Question

Which of the following bases can remove a proton from a terminal alkyne in a reaction that favors products? (CHECK ALL) A) CH3O− B) CH2=C−H C) NH3 D) F− E) CH3C−H2

Answer 1

The bases that can remove a proton from a terminal alkyne favoring the products are methoxide (CH3O−), vinyl carbanion (CH2=C−H), fluoride ion (F−), and alkyl carbanion (CH3C−H2).

Step-by-step explanation:

To determine which bases can remove a proton from a terminal alkyne favoring the products, we need to look for bases that are strong enough to deprotonate the alkyne (given their pKa of approximately 25). Given the information, we can assess the given options:

• A) CH3O−: Methoxide is a strong base and can deprotonate terminal alkynes.
• B) CH2=C−H: This species represents a vinyl carbanion, which is a strong base due to its instability and can deprotonate terminal alkynes.
• C) NH3: Ammonia is a weak base and cannot deprotonate terminal alkynes effectively.
• D) F−: Fluoride ion is a strong base and can deprotonate terminal alkynes.
• E) CH3C−H2: This species represents an alkyl carbanion, which is also a strong base and capable of deprotonating terminal alkynes.

Therefore, the correct bases that can remove a proton from a terminal alkyne are: A) CH3O−, B) CH2=C−H, D) F−, and E) CH3C−H2.

Answer 2

The bases that can remove a proton from a terminal alkyne favoring products are methoxide (CH3O−) and a carbanion (CH2=C−H), while ammonia (NH3) and ethanide (CH3C−H2) are not sufficiently strong, and fluoride (F−) is less likely due to high electronegativity.

Step-by-step explanation:

To determine which bases can remove a proton from a terminal alkyne in a reaction that favors products, we need to consider the acidity of the terminal alkyne and the basicity of the potential bases. Terminal alkynes have relatively acidic protons with a pKa of approximately 25, which means they require a sufficiently strong base to be deprotonated effectively.

CH3O− (methoxide) is a strong base, capable of deprotonating terminal alkynes.

CH2=C−H (a carbanion) is also a strong base and will remove a proton from a terminal alkyne.

NH3 (ammonia) is a weaker base compared to methoxide and carbanions, and does not favor the deprotonation of a terminal alkyne.

F− (fluoride) is a strong base, but due to its high electronegativity, it is less likely to act as a base in deprotonating terminal alkynes compared to the charged carbon species.

CH3C−H2 is not typically considered a strong base and is less likely than methoxide or a carbanion to deprotonate a terminal alkyne.

Therefore, the bases that can effectively remove a proton from a terminal alkyne are CH3O− (methoxide) and CH2=C−H (a carbanion).