QSAR Classification Model Quiz

1. What does the symbol P represent in a QSAR equation?

PH

Plasma Concentration

Partition coefficient

None of the above

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.

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. The QSAR equation relating to the insecticidal activity of a series of diethyl phenyl phosphonate versus σ is shown below.

What does r represent?

The number of compounds tested

The regression or correlation coefficient

Mean Square Error

The F Statistic

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.

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.

3. What value does the regression coefficient have for a perfect fit?

0.1

1

100

0

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.

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.

4. Calculate the logP value for the structure shown; logP for benzene = 2.13; π(OH) -0.67; π(CH3) 0.52 ?

3.32

1.98

1.53

2.12

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.

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.

5. What does MR represent in a QSAR equation?

Molar refractivity is a steric factor

Molar refractivity is an electronic factor

Molar refractivity is a hydrophobic factor

Molar refractivity is a stereoelectronic factor

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.

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.

6. What does a negative value of σ signify for a substituent?

It is electron donating

It is electron withdrawing

It is neutral

It is hydrophobic

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.

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.

7. What is the symbol π in a QSAR equation?

The electronic effect of a substituent

The substituent hydrophobicity constant

The hydrophobicity of the molecule

Steric parameter

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.

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.

8. Using the same equation in question 9 What does the term Σ πX represent in the equation?

The sum of the hydrophobic factors corresponding to the substituent X present in the molecule.

The sum of the electronic factors corresponding to the substituent X present in the molecule

The largest hydrophobic factor of the substituent X present in the molecule.

The smallest hydrophobic factor of the substituent X present in the molecule.

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.

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.

9. Which of the following statements is untrue when comparing 3D QSAR with conventional QSAR?

3D QSAR has a predictive quality unlike QSAR.

Experimental parameters are not required by 3D QSAR, but are for QSAR.

Only drugs of the same structural class should be studied by 3D QSAR or QSAR.

3D QSAR has a predictive quality unlike QSAR.

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.

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.

10. A series of phenanthrene derivatives are tested for antimalarial activity and found to fit the following Hansch equation:

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.

It indicates that activity falls to a minimum value as πsum increases to an optimum value, then rises again as πsum increases beyond that value.

It indicates that activity rises to a maximum value as πsum decreases to a certain value, then falls again as πsum decreases beyond that value.

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.

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.