Question 1

Which of the following compounds would you expect to be aromatic according to Hückel's rule?

Accepted Answer

Benzene

Question 2

Carbocation rearrangements are:

Accepted Answer

Common for Friedel-Crafts alkylations

Question 3

Given the following Friedel-Crafts reactions, how many are expected to succeed?

1. $\mathrm{CH_3{-}C_6H_5 + CH_3Cl \xrightarrow{AlCl_3}}$
2. $\mathrm{C_6H_5{-}Cl + CH_3Cl \xrightarrow{AlCl_3}}$
3. $\mathrm{C_6H_5{-}Br + CH_3Cl \xrightarrow{AlCl_3}}$

Accepted Answer

Reaction 1 only

Question 4

Which of the following is a necessary condition for a compound to be aromatic?

Accepted Answer

It must be cyclic, planar, and follow the $4n+2$ rule for pi electrons

Question 5

Which of the following statements about Friedel-Crafts alkylation is correct?

Accepted Answer

It is inhibited by electron-withdrawing groups on the aromatic ring

Question 6

A student attempts a Friedel-Crafts acylation on benzene using acetyl chloride and $\mathrm{AlCl_3}$. What is the major product?

Accepted Answer

$\mathrm{C_6H_5COCH_3}$ (acetophenone)

Question 7

Which of the following is NOT a limitation of the Friedel-Crafts alkylation reaction?

Accepted Answer

Formation of acylium ion

Question 8

Which of the following substituents will deactivate the benzene ring toward electrophilic aromatic substitution?

Accepted Answer

$\mathrm{-NO_2}$

Question 9

Which of the following is the correct order of reactivity toward electrophilic aromatic substitution for the following compounds?

$\mathrm{C_6H_5{-}NO_2}$, $\mathrm{C_6H_5{-}CH_3}$, $\mathrm{C_6H_6}$

Accepted Answer

$\mathrm{C_6H_5{-}CH_3} > \mathrm{C_6H_6} > \mathrm{C_6H_5{-}NO_2}$

Question 10

Which of the following is a correct statement about the acylium ion ($\mathrm{RCO^+}$) in Friedel-Crafts acylation?

Accepted Answer

It is formed by reaction of an acyl chloride with $\mathrm{AlCl_3}$

Question 11

A chemist wants to synthesize tert-butylbenzene from benzene. Which reagent should be used in the Friedel-Crafts alkylation?

Accepted Answer

$\mathrm{(CH_3)_3CCl}$ and $\mathrm{AlCl_3}$

Question 12

Which of the following is a reason why Friedel-Crafts alkylation fails with nitrobenzene?

Accepted Answer

The nitro group is a strong electron-withdrawing group

Question 13

Which of the following is the correct formula for the number of pi electrons required for aromaticity according to Hückel's rule?

Accepted Answer

$4n+2$

Question 14

Which of the following is a product of the reaction of benzene with $\mathrm{CH_3Cl}$ and $\mathrm{AlCl_3}$?

Accepted Answer

Toluene ($\mathrm{C_6H_5CH_3}$)

Question 15

Which of the following statements about carbocation rearrangements in Friedel-Crafts alkylation is correct?

Accepted Answer

They can lead to unexpected products due to hydride or alkyl shifts

Question 16

Which of the following is a limitation of Friedel-Crafts acylation compared to alkylation?

Accepted Answer

It does not result in polyacylation

Question 17

Which of the following is the best explanation for why Friedel-Crafts alkylation can result in polyalkylation?

Accepted Answer

Alkyl groups activate the ring toward further substitution

Question 18

Which of the following is the correct mechanism for the formation of the acylium ion in Friedel-Crafts acylation?

Accepted Answer

$\mathrm{RCOCl + AlCl_3 \rightarrow RCO^+ + AlCl_4^-}$

Question 19

Which of the following is a correct statement about the reactivity of halobenzenes in Friedel-Crafts alkylation?

Accepted Answer

Halobenzenes are less reactive due to the electron-withdrawing effect of halogens

Aromaticity and Friedel-Crafts Reactions: Study Notes

Study Guide - Practice Questions

Study Guide - Flashcards