Question 1

Which of the following statements best describes the mechanism of halogenation of alkenes using $$\mathrm{Br_2$} or$$ $$\mathrm{Cl_2$}$$?

Accepted Answer

It forms a cyclic bromonium or chloronium ion intermediate, resulting in anti addition.

Question 2

During hydrohalogenation of an asymmetrical alkene with $$\mathrm{HBr}$$, which product is favored and why?

Accepted Answer

The product where Br adds to the more substituted carbon, due to Markovnikov's rule and carbocation stability.

Question 3

Which reagent is commonly used to convert an alkene into an epoxide via syn addition?

Accepted Answer

Meta-chloroperoxybenzoic acid ($$\mathrm{mCPBA})$$

Question 4

What is the major product when 1-butene reacts with $$\mathrm{Br_2$} in $$water?

Accepted Answer

3-bromo-2-butanol

Question 5

Which statement correctly describes the difference between acid-catalyzed hydration and oxymercuration-demercuration of alkenes?

Accepted Answer

Oxymercuration-demercuration avoids carbocation rearrangements by forming a mercurinium ion intermediate.

Question 6

Which of the following best explains why halohydrin formation is an anti addition?

Accepted Answer

The cyclic halonium ion intermediate forces the nucleophile to attack from the opposite side.

Question 7

Which reagent combination is used for syn dihydroxylation of alkenes to form 1,2-diols?

Accepted Answer

Osmium tetroxide ($$\mathrm{$$OsO_4$$}) $$and N-methylmorpholine N-oxide (NMO)

Question 8

Which of the following is true about the oxidation and reduction of alkenes?

Accepted Answer

Reduction of an alkene involves the addition of $$\mathrm{H_2$}$$ across the double bond, forming an alkane.

Question 9

What is the role of potassium permanganate ($$\mathrm{$$KMnO_4$$}) in $$alkene chemistry?

Accepted Answer

It fully oxidizes alkenes, cleaving both $$\sigma$$ and $$\pi$$ bonds to form carboxylic acids or ketones.

Question 10

Which statement about hydroboration-oxidation of alkenes is correct?

Accepted Answer

It adds an OH group to the less substituted carbon (anti-Markovnikov) in syn fashion.

Question 11

Which of the following best describes the product of ozonolysis of cyclohexene?

Accepted Answer

A single molecule of adipic acid (hexanedioic acid)

Question 12

What is the expected stereochemistry of the product when $$\mathrm{H_2$} is $$added to an alkene using a palladium on carbon catalyst?

Accepted Answer

Syn addition, forming cis-alkane products.

Question 13

Which intermediate is NOT formed during the halogenation of alkenes with $$\mathrm{Cl_2$} or$$ $$\mathrm{Br_2$}$$?

Accepted Answer

Carbocation

Question 14

Which of the following reactions would you use to convert an alkene into a cyclopropane ring?

Accepted Answer

Reaction with $$\mathrm{CH_2I_2}$$ and $$\mathrm{Zn(Cu)}$$

Question 15

In the acid-catalyzed hydration of an alkene, which atom acts as the nucleophile in the key step?

Accepted Answer

Water ($$\mathrm{H_2O})$$

Question 16

Which of the following is a correct statement about the formation of halohydrins from alkenes?

Accepted Answer

The halogen adds to the less substituted carbon and water adds to the more substituted carbon.

Question 17

Which of the following is NOT a product of alkene oxidation using $$\mathrm{mCPBA}$$?

Accepted Answer

Alkyl halide

Question 18

Which reaction mechanism allows for rearrangement and formation of multiple products due to carbocation intermediates?

Accepted Answer

Acid-catalyzed hydration

Question 19

Which of the following statements about carbenes is correct?

Accepted Answer

Carbenes are highly reactive intermediates with only 6 valence electrons.

Ochem: Chapter 8 Alkene Reactions

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