Carbon tetrachloride, as solvent for

More recently Penczek and his collaborators (134) have used l,3-dioxolan-2-ylium salts to initiate the polymerisation of THF in a variety of solvents. In these systems initiation is clean and efficient, and in the case of carbon tetrachloride as solvent, the only significant ionic species present are ion pairs. Rate constants /c for propagation in this solvent were obtained directly from conversion/time data and are a measure of the reactivity of ion pairs. At 25° C (tTHF]0 = 8.0 M) the value of /c (4.0 x 10 2 M-1 sec-1) was independent of the counter-ion employed, in the series AsFg, PFg, and SbFg. 

In Fig. 19 the spectra of the methyl methacrylate-styrene copolymers are shown, together with those of the homopolymers. The spectra of the homopolymers and of the copolymers from the 10 90 and 25 75 methyl methacrylate-styrene feed ratios are shown as recorded. For the other copolymers, the left-hand portion of the spectrum with the aromatic peaks is shown as recorded in carbon tetrachloride as solvent the remainder of the spectrum is shown as recorded in chloroform as solvent. 

For the reaction of (122) with TCNE to form (123) the rate increase in going from carbon tetrachloride as solvent to acetonitrile is about 49(X), while for the reaction of (124) with (125) to produce (126) there is only about a factor of six increase in rate for reaction in acetonitrile relative to reaction in toluene there is no spectacular solvent effect. Does the latter reaction have a fundamentally different mechanism than is operative in [2 + 2] cycloadditions of enol ethers with TCNE Are the tetramethylene intermediates of quite different dipolar character ... 

The berkelium (IV) extraction coefficients have been determined by stripping solvents previously loaded with tetravalent cerium and berkelium in the presence of sodium bismuthate. Sodium bismuthate has been found to be an efficient oxidizing agent for trivalent cerium. Because of its small solubility it does not affect the distribution coefficients of tetravalent cerium. These two properties have been demonstrated by comparing the distribution coefficients of cerium (IV) measured by spectrophotometry with those of cerium oxidized by sodium bismuthate and measured by beta counting of the cerium isotope tracer. The data are summarized in Table I and indicate no real difference in the distribution coefficients of cerium obtained by these two methods when using trilaurylmethylammonium salts-carbon tetrachloride as solvent. 

Here Ki and refer to K values for a particular compound eluted from a given adsorbent of activity a by solvents 1 and 2, respectively, and Ca are the e values of solvents 1 and 2. In a first example we have the elution (,f aniline by carbon tetrachloride, benzene, and methylene chloride from 3.7% H.a0-Ala03. Given that log for carbon tetrachloride as solvent is equal to 1.46, what are the values of log for elution by each of the remaining two solvents Let solvent 1 be carbon tetrachloride and solvent 2 refer to one of the other two solvents. From Table 6-1 we have a = 0.65. From Table 8-1 values of for carbon tetrachloride, benzene, and methylene chloride (on alumina) are 0.18, 0.32, and 0.42, respectively. T, for aniline can be calculated as in a preceding sample = 7.5. 

More evidence has appeared showing that the olefin metathesis reaction can tolerate the presence of functional groups. The catalytic system Re207-Al203, promoted by a small amount of tetramethyltin, effects metathesis of olefins in fair yield (17—40%) in the presence of unsaturated ethers and ketones, alkenyl esters, and halogeno-alkenes. The reaction is performed in carbon tetrachloride as solvent at room temperature over 6 h. Electro-reduction of tungsten hexa-chloride with an aluminium anode in halogenated solvents appears to form a complex suitable for a clean metathesis, exemplified by the conversion of pent-2-ene into its equilibrium mixture with but-2-ene and hex-3-ene. ... 

The zeroth-order rates of nitration depend on a process, the heterolysis of nitric acid, which, whatever its details, must generate ions from neutral molecules. Such a process will be accelerated by an increase in the polarity of the medium such as would be produced by an increase in the concentration of nitric acid. In the case of nitration in carbon tetrachloride, where the concentration of nitric acid used was very much smaller than in the other solvents (table 3.1), the zeroth-order rate of nitration depended on the concentrationof nitric acid approximately to the fifth power. It is argued therefore that five molecules of nitric acid are associated with a pre-equilibrium step or are present in the transition state. Since nitric acid is evidently not much associated in carbon tetrachloride a scheme for nitronium ion formation might be as follows ... 

As we saw when discussing allylic brommation m Section 10 4 N bromosuccm imide (NBS) is a convenient free radical brommatmg agent Benzylic brommations with NBS are normally performed m carbon tetrachloride as the solvent m the presence of peroxides which are added as initiators As the example illustrates free radical bromi nation is selective for substitution of benzylic hydrogens... 

Comparative x-ray absorption measurements were used in the identification of various new compounds that could contain at most the following elements carbon, hydrogen, fluorine, and chlorine. The presumed composition of each compound, known in advance, was duplicated by properly blending carbon tetrachloride, benzotrifluoride, heptane, and benzene the latter also was used as solvent for the unknown. Under conditions intended to be identical, the amount of unknown... 

Dichloromethane (CH2C12, methylene chloride), trichloromethane (CHCI3, chloroform), and tetrachloromethane (CCI4, carbon tetrachloride) are often used as solvents for nonpolar and moderately polar compounds. 

When a solution is tested, both analyte and solvent absorption bands will be present in the spectrum, and identification, if that is the purpose of the experiment, is hindered. Some solvents have rather simple IR spectra and are thus considered more desirable as solvents for qualitative analysis. Examples are carbon tetrachloride (CC14, only C-Cl bonds), choloroform (CHC13), and methylene chloride (CH2C12). The infrared spectra of carbon tetrachloride and methylene chloride are shown in Figure 8.21. There is a problem with toxicity with these solvents, however. For quantitative analysis, such absorption band interference is less of a problem because one needs only to have a single absorption band of the analyte isolated from the other bands. This one band can be the source of the data for the standard curve since the peak absorption increases with increasing concentration (see Section 8.11 and Experiment 25). See Workplace Scene 8.2. 

Prior to our original report7 on this method, acceptable and general preparative routes to a-iodocycloalkenones had not been described. Treatment of a p-substituted cycloalkenone with trimethylsilyl azide and a mixture of iodine and pyridine sequentially in dichloromethane has now been reported as a method for the preparation of p-substituted-a-iodocycloalkenones.8 The combination of iodine and pyridinium dichromate has also been reported to provide a-iodoenones from enones as well as from ethynyl carbinols.9 10 Some successes have also been achieved with enones and iodine azide (IN3)11 and iodine/ceric ammonium nitrate.12-14 The submitters first variant5 of the present procedure used carbon tetrachloride as a solvent. In this procedure this solvent has been replaced with the more benign diethyl ether. 

The more powerful the solvent-solute interaction, the more pronounced will solvent broadening be for this reason, saturated hydrocarbons are preferred as solvents for spectroscopy, and such strongly interacting media as methylene chloride and chloroform are to be avoided. It is obvious that the requirements of spectroscopy and those of solubility are in direct conflict. Carbon tetrachloride and carbon disulphide are often used as compromise solvents ) (although both of these react thermally or photochemically with many carbonyl complexes) but are generally inferior spectroscopically to alkanes. 

As in the preparation of the /3-bromopropionic acid, bemiene must not be substituted for the carbon tetrachloride, as it has been found impossible to make a satisfactory separation of this solvent from the ester. 

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