Quiz 5: Friedel-Crafts Reaction of 1,4-dimethoxybenzene

Question 1

What is the theoretical yield of product (250.38 g/mol) in mg if you started with 250 mg of 1,4-dimethoxybenzene (MW = 138.16 g/mol) and 0.45 mL of t butanol (MW = 74.12 g/mol | D = 0.775 g/mL)?

A. 450 mg
B. 360 mg
C. 620 mg
D. 530 mg

Answer 1

A

Question 2

How many different signals are observed in 1H NMR for the product of the Friedel-Crafts reaction of 1,4-dimethoxybenzene?

A. 2
B. 3
C. 4
D. 5

Answer 2

B

Question 3

What is the integration value of the peak of the most shielded proton in the product in 1H NMR spectrum?

A. 2
B. 3
C. 6
D. 18

Answer 3

D

Question 4

TLC of the product was conducted on a silica plate using 6:4 hexane:ethyl acetate as solvent. A Rf value of 0.97 was determined. How should the conditions be changed for a better TLC plate?

A. change ratio to 8:2 of hexane : ethyl acetate, increasing the amount of hexane
B. increase sample amount
C. add a few drops of methanol to hexane : ethyl acetate solvent mixture
D. both a (change ratio of 8:2) and c (add drops of methanol) could be done

Answer 4

A

Question 5

What is the role of sulfuric acid in this reaction?

A. help solubilize reactants
B. catalyzes generation of nucleophile
C. protonates 1,4-dimethoxybenzene in the 1st step of the electrophilic substitution reaction
D. catalyzes the generation of the electrophile in the reaction

Answer 5

D

Question 6

How many different signals are expected in the 13C NMR spectrum of the product in the Friedel-Crafts reaction of 1,4-dimethoxybenzene?

A. 4
B. 5
C. 6
D. 7

Answer 6

C

Question 7

What is the expected splitting pattern of the aromatic protons in 1H NMR of the product?

A. singlet
B. doublet
C. triplet
D. multiplet

Answer 7

A

Question 8

During the alkylation of 1,4-dimethoxybenzene, concentrated sulfuric acid is added slowly to the reaction mixture. Why are the acid and the reaction mixture are kept cold during the addition?

A. minimize rearrangement reactions
B. prevent evaporation of solvent
C. prevent t-butanol from solidifying
D. addition of the acid is exothermic and the temperature must be kept under control

Answer 8

D

Question 9

Which of the following statements are true?

A. 1,4-dimethoxybenzene is activated towards aromatic substitution reactions
B. further alkylation of product is likely due to steric interactions
C. methoxy groups in reactant are meta directors in aromatic substitution reactions
D. all of the above

Answer 9

A

Question 10

What is the electrophile in this reaction?

Answer 10

a tertiary carbocation from t-butanol