Interactions Between Molecules Flashcards
Describe the important features of Ionic bonding?
Electrostatic attraction between oppositely charged ions which are produced from electron transfer between atoms.
* Cations (+ve) – removal of electrons. Mainly metals
* Anions (-ve) – gain of electrons. Mainly non-metallic elements.
Characteristics:
* Strong forces – tend to be solids have high boiling and melting points.
* Soluble in water
* Conduct electricity
Describe the important features of Covalent bonds?
Atoms share electrons – one donated from each atom and they are held together by forces of attraction between the +ve nuclei and -ve charged electrons.
* Usually non-metallic elements
* Often liquids or gases with low boiling points.
* Tend to be weaker than ionic bonds
Some exceptions in which covalent structures form very strong lattice formations such as in diamonds
What is a coordinate bond?
A type of covalent bond in which 1 atom supplies both their electrons to form a bond shared with another atom.
These atoms usually have a lone pair of electrons (not already involved in a covalent bond).
What are intermediate bonds?
It is a bond that has covalent and ionic properties.
It occurs with 2 atoms sharing electrons but where one atom has a larger share of the electrons and creates a slight (but not full) charge.
This molecule would be referred to as polar. The degree of polarity depends on the electronegativity of the bond which describes the proportion of how much each atom attracts the electron. This depends on the position in the periodic table.
For example F has higher electronegativity than Cl.
Describe why desflurane is harder to metabolise than isoflurane?
Isoflurane and desflurane have the same structure except for desflurane having an extra F in place of isoflurane Cl.
As F has greater electronegativity it forms a more polar intermediate bond. This makes desflurane harder to metabolise.
Isoflurane: HCF2-O-CHCLCF3
Desflurance: HCF2-O-CHFCF3
What are the different types of intermolecular bonds?
**Vand der Vaals: **Formed from the orbit of electrons round an atom at high speeds creating spontaneous dipole charges influencing the neighbouring dipole.
Dipole-Dipole: Permanent dipoles exist in polar molecules from the difference in electronegativity.
Hydrogen bonds: These are the strongest type of intermolecular attractive force. Occurs as a result of hydrogen
bonding to a strongly electronegative atom i.e. Oxygen, fluorine, nitrogen.
The polarity is much increased and is therefore a form of dipole-dipole.
attraction
In terms of drug receptor interactions, what is needed for a drug to exert an effect at a receptor?
To exert a response to a receptor, the drug needs to bind to its receptor and hold it there long enough to exert its effect. The primary attraction needs to:
1. Form rapidly
2. Be strong enough to hold the interaction together
3. Exert its attraction at a distance from the receptor
An ionic bond can fulfil these criteria (1 and 3) but needs extra hydrogen bonds or Van der Waal forces to hold the drug-receptor complex together for long enough to exert its effect.
What are the 2 ways in which covalent bonds are broken?
1. Homolytic fission
The bond breaks and each element take one of the electrons so now each element has a single electron free radicals. This requires UV light or high temperatures for this reaction.
2. Heterolytic fission
The more electronegative element takes both electrons and forms 2 oppositely charged ions. A positively charged ion (an electrophile) and a negatively charged ion (a nucleophile).
