Why LiAlH4 reduces esters but NaBH4 Cannot reduce them?

The key difference between LiAlH4 and NaBH4 is that LiAlH4 can reduce esters, amides and carboxylic acids whereas NaBH4 cannot reduce them. But LiAlH4 is a very strong reducing agent than NaBH4 because the Al-H bond in the LiAlH4 is weaker than the B-H bond in NaBH4. This makes the Al-H bond less stable.

Why does NaBH4 not reduce carboxylic acids?

Reduction of Carboxylic Acids The carbonyl carbon of a carboxylic acid is even more electrophilic than the carbonyl carbon in an aldehyde or ketone. However, there is also an acid proton from the carboxylic acid that can react with hydride reagents. For this reason, sodium borohydride does not reduce a carboxylic acid.

Why is NaBH4 used instead of LiAlH4?

Sodium borohydride NaBH4 is less reactive than LiAlH4 but is otherwise similar. It is only powerful enough to reduce aldehydes, ketones and acid chlorides to alcohols: esters, amides, acids and nitriles are largely untouched. It can also behave as a nucleophile toward halides and epoxides.

What is the functional group that is reduced by LiAlH4 but not by NaBH4?

A significant number of functional groups react with LiAlH4 but not with NaBH4; among such groups are alkyl halides, alkyl tosylates, and nitro groups. Sodium borohydride can be used as a reducing agent in the presence of these groups.

What happens when reduction of carboxylic acid with LiAlH4?

Carboxylic acids can be converted to 1o alcohols using Lithium aluminum hydride (LiAlH4). An aldehyde is produced as an intermediate during this reaction, but it cannot be isolated because it is more reactive than the original carboxylic acid.

Can NaBH4 reduce carboxylic acids?

Standard organic chemistry texts discuss the lower re- activity of NaBH4 compared with lithium aluminum hy- dride, LiAlH4: whereas LiAlH4 reduces carboxylic acids to primary alcohols, NaBH4 does not reduce carboxylic acids.

What does LiAlH4 do to esters?

Ch20: Reduction of Esters using LiAlH4 to 1o alcohols. Carboxylic esters are reduced give 2 alcohols, one from the alcohol portion of the ester and a 1o alcohol from the reduction of the carboxylate portion. Esters are less reactive towards Nu than aldehydes or ketones.

Does LiAlH4 reduce ethers?

Lithium Aluminium Hydride (LiAlH4, LAH) – much more reactive than NaBH4. LiAlH4 (in ether) reduces aldehydes, carboxylic acids, and esters to 1° alcohols and ketones to 2° alcohols.

How do carboxylic acids reduce to Ester?

Carboxylic acids, acid halides, esters, and amides are easily reduced by strong reducing agents, such as lithium aluminum hydride (LiAlH 4). The carboxylic acids, acid halides, and esters are reduced to alcohols, while the amide derivative is reduced to an amine.