22 Questions
What is the impact of replacing a methoxy group with a SOMe group on the log P value?
Decreases log P to 1.2
How are log P values typically determined?
Experimental determination
What does a positive hydrophobicity constant (π) indicate about a substituent compared to hydrogen?
More hydrophobic than H
How are log P values calculated for lead compounds when modified with different substituents?
Based on π values
What is the role of Hammett substituent constant (σ) for aromatic substituents?
Expresses electronic effects
How are steric effects quantified in drug design?
Difficult to quantify
What is the interpretation for the lower activity of 4‐Br in comparison to Cl?
The lower activity of 4‐Br could be due to the larger hydrophobicity.
Why is the 4-Nitro derivative considered to have the highest activity?
The NO2 group has a smaller hydrophobicity and a large electron-withdrawing effect.
What is the general trend observed for high activities in relation to hydrophobicity and electronic effects?
High activities are obtained with a large value of σ and a smaller value of π.
Why are tables of substituent constants useful in drug design?
Tables of substituent constants help decide which bioisosteres to use in drug design.
What is the rule-of-thumb suggested for the number of molecules to be synthesized per parameter studied in QSAR studies?
At least 5 molecules should be synthesized per parameter studied.
Why is it recommended not to use substituents that could ionize or be metabolized in initial QSAR studies?
To avoid interference with the initial QSAR equation generation.
What is the purpose of QSAR studies?
To identify/quantify physicochemical properties of a drug and establish their effect on biological activity.
Why is it best to focus on two or three physicochemical properties in QSAR?
To establish relationships with molecules that vary in one property at a time while keeping the other properties roughly constant.
What is the significance of the partition coefficient, P, in QSAR studies?
The hydrophobic character of a molecule is crucial for interactions with targets and crossing membranes.
What does a small range of log P values imply in a linear relationship?
A small range of log P values results in a linear relationship between hydrophobicity and biological activity.
What happens when the hydrophobicity of a molecule increases beyond log P = 4?
The molecule may become insoluble or remain in the lipid bilayer, potentially decreasing its biological activity.
What log P value is associated with the highest biological activity for general anaesthetics?
A log P of 2.3 is associated with the highest biological activity for general anaesthetics.
What type of relationship is often obtained when analyzing the anaesthetic properties of ethers?
A parabolic relationship is often obtained, with the maximum indicating the highest biological activity.
What does a linear relationship between log P values and biological activity suggest?
A linear relationship suggests a direct correlation between hydrophobicity and biological activity.
How can changing log P values affect the presence of side effects like CNS effects?
Changing log P values can help remove CNS side effects by altering the drug's ability to enter the CNS.
Why is it important to fit QSAR data using various equations and consider errors?
Fitting data using different equations and considering errors helps make accurate predictions for new molecules.
Test your knowledge on how substituent groups impact the log P value of compounds and their physiological effects. Learn about experimental determination of log P values and estimating them using substituent hydrophobicity constants.
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