Q: Which product is formed when 2-methyl-2-butene reacts with HBr in the presence of peroxides?

$$\mathrm{1\text{-}Bromo\text{-}2\text{-}methylbutane}$$

Question 1

Which of the following statements best describes the stereochemistry of catalytic hydrogenation of alkenes using a metal catalyst such as Pt, Pd, or Ni?

Accepted Answer

The hydrogen atoms add to the same side of the alkene (syn addition).

Question 2

In the presence of peroxides (ROOR), the addition of HBr to an alkene proceeds via which mechanism and leads to which regioselectivity?

Accepted Answer

Radical mechanism, anti-Markovnikov addition

Question 3

Which of the following best explains why hydroboration-oxidation of 1-hexene yields 1-hexanol as the major product?

Accepted Answer

The boron atom adds to the less substituted carbon, resulting in anti-Markovnikov orientation.

Question 4

Which product is formed when 2-methyl-2-butene reacts with HBr in the presence of peroxides?

Accepted Answer

$$\mathrm{1	ext{-}Bromo	ext{-}2	ext{-}methylbutane}$$

Question 5

Which of the following statements about the halogenation of alkenes (e.g., addition of Br$$_2) is $$correct?

Accepted Answer

The addition is anti, resulting in bromines on opposite sides.

Question 6

A student treats cyclohexene with Br$$_2 in $$CCl$$_4. $$Which stereochemical outcome is expected for the product?

Accepted Answer

A racemic mixture of trans-1,2-dibromocyclohexane enantiomers

Question 7

Which of the following best describes the product mixture when an optically inactive alkene undergoes hydrohalogenation with HCl?

Accepted Answer

The product mixture is optically inactive (either achiral or racemic).

Question 8

Which reagent(s) would you use to convert 1-hexene to 2-hexanol with Markovnikov regioselectivity and no carbocation rearrangement?

Accepted Answer

$$\mathrm{1.\ Hg(OAc)_2,\ H_2O,\ 2.\ $$NaBH_4$$}$$

Question 9

Which of the following is true regarding the Simmons–Smith reaction?

Accepted Answer

It converts alkenes to cyclopropanes using $$\mathrm{CH_2I_2}$$ and Zn(Cu).

Question 10

Which of the following best explains why rearrangement occurs during the acid-catalyzed hydration of 3,3-dimethyl-1-butene?

Accepted Answer

The reaction proceeds via a carbocation intermediate, which can rearrange to a more stable carbocation.

Question 11

Which of the following reagents would you use to achieve syn dihydroxylation of an alkene?

Accepted Answer

$$\mathrm{$$OsO_4$$}$$, $$\mathrm{$$NaHSO_3$$}$$

Question 12

A student performs ozonolysis on an unknown alkene and isolates two products: ethanal ($$\mathrm{CH_3CHO}) $$and propanone ($$\mathrm{CH_3COCH_3}). $$What was the original alkene?

Accepted Answer

$$\mathrm{2	ext{-}Methyl	ext{-}2	ext{-}butene}$$

Question 13

Which of the following statements about oxymercuration-demercuration is correct?

Accepted Answer

It is regioselective for Markovnikov addition and does not allow carbocation rearrangement.

Question 14

Which of the following best describes the stereochemistry of the addition of Br$$_2 to (E)-2-$$butene?

Accepted Answer

The product is meso-2,3-dibromobutane.

Question 15

Which of the following is a key feature of the mechanism for halohydrin formation from an alkene and Br$$_2 in $$water?

Accepted Answer

The nucleophile (water) attacks the more substituted carbon of the bromonium ion.

Question 16

Which of the following statements about the addition of carbenes to alkenes is correct?

Accepted Answer

The stereochemistry of the alkene is retained in the cyclopropane product.

Question 17

Which of the following best explains why only two stereoisomers are formed in the bromination of trans-2-butene?

Accepted Answer

The addition is anti, so only the meso compound is formed.

Question 18

Which of the following is the correct sequence of steps for the acid-catalyzed hydration of an alkene?

Accepted Answer

Protonation of the alkene, nucleophilic attack by water, deprotonation

Question 19

Which of the following reagents would you use to convert an alkene to an epoxide?

Accepted Answer

A peracid such as $$\mathrm{mCPBA}$$

Addition Reactions of Alkenes: Mechanisms, Stereochemistry, and Synthetic Applications

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