Interactions between molecules (bonding) Flashcards
(20 cards)
What are the two most common types of intramolecular bonds?
A: Ionic bonds and covalent bonds.
Term: Ionic bond
Definition: A bond formed via electrostatic attraction between oppositely charged ions resulting from the transfer of electrons.
Cations (+): lose electrons (usually metals)
Anions (–): gain electrons (usually non-metals)
What are the key characteristics of ionic compounds?
Strong electrostatic forces
High boiling and melting points
Water solubility
Conduct electricity in solution
Term: Covalent bond
Definition: A bond where atoms share electron pairs—each atom donates one electron to the bond.
Occurs usually between non-metals
Often forms gases or liquids
Lower boiling points
What is a co-ordinate (dative covalent) bond?
A: A type of covalent bond where both electrons in the shared pair come from one atom (usually one with a lone pair), bonding with an electron-deficient atom like H⁺.
Give two biological examples of co-ordinate bonding.
Water (H₂O) + H⁺ → Oxonium ion (H₃O⁺)
Ammonia (NH₃) + H⁺ → Ammonium ion (NH₄⁺)
Term: Polar covalent bond
A covalent bond where electrons are not shared equally due to a difference in electronegativity, resulting in partial charges on atoms.
How does electronegativity affect drug metabolism? Use volatile anaesthetics as examples.
Desflurane (C-F bond): Fluorine is highly electronegative → stronger polar bond → greater resistance to metabolism
Isoflurane (C-Cl bond): Chlorine is less electronegative → less resistance to metabolism
Term: Polarisation
Definition: The distortion of the electron cloud in an anion by a cation, leading to increased covalent character in what is typically an ionic bond.
What are the three types of intermolecular forces?
Van der Waals forces – Weakest; due to transient dipoles
Dipole-dipole interactions – Between permanent dipoles
Hydrogen bonding – Strongest; between H and highly electronegative atoms (O, N, F)
Q: What is the significance of hydrogen bonding in anaesthetic action?
General anaesthetics may disrupt hydrogen bonds in membranes or receptor binding sites, altering neurotransmission or receptor activity.
How do anaesthetics interact with amino acids?
Anaesthetic molecules can form hydrogen bonds with amino acid side chains (e.g. aromatic rings), enhancing drug binding.
What are the three essential properties for effective drug-receptor binding?
Rapid bond formation
Sufficient binding strength
Ability to attract the receptor from a distance
Which type of bond meets the criteria for drug-receptor attraction at a distance and rapid formation?
Ionic bonds
Why are multiple types of bonds needed in drug-receptor interactions?
Ionic bonds provide initial attraction, but Van der Waals and hydrogen bonds ensure specificity and duration of binding.
Example: How does acetylcholine bind its receptor?
Ionic bond via quaternary ammonium group
Hydrogen bonds and Van der Waals forces stabilize and specify the interaction
Term: Homolytic fission
Definition: A covalent bond breaks evenly; each atom keeps one electron → forms free radicals.
Requires: UV light or high temperature
Term: Heterolytic fission
Definition: A covalent bond breaks unevenly; the more electronegative atom takes both electrons.
Results in:
Electrophile (⁺ ion): electron-seeking
Nucleophile (⁻ ion): donates lone pair to form a new bond
What properties must a nucleophile have?
A lone pair of electrons
Negative or neutral charge
Attracted to electron-deficient (positive) atoms
Rank the following from strongest to weakest:
Ionic
Covalent
Hydrogen bond
Van der Waals force
S - Covalent
Ionic
Hydrogen bond
W - Van der Waals force
