HardChemistryHigh School (11–12)Organic Compounds with Functional Groups › Alcohols, Phenols and EthersNumerical
Pentan-1-ol is made from 1-bromobutane. The bromide is converted to its Grignard reagent with…
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Pentan-1-ol is made from 1-bromobutane. The bromide is converted to its Grignard reagent with magnesium in dry ether. Methanal is added, and then water. Use of 1-bromobutane, for magnesium and for pentan-1-ol. Find the number of carbons in the product, the least mass of magnesium needed, and the mass of pentan-1-ol obtained from the whole route at a overall yield.
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. of 1-bromobutane, overall.
Step 1. Carbons. Four from the butyl group and one from methanal: 5.
Step 2. Magnesium. One for each bromide: .
Step 3. Alcohol. . Mass: .
Check. The product is a primary alcohol, as every Grignard reagent with methanal gives. The dry ether must be free of water, which would destroy the reagent.
Answer: 5 carbons, and .
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