Chemical Concepts and Definitions Quiz

Definitions

• Bioisosteres: Chemical substituents with similar physical or chemical properties, producing similar biological properties.
• Conformation (of a molecule): One of the infinite spatial arrangements of atoms in a molecule, resulting from rotations about single bonds without breaking them.
• Configuration (of a molecule): The permanent geometry of a molecule, resulting from the spatial arrangement of bonds. Changing configuration requires breaking sigma bonds (e.g., R, S, E, Z).
• Coulomb Law: Equation calculating the force between two point charges, affected by the magnitude of the charges, the distance between them, and the dielectric constant of the medium.
• Covalent inhibitor: Inhibitors that bind to their target in two steps, commencing with equilibrium bond formation, followed by covalent bond formation.
• Craig plot: A plot of substituent parameters (like Hansch-Fujita π and Hammett σ constants) in rational drug design.
• Dielectric constant: A constant describing how easily a dielectric medium can be polarized, correlating with solvent polarity.
• Dipole moment: A measure of the separation of positive and negative charges in a system.
• Electronegativity: An atom's tendency to attract bonding electrons.
• H2L (Hit-to-lead): A stage in early drug discovery, involving evaluating small molecule hits from a high-throughput screen (HTS) and optimizing them to identify promising lead compounds.
• Halogen bond: Electrostatic interaction between an electrophilic region of a halogen and a nucleophilic region in another, or the same molecular entity.
• Hammett constant σ: A constant quantifying the electronic properties of a substituent (electron donating/withdrawing).
• Hammett constants (modified) σ⁺, σ⁻: Constants describing substituent electronic properties, considering how they stabilize positive (σ⁺) or negative (σ⁻) charges through conjugation.
• Hansch equation: An equation relating a compound's biological activity to various molecular parameters.
• Hansch-Fujita constant: A constant quantifying substituent hydrophobicity.
• Henderson-Hasselbalch equation: An equation relating the ratio of protonated and deprotonated forms of a molecule to its pKa and the pH of the solution.
• Hydrogen bond: Electrostatic interaction between an atom with a basic lone pair of electrons and a hydrogen atom that has gained partial positive charge.

Equations

• Coulomb's Law: F = Q₁Q₂/(εr²)
• pKa Definition: pKa = -logKa
• Henderson-Hasselbalch Equation: pH = pKa + log([A⁻]/[AH])

Rules

• Lipinski Rule of 5: A rule of thumb for evaluating drug-likeness, considering factors like hydrogen bond donors/acceptors, molecular weight, and lipophilicity (cLogP).
• Verber Rules: A refinement of the Lipinski Rule, questioning the 500 Da molecular weight cutoff and suggesting a focus on rotatable bonds and polar surface area.