Dipole meter

The dipole moment of atenolol was determined in propionic acid solutions, at 2o°C, using a Dipol-meter DM ol (Wiss.-Techn. V/erksl atten, D 812 Weil-heim). The value found was 5.71-o.2o D.(5)... 

With the advent of inexpensive, fast frequency counters, which count the individual cycles over a precisely fixed period (usually 1 s) and display the frequency digitally, it is more convenient to connect the radio-frequency output of the variable-frequency oscillator directly to the frequency counter and determine the total capacitance with the aid of Eq. (27). This technique is highly suitable for the present experiment if a WTW Dipol-meter or another LC oscillator is available or can be constructed. (With the Dipolmeter only the variable-frequency oscillator is used.) A simple LC oscillator circuit that can be constructed from inexpensive components has been described by Bonilla and Vassos this circuit, with a small modification to provide for one side of the tank to be grounded, is shown in Fig. 2. In this circuit, as in the WTW Dipolmeter circuit, all tank capacitances are in parallel. [This is not true of the circuit described in Ref. 4 of Exp. 30, as that circuit incorporates some series capacitance. If that circuit is employed, Eqs. (28) to (30) are not valid and Eqs. (30-3) to (30-5) must be used instead, unless the null mode is employed.]... 

Also, Aaron, Parkanyi and co-workers ([25] and references therein) measured the ground-state dipole moments of BPHT derivatives (compounds 2-8) in dioxane with a dipole meter at 20 °C (Table 5). While the dipole moments of compounds 5 and 8 were lower than that of phenothiazine (1), the remaining derivatives displayed higher ground-state dipole moment values, ranging between 3.4 and 5.53 D. 

The dielectric constants needed for the determination of dipole moments are obtained by a heterodyne beat method or the resonance and bridge methods. The instrument specifically adapted for measurements of dielectric constants for dipole moments is a dipole meter model DM-01 manufactured by Wissenschaflich-Technische Werkstatten, Weilheim, Germany, equipped with two different thermostatted cells for two ranges of dielectric constants (cell DFL-1, e 1.0 to 3.4, cell DFL-2, e 2 0 to 6.9). The other dipole meter which used to be available from Toshniwal Brothers, Ltd., Madras, India, is not sufficiently sensitive for measurements of dielectric constants of diluted solutions and is better suited for measurements of large differences, such as the dielectric constants and dipole moments of different solvents. 

At 25 °C unless indicated otherwise. The data were taken from the literature, from several reference sources. The table lists solvents with low dielectric constants, suitable for use with the dipole meter DM-01. 24°C. 20°C. 23.5 C. 

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. 

Consideration of the structure of polyvinylidene fluoride (65) assuming a barrier of 3 kilo cal per mole for rotational minima of conformation of the chain by A. E. Tonelli (66) led to detailed conformation and its implications for dipole structure (Fig. 22). Indeed, the material can approximate a ferro electric. It is thus of interest in our expectations of the environments that polymers can provide for the creation of new phenomena. The total array of dipoles in polyvinylidene fluoride will switch in about 3 microseconds at 20°C with 200 megavolts per meter field. The system becomes much slower at lower temperatures and fields. But we do have a case of macroscopic polarization intrinsic to the polymer molecules, which thus supplements the extensive trapping and other charge of distribution phenomena that we have discussed in connection with electrets. 

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. 

Duhm S, Heimel G, Salzmarm I, Glowatzki H, Johnson RL, Volhner A, Rabe JP, Koch N (2008) Orientation-dependent ionization energies and interface dipoles in ordered molecular assemblies. Nat Meter 7 326... 

Dipole moments are usually given in Debye units. In the rationalized SI system, the unit used is Coulomb meter (C m) 1 Debye = 3.33 x 10 30 C m. 

Note Dipole moment //-Dipole = charge x distance in mks units, coulombs x meters in cgs units, statcoulombs x centimeters. 

Dipole moments are expressed in units of the debye (D), where 1 debye = 3.34 X 1CT30 coulomb meters. If a proton and an electron (charge 1.60 X 10-19 coulomb) were 1 A apart (distance 10-1" meter), the dipole moment would be... 

Polarizability (of a molecule) — There are numerous different mechanisms that contribute to the total polarizability of a molecule. The three most important of these are termed electron polarizability, molecular-distortion polarizability, and orientation polarizability. All these parameters are measured as statistical averages over large numbers of molecules present in the bulk phase. (1) -> Electron polarizability a is a measure of the ease with which electrons tend to be displaced from their zero-field positions by the applied -> electric field. Thus, the electron polarizability of a molecule is defined as the ratio of induced dipole moment pincj (coulomb meters) to the inducing electric field E (volts per meter) ... 

The dipole moments were determined at 25 °C in benzene (five solutions, weight fraction 1.8x10 to 1.lxlO 3), showing the 3.84 D value for (1), 5,47 D for (2), 5.49 D for (3) and 5.34 D for (4). Relative permitivities were measured at 6 MHz on a homemade DK-meter with direct frequency reading,8 and refractive indices were measured... 

Van der Waals forces arise from dipole-dipole interactions. In a dipolar molecule, there is a separation of positive from negative charge. For example, if the molecule contains charges -Fq and —q separated by a distance vector r, then the molecule has a dipole moment of u = rq. Dipolar moments are often measured in units of the Debye D, where 1 D = 3.336 X 10 coulomb-meter. While alkanes have no permanent dipole moments,... 

The dipole moment, /x (Greek mu), is defined as the magnitude of the charge Q at either end of the molecular dipole times the distance r between the charges, = Q x r. Dipole moments are expressed in debyes (D), where 1 1) = 3.336 X coulomb meter (C m) in SI units. For example, the unit... 

---