Question

QUESTIONS ON HYDROGEN ACIDITY AND SUBSTITUTION REACTIONS. EXPLANATIONS TOO PLEASE.

8) Which of the labeled H atoms (1 -5) in the following molecule would be predicted to be themost はa (lic? 4 H 3 2 H A) 1 B) 2 C) 3 D) 4 E) 5

Answer 1

10) Which of the following is the most reactive toward nucleophilic aromatic substitution? Cl Since -NO2 is an electron withdrawing group it activates benzene ring towards nucleophilic substitution Compound IV, having two NO2 gr will be most reactive towards nucleophilic substitution NO2 IV. Cl NO2 Cl C1 но NO2 CH3 Cl A) I C) IlI D) IV E) V

9) Based upon the following energy profile diagram for the first step of an electrophilic aromatic substitution reaction, which of the following substituents is X mostly likely to be? ortho para meta benzene E+ tiine A) OCH3 B) CH3 C) CO2H D) CI Since -OCH3 is a strong electron donating group so when X is -OCH3, it will strongly acitvate the benzene ring towards electrophilic suhstitution (ortho/para substitution) rather than -CH3, -CI which are less strong electron donating group. Moreover, -CO2H gr which is a electron with drawing gr will deacitvate the benzene ring towards electrophilic suhstitution and only meta subštitution is preferred. So in the energy profile diagram, ortho.para pdt will have highest energy in case of-CO2H

8) Which of the labeled H atoms (1-5) in the following molecule would be predicted to be the most acidic? H's atom marked 1 & 2 are allylic protons so they are acidic as the corresponding conjugate bases will be resonance stabilized as is it in conjugation with C C bond Whereas H's atom marked 3, 4 & 5 are vinylic protons so they are much less acidic as the corresponding conjugate bases cannot bve stabilized by resonance as is it directly attached with C C bond Now, between H's atom marked 1 & 2, H marked 1 will be more acidic as resulting conjugate base is a 6e system which is aromatic in character. However, for H marked 2 the resulting conjugate base is a 4Tte system which is not aromatic in character. 5 H3C H 3 C)3 D) 4 5 НН