Ground states ionic character

The charge distribution of neutral polar molecules is characterized by a dipole moment which is defined classically by jx = E, , , where the molecular charge distribution is defined in terms of the residual charges (qt) at the position r,. The observed molecular dipole moment provides useful information about the charge distribution of the ground state and its ionic character. 

Ground states, 22 charge distribution of, 48, 52 desolvation of, by enzymes, 211-215 ionic character of, 22... 

The observed value of the electric dipole moment of the molecule is 0.297 D, which corresponds to 0.24 D for the moment of the bond. The value of tr, 6.67 D, leads to 3.60% as the contribution of each of the two structures of type 6 to the ground state of the molecule. The ionic character corresponding to Ax = 0.5 is 6.06% from Equation 1-1, which gives bond moment 0.41 D, which would lie close to the straight line in Figure 1-3. 

Comparison of entropies of activation for propagation on macroions and on macroion-pairs leads to conclusions being hand in hand with the analysis of enthalpies. The large negative entropy observed for macroion-pairs (-52.0 cal mole-1 deg ) may reflect formation of transition state with more ionic character. Thus, some of the solvent and monomer molecules may even become more firmly oriented than in the corresponding ground state. 

From the preceding calculation we see that the hypothetical ion pair for ethane lies about 57 kcal. above the energy of two adjacent methyl free radicals. While this is large it still permits us to consider that the ground state of two adjacent CHs may contain a small amount of partial ionic character. If we had made our calculation for a separation of 2.0 A. between the two C atoms of the methyl groupsf then Qc would... 

From our discussion on the CHs-CH3 ion pair, we would expect that the C2H4 biradical ion pair with a distance of only 1.54 A. between C atoms would be even more stable. If such a model is correct it would imply that there is a considerable amount of ionic character even in the ground states of double bonds, f... 

Mulliken State Symbols.—In this classification, states are represented by different capital letters, e.g., N, Q, V, T, R, etc. (17), where N (normal) stands for the, ground state and F, for example, stands for an excited state having large ionic character. Thus the absorption of hydrogen at 1100 A.,... 

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