Debye unit of dipole moment

Second virial coefficient Third virial coefficient Fourth virial coefficient Debye (unit of dipole moment equal to 10 e.s.u.-cm)... 

It was the merit of the theory to have attracted attention to the large variations (2 to 5 Debye units) of dipole moments possibly associated with such tautomerism and to the specific directions of the variation following the nature of the purine. Thus the prediction was that, while the dipole moment of the N(7)H tautomer of purine should be greater than that of its N(9)H tautomer, the dipole moment of the N(7)H tautomer of xanthine should be smaller than... 

Values of the dipole moment of some diatomic molecules are given in Table 2.11. The SI unit of dipole moment is the coulomb-meter (C-m). This is a very large unit, so in Table 2.11 we use the unit 10-30 C-m. Dipole moments are often quoted in an older unit, the debye (D) 1 D = 3.24 X 1CT30 C-m. We can see from Table 2.11 that the dipole moment of a diatomic molecule usually reflects the difference between the electronegativities of the two atoms. 

The unit of Dipole Moment is DEBYE (D) after the name of the researcher. 

Since hv has units of energy, the third term has units J (m3)2 = J m6. The debye is widely used as a unit of dipole moment. It is equal to 10 18 esu cm. To convert this to SI we write... 

Equations (4.35) and (4.36) show that the SI unit of dipole moment is the product of the SI units of charge and distance, which are the coulomb and the metre, respectively. However, the unit of C m is a rather cumbersome one, and the old unit of the Debye (D) is still commonly used for the reason that molecular dipole moments are conveniently of the order of 1 D. The units are related by... 

Quantitatively, using the Debye unit, the dipole moments of NH3 (1.47 D), NF3 (0.2 D) and C6H5CH3 (0.36 D) confirm the simple arguments which we have made about their magnitudes. 

Conversion factors for a few other units, which are not related to SI but which are necessary to read the existing literature, are as follows. One atomic unit of length equals 0.52918 Angstroms (A). One atomic unit of dipole moment (two unit charges separated by ao) equals 2.5418 Debyes (D), and one atomic unit of energy equals 27.211 electron volts (eV) or 627.51 kcal/mole. 

The SI unit of dipole moment is the coulomb-meter (C m), but dipole moments for molecules are often more conveniently expressed in debye units (D), named for Peter Debye." The conversion factor is... 

It can be seen that the unit of dipole moment measurement is C m. This is a very large value and therefore a significantly smaller one is used in chemistry, namely 1 Debye (D) 1 D is equal to 3.33 X 10 ° C m. 

The dipole moment is a fundamental property of a molecule (or any dipole unit) in which two opposite charges are separated by a distance . This entity is commonly measured in debye units (symbolized by D), equal to 3.33564 X 10 coulomb-meters, in SI units). Since the net dipole moment of a molecule is equal to the vectorial sum of the individual bond moments, the dipole moment provides valuable information on the structure and electrical properties of that molecule. The dipole moment can be determined by use of the Debye equation for total polarization. Examples of dipole moments (in the gas phase) are water (1.854 D), ammonia (1.471 D), nitromethane (3.46 D), imidazole (3.8 D), toluene (0.375 D), and pyrimidine (2.334 D). Even symmetrical molecules will have a small, but measurable dipole moment, due to centrifugal distortion effects. Methane " for example, has a value of about 5.4 X 10 D. 

Steady-State Fluorescence. The fluorescence characteristics of PRODAN are extremely sensitive to the physicochemical properties of the solvent (38). As benchmarks, the steady-state emission spectra for PRODAN in several liquid solvents are presented in Figure 1. It is evident that the PRODAN emission spectrum red shifts with increasing solvent polarity. This red shift is a result of the dielectric properties of the surrounding solvent and the large excited-state dipole moment (ca. 20 Debye units) of PRODAN (38). It is the sensitivity of the PRODAN fluorescence that will be used here to investigate the local solvent composition in binary supercritical fluids. 

Accuracy of dipole moments (in Debye units) calculated by different QC methods for 64 compounds of elements C, H, and O (for more details see [CIO])... 

Figure 3. Dependence of dipole moments of negative ions (debye units) on n...

Displacements in units of a. Positive values indicate movements in direction of outward normal. Direction and magnitude of dipole moments (debye units) indicated by arrows. For negative ions length of arrow corresponds to one tenth of dipole moment... 

The quantity at the right, the Debye unit, is still commonly used to express dipole moments. It was named after Peter Debye (1884-1966), the Dutch physicist who pioneered the study of dipole moments and of electrical interactions between particles, and won the Nobel Prize for Chemistry in 1934. 

Pyrazine forms an azeotrope with water [60% pyrazine-40% water, b.p. 95.5° (uncorr.) (760mmHg) /ip 1.4510] (578). A method of assay for pyrazine and some common impurities has been developed (579). The dipole moment (Debye units) of pyrazine has been determined in dioxane, cyclohexane, and benzene as zero (580, cf. 581) and it has also been calculated as zero (133, 582). The e.s.r. spectrum (583) and the polarized single-crystal absorption spectra of pyrazine (and tetramethylpyrazine) (584) have been recorded. The photoelectron spectra of pyrazine and tetramethylpyrazine have been determined and suggest a different behavior towards electrophilic attack in the two cases (585). 

In the expressions above, D is the Debye unit of electric dipole moment, and B the Buckingham unit for the electric quadrupole moment. 

As far as possible only SI units have been used in writing equations and presenting experimental data. Angstroms and calories, which still appear in the scientific literature, are avoided. Instead, nanometers and picometers are used for atomic and molecular dimensions, and joules for units of energy. Pressure is discussed in terms of pascals and bars rather than torrs and atmospheres. Equations involving the molecular dipolar properties, namely the dipole moment and polarizability, assume units of coulomb meters and farad square meters, respectively, for these quantities. However, tabulated data are given in the more familiar cgs system with debyes for the dipole moment and cubic nanometers for the polarizability. This follows the usage in most data tabulations at the present time. The connection between the SI and cgs units is explained in chapter 2. The symbols recommended by the International Union of Pure and Applied Chemistry [1] are used as much as possible. 

Because the charge on an electron is 4.80 X 10 ° electrostatic units (esu) and the distances within a molecule typically fall in the 10 cm range, molecular dipole moments are on the order of 10 esu cm. In order to simplify the reporting of dipole moments this value of 10 esu cm is dehned as a debye, D. Thus the experimentally determined dipole moment of hydrogen fluoride, 1.7 X 10 esu cm is stated as 1.7 D. 

Dipole Moments (Debye Units) of 2-SuBsmvrBD Derivatives of Furan, Thiophene, Sblenophene, and Tellurophbne in Benzene... 

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