Write a route from ethanal to butan-1-ol, with the reagent of each step…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Write a route from ethanal to butan-1-ol, with the reagent of each step. Count the carbons in the starting material and the product, and say which kind of reaction joins them. How many steps does your route have? Say which one step makes the carbon-carbon bond.
Need a reminder? The key ideaShow
Work backwards from the target and count the carbons first. Cyanide and RMgX with CO add one carbon, an aldol joins two molecules, and soda lime or the haloform reaction removes one. The overall yield of a route is the product of the step yields. The degree of unsaturation is . The tests are 2,4-DNP (any aldehyde or ketone), Tollens (aldehydes), Fehling (aliphatic aldehydes) and iodoform (CHCO-).
The worked solution
Have you tried it?
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.
Step 1. Ethanal has 2 carbons and butan-1-ol has 4. Two molecules of ethanal must join, so use the aldol reaction.
Step 2. First step. Dilute sodium hydroxide, then heat. This gives but-2-enal, . This is the step that makes the carbon-carbon bond.
Step 3. Second step. Hydrogen with nickel (or palladium) reduces the C=C and the C=O. The product is butan-1-ol.
Answer: 2 steps, and the product has 4 carbons.
Check. Count the hydrogen added: but-2-enal, , takes two molecules of to give .
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