What functional group is used to protect aldehydes and ketones?
Acetals
Acetals are commonly used to protect the carbonyl groups of aldehydes and ketones from basic, nucleophilic reagents.
Which are good protecting groups for aldehyde?
Cyclic acetals and ketals are the most useful carbonyl (aldehyde or ketone) protecting groups.
How can we protect aldehydes and ketones?
Aldehydes and ketones were protected as their thioacetals in the presence of a catalytic amount of iodine. These mild reaction conditions were also applied in the transthioacetalization of O,O-acetals, O,O-ketals, O,S-acetals, and acylals.
What are good protecting groups?
Protecting groups are used in synthesis to temporarily mask the characteristic chemistry of a functional group because it interferes with another reaction. A good protecting group should be easy to put on, easy to remove and in high yielding reactions, and inert to the conditions of the reaction required.
Which reagent is useful for protecting an aldehyde functional group in synthesis?
Grignard reagents
Since, Grignard reagents resemble carbanion, so they are strong nucleophile and strong base. Their most useful nucleophilic reaction is addition to carbonyl group.
How can we protect alkenes?
The presence of a bromide substituent, instead of a hydrogen or methyl group, on a carbon–carbon double bond, protects the alkene from addition reactions when exposed to trifluoroacetic acid.
What are protecting group give example?
When a reduction of an ester is required in the presence of a carbonyl, the attack of the hydride on the carbonyl has to be prevented. For example, the carbonyl is converted into an acetal, which does not react with hydrides. The acetal is then called a protecting group for the carbonyl.
What are the uses of aldehydes in organic chemistry?
They can be used, for example, when a selective reduction of an ester is needed in the presence of an aldehyde or a ketone: Remember, aldehydes are more reactive than esters and when mixed with, for example LiAlH 4, they will react first before the ester is reduced and that is when the aldehyde is mostly gone:
How do you remove the protecting acetal from a diol ester?
So, what we do is first react the molecule with a diol forming a cyclic acetal, then reduce the ester with LiAlH 4 to an alcohol, and lastly, remove the protecting acetal by acid catalysis:
What happens to aldehydes when they are mixed with esters?
Remember, aldehydes are more reactive than esters and when mixed with, for example LiAlH 4, they will react first before the ester is reduced and that is when the aldehyde is mostly gone:
What is an example of a silyl ether protecting group?
Another very useful example uses tert-butyldimethylsilyl chloride (TBDMSCl) and imidazole to protect the alcohol as a silyl ether. The silyl ether protecting group can be removed by reaction with an aqueous acid or the fluoride ion.