Why is dilute base used in aldol condensation?

Well, we know that we use dilute base in Aldol Condensation because In Aldol Condensation we have a Aldehyde or ketone having alpha Hydrogen ( which should be acidic in nature) , now as we know that OH- is a Nucleophilic base i.e it can act both as a base and as a Nucleophile (when acidic Hydrogen is absent).

Why conc NaOH is not used in aldol condensation?

NaOH) and alkoxides (e.g., NaOCH2CH3) are usually not be suitable because they produce only low concentrations of the enolate anions, and the remaining -OH or -OR can cause unwanted side reactions. In other words, these nucleophilic bases will simply react directly with the alkyl halide via an SN2 reaction.

Which base is used in aldol condensation?

The aldol addition product can be dehydrated via two mechanisms; a strong base like potassium t-butoxide, potassium hydroxide or sodium hydride deprotonates the product to an enolate, which eliminates via the E1cB mechanism, while dehydration in acid proceeds via an E1 reaction mechanism.

Why is conc NaOH used in Cannizzaro reaction?

A 50\% concentrated NaOH solution is generally used in Cannizaro reaction as it is used for aldehydes which do not have α-H. (There are a few exceptions though) In normal aldol condensation, alpha hydrogens are more acidic so a weaker base can abstract it.

What is the difference between aldol condensation and crossed aldol condensation?

Aldol condensation: An addition reaction between two aldehydes, two ketones, or an aldehyde and a ketone, resulting in a β-hydroxy aldehyde or a β-hydroxy ketone. A crossed aldol condensation uses two different aldehyde and/or ketone reactants.

Why strong base is used in Cannizzaro reaction?

It is important to remember that the the Cannizzaro reaction is restricted to non-enolizable aldehydes. The strong base used for this reaction would initiate aldol and other reactions that take place via enolate anions. In this reaction the alcohol and acid products combine to form an ester.

What does the base do in an aldol condensation reaction?

In an aldol condensation, an enolate ion reacts with a carbonyl compound in the presence of acid/base catalyst to form a β-hydroxy aldehyde or β-hydroxy ketone, followed by dehydration to give a conjugated enone. It is a useful carbon-carbon bond-forming reaction.

Which compound does not give aldol condensation?

Thus, propanal and ethanal are the aldehydes that can undergo aldol condensation. However, methanol though does not contain α− hydrogen atom yet undergoes cross aldol condensation in the presence of limewater. Thus, aldehydes that do not undergo aldol condensation are trichloroethanal, benzaldehyde and methanal.

What happens when aldehyde reacts with conc NaOH?

Reagents : commonly a base such as NaOH or KOH is added to the aldehyde. The reaction involves an aldehyde enolate reacting with another molecule of the aldehyde. The products of these reactions are β-hydroxyaldehydes or aldehyde-alcohols = aldols. The simplest aldol reaction is the condensation of ethanal.

Why is aldol condensation base catalysed?

The reaction proceeds with the condensation of an aldehyde (or carbonyl compound) with an enol. The product formed has an aldehyde (or carbonyl) group and a β-hydroxy (alcohol) group, giving the product the name aldol (or if the carbonyl compound is a ketone it maybe called a ketol).

Why ketones do not give Cannizzaro reaction?

Cannizzaro reaction involves a hydride ion shift from the carbonyl carbon that is attacked by the base to another carbonyl carbon (as depicted in the mechanism). Since, there is no hydrogen attached to the carbonyl carbon in a ketone therefore it does not undergo cannizzaro reaction.