Question 1

Which of the following statements best explains why ethynylestradiol is more potent than its naturally occurring analogues in oral contraceptives?

Accepted Answer

It contains a carbon–carbon triple bond, which increases its metabolic stability.

Question 2

What is the IUPAC name for the following compound: a straight-chain alkyne with eight carbons, a triple bond between C3 and C4, and two methyl groups at C6?

Accepted Answer

6,6-dimethyloct-3-yne

Question 3

Which of the following best describes the hybridization and geometry of the carbon atoms in acetylene ($$HC \equiv CH$$)?

Accepted Answer

sp hybridized, linear geometry, 180° bond angles

Question 4

Which base is strong enough to deprotonate a terminal alkyne such as acetylene?

Accepted Answer

$$NH_2$$^-$$

Question 5

When but-1-yne is treated with two equivalents of HBr, what is the major organic product?

Accepted Answer

2,2-dibromobutane

Question 6

Which of the following statements about the addition of water to an alkyne in the presence of $$H_2SO_4$$ and $$HgSO_4 is $$correct?

Accepted Answer

The initial product is an enol, which rapidly tautomerizes to a ketone.

Question 7

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

Accepted Answer

The sp hybridized carbon in alkynes has more s-character, stabilizing the negative charge on the conjugate base.

Question 8

A student wants to synthesize hex-1-yne ($$HC \equiv CCH_2CH_2CH_2CH_3) $$from an alkene. Which sequence of reactions would achieve this transformation?

Accepted Answer

Halogenation of the alkene to form a vicinal dihalide, followed by two successive E2 eliminations with a strong base

Question 9

Which product is formed when a terminal alkyne undergoes hydroboration–oxidation ($$1. R_2BH; 2. H_2O_2, HO^-$$)?

Accepted Answer

An aldehyde

Question 10

Which of the following is a limitation when using acetylide anions in nucleophilic substitution reactions with alkyl halides?

Accepted Answer

2° and 3° alkyl halides undergo elimination (E2) rather than substitution (SN2)

Question 11

Which of the following best describes the product when an acetylide anion reacts with an epoxide followed by aqueous workup?

Accepted Answer

An alcohol with a new carbon–carbon bond at the less substituted end of the epoxide

Question 12

Which of the following is a key advantage of using retrosynthetic analysis in organic synthesis?

Accepted Answer

It allows chemists to work backwards from the target molecule to identify simpler precursors and logical synthetic steps.

Question 13

Which of the following statements about the addition of hydrogen halides (HX) to alkynes is correct?

Accepted Answer

The reaction follows Markovnikov's rule, with both H atoms adding to the less substituted carbon.

Question 14

Which of the following best explains why resonance stabilization is important in the addition of HX to alkynes?

Accepted Answer

Resonance delocalizes the positive charge in the carbocation intermediate, increasing its stability and favoring Markovnikov addition.

Question 15

Which of the following is a real-world application of the chemistry of alkynes discussed in the study materials?

Accepted Answer

The use of synthetic alkynes in oral contraceptives to regulate hormone levels and prevent pregnancy

Question 16

Which of the following best describes the outcome when a vicinal dihalide is treated with two equivalents of a strong base such as $$NaNH_2$$?

Accepted Answer

An alkyne is formed by two successive E2 eliminations

Alkynes: Structure, Properties, Reactions, and Synthesis

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