Organic Chemistry : Help with Alkyne Synthesis
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Example Question #2 : Hydrocarbons
What is the best reagent for abstracting a hydrogen from ethyne?
None of these
The triple bond in ethyne makes the hydrogens slightly more acidic than those found in ethane. A very strong base, such as the conjugate base of ammonia, would be able to abstract that hydrogen. The abstraction turns the base into ammonia. It also creates a carbanion that can be used for chain extension and alkyne synthesis.
Example Question #1 : Organic Chemistry
What is the product of the compound when it reacts with two equivalents of base?
2-pentyne
1-pentyne
1-pentene
None of these
2-pentene
2-pentyne
For each equivalent of base, a pi bond is formed between the carbons initially bound to the bromine atoms. For each bond formed, a bromine leaving group leaves the hydrocarbon. One equivalent of base abstracts a hydrogen. The electrons from the bond to the hydrogen create a pi bond. This occurs twice, and a triple bond is formed. The result is a 5-carbon chain with a triple bond between the second and third carbons. This molecule is 2-pentyne.
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