Question 1

Which of the following statements best describes the stereochemistry of halogenation (e.g., Br$_2$ addition) of alkenes in an inert solvent such as CH$_2$Cl$_2$?

Accepted Answer

The addition is anti, and the two bromines add to opposite faces of the double bond.

Question 2

What is the major organic product when 1-butene reacts with Br$_2$ in water?

Accepted Answer

2-bromo-1-butanol

Question 3

Which reagent would you use to convert cyclohexene into a trans-1,2-cyclohexanediol?

Accepted Answer

1. mCPBA, 2. H$_3$O$^+$

Question 4

Which of the following best explains why no carbocation rearrangement occurs during the halogenation of alkenes?

Accepted Answer

The reaction proceeds via a concerted mechanism with a cyclic halonium ion intermediate.

Question 5

What is the product of the reaction between 2-methyl-2-butene and mCPBA?

Accepted Answer

A single epoxide, 2,3-epoxy-2-methylbutane

Question 6

Which of the following statements about catalytic hydrogenation of alkenes is correct?

Accepted Answer

The reaction requires a palladium or platinum catalyst and results in syn addition.

Question 7

Which of the following best describes the product(s) when 1,2-dimethylcyclohexene is treated with OsO$_4$ followed by NaHSO$_3$?

Accepted Answer

A mixture of cis-1,2-diol enantiomers

Question 8

Which of the following is true regarding the formation of halohydrins from alkenes?

Accepted Answer

The hydroxyl group adds to the more substituted carbon due to nucleophilic attack by water.

Question 9

Which of the following reactions would produce a racemic mixture of enantiomers?

Accepted Answer

Addition of HBr to 2-butene

Question 10

What is the expected product when 1-hexene is treated with ozone followed by dimethyl sulfide (DMS)?

Accepted Answer

Propanal and butanal

Question 11

Which of the following statements about the stereochemistry of dihydroxylation using OsO$_4$ is correct?

Accepted Answer

The two hydroxyl groups add to the same face of the double bond (syn addition).

Question 12

Which of the following best describes the mechanism of epoxidation of alkenes with peroxyacids?

Accepted Answer

It proceeds via a concerted mechanism with syn addition.

Question 13

A student treats 2-methyl-2-butene with Br$_2$ in CH$_2$Cl$_2$. Which of the following is the major product?

Accepted Answer

2,3-dibromo-2-methylbutane

Question 14

Which of the following is a key difference between halogenation and hydrohalogenation of alkenes?

Accepted Answer

Halogenation proceeds via a cyclic halonium ion, while hydrohalogenation proceeds via a carbocation intermediate.

Question 15

Which of the following statements about the stereochemistry of catalytic hydrogenation is correct?

Accepted Answer

The hydrogens add to the same face of the double bond (syn addition), producing cis products.

Question 16

Which of the following best describes the product(s) when 1,2-dimethylcyclohexene is treated with mCPBA?

Accepted Answer

A racemic mixture of cis-epoxides

Question 17

Which of the following is true about the formation of stereoisomers in the addition of Br$_2$ to (E)-2-butene?

Accepted Answer

Both enantiomers and diastereomers are formed.

Question 18

Which of the following statements about the formation of diols from alkenes is correct?

Accepted Answer

Syn diols are formed by OsO$_4$ or cold KMnO$_4$, while anti diols are formed by epoxidation followed by acid hydrolysis.

Question 19

A chemist wants to convert cyclohexene into a cyclohexane. Which reagent should they use?

Accepted Answer

H$_2$, Pd/C

Question 20

Which of the following best describes the product(s) when 1-methylcyclohexene is treated with Br$_2$ in water?

Accepted Answer

Trans-2-bromo-1-methylcyclohexanol

Chapter 9: Alkenes (Part 2) – Addition Reactions and Stereochemistry

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