Propan-2-ol is to be changed into propanoic acid…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Propan-2-ol is to be changed into propanoic acid. Use only these arrows: secondary alcohol to alkene (concentrated sulphuric acid); alkene to primary alcohol (borane, then alkaline peroxide); primary alcohol to carboxylic acid (acidified dichromate under reflux). Find the number of steps. Each step has an yield. Find the overall yield, and the mass of propanoic acid from () of propan-2-ol. Use for propanoic acid.
Need a reminder? The key ideaShow
Work from the target backwards. A Grignard reagent adds its R group to a carbonyl carbon. A carbocation can shift a hydrogen or a methyl group to a more stable cation. The overall yield of a route is the product of its step yields, and a count of the starting material divides by that yield.
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.
Given. Three arrows, per step, of start.
Step 1. The route. Secondary alcohol to alkene (propene), alkene to primary alcohol (propan-1-ol), primary alcohol to acid: 3 steps.
Step 2. Overall yield. , which is .
Step 3. Mass. .
Check. No other route is shorter, because the secondary alcohol cannot be oxidised to an acid directly, and the acid needs a primary alcohol.
Answer: 3 steps, and .
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