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Download as PDF; Printable version; ... Dipole moment: 1.46 D: Dielectric constant: 22 ... Std Gibbs free energy change of formation, ...
The ammonia-borane adduct (H 3 N → BH 3) is given as a classic example: the bond is weak, with a dissociation energy of 31 kcal/mol (cf. 90 kcal/mol for ethane), and long, at 166 pm (cf. 153 pm for ethane), and the molecule possesses a dipole moment of 5.2 D that implies a transfer of only 0.2 e – from nitrogen to boron.
Reaction of diborane with ammonia mainly gives the diammoniate salt [H 2 B(NH 3) 2] + [BH 4] − (diammoniodihydroboronium tetrahydroborate). Ammonia borane is the main product when an adduct of borane is employed in place of diborane: [5] BH 3 + NH 3 → BH 3 NH 3 + THF. It can also be synthesized from sodium borohydride.
Amines can be formed by the reaction of ammonia with alkyl halides or, more commonly, with alcohols: CH 3 OH + NH 3 → CH 3 NH 2 + H 2 O. Its ring-opening reaction with ethylene oxide give ethanolamine, diethanolamine, and triethanolamine. Amides can be prepared by the reaction of ammonia with carboxylic acid and their derivatives.
Note that the dipole moments drawn in this diagram represent the shift of the valence electrons as the origin of the charge, which is opposite the direction of the actual electric dipole moment. The bond dipole moment [5] uses the idea of electric dipole moment to measure the polarity of a chemical bond within a molecule. It occurs whenever ...
The electric dipole moment is a measure of the separation of positive and negative electrical charges within a system: that is, a measure of the system's overall polarity. The SI unit for electric dipole moment is the coulomb-metre (C⋅m). The debye (D) is another unit of measurement used in atomic physics and chemistry.
The polarizability of an atom or molecule is defined as the ratio of its induced dipole moment to the local electric field; in a crystalline solid, one considers the dipole moment per unit cell. [1] Note that the local electric field seen by a molecule is generally different from the macroscopic electric field that would be measured externally.
Transition dipole moment, the electrical dipole moment in quantum mechanics; Molecular dipole moment, the electric dipole moment of a molecule; Bond dipole moment, the measure of polarity of a chemical bond; Electron electric dipole moment, the measure of the charge distribution within an electron; Magnetic dipole moment, the measure of the ...