Question

How are 1-butyne and 2-butyne different from each other?

Answer 1

Answer on Question #43825 - Chemistry - Inorganic Chemistry

Question:

How are 1-butyne and 2-butyne different from each other?

Solution:

1-butyne and 2-butyne both belong to alkyne hydrocarbons. The molecular formula of these compound is $\mathrm{C_4H_6}$ , but their structures are different. As these compounds are alkynes, there is triple bond C-C, but the position of triple bond is changed. So, 1-butyne and 2-butyne are geometric isomers with position isomerism.

It is clear that the position of triple bond in 2-butyne is more sterically restricted than one in 1-butyne. Therefore, 1-butyne is more active in chemical reactions that its isomer. It is flammable and is more active in addition reactions. In addition, intermolecular bonds in 1-butyne are weaker than in 2-butyne because of asymmetric position of triple bond in 1-butyne.

1-butyne can react with ammonia mixture of Ag or Cu (I) oxides, butyllithium, sodium amide, Grignard reagent, instead of 2-butyne, which does not react with such oxides. This type of chemical reaction is qualitative for terminal (triple bond is located near the first carbon atom) alkynes:

$$\begin{array}{l} C _ {2} H _ {5} - C \equiv C - H + \left[ \mathrm {A g} \left(\mathrm {N H} _ {3}\right) _ {2} \right] \mathrm {O H} \rightarrow C _ {2} H _ {5} - C \equiv C - \mathrm {A g} \downarrow + 2 \mathrm {N H} _ {3} + 2 \mathrm {H} _ {2} \mathrm {O} \\ C _ {2} H _ {5} - C \equiv C - H + N a N H _ {2} \rightarrow C _ {2} H _ {5} - C \equiv C - N a + N H _ {3} \\ C _ {2} H _ {5} - C \equiv C - H + \mathrm {L i C} _ {4} H _ {9} \rightarrow C _ {2} H _ {5} - C \equiv C - \mathrm {L i} + C _ {4} H _ {1 0} \\ C _ {2} H _ {5} - C \equiv C - H + R M g B r \rightarrow C _ {2} H _ {5} - C \equiv C - M g - X + H B r \\ \end{array}$$

Answer: 1-butyne and 2-butyne are geometric isomers with different position of functional group. Their physical and chemical properties differ.

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