show how you would use acetylene and any necessary alkyl halides, organic reagents, and/or inorganic reagents to synthesize trans-2-pentene
Submitted by lbell3
Replies
Submitted by Matt
This is an alkyne synthesis question.
Here's the general strategy to form a new carbon-carbon bond in first semester organic chemistry:
1. Starting with a terminal alkyne, form an acetylide ion (which is a nucleophile) using a strong base, such as sodium amide (NaNH2).
2. Now that you have a nucleophile, add an alkyl halide (which is an electrophile). The acetylide will attack the alkyl halide, forming a new carbon-carbon bond.
3. That's most of the work. But in this problem, you're not done yet. The last step is to convert an alkyne to a trans-alkene. This is done using dissolving metal conditions- Na or Li in ammonia. (If you wanted the cis alkene, you would use H2/ Lindar's catalyst.
See the image.
Submitted by Matt
Hmm, and I realize I misread the question somewhat:
We're not starting with "some alkyne." We have to start with acetylene, C2H2. So the first two steps of the reaction would be to make the three-carbon alkyne I started with in the attached image (propyne).
So the first two steps would be:
1. Acetylene + NaNH2 -> Acetylide
2. Acetylide + methyl bromide -> propyne.
