1.
What does the symbol P represent in a QSAR equation?
Correct Answer
C. Partition coefficient
Explanation
The symbol P represents the partition coefficient in a QSAR equation. The partition coefficient is a measure of the distribution of a compound between two immiscible phases, typically a hydrophobic and a hydrophilic phase. It quantifies the tendency of a compound to distribute between these phases and is an important parameter in predicting the behavior of a compound in biological systems.
2.
What is the symbol π in a QSAR equation?
Correct Answer
B. The substituent hydrophobicity constant
Explanation
The symbol π in a QSAR equation represents the substituent hydrophobicity constant. In QSAR (Quantitative Structure-Activity Relationship), this constant is used to quantify the hydrophobicity of a substituent in a molecule. It helps in predicting the biological activity or properties of a compound based on its structure and the presence of different substituents.
3.
Calculate the logP value for the structure shown; logP for benzene = 2.13; π(OH) -0.67; π(CH3) 0.52 ?
Correct Answer
B. 1.98
Explanation
The logP value for a compound is a measure of its hydrophobicity, or how likely it is to dissolve in a nonpolar solvent. It is calculated based on the presence of different functional groups in the compound. In this case, benzene has a logP value of 2.13. The presence of an OH group decreases the logP value by -0.67, while the presence of a CH3 group increases the logP value by 0.52. Therefore, the logP value for the given structure can be calculated as follows: 2.13 - 0.67 + 0.52 = 1.98.
4.
What does MR represent in a QSAR equation?
Correct Answer
A. Molar refractivity is a steric factor
Explanation
Molar refractivity is a steric factor in a QSAR equation. Steric factors refer to the spatial arrangement and interactions between atoms and molecules. In the context of QSAR (Quantitative Structure-Activity Relationship), molar refractivity is used to describe the molecular size and shape, which can influence the biological activity of a compound. Therefore, the correct answer is that molar refractivity represents a steric factor in a QSAR equation.
5.
What does a negative value of σ signify for a substituent?
Correct Answer
A. It is electron donating
Explanation
A negative value of σ signifies that the substituent is electron donating. This means that the substituent donates electrons to the molecule it is attached to, which can result in increased electron density in the molecule. This electron donation can affect the reactivity and properties of the molecule, making it more nucleophilic or basic.
6.
Which of the following statements is untrue when comparing 3D QSAR with conventional QSAR?
Correct Answer
C. Only drugs of the same structural class should be studied by 3D QSAR or QSAR.
Explanation
The statement "Only drugs of the same structural class should be studied by 3D QSAR or QSAR" is untrue when comparing 3D QSAR with conventional QSAR. Both 3D QSAR and QSAR can be used to study drugs of different structural classes, not just drugs of the same structural class.
7.
The QSAR equation relating to the insecticidal activity of a series of diethyl phenyl phosphonate versus σ is shown below.
What does r represent?
Correct Answer
B. The regression or correlation coefficient
Explanation
The variable "r" in the QSAR equation represents the regression or correlation coefficient. This coefficient measures the strength and direction of the relationship between the diethyl phenyl phosphonate and its insecticidal activity. It indicates how well the observed data points fit the regression line or how closely they are correlated. A high value of "r" close to 1 indicates a strong positive correlation, while a value close to -1 indicates a strong negative correlation.
8.
A series of phenanthrene derivatives are tested for antimalarial activity and found to fit the following Hansch equation:
Correct Answer
A. It indicates that activity rises to a maximum value as πsum increases to an optimum value, then falls again as sum increases beyond that value.
Explanation
The given Hansch equation suggests that the activity of the phenanthrene derivatives increases to a maximum value when the πsum (a measure of the electronic properties of the molecule) increases to an optimum value. However, beyond this optimum value, as the πsum continues to increase, the activity of the derivatives starts to decrease again. This indicates that there is an optimal range of electronic properties for the derivatives to exhibit maximum antimalarial activity.
9.
Using the same equation in question 9
What does the term Σ πX represent in the equation?
Correct Answer
A. The sum of the hydrophobic factors corresponding to the substituent X present in the molecule.
Explanation
The term ΣπX represents the sum of the hydrophobic factors corresponding to the substituent X present in the molecule. This means that it is the sum of the values assigned to each substituent X based on its hydrophobicity. The hydrophobic factor represents how hydrophobic or nonpolar the substituent is, with higher values indicating higher hydrophobicity. Therefore, ΣπX calculates the total hydrophobicity of all the substituents X in the molecule by summing up their individual hydrophobic factors.
10.
What value does the regression coefficient have for a perfect fit?
Correct Answer
B. 1
Explanation
The regression coefficient represents the change in the dependent variable for a one-unit change in the independent variable. In a perfect fit, all data points lie exactly on the regression line, indicating that there is a perfect linear relationship between the variables. Therefore, the regression coefficient would be equal to 1, meaning that for every one-unit increase in the independent variable, the dependent variable increases by exactly one unit.