Chloroformates, dipole moments

In each case the left-hand atom of the pair as written is the least electronegative. Since dipole moments have direction as well as magnitude it is necessary to add the moments of each bond vertically. For this reason the individual dipole moments cancel each other out in carbon tetrachloride but only partially in chloroform. In other molecules, such as that of water, it is necessary to know the bond angle to calculate the dipole moment. Alternatively since the dipole moment of the molecule is measurable the method may be used to compute the bond angle. 

If the four atoms attached to the central atom in a tetrahedral molecule are the same, as in tetrachloromethane (carbon tetrachloride), CCI4 (30), the dipole moments cancel and the molecule is nonpolar. However, if one or more of the atoms are replaced by different atoms, as in trichloromethane (chloroform), Cl ICI, or by lone pairs, as in NH3, then the dipole moments associated with the bonds are not all the same, so they do not cancel. Thus, the CHCI, molecule is polar (31). 

Bond polarity in a molecule can often be measured by a dipole moment, expressed in Debye imits (D). However, the physical measurement provides only the overall dipole moment, i.e. the snm of the individual dipoles. A molecule might possess bond polarity without displaying an overall dipole if two or more polar bonds are aligned so that they cancel each other out. The C-Cl bond is polar, but although chloroform (CHCI3) has a dipole moment (1.02 D), carbon tetrachloride (CCI4) has no overall dipole. Becanse of the tetrahedral orientation of the dipoles in carbon tetrachloride, the vector sum is zero. 

Yellowish red oily liquid pungent penetrating odor fumes in air refractive index 1.670 at 20°C density 1.69 g/mL dipole moment 1.60 dielectric constant 4.9 at 22°C freezes at -77°C boils at 137°C reacts with water soluble in ethanol, benzene, ether, chloroform, and carbon tetrachloride dissolves sulfur at ambient temperature (67 g/100 g sulfur chloride). 

Water freezes to ice at 0°C expands by about 10% on freezing boils at 100°C vapor pressure at 0°, 20°, 50°, and 100°C are 4.6, 17.5, 92.5, and 760 torr, respectively dielectric constant 80.2 at 20°C and 76.6 at 30°C dipole moment in benzene at 25°C 1.76 critical temperature 373.99°C critical pressure 217.8 atm critical density 0.322 g/cm viscosity 0.01002 poise at 20°C surface tension 73 dynes/cm at 20°C dissolves ionic substances miscible with mineral acids, alkalies low molecular weight alcohols, aldehydes and ketones forms an azeotrope with several solvents immiscible with nonpolar solvents such as carbon tetrachloride, hexane, chloroform, benzene, toluene, and carbon disulfide. 

The complexes of the monothio-/3-diketonate RC(SH)=CHCOR (R = R = phenyl R = phenyl, 2-thienyl, j8-naphthyl R = CF3), which are acetylacetonate analogues have been synthesized (242).1143 Dipole moment measurements are consistent with facial structures (243). Mass spectra indicate no metal-containing peaks for the complex [Cr(PhC(S)=CHCOPh)3)] however, for the fluorinated monothio-j8-diketonates, various metal-containing peaks, e.g. M—2b=F, were observed. Such ions involve fluoride migration. Monothiooxalate complexes of chromium(III) have been prepared fairly unusual complexes, exemplified by [Cr (C2S03)Cu(Ph3)2 3], were reported. On refluxing under chloroform (7h) reactions of the kind illustrated were alleged to occur (equation 55). 44... 

Early work on the experimentally established conformational preferences in solution for a variety of other 2-substituted heterocycles is summarized in Table 30. Most of these conclusions have been deduced either from dipole moment measurements in benzene or by the use of lanthanide induced shifts for chloroform solutions. The aforementioned MO studies correctly predict the preferred conformations, (63, R = H) or (64, R = H), of pyrrole-2-carbaldehyde, thiophene-2-carbaldehyde and furfural in the gas phase. 

Arsenic triiodide is soluble in carbon disulphide, alcohol, ether, chloroform, benzene, toluene and the xylenes.5 The solution in carbon disulphide gradually darkens owing to absorption of oxygen and liberation of iodine.6 With alcohol at 150° C. ethyl iodide is formed. In methylene iodide 5 the triiodide dissolves to the extent of 17-4 parts of AsI3 in 100 parts of solvent at 12° C. The dipole moment in various solvents has been determined.7... 

The subscript s refers to the values of the pure solvent and fs = P ps / Ms. d ldxD and dn2 Id Xp were determined by linear regression of and n2 as a function of dye concentration for typically five different solutions of mol fraction less than 10 3. In all cases, the linear approximation was fully justified within the experimental error. Figure 5 shows, as an example, as a function of concentration for X in chloroform. For molecules with large dipole moments, like the ones discussed in this paper, the contribution of dp IdXp can be neglected since even the extreme assumption of dp Id Xp =1 g/cm3 changes the value of iD by only 0.4%. Similarly, the term proportional to dn2 Idxp contributes less than 4% to the... 

For one-carbon halogenated aliphatics, the dipole moment decreases as the number of chlorines increases. The dataset consists of chloromethane, dichloromethane, chloroform, and carbon tetrachloride. The dipole moment represented 85.89% of the variance in the linear regression equation therefore, the probability of getting a correlation of -0.9268 for a sample size of three is between 5 and 10% ... 

The mobile phases used in normal-phase chromatography are based on nonpolar hydrocarbons, such as hexane, heptane, or octane, to which is added a small amount of a more polar solvent, such as 2-propanol.5 Solvent selectivity is controlled by the nature of the added solvent. Additives with large dipole moments, such as methylene chloride and 1,2-dichlor-oethane, interact preferentially with solutes that have large dipole moments, such as nitro- compounds, nitriles, amines, and sulfoxides. Good proton donors such as chloroform, m-cresol, and water interact preferentially with basic solutes such as amines and sulfoxides, whereas good proton acceptors such as alcohols, ethers, and amines tend to interact best with hydroxylated molecules such as acids and phenols. A variety of solvents used as mobile phases in normal-phase chromatography are listed in Table 2.2, some of which may need to be stabilized by addition of an antioxidant, such as 3-5% ethanol, because of the propensity for peroxide formation. 

The polarity of molecules depends on the functional groups present in the molecule. A molecule will be polar and have a dipole moment if it has a polar functional groups like an alcohol, amine or ketone. Polarity also determines solubility in different solvents. Polar molecules dissolve in polar solvents like water or alcohols, whereas non-polar molecules dissolve in non-polar solvents like ether and chloroform. Polar molecules that can dissolve in water are called hydrophilic (water-loving) while nonpolar molecules are called hydrophobic (water-hating). 

Molecules of 1,3,5-trinitrobcnzene or p- dinitrobenzene have no electric dipole moments but they have moments in solutions where molecular compounds are formed. For example they have no moments in carbon tetrachloride or chloroform, but they do have moments in benzene, naphthalene, or dioxane. 

Carbon tetrachloride (CC14) has zero dipole moment, yet its boiling point is higher than that of chloroform (/x = 1.0 D). Clearly, there must be some kind of force other than dipole-dipole forces holding the molecules of carbon tetrachloride together. 

The dipole moments of nitroazoles measured in chloroform are lower than the values obtained in dioxane (Table 3.72) [1268], This effect is supposed to be caused by mutual orientation of the substrate and chloroform dipoles, which leads to partial compensation of charges and, hence, to the reduction of polarization. The substitution of hydrogen atom of the NH-fragment by a methyl group does not influence much the dipole moment value of nitroazole. Nevertheless, the dipole moment is, for example, sensitive to substitution in position 5 of the 1,2,4-triazole cycle [1268], The introduction of electron-donating substituent (methyl group)... 

An example of reaction type (c) in Table 5-4 is the well-known Menschutkin reaction [30] between tertiary amines and primary haloalkanes yielding quaternary ammonium salts. Its solvent dependence was studied very thoroughly by a number of investigators [51-65, 491-496, 786-789]. For instance, the reaction of tri-n-propylamine with iodomethane at 20 °C is 120 times faster in diethyl ether, 13000 times faster in chloroform, and 110000 times faster in nitromethane than in -hexane [60]. It has been estimated that the activated complex of this Menschutkin reaction should have a dipole moment of ca. 29 10 Cm (8.7 D) [23, 64], which is much larger than the dipole moments of the reactant molecules (tris- -propylamine 2.3 10 Cm = 0.70 D iodomethane 5.5 10-3 1 64 D) [64]. 

The terms polar, apolar and dipolar are often used to describe solvents and other molecules, but there is a certain amount of confusion and inconsistency in their application. Dipolar is used to describe molecules with a permanent dipole moment, e.g. ethanol and chloroform. Apolar should be used rarely and only to describe solvents with a spherical charge distribution such as supercritical xenon. All other solvents should, strictly speaking, be considered polar Therefore, hexane is polar because it is not spherical and may be polarized in an electric field. This polarizability is important when explaining the properties of such solvents, which do not have a permanent dipole and give low values on most polarity scales. Therefore, they are widely termed non-polar and, although... 

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