Question 1

Which of the following statements best explains why N-bromosuccinimide (NBS) is commonly used for allylic bromination in organic synthesis?

Accepted Answer

NBS generates Br$$_2 in $$situ, allowing for selective radical bromination at the allylic position without excess bromination.

Question 2

A chemist reacts 1-bromopropane with sodium ethoxide in ethanol. Which mechanism is most likely, and what is the major product?

Accepted Answer

E2 mechanism; the major product is propene ($$\mathrm{CH_2$=$$CHCH_3$$}).$$

Question 3

Which of the following alkyl halides would react fastest in an SN2 reaction with a strong nucleophile?

Accepted Answer

Ethyl bromide ($$\mathrm{CH_3CH_2Br})$$

Question 4

A Grignard reagent ($$\mathrm{RMgBr}) is $$reacted with carbon dioxide, followed by acid workup. What is the final organic product?

Accepted Answer

A carboxylic acid ($$\mathrm{RCOOH})$$

Question 5

Which of the following best describes the difference between SN1 and SN2 mechanisms?

Accepted Answer

SN1 involves a carbocation intermediate and is favored by polar protic solvents; SN2 is concerted and favored by polar aprotic solvents.

Question 6

Which reagent would best convert a primary alcohol to an alkyl chloride?

Accepted Answer

SOCl$$_2 ($$thionyl chloride)

Question 7

In the Suzuki-Miyaura reaction, which of the following is a necessary component for successful cross-coupling?

Accepted Answer

A palladium catalyst

Question 8

Which of the following statements about E2 elimination reactions is correct?

Accepted Answer

E2 reactions are favored by strong bases and anti-periplanar geometry between the leaving group and hydrogen.

Question 9

A student is asked to predict the major product of the following reaction: 2-bromobutane is treated with potassium tert-butoxide. Which product is favored and why?

Accepted Answer

1-butene, because the bulky base favors the less substituted (Hofmann) alkene.

Question 10

Which of the following statements about the use of Grignard reagents is correct?

Accepted Answer

Grignard reagents are strong nucleophiles and bases, and react with carbonyl compounds to form alcohols.

Question 11

Which of the following is the correct order of reactivity for alkyl halides in SN1 reactions?

Accepted Answer

Tertiary \u003e Secondary \u003e Primary

Question 12

A chemist wants to prepare an alkyl halide from an alcohol. Which method is most appropriate for converting a secondary alcohol to a secondary alkyl bromide?

Accepted Answer

React the alcohol with PBr$$_3 ($$phosphorus tribromide)

Question 13

Which of the following best describes the role of Zaitsev's rule in elimination reactions?

Accepted Answer

It predicts that the most substituted alkene will be the major product.

Question 14

Which of the following is a key difference between a Gilman reagent and a Grignard reagent?

Accepted Answer

Gilman reagents are organocuprates and react selectively with acid chlorides, while Grignard reagents are organomagnesium compounds and react with a wide range of electrophiles.

Question 15

A student is given the following reaction: $$\mathrm{CH_3CH_2Br}$$ + $$\mathrm{NaCN}$$ $$\rightarrow$$ ? Which product is formed and by which mechanism?

Accepted Answer

$$\mathrm{CH_3CH_2CN}$$ via SN2 mechanism

Question 16

Which of the following statements about the oxidation of alcohols is correct?

Accepted Answer

Primary alcohols can be oxidized to aldehydes and further to carboxylic acids.

Question 17

Which of the following is a common misconception about the SN2 reaction mechanism?

Accepted Answer

SN2 reactions are faster with tertiary alkyl halides.

Question 18

A chemist is analyzing the products of an E1 elimination reaction of 2-butanol. Which of the following is most likely to be the major product?

Accepted Answer

2-butene ($$\mathrm{CH_3CH=$$CHCH_3$$})$$

Question 19

Which of the following best explains why tertiary alkyl halides undergo E2 elimination more readily than SN2 substitution?

Accepted Answer

Steric hindrance prevents nucleophilic attack, favoring elimination over substitution.

Exam 4 Study Guide: Alkyl Halides, Substitution & Elimination, and NMR Spectroscopy

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