equation (9.17), we can say that... 

In this closed system, any loss of iodine from the water phase is accompanied by an equivalent gain in the carbon tetrachloride thus. 

The iodine value (IV) is used to determine the level of unsaturation in a fat/oil system. It is expressed as the number of grams of iodine that add to/react with 100 g of sample. The traditional iodine value method using the Wijs reagent requires carbon tetrachloride (CC14). For safety reasons, CC14 is no longer considered to be an acceptable chemical and it is not readily available for purchase, and if offered it is extremely expensive. Therefore the traditional method has been modified to a more human-friendly system which uses cyclohexane. 

A glass jar is partially filled with carbon tetrachloride and water, which form two immiscible phases. Air in the system constitutes another phase. A small amount of iodine is introduced into the system the iodine distributes selectively into the carbon tetrachloride. The jar is capped. Sketch the chemical potential profile /ll = /Lt° of the iodine along the entire axis of the jar, extending from a point just outside the lid (x = 0) to a point 1 mm within the glass bottom (x = h). 

The bromination of cinnamic acid dissolved in carbon tetrachloride or other inert solvent.offers a convenient system for study. The dibromocinnamic acid produced remains in the carbon tetrachloride solution. The thermal reaction is so slow that it can barely be measured at room temperature and it is entirely negligible in comparison with the photochemical reaction at ordinary intensities. The quantum yield is so large that considerable reaction occurs even if the intensity of light is much reduced by the monochromator or other device for confining the light to a narrow range of frequencies. Furthermore, the reaction is easily and accurately followed by titration with sodium thiosulfate. Potassium iodide is added and the iodine liberated is a measure of the remaining bromine. 

The concept of intra-intermolecular or cydopolymerization was first described in 1957 for free radical systems (102) and shortly thereafter extended to cationic initiators. Jones (103) polymerized alloocimene with boron trifluoride etherate in ethyl chloride at 0° C. The product was a low melting (85—87° C.) soluble (benzene, carbon tetrachloride, etc.) material. The iodine number of the polymer indicated one residual double bond per monomer unit. The following polymerization mechanism was proposed ... 

The chemistry of 149 is rather unusual from the point of view of the typical reactivity pattern observed for ordinary small-ring systems. Especially striking is the ease of central bond opening in radical reactions. Thus 149 spontaneously reacts with iodine, thiophenol, and even with carbon tetrachloride to give almost quantitative yields of the respective 1,3-adducts 153a-c (Scheme 4.51). A number of other additions, including those leading to the formation... 

Distribution experiments on iodine-iodide systems between water and carbon tetrachloride [M. Davies and E. Gwynne, J. Am. Chem. Soc., 74, 2748 (1952)] seem to indicate possible existence of I " ions. The interpretation of these data is somewhat controversial. 

Figure 10.2-1 (a) Equilibrium-total pressure versus composition for the ethyl iodine-carbon tetrachloride system at T = 49.99°C. b) Equilibrium total pressure versus composition for the carbon disulfide-acetone system at 7 = 35.17°C. (c) Equilibrium total pressure versus composition for the chloroform-acetone system at 7 = 35.17°C. (d) The x-y diagram for the chloroform-acetone systerp at 7 = 35.17°C. 

In addition, miscible liquid-solid systems can display phase behavior more complex than vapor-liquid systems. For example, mixtures of carbon tetrachloride and cyclohexanone form a compound from one molecule of each pure this compound (xj = 0.5) melts at -39.6°C. Below this temperature, the compound exhibits two minimum melting temperatures so the melting curve for this binary has three extrema, two minima and a maximum, and all three lie below the melting points of the pure components. Compound formation in a solid phase can also cause constant-composition melting without an extremum in temperature. This occurs in mixtures of bromine and iodine. At 40°C the compound IBr melts at constant composition, although this temperature lies between the melting points of pure iodine and pure bromine. Phase diagrams for these kinds of solid systems can be found in the book by Walas [5]. 

Wilke and Chang, 1955 (32) studied the diffusivity of both iodine and toluene in alkanes and included in their analysis other systems from the literature. They investigated the influence of solvent properties, such as, viscosity, molar volume, molecular weight and heat of vap>orization and found a linear relationship between Log (Dpg/T) and Logp with a slope of (0.5). They examined also the influence of solute properties, by collecting diffusion data for a variety of solutes in the solvents, water, methanol, ethanol, hexane, toluene and carbon tetrachloride and they observed a linear relationship between Log (Dpg/T) and log V, the slope being (-0.6). They proposed the following equation... 

The study of such solutions as iodine in benzene, carbon tetrachloride or heptane, tin tetrachloride in benzene, chloroform, ether or carbon tetrachloride, and gases such as hydrogen and deuterium in carbon bisulphide, benzene, toluene, carbon tetrachloride as well as of other systems that possess the characteristics of regular solutions [13] has played an important part in the development of the theory of regular solutions. 

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