Question 1

Which of the following statements best explains why terminal alkynes are more acidic than alkenes or alkanes?

Accepted Answer

The sp-hybridized carbon in alkynes holds the negative charge closer to the nucleus, increasing acidity.

Question 2

What is the product of the reaction between 1-butyne and sodium amide ($$\mathrm{$$NaNH_2$$}) $$followed by reaction with ethyl bromide ($$\mathrm{C_2H_5Br}$$)?

Accepted Answer

$$\mathrm{CH_3CH_2C \equiv CCH_2CH_3}$$

Question 3

Which reagent would you use to selectively hydrogenate an alkyne to a cis-alkene?

Accepted Answer

Lindlar's catalyst

Question 4

A compound with the formula $$\mathrm{C_6H_{10}}$$ reacts with $$\mathrm{Br_2$} to $$give a single dibromo product. Which of the following structures is most consistent with this observation?

Accepted Answer

A symmetrical alkyne such as 2-butyne

Question 5

Which of the following statements about enantiomers is correct?

Accepted Answer

Enantiomers have identical physical properties except for their interaction with plane-polarized light.

Question 6

How many stereoisomers are possible for 2,3-dibromobutane?

Accepted Answer

3

Question 7

Which of the following best describes the product(s) formed when 2-butyne is treated with excess $$\mathrm{Br_2$} in$$ $$\mathrm{$$CCl_4$$}$$?

Accepted Answer

Tetrabromoalkane

Question 8

Which of the following is the correct IUPAC name for the compound $$\mathrm{CH_3C \equiv CCH_2CH_3}$$?

Accepted Answer

2-pentyne

Question 9

Which of the following reagents will convert a terminal alkyne into a carbanion suitable for nucleophilic substitution?

Accepted Answer

Sodium amide ($$\mathrm{$$NaNH_2$$})$$

Question 10

Which of the following statements about SN2 reactions is correct?

Accepted Answer

The reaction rate depends on both the substrate and the nucleophile concentrations.

Question 11

What is the major product when 1-hexyne undergoes hydroboration-oxidation using $$\mathrm{Sia_2BH}$$ followed by $$\mathrm{H_2O_2/NaOH}$$?

Accepted Answer

Hexanal ($$\mathrm{CH_3CH_2CH_2CH_2CH_2CHO})$$

Question 12

Which of the following best describes the stereochemistry of the product formed when an alkyne undergoes reduction with sodium in liquid ammonia?

Accepted Answer

Trans-alkene

Question 13

Which of the following is NOT a factor that affects the rate of an SN1 reaction?

Accepted Answer

Strength of the nucleophile

Question 14

A racemic mixture is best described as:

Accepted Answer

A 1:1 mixture of two enantiomers

Question 15

Which of the following reactions will produce a meso compound?

Accepted Answer

Syn addition of $$\mathrm{Br_2$} to $$cis-2-butene

Question 16

Which of the following best describes the product of ozonolysis of 2-butyne?

Accepted Answer

Two molecules of acetic acid ($$\mathrm{CH_3COOH})$$

Question 17

Which of the following is the correct R/S designation for the chiral center in (R)-2-butanol?

Accepted Answer

The OH group is on the right in the Fischer projection.

Question 18

Which of the following statements about the reaction of acetylide ions with epoxides is correct?

Accepted Answer

The acetylide ion attacks the less substituted carbon of the epoxide, opening the ring.

Question 19

Which of the following best explains why tertiary alkyl halides favor elimination (E2) over substitution (SN2) reactions?

Accepted Answer

Steric hindrance prevents backside attack by the nucleophile in SN2 reactions.

Question 20

Which of the following is the correct rate law for an SN1 reaction?

Accepted Answer

$$\mathrm{rate = k[substrate]}$$

Organic Chemistry 3rd Exam Study Guide

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