Question 1

Which intermediate is formed during the halogenation of an alkene with bromine?

Accepted Answer

Bridged bromonium ion

Question 2

If the initial intensity of light ($$I_0) is 100 $$units and the transmitted intensity ($$I) is 10 $$units, what is the absorbance ($$A) of $$the solution according to the Beer-Lambert Law?

Accepted Answer

$$A = 2$$

Question 3

In a Diels–Alder reaction between cyclopentadiene and a dienophile with two aldehyde groups, what is the major product?

Accepted Answer

A bicyclic compound with two aldehyde groups at the bridgehead positions

Question 4

Which of the following annulenes is aromatic? (Assume all are planar and fully conjugated.)

Accepted Answer

A 14-$$\pi$$ electron annulene

Question 5

How many $$\pi$$ electrons are present in the compound propyne ($$C_3H_4$$)?

Accepted Answer

2

Question 6

Given the following compounds, classify them: A: ethyl chloride, B: vinyl chloride, C: chlorobenzene.

Accepted Answer

A: Alkyl halide, B: Vinyl halide, C: Aryl halide

Question 7

A molecule is cyclic, planar, fully conjugated, and contains 4 $$\pi$$ electrons. According to Hückel's rule, how is this molecule classified?

Accepted Answer

Antiaromatic

Question 8

The anion shown below is cyclic, planar, and fully conjugated with 10 $$\pi$$ electrons. According to Hückel's rule, what is its aromaticity and value of $$n$$?

Accepted Answer

Aromatic, $$n = 5$$

Question 9

Which of the following is a limitation of Friedel–Crafts alkylation?

Accepted Answer

Overalkylation occurs because adding alkyl groups to benzene activates the ring and makes it more reactive, thus promoting more alkylation.

Question 10

Why is acetylation a useful step in synthesizing para-substituted aniline compounds?

Accepted Answer

It prevents polysubstitution and directs electrophilic attack to para position.

Question 11

Which of the following statements best explains why sulfonic acid is a strong meta director in electrophilic aromatic substitution?

Accepted Answer

Its electron-withdrawing nature.

Question 12

A benzene ring with an electron-donating group undergoes bromination. What is the expected ratio of ortho to para isomers, and why?

Accepted Answer

2:1, because there are two ortho positions and one para position available for substitution.

Question 13

In the benzyne mechanism, why does the presence of an electron-withdrawing group lead to a highly regioselective product?

Accepted Answer

Because the electron-withdrawing group stabilizes the negative charge in the intermediate, favoring attack at a specific position.

Question 14

Which of the following best describes the mechanism for the reaction of aniline with $$Cl_2$$ and the reaction of 2-bromopyridine with $$NaOCH_3$$?

Accepted Answer

i) Electrophilic aromatic substitution; ii) Nucleophilic aromatic substitution

Question 15

A solution absorbs light such that $$I_0 = 200$ units and I = 20$ units. What is the absorbance (A$)?

Accepted Answer

$$A = 2$$

Question 16

Which of the following is the correct structure for the original compound if nitration of $$C_6H_4Cl_2$$ yields three isomeric products?

Accepted Answer

1,2-dichlorobenzene

Question 17

Which of the following best explains why a 14-$$\pi$$ electron annulene is aromatic?

Accepted Answer

It is planar, cyclic, fully conjugated, and follows Hückel's rule ($$4n+2$$ $$\pi$$ electrons, $$n=3).$$

Question 18

Which of the following is a correct statement about the product of side-chain oxidation of an alkylbenzene with $$H_2CrO_4$$ and heat?

Accepted Answer

All benzylic alkyl groups are oxidized to carboxylic acids.

Diels–Alder Reactions: Predicting Bridged Products and Stereochemistry

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