Lesson PH101 Recapuring……. physical properties of drug molecules
2. INDUCED POLARIZATION
- Polarizability is defined as the ease with which an ion or a molecule can be polarized by an external force, whether it is an electric field or light energy or through interaction with another molecule.
- Large anions have large polarizabilities because of their loosely held outer electrons.
- When a nonpolar molecules like pentane are placed in a suitable solvent between the plates of a charged capacitor, an induced polarization of the molecules can occur.
- Again this induced dipole occurs because of the separation of electric charge within the molecule due to the electric field generated between the plates.
- The displacement of electrons and nuclei from their original positions is the main result of the induction process.
- This temporary induced dipole moment is proportional to the field strength of the capacitor and the induced polarizability, which is a characteristic property of the particular molecule
- Polarizability is defined as the ease with which an ion or a molecule can be polarized by an external force, whether it is an electric field or light energy or through interaction with another molecule.
- Large anions have large polarizabilities because of their loosely held outer electrons.
- When a nonpolar molecules like pentane are placed in a suitable solvent between the plates of a charged capacitor, an induced polarization of the molecules can occur.
- Again this induced dipole occurs because of the separation of electric charge within the molecule due to the electric field generated between the plates.
- The displacement of electrons and nuclei from their original positions is the main result of the induction process.
- This temporary induced dipole moment is proportional to the field strength of the capacitor and the induced polarizability, which is a characteristic property of the particular molecule
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04/04/2025
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- PH 101 LECTURE SERIES Recapuring . PHYSICAL PROPERTIES OF DRUG MOLECULES April 4, 2025 1
- Recapturing . An atom consist of a nucleus, made up of neutrons (neutral in charge) and protons (positively charged), with each particle carrying a weight of approximately 1 g/mole. In addition, electrons (negatively charged) exist in atomic orbits surrounding the nucleus and have a significantly lower weight. April 4, 2025 2
- Recapturing . Charged atoms arise from imbalance in the number of electrons and protons can lead to ionic interactions. The atomic mass is derived from counting the number of protons and neutrons in a nucleus. Isotopes may also exist for a given type of an atom. April 4, 2025 3
- Recapturing . 1. Dielectric constant 2. Induced polarization 3. Dipole moment 4. Refractive index 5. Molar refraction 6. Optical rotatory dispersion April 4, 2025 4
- Recapturing Binding forces and intermolecular forces Drugs, Drug targets (lipids, carbohydrates, nucleic acids, proteins) and binding sites Binding regions and binding groups Association and Dissociation equilibria April 4, 2025 5
- PH 101 LECTURE SERIES CHAPTER III PHYSICAL PROPERTIES OF DRUG MOLECULES April 4, 2025 6
- 1. DIELECTRIC CONSTANT Electricity is related to the nature of charges in a dynamic state (e.g. electron flow). When a charged molecule is at rest, its properties are defined by electrostatics. For two charges separated by a distance ‘r’, their potential energy is defined by Coulumb’s law. U(r) = q1q2/4πεor April 4, 2025 7
- DIELECTRIC CONSTANT/Cont . Dielectric constant is a quantity that has no dimensions since is the ratio of two capacitances. Thus additional charge can be placed on the plates per unit of applied voltage. The capacitance of a condenser filled with a material, Cx, divided by the reference standard Co, is referred to as dielectric constant, ε = Cx/ Co, April 4, 2025 8
- DIELECTRIC CONSTANT/Cont . Dielectric constant of a vacuum is a unity. The dielectric constants of solvents mixtures can be related to drug solubility and ε for drug vehicles can be related to drug plasma concentration. Dielectric constant is a measure of the ability of a molecule to resist charge separation. April 4, 2025 9
- 2. INDUCED POLARIZATION Polarizability is defined as the ease with which an ion or a molecule can be polarized by an external force, whether it is an electric field or light energy or through interaction with another molecule. Large anions have large polarizabilities because of their loosely held outer electrons. When a nonpolar molecules like pentane are placed in a suitable solvent between the plates of a charged capacitor, an induced polarization of the molecules can occur. April 4, 2025 10
