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Reduction (and removal of labels) of aldehydes and ketones from sodium borohydride (NaBH4)

In the open plugin for the Reagent Guide, I discuss the different reagents commonly found in Org 1/Org 2 every Friday. Version 1.2 has just been released with various fixes and a new page index.

Having talked about the oxidation ladder, it makes sense to start working on reagents for oxidation and reduction reactions.

Sodium borohydride (NaBH4)

Uses: Sodium borohydride is a good reducing agent. Although not as strong as lithium aluminum hydride (LiAlH4), it is very effective at reducing aldehydes and ketones to alcohol. It generally does not reduce esters, carboxylic acids, or amides (although it does reduce acid chlorides to alcohols). It is used in the second stage of the oxymorcurium reaction, replacing mercury (Hg) with H.

Reduction Of Aldehydes And Ketones With NaBH4

For our purposes, sodium borohydride is good for one thing: it reduces aldehydes and ketones. In this sense, climb a rung on the ladder of oxidation. Here are some practical examples.
Consider this pattern: we break the C-O key and replace it with the C-H key. This helps us classify the response as a reduction.

Note also that we form the O – H bond. Textbooks and other sources are sometimes unclear here: To make alcohol, the oxygen must extract the proton (H+) from the water or acid added after it is complete the reaction (note). : This is commonly called work).

Reduction Of Aldehydes And Ketones With NaBH4

The reaction mechanism of sodium borohydride with aldehydes and ketones proceeds in two steps. In the first step, H(-) is separated from BH4(-) and added to the carbonyl carbon (example of [1,2] coupling). It forms a CH bond and breaks the CO bond, creating a new pair of electrons on the oxygen, negatively charged oxygen (FYI: we call these negatively charged oxygens alkoxides because they are deprotonated alcohol). In the second step, protons (or acid, such as NH4Cl) add to the alcohol to form the alcohol. This is done at the end of the action, called a run-in.

Alcohols of Carbonyl Compounds: Reduction

Aldehydes, ketones, and alcohols are common properties of biomolecules. Mutation between these compounds is a common occurrence in many biological pathways. However, there are no semiotic compounds like sodium borohydride in the battery. Instead, some borohydride donors play a similar role.

NADH is a common biological reducing agent. Unlike ion donors that donate hydrides to carbonyl groups, NADH is actually a neutral donor. Provides carbonyl hydride under specific conditions. In the process, it forms cationic NAD+. However, since the nicotinamide ring is aromatic, NAD+ is stable. It is not aromatic in NADH.

Reduction of carboxylic acids and esters

Carboxylic acids can be converted to alcohols using lithium aluminum hydride (LiAlH4). Note that NaBH4 is not strong enough to convert carboxylic acids or esters to alcohols. The aldehyde is produced intermittently during this reaction, but cannot be isolated as it is more reactive than the parent carboxylic acid.

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