Question

substituents can be rationalized in terms of inductive and to your knowledge of these effects explain the following observat igma (o) constants associated with meta and para terms of inductive and resonance influences. Using The o constant for the nitro group (-NO2) is more positive than in the meta position (cm=0.71). oup (-NO2) is more positive (p = 0.78) in the para position [3 marks] d. Predict the signs (positive or following reactions and briefly justify your answer by illust cons and briefly justify your answer by illustrating the mechanisms. ve) of the reaction constant, p, in each of the ÇOCHE ÇOCH Br + Brz HBr NaOAc, AcOH OEt + HCI o + CH3CH2OH .com 25 °C 0 [2 x 2 marks]

Answer 1

Sigma constant (substitution constant) define the effect of various substituents on the reaction rates that is either promoting the reaction or inhibiting the reaction.
Answer ay (substitution constant) is a measure of the ability of the substituent to modify the properties of son like acidic strength, rate of the okwek. of the Rebeld To Substituent has no effect Tatue e promoting the reaction ra-ves in freipting the sow windo' which will proceed easily without substitution. for example - Taking the acidic strength of benzoic acid. 70 verkon — xe o eleefron density incsenges at -coon carbon ultim- -ately electron density Pancreases om benzene ving S0, 44 X=4 o no effes on veidie strong th x = e with drawing group Increases the acidic strength T = +ve x = e-donating group & decreases the acidic strength o -ve & estee Similarly in case of base catalysed hydrolysis of dan o o cost doet 7 d oet . do 6 e-density for high at Corbemyl carbon so for inhensement of reception é-density must be decrease.

Answer ay (substitution constant) is a measure of the ability of the substituent to modify the properties of son like acidic strength, rate of the okwek. of the Rebeld To Substituent has no effect Tatue e promoting the reaction ra-ves in freipting the sow windo' which will proceed easily without substitution. for example - Taking the acidic strength of benzoic acid. 70 verkon — xe o eleefron density incsenges at -coon carbon ultim- -ately electron density Pancreases om benzene ving S0, 44 X=4 o no effes on veidie strong th x = e with drawing group Increases the acidic strength T = +ve x = e-donating group & decreases the acidic strength o -ve & estee Similarly in case of base catalysed hydrolysis of dan o o cost doet 7 d oet . do 6 e-density for high at Corbemyl carbon so for inhensement of reception é-density must be decrease.