Dipole moment of nitrobenzene

The dipole moment of nitrochlorobenzene, /x, = 2 78 D, is less than the dipole moment of nitrobenzene, /x, = 4 01 D, which indicates that the... 

Worth recalling is the case of nitrobenzene - u-alkane mixtures. " Their technological importance arises from the large dielectric permittivity and dipole moment of nitrobenzene and the ability to solvate some environmentally hazardous agents. Basic properties of such mixtures are presented... 

The first recorded correlation of dipole moments with substituent constants was observed by Taft (3), who reported results for alkyl cyanides, chlorides, iodides, and tertiary amines. Kross and Fassel (31) have reported the correlations of dipole moments for 4-substituted nitrobenzenes with the simple Hammett equation. Rao, Wohl, and Williams (32) have studied the correlation of dipole moments of disubstituted benzenes with eq. (1) and of monosubstituted benzenes with the equation... 

Remarkable data on primary hydration shells are obtained in non-aqueous solvents containing a definite amount of water. Thus, nitrobenzene saturated with water contains about 0.2 m H20. Because of much higher dipole moment of water than of nitrobenzene, the ions will be preferentially solvated by water. Under these conditions the following values of hydration numbers were obtained Li+ 6.5, H+ 5.5, Ag+ 4.4, Na+ 3.9, K+ 1.5, Tl+ 1.0, Rb+ 0.8, Cs+0.5, tetraethylammonium ion 0.0, CIO4 0.4, NO3 1.4 and tetraphenylborate anion 0.0 (assumption). 

Some reactants have rate constants higher than 3xl0 M sec examples are nitrobenzene and o-dinitrobenzene. These two compounds have large dipole moments of 4.1 and 6.1 Debye, respectively, and it has been shown [110] that the rate constants in cyclohexane increase with dipole moment because the reaction radius increases. That dependence is given by [117] ... 

It is obvious that a non-polar molecule cannot penetrate into the crystals of an electrolyte, nor dissolve it. This explains why, for example, NaCl is insoluble in benzene, CC14, CS2, etc., which are non-polar. On the other hand, nitrobenzene is not a solvent for salts either, yet its dipole moment of 4 X 10-18 is larger than that of water. It must, however, be remembered that the molecule C6H6N02 is also much larger than that of water, and consequently the larger dipole cannot approach as closely to the charges of the ions. A liquid, to produce easy dissociation, must have small molecules with large dipole moments. 

The dipole moment is a property of the molecule that results from charge separations like those discussed above. However, it is not possible to measure the dipole moment of an individual bond within a molecule we can measure only the total moment of the molecule, which is the vectorial sum of the individual bond moments.32 These individual moments are roughly the same from molecule to molecule,33 but this constancy is by no means universal. Thus, from the dipole moments of toluene and nitrobenzene (Figure 1.10)34 we should expect the moment of p-nitrotoluene to be about 4.36 D. The actual value 4.39 D is reasonable. However, the moment of p-cresol (1.57 D) is quite far from the predicted value of 1.11 D. In some cases, molecules may have substantial individual bond moments but no total moments at all because the individual moments are canceled out by the overall symmetry of the molecule. Some examples are CC14, tr[Pg.16]

To confirm the formula II, reference is made to the fact that the dipole moment of p- nitroaniline (p = 6.45) is much higher than that which would be deduced from the total of the dipole moments of aniline (p = 1.52) and nitrobenzene (p = 3.96). 

Use Spartan View to obtain the dipole moments of aniline, nitrobenzene, and 4-nitro-aniline. Is the dipole moment of 4-nitroani ine the sum of the dipole moments of aniline and nitrobenzene Compare electrostatic potential maps and geometries for all three structures, and draw resonance structures for 4-nitroaniline that account for your observations. 

Specific interaction between particular atoms of the solvent and solute molecules explains, for example, the much greater solubilities of aniline (CgHsNH2) and phenol (CgHjOH) in water than in nitrobenzene in spite of the much larger dipole moment of the latter (4-19 D) as compared with water (1-85 D). 

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