0 votes
in Chemistry by (29.7k points)

Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile, E+ 

(a)Chlorobenzene, 2,4-dinitrochlorobenzene, p-nitrochlorobenzene 

(b)Toluene, p-H3C–C6H4–NO2, p-O2N–C6H4–NO2

1 Answer

+1 vote
by (128k points)
selected by
Best answer

Electrophiles are reagents that participate in a reaction by accepting an electron pair in order to bond to nucleophiles. The higher the electron density on a benzene ring, the more reactive is the compound towards an electrophile, E+ (Electrophilic reaction). 

(a) The presence of an electron withdrawing group (i.e., NO2and Cl) deactivates the aromatic ring by decreasing the electron density. Since NO2group is more electron withdrawing (due to resonance effect) than the Cl group (due to inductive effect), the decreasing order of reactivity is as follows: Chlorobenzene > p – nitrochlorobenzene > 2, 4 – dinitrochlorobenzene 

(b) While CH3 is an electron donating group, NO2 group is electron withdrawing. Hence, toluene will have the maximum electron density and is most easily attacked by E+. NO2 is an electron withdrawing group. Hence, when the number of NO2– substituents is greater, the order is as follows: Toluene > p–CH3–C6H4–NO2, p –O2 N–C6H4–NO2

Welcome to Sarthaks eConnect: A unique platform where students can interact with teachers/experts/students to get solutions to their queries. Students (upto class 10+2) preparing for All Government Exams, CBSE Board Exam, ICSE Board Exam, State Board Exam, JEE (Mains+Advance) and NEET can ask questions from any subject and get quick answers by subject teachers/ experts/mentors/students.