Sodium butanoate, CH₃CH₂CH₂COONa, and 1-bromobutane are the starting materials for three…
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Sodium butanoate, , and 1-bromobutane are the starting materials for three preparations.
- The salt is heated with soda lime.
- A concentrated solution of the salt is electrolysed.
- 1-Bromobutane is warmed with sodium in dry ether.
Find the number of carbon atoms in the alkane that each method makes, and name each alkane.
Need a reminder? The key ideaShow
Hydrogenation and reduction of an alkyl halide keep the number of carbon atoms. The Wurtz reaction doubles the carbon atoms of the halide. Heating a sodium salt with soda lime removes the carboxyl carbon. Kolbe electrolysis joins two alkyl groups, each with the carboxyl carbon removed. An alkane has the formula .
The worked solution
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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Plan. The salt has carbon atoms. Its alkyl group, , has . The halide has .
Step 1. Soda lime. The carboxyl carbon leaves as carbonate: carbon atoms. The alkane is propane.
Step 2. Kolbe. Two alkyl groups of carbon atoms join: . The alkane is hexane.
Step 3. Wurtz. Two groups of carbon atoms join: . The alkane is octane.
Answer: (a) , propane. (b) , hexane. (c) , octane.
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