The influence of the substituent X on dopamine D2 receptor antagonism in a serie
ID: 140718 • Letter: T
Question
The influence of the substituent X on dopamine D2 receptor antagonism in a series of potential anti-psychotic salicylamides (structure shown below) has been studied. A Hansch analysis yielded the following equation:
please answer b and d
Q1. The influence of the substituent X on dopamine Dz receptor antagonism in a series of potential anti-psychotic salicylamides (structure shown below) has been studied. A Hansch analysis yielded the following equation: log (1 / ICso)-1.28 -0.5 18 -_ 0.692 meta + 1.495 Et OCH3 (a) Explain the significance of the sign and magnitude of the coefficient to the structure-activity relationship. (2 marks) (b) Explain the significance of the sign and magnitude of the t coefficient to the structure-activity relationship. (2 marks) (c) Explain the significance of the sign and magnitude of the net, coefficient to the structure-activity relationship. (2 marks) (d) Which compound should be the more potent D, receptor antagonist-the derivative where X- Br or X-NO? Support your answer. (Use the table of substituent constants provided) (3 marks)Explanation / Answer
B) lipophilicity constant. It is the contribution of individual atoms and groups to the partition coefficient, it allows to predict the contribution of substituents to lipophilicity.
D) the Ic50 is the concentration that produces 50% inhibition or antagonism to the receptor, applying the hansch equation Br = 2.05 and No2 = 0.6053, then we can suppose that the best antagonist is NO2 since it requires a lower concentration to produce its antagonistic activity. Furthermore, the inductive effect to attract electrons from the NO2 group leaves the non-binding electrons of the OH group of dopamine less available and reduces the affinity of these functional groups for the aqueous phase. This then increases its liposolubility.
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