Question
Steric hindrance can be used to control ____
Answer
Steric hindrance can be used to control where a reaction occurs in a molecule.
How? Protecting groups may make it too hard for a nucleophile, oxidizing agent, or reducing agent to access or react with a part of the molecule.
Example: Aldehydes and ketones will readily react with strong reducing agents like LiAlH4—but this can be prevented by first reacting the aldehyde or ketone with two equivalents of alcohol, producing a nonreactive acetal or ketal. After we complete the rest of the desired reactions, we can then regenerate the carbonyl with aqueous acid.
Note: In addition to making hydroxyl groups of alcohols into better leaving groups for nucleophilic substitution reactions, mesyl and tosyl groups can also serve as protecting groups when we do not want alcohols to react.
In Summary: The leaving-group ability of a substituent correlates with the strength of its conjugate acid. Both depend on the ability of the leaving group to accommodate negative charge. In addition to the halides Cl2, Br2, and I2, sulfates and sulfonates (such as methane and 4 methylbenzenesulfonates) are good leaving groups. Good leaving groups are weak bases, the conjugate bases of strong acids.
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Under ____ conditions, mixtures of carboxylic acids and alcohols will condense into esters.
Under acidic conditions, mixtures of carboxylic acids and alcohols will condense into ____.
Under acidic conditions, mixtures of ____ will condense into esters.
Treating triacylglycerols with NaOH will produce ____.
Treating ____ will produce fatty acid salts (soap) as well as glycerol.
Certain cyclic anhydrides can be formed simply by ____ carboxylic acids.