Absorption Of Molecules 1

Question 1

Question: What are the three stages involved in the solution process of a drug molecule?

Answer 1

Removal of the drug molecule from its crystal.

Creation of a cavity from the molecule in the solvent.

Insertion of the drug molecule into this cavity.

Question 2

Question: How is the solubility of a substance defined?

Answer 2

Answer: The solubility of a substance is defined as the amount that goes into a solution when equilibrium is established between the solute in solution and the excess (undissolved) substance.

Question 3

Question: How is a solution described when it contains a drug at the limit of its solubility at a specific temperature and pressure?

Answer 3

Answer: When a solution contains a drug at the limit of its solubility at any given temperature and pressure, it is described as saturated.

Question 4

Question: What may occur if the solubility limit of a substance is exceeded in a solution?

Answer 4

Answer: If the solubility limit is exceeded, solid particles of the solute may be present in the solution.

Question 5

Question: What is the distinction between the dissolution rate and solubility of a substance?

Answer 5

Answer: The dissolution rate and solubility are not the same; the dissolution rate refers to how quickly something dissolves, while solubility refers to the amount that can be dissolved.

Question 6

Question: What are the factors that can influence the solubility of drugs in a solution?

Answer 6

• Temperature
• Molecular structure of the drug
  a) Shape and surface area
  b) Hydrophobicity and degree of ionization (influenced by pH)
• Nature of the solvent
  a) pH, cosolvents, solubilizing agents
• Crystal characteristics

Question 7

Question: What is the relationship between temperature and the solubility of a drug?

Answer 7

Answer: The solubility of a drug typically depends on temperature.

Question 8

Question: What do the melting and boiling points of a substance reflect?

Answer 8

Answer: The melting and boiling points of a substance reflect the strengths of interactions between the molecules.

Question 9

Question: How does the surface area of a drug molecule affect solubility?

Answer 9

Answer: The surface area of the drug molecule affects solubility because placing the solute molecule in the solvent cavity requires a number of solute-solvent contacts.

Question 10

Question: How do polar groups, such as -OH, in a drug molecule influence solubility?

Answer 10

Answer: Polar groups, such as -OH, capable of hydrogen bonding with water molecules, give higher solubility.

Question 11

Question: What effect do non-polar groups, such as -CH3 and -Cl, have on the solubility of a drug?

Answer 11

Answer: Non-polar groups, such as -CH3 and -Cl, are hydrophobic and impart low solubility.

Question 12

Question: How does ionization impact the solubility of a drug?

Answer 12

Answer: Ionization increases solubility.

Question 13

Question: Provide examples of relatively hydrophilic and hydrophobic functional groups.

Answer 13

Question 14

Question: How does ionization impact the hydrophilicity of a molecule?

Answer 14

Answer: Ionization causes increased hydrophilicity.

Question 15

Question: Define partitioning of drugs between immiscible solvents.

Answer 15

Answer: Partitioning refers to the distribution of drugs between solvents, typically occurring due to differences in solubility in different phases.

Question 16

Question: Provide an example of partitioning involving aqueous and lipid phases.

Answer 16

Answer: Drugs moving across cell walls, interacting with both aqueous and lipid phases.

Question 17

Question: How can antibiotics be involved in partitioning?

Answer 17

Answer: Antibiotics may partition into micro-organisms, reflecting their distribution between aqueous and lipid components in microbial cells.

Question 18

Question: Give an instance of drugs partitioning into materials like plastics.

Answer 18

Answer: Drugs may partition into plastics, indicating their distribution between the drug and the plastic material.

Question 19

Question: What does “Log P” refer to in molecular properties?

Answer 19

Answer: Log P is the logarithm of the partition coefficient, a measure indicating the lipophilicity or hydrophilicity of a molecule when it is in a unionized state.

Question 20

Question: How is Log P related to a drug’s ability to cross lipid membranes?

Answer 20

Answer: Log P is a crucial factor in a drug’s ability to cross lipid membranes, as it reflects the balance between a drug’s affinity for lipids (lipophilicity) and water (hydrophilicity).

Question 21

Question: What does the term “partition coefficient” signify in the context of Log P?

Answer 21

Answer: The partition coefficient, represented by Log P, measures the distribution of a substance between a lipophilic solvent (usually octanol) and a hydrophilic solvent (usually water).

Question 22

Question: How do you calculate Log P?

Answer 22

Answer:
𝐿𝑜𝑔 𝑃=𝐿𝑜𝑔 ([𝐶𝑜])/([𝐶𝑤])

It calculated as the ratio of the concentration of a compound in an organic solvent ([Co]) to its concentration in water ([Cw]).

Question 23

Question: What does a positive Log P value indicate about a molecule?

Answer 23

Answer: A positive Log P value suggests that the molecule is lipophilic, meaning it has a higher affinity for lipid (organic) phases.

Question 24

Question: How is a negative Log P interpreted in terms of a molecule’s properties?

Answer 24

Answer: A negative Log P value indicates hydrophilicity, signifying a greater affinity for water or aqueous phases.

Question 25

Question: What is the fundamental characteristic of crystals in terms of molecular arrangement?

Answer 25

Answer: Crystals exhibit highly ordered arrays of molecules and atoms, held together by non-covalent interactions.

Question 26

Question: Describe the variation observed in crystals of a particular substance.

Answer 26

Answer: Crystals of a given substance can vary in terms of size, the number of faces, and the types of faces present.

Question 27

Question: Provide examples of substances that form ionic solids.

Answer 27

Answer: Ionic solids include compounds such as aluminum hydroxide (Al(OH)₃), magnesium carbonate (MgCO₃), and magnesium trisilicate (Mg₂(Si₃O₈)).

Question 28

Question: Name a representative example of a molecular solid.

Answer 28

Answer: Omeprazole is an example of a molecular solid.

Question 29

Question: What characterizes molecular salts, and provide an example

Answer 29

Answer: Molecular salts are compounds formed between molecular substances and salts. An example is loperamide hydrochloride.

Question 30

Question: What influences the crystalline habits of compounds during crystallization?

Answer 30

Answer: Crystalline habits depend on the conditions of crystallization when compounds precipitate out of a solution.

Question 31

Question: What is a common feature of crystal habits formed under different conditions?

Answer 31

Answer: Crystal habits formed under different conditions typically have the same internal structure.

Question 32

Question: Can compounds crystallize with different internal structures, and what is this phenomenon called?

Answer 32

Answer: Yes, compounds can crystallize with different internal structures, and this phenomenon is known as polymorphism.

Question 33

Question: How do molecules arrange themselves in polymorphism?

Answer 33

Answer: In polymorphism, molecules can arrange themselves in different ways within the crystal structure.

Question 34

Question: What is the term commonly used to refer to different polymorphs?

Answer 34

Answer: Different polymorphs are often referred to as “Forms.”