Dipole moment value

AHC197).Tlie experimental dipole moment values of the three 1-alkyl-4-azolylidene-l,4-dihydropyridines 72a and 72b and 73b are high and in the range of 9.0-9.7 D, which implies a substantial charge separation. 

Dipole moments for dioxan solutions of both CHO or P-Cl terminated dendrimers were measured at 25 °C. Remarkably, values of dipole moment vs generation increase exponentially from 8.43 (10-[G1])to258 (10-[G10]) and from 8.27 (10-[G ]) to 328 (10-[GnD debyes (Fig. 10a), the highest dipole moment values... 

Even if attention has not been focussed on the physical properties of phosphorus-containing dendrimers in this review, one can mention the high dipole moment values observed for these polymers up to 328 debyes for generation 11. 

Although we do not have an exact value for the molecular dipole moment, we will consider the implications of dipole moments in the range of 2 to 30D. Taking a 35° as a noncritical estimate of the angle of the dipole with respect to the polar axis, values of L for a series of dipole moment values are shown in Columns 1 and 2 of Table II. In the range of dipoles moments of interest, the limit on L is 0.1 eV. These limits are comparable to the heats of fusion of molecular crystals which makes the limit quite reasonable. 

The thermodynamic theory for exp-6 mixtures of polar materials is now implemented in the thermochemical code Cheetah.32 We considered first the major polar detonation products H20, NH3, CO, and HF. The optimal exp-6 parameters and dipole moment values for these species were determined by fitting to a variety of available experimental data. We find, for example, that a dipole moment of 2.2 Debye for water reproduces very well all available experiments. Incidentally, this value is in very good agreement with values typically used to model supercritical water.50... 

We have found that we can obtain a particularly accurate representation of the ab initio dipole moment values by introducing the projections... 

We have also checked the effect on the rms deviation of including higher order terms in equation (46). Extending the expansion in equation (46) to sixth order, we obtain an rms deviation of 0.00006 D in the fitting to the 3X14,440 ab initio dipole moment values. However, the number of parameters required is about 400, substantially more than with the fourth-order expansion. These results demonstrate the very high internal consistency (i.e., smoothness) of the ab initio dipole moment surface. 

In spite of the fact that we have introduced the factor of exp(—) in equation (47), our analytical expression for the dipole moment does not have a qualitatively correct asymptotic behaviour for the bond lengths r,—> 00. The function does not converge to the dipole moment of the NH2 fragment if we remove a hydrogen atom. However, neither does it diverge The calculated dipole moment values at large r, are around 2-3 D depending on which dissociation path we use. Obviously, the asymptotic behaviour of the dipole moment is of no importance for the simulations carried out in the present work we are only concerned with molecular states well below dissociation. 

Since, with the definition in equation (61), i h (tt/2) = 0, no inconsistency arises because of equation (62). If we allowed only odd powers s in the sum of equation (61), we could let this equation define i h (p) in the entire interval 0[Pg.228]

Having derived the symmetry relations between the expansion parameters in equation (55), we can proceed to fit the expansions through the ab initio dipole moment values. The expansion parameters in the expressions for and fiy are connected by symmetry relations since these two quantities have E symmetry in and so and fiy must be fitted together. The component ji, with A" symmetry, can be fitted separately. The variables p in equation (55) are chosen to reflect the properties of the potential surface, rather than those of the dipole moment surfaces. Therefore, the fittings of fi, fiy, fifi require more parameters than the fittings of the MB dipole moment representations. We fitted the 14,400 ab initio data points using 77 parameters for the component and 141 parameters for fi, fiy. The rms deviations attained were 0.00016 and 0.0003 D, respectively. 

Estimates of the percentage ee conformation in other V,/V-dialkylhexahy-dropyrimidines are given in Table XXVI. Some disagreement exists between the positions of equilibria for the Af,Al-diisopropylhexahydropyrimidine based on dipole moment and on H-NMR chemical-shift measurements but in this case the higher (dipole moment) value is probably more representative of the true state of the equilibrium. 

The discussion of dipole-moment values in relation to resonance is continued in Chapter 8. 

On the basis of the dipole moment values and viscosity measurements of the two forms of nitroglycerine, de Kreuk [20] considered that the difference between the two forms is produced by rotational isomerism. According to this hypothesis the labile and stable forms would correspond to cis- and trans-isomers respectively. In a non-polar solvent the traits form predominates. In a polar solvent the content of the cis form increases and reaches a maximum in liquid nitroglycerine. 

The solubility of high-nitrated cellulose (13.46% N) in a mixture of formic and acetic acid esters with ethyl alcohol was followed by T. Urbanski [51]. The author established that for a range of homologous esters of both acids, the capacity of dissolving nitrocellulose increased in proportion with the value of the dipole moment of the ester. According to T. Urbanski the sequence of formic acid esters corresponding with an increasing capacity to dissolve nitrocellulose is paralleled by the dipole moment values, as follows ... 

In 1,2-diketones or their functional derivatives no conjugation is apparent in the dipole moment values, but these can serve for determining conformation on the central, formally single bond. In ( )- and (Z)-benzil monoximes (62) the configuration on C=N was known, and the ap conformation on N—O was assumed (and finally confirmed) from dipole... 

The approximate dipole moment values filh can be readily obtained by semiempirical methods (for example Hiickel-MO or CNDO/s-CI63,69). 

D. It was found that the [2,3-6]-annelated parent thienothiophenes, selenoloselenophenes, and selenolothiophenes exhibit higher dipole moment values than the [3,4-6]- or [2,3-c]-annelated systems <84CHEC-I(4)1037>. Other parent diheteropentalene dipole moments do not appear to have been measured. 

The introduction of highly polar nitro group into molecule usually increases the dipole moment value. Dipole moments (p) of some nitroazoles are presented in Table 3.72. For example, the dipole moment of 1-methyl- and 3,5-dimethylpyrazole is 2.28 and 2.31 D [1264-1266], and those of their nitro derivatives are 6.26 and... 

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)... 

The calculated dipole moment values of 5-substituted (including nitrotetrazole) correlate well with <3p constants of substituents [1271],... 

Among the variety of compounds emerging from prototype structures 10-28 mentioned in the Introduction (Table I), X-ray structural determinations have been performed on six representative examples the mesomeric betaines 55, 116, 117, and 120 the higher homologue 119 and the novel aza analogue of sesquifulvalene with a betaine character 118 (Scheme 9 and Table VIII). As mentioned earlier, the experimental dipole moments for molecules 55,116-119 were found to be in the range 9 to 13 D (III,B, Scheme 8 and Table Vll). Comparison of the experimental molecular geometries and dipole moment values with those obtained from semiempir-ical molecular orbital calculations is discussed below (III,D). 

Running the calculations in the same way as for betaines 22, 23, four selected molecules, 122-125, from the ensemble constituted by the inner salts 15, 16 and 19, 20 have been studied (92PC3). Both the AMI and MNDO methods have predicted high dipole moments for the unknown betaines 122 and 123, ca. 17 D. A similar situation holds for compounds 124 (13.9 D) and 125 (17.7 D), whereas the best measured dipole moment values were 13 D for 124 and >10.4 for 125 (III,B, Table VII). 

The magnitude of the induced dipole moment that is produced when an indole molecule in its ground Sq and electronically excited Si states is polarized by the attachment of a hydrogen-bonded water molecule in the gas-phase complex indole-H20 have been determined as /i I(So) = 0.7 D atid /t I(Si) = 0.5 D <2005JCP1743011>. The permanent dipole moment values for the complex (/tlW(So) =4.4D and /tlW(Si) = 4.0 D) are substantially different from calculated values based on vector sums of the dipole moments of the component parts. The orientation of the induced moment is also significantly different in the two electronic states. 

---