Dipole moment dichloromethane

Carbon tetrachloride with four polar C—Cl bonds and a tetrahedral shape has no net dipole moment because the result of the four bond dipoles as shown m Figure 1 7 is zero Dichloromethane on the other hand has a dipole moment of 1 62 D The C—H bond dipoles reinforce the C—Cl bond dipoles... 

Physical properties of the solvent are used to describe polarity scales. These include both bulk properties, such as dielectric constant (relative permittivity), refractive index, latent heat of fusion, and vaporization, and molecular properties, such as dipole moment. A second set of polarity assessments has used measures of the chemical interactions between solvents and convenient reference solutes (see table 3.2). Polarity is a subjective phenomenon. (To a synthetic organic chemist, dichloromethane may be a polar solvent, whereas to an inorganic chemist, who is used to water, liquid ammonia, and concentrated sulfuric acid, dichloromethane has low polarity.)... 

Four examples of dipole moments are instructive. First, the dipoles for chloromethane and dichloromethane are 1.87D and 1.60D, respectively. Although two chlorine-carbon bonds are present in the latter, the dipole is not along either but rather bisects the angle between them. This is illustrated schematically using the stylized arrow with its positive end in the form of a cross. The orientation question is shown clearly in the rigid dichlorobenzene framework. The dipole is 2.13D for the ortho-isomer and 0D when the dipoles exactly oppose each other. 

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 cis/trans conformational change of the rotamers of chloroacetaldehyde, C1CH2C(H)=0, is another case in point the c/ s-form has a higher dipole moment and is stabilized by the more polar solvents. Its mole fraction is 45% in cyclohexane, 61% in dichloromethane, 72% in acetone and 84% in dimethylsulfoxide (Reichardt 1988). 

Inspection of Table 4-9 reveals that the axial cis isomer (34a), which is the con-former with the higher dipole moment, becomes more favoured as the solvent polarity increases. In the most polar solvent studied, acetonitrile, AG° is nearly zero. Benzene, toluene, trichloromethane, dichloromethane, and methanol are seen to behave as more polar solvents than their relative permittivities would lead one to predict. The deviation for trichloromethane was particularly dilficult to explain (for a full discussion, see reference [89]). In general, good correlations between values and other solvent-... 

FIGURE 1.13 Contribution of individual bond dipole moments to the molecular dipole moments of (a) carbon tetrachloride (CCI4) and (6) dichloromethane (CH2CI2). 

Fig. 3.34 Proposed structures of [(CH3CONHC5H4)Fe(C5H4CONHCH3)] and [(CH3CONHC5H4) Fe(C5H4CONHC5H4)Fe(C5H4CONHCH3)] in the solid state (a) and in dichloromethane (b). The dotted lines and arrows indicate hydrogen bonds and the dipole moments of amide groups, respectively. The values of v(NH) are shown near the corresponding amide NH in cm unit. The v(NH) band of the bridging amide group is involved in the broad signal at ca. 3,300 cm ...

In chloromethane, the tetrahedral shape is clear, but there is only one polarized bond and the dipole for the molecule is easily predicted. In dichloromethane, however, there are two bond moments, and the dipole for the molecrde is the vector sum of these two bond moments (magnitude and direction). The dipole is shown. For trichloromethane (chloroform), the magnitude and direction of the three polarized C-Cl bonds lead to the molecular dipole moment shown. Carbon tetrachloride is interesting. There are four C-Cl bonds with equal bond polarization and dipole moments. Summing all four dipole moments for the bonds, which are directed to the corners of a regular tetrahedron, leads to a dipole moment of zero because the magnitudes of the individual bond moments cancel. 

Molecular models for chloromethane, dichloromethane, and trichloromethane are given to show the direction of the dipole of molecule more clearly. Calculated dipoles for these three molecules are 2.87, 2.50, and 1.72 Debye, respectively, and it is clear that the directional nature of the individual bond dipoles plays a role in the overall magnitude of the dipole moment for the molecrde. With three chlorine atoms directed to different regions of space, chloroform is the least polar of the three molecules, despite the presence of three polarized bonds. 

The molecular dipole moment of dichloromethane is the net sum of all dipole moments in the compound. 

Chloromethane was a simple example, because it has only one polar bond. When dealing with a compound that has more than one polar bond, it is necessary to take the vector sum of the individual dipole moments. The vector sum is called the molecular dipole moment, and it takes into account both the magnitude and the direction of each individual dipole moment. For example, consider the structure of dichloromethane (Figure 1.45). The individual dipole moments partially cancel, but not completely. The vector sum produces a dipole moment of 1.14 D, which is significandy smaller than the dipole moment of chloromethane because the two dipole moments here partially cancel each other. 

Determine if the following species have permanent dipole moments, (a) Dichloromethane, CHjClj (b) Chlorobenzene, CjHsCI (c) Ammonia, NH3 (d) Carbon dioxide, CO2... 

However, CCI4 does not have a dipole moment because the vector sum of the symmetrically arranged C—Cl bonds around carbon is zero. In contrast, dichloromethane has a dipole moment of 1.62 D. The vector sum of the two C—Cl bonds is located at an angle bisecting the Cl—C—Cl bond angle. The C—Cl bonds are largely responsible for the observed dipole moment. The resultant of the two smaller C—H bond moments is in the same direction as the net resultant of the two C—Cl bond moments. The small resultant of the two C—H bond moments therefore reinforces the C—Cl bond moments. 

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