Download Discussion Sheet 11

Discussion Worksheet #11
Alcohols As Key Intermediates in Multistep Synthesis
Skill 1: Alcohols as functional group intermediates
 Alcohols can be made from many functional groups
 Alcohols can be made into many functional groups
Problem 1. Fill in the reagents for these reactions
Problem 2. Fill in the reagents for these reactions, as well as functional group names.
Problem 3. Use problems 1 and 2 as a flow chart to propose two step transformations with
alcohols as synthetic intermediates.:
Skill 2: Alcohols can be made into leaving groups
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Alcohols can be made into a variety of leaving groups
This opens up possibilities for Sn2 and E2 reactions.
Problem 4: Elimination of alcohols can be performed with POCl3 or concentrated sulfuric acid,
but these are sometimes limited. Explain why the following reaction won’t work, and propose an
alternative.
Problem 5. Explain why the following substitution reaction will not work, and provide an alternative.
Skill 3: Reactions of alcohols are key C-C bond forming steps in multistep synthesis
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Oxidation of alcohols produce electrophiles that can be used in a future C-C bond
forming step
Transformation of an alcohol into an alkylhalide, followed by Grignard formation, allows
an alcohol to be made into a nucleophile
Problem 6: Is an electrophile or nucleophile needed in each reaction? Provide the necessary
reagents.
Skill 4: Protecting groups
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Alcohols are week acids. If a strong base is used in a reaction, the alcohol must be
protected.
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Silyl ethers are good options to protect alcohols because they are unreactive under basic
conditions, but then can be removed easily.
Problem 7. Use a protecting group in each of these syntheses. Explain why it is necessary in each
case.