Acetonitrile molecular dipole moment

Of these, probably the most decisive are type 2 and the combination of types 1 and 3. It is difficult to rationalize the weak H bonds formed by acetonitrile as a base (molecular dipole moment of 3.44 d) and the strong H bonds formed by trimethylamine (molecular dipole moment of 0.7 d) together with the interpretation that an acid A—H forms H bonds with these bases because of the electrostatic interaction of the A—H dipole with point charges on the nitrogen atoms. Another interesting comparison is afforded by the approximately equal H bond properties of acetone, diethyl ether, and dioxane, with dipole moments of 2.85 D, 1.15 D, and 0.4 d, respectively. These qualitative discrepancies can be backed by a substantial body of quantitative data. Table 8-1 collects some of these data, and verifies the absence of any systematic dependence of enthalpy of H bond formation upon the molecular dipole moment. Compilations of At, (814) and of AFshow that these properties are similarly unrelated to /i- Certainly these data show that the strength and behavior of a H bond are not determined in a direct way by the dipole moment. This lack of dependence is not easily reconciled with... 

Heating of 5-ethoxy-1,2,3,4-thiatriazolium tetrafluoroborate (161) with malononitrile and tri-ethylamine in acetonitrile solution gave crystalline l,2,3,4-thiatriazolium-5-dicyanomethylide (22) (Equation (13)) <79JCS(P1)744>. The structure is supported by spectral properties. The IR spectra show C=C (1500 cm ) and CN (2200 cm ) stretching vibrations and the mass spectra shows the correct molecular ions. A dipole moment of 8.8 D (R = Ph) was measured in benzene in good agreement with the proposed structure (22). 

Because C02 has weak dissolving capabilities, it is suitable as an extraction medium in SFE only for compounds of small and medium molecular mass and of low polarity. As a result, suitable modifiers must be added in order to extract polar substances. Modifiers are polar organic solvents, that is, with a nonzero dipole moment (methanol, acetonitrile, tetrahydrofuran, or water are the most commonly used) that enhance the diffusibility of polar analytes in nonpolar extraction media such as C02. 

The stmcture, stereochemistry, and potential conformational equilibria (Scheme 1) of 1,3,2-dioxathian 12 have not yet been studied theoretically but ab initio molecular orbital (MO) calculations at the MP2 level of its 2-oxide 13, both in the gas phase and in various solvents, have been reported <2000JP0187>. In the gas phase and in low-polarity solvents, 13-ax proved to be the only conformer present. In medium-polarity solvents such as acetonitrile or dimethyl sulfoxide, the equatorial counterpart 13-eq is of importance and participates up to 12% in the conformational equilibrium. In addition, both the dipole moments (/ii3.ax = 3.87 D /ti3 eq = 6.57 D) and the S=0 stretching vibrations (13-ax 1177-1180 cm ... 

To see the effect of dipole—dipole forces, we compare the boiling points of two compounds of similar molecular weight acetonitrile (CH3CN, MW 41 amu, bp 355 K) and propane (CH3CH2CH3, MW 44 amu, bp 231 K). Acetonitrile is a polar molecule, with a dipole moment of 3.9 D, so dipole—dipole forces are present. However, propane is essentially nonpolar, which means that dipole—dipole forces are absent. Because acetonitrile and propane have similar molecular weights, dispersion forces are similar for these two molecules. Therefore, the higher boiling point of acetonitrile can be attributed to dipole-dipole forces. 

Molecular modeling of the Et NBr activated hydroperoxides decomposition. On the base of experimental facts mentioned above we eon-sider the salt anion and eation as well as acetonitrile (solvent) moleeule participation when model the possible stmcture of the reactive hydroperoxide - catalyst complex. Model of the substrate separated ion pair (Sub-SIP) is one of the possible realization of join action of the salt anion and eation in hydroperoxide moleeule activation. In this complex hydroperoxide molecule is located between cation and anion species. For the sym-metrie molecules such as benzoyl peroxide [16], lauroyl peroxide [17], and dihydroxydicyclohexyl peroxide [18] attack of salts ions is proposed to be along direction of the peroxide dipole moment and perpendicularly to the peroxide bond. Hydroperoxides are asymmetric systems, that is why different directions of ion s attack are possible. The solvent effect can be considered by means of direct inclusion of the solvent molecule to the complex stmcture. From the other hand methods of modem computer... 

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