Debye dipolar units

It should be borne in mind, however, that enzyme proteins, like other proteins, are dipolar ionic structures surrounded by an intense electrostatic field. Horse carboxyhemoglobin, for example, has a dipole moment of 480 Debye units (molecular weight, 67,000). Compared with amino acids, sugars have a rather low dipole moment, due mainly to a considerable measure of mutual cancellation of the constituent link moments resulting from their disposition in space (glycine = 15, a- and... 

Dipolar molecules will form localized structures in a bulk solvent by orientation of these permanent dipoles, and Figure 1.9 shows two different ways in which two molecules with permanent dipoles may align with one another. With several molecules and three dimensions, a wide range of localized structures are possible. Dipole moments have units of coulomb metres (C m) or Debyes (D, 1D = 3.34 x 10-30 Cm). 

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,... 

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. 

The distance the charges are separated from each other is the dipole moment which is measured in units of debyes (D). In a molecule like water, H2O, the oxygen holds the electrons more tightly causing a polar separation and the dipolar moment is 1.94 D. In SI units, dipole moments are measured in coulomb meters (Cm),... 

The commonly used solvents for electrolytes are all dipolar and the dipole moments, n, of the molecules of these solvents range from 1.66D (ID (Debye unit)=3.33564 x 10 Cm) for ethanol and the two isomeric propanols to 5.54D for HMPT. Several of the solvents listed in Table 3.5 are very polar having dipole moments >4D propylene carbonate, y-butyrolactone, Af-methylpyrrohdinone, benzonitrile, nitrobenzene, dimethyl-sulfoxide, sulfolane, and HMPT. The polarizabihty a and the polarity (dipole moment) together with some chemical properties dealt with in Section 3.3 bear on the ability of the solvents to solvate the ions in electrolyte solutions. 

It is sometimes stated that measurement of dipole moments is a discriminating test for the detection of zwitterions, which, it is supposed, should have a dipole moment of at least 15 D (Debye units) as compared with a maximum of 6 5 D for a highly dipolar (but non-ionized) molecule such as p-nitroaniline. This was found not to be true for a series of aromatic zwitterions whose dipole moments were measured in dioxan (Serjeant, 1964). For example, a substance which was found to be over 90% zwitterionic in water had a dipole moment in dioxan differing by only O 18 D from that of the corresponding ester (both... 

Each conformation of a polymer chain has a dipole moment, /x, in Debye units D(=10 x u.e.e. x 1 cm or 3.338 X 10 C X m), equal to the vectorial sum of the moments of N dipolar groups along the chain, that is, = J3j./H/,where m, is the dipole moment associated with the skeletal bond i in the conformation C- The mean-square dipole moment p ) ean be written as (22,91)... 

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