Points to remember in Aldehyde and ketone

PYQ-2023 Aldehydes and Ketones Q4

Aldol condensation

PYQ-2023 General Organic Chemistry Q13

PYQ-2023 Aldehydes and Ketones Q5

PYQ-2023 Carboxylic Acid and Derivatives Q1

Carbonyl compounds having acidic $\mathrm{sp}^{3} \alpha-\mathrm{H}$ shows this reaction in presence of dil. $\mathrm{NaOH}$ or dil. acid.

Cannizzaro reaction

PYQ-2024-Aldehydes_and_Ketones-Q6, PYQ-2023 Carboxylic Acid and Derivatives Q2

Reimer Tiemann Reaction

PYQ-2024-Alcohols-Q4, PYQ-2024-Alcohols-Q6

Perkin reaction

When benzaldehyde (or any other aromatic aldehyde) is heated with the anhydride of an aliphatic acid (containing two $\alpha$-hydrogen atoms) in the presence of its sodium salt, condensation takes place to form a $\beta$-aryl acrylic acid ; e.g., with acetic anhydride and sodium acetate, cinnamic acid is formed.

$ C_6 H_5 CHO + ( CH_3 CO)_2 O \xrightarrow{ CH_3 CO_2 Na} C_6 H_5 CH = CHCO_2 H $

Mechanism

Haloform reaction

PYQ-2023 Aldehydes and Ketones Q3

Acetaldehyde and methylalkyl ketones react rapidly with halogen $(Cl_2, Br_2$ or $I_2$ ) in the presence of alkali to give haloform and acid salt.

contains acidic hydrogen atom and rest-part of alkyl methyl ketone give acid salt having carbon atom corresponding to alkyl ketone. Preparation of haloform from methylketone involves two steps.

(i) Halogenation

(ii) Alkaline hydrolysis

Other reactions :

- Oxidation of Alcohol

PYQ-2023 Aldehydes and Ketones Q9

PYQ-2023 Aldehydes and Ketones Q2

(i)

(ii)

(iii)

(iv)

(v)

Semicarbazide

PYQ-2024-Aldehydes_and_Ketones-Q5

Semicarbazide is frequently reacted with aldehydes and ketones to produce semicarbazones via a condensation reaction. This is an example of imine formation resulting from the reaction of a primary amine with a carbonyl group.

Acidity of $\alpha$-hydrogens of aldehydes and ketones:

The aldehydes and ketones undergo a number of reactions due to the acidic nature of a-hydrogen. The acidity of $\alpha$-hydrogen atoms of carbonyl compounds is due to the strong electron withdrawing effect of the carbonyl group and resonance stabilization of the conjugate base.

Keto and Enol content

PYQ-2024-Genral_Organic_Chemistry-Q10

The amount of keto or enol content depends on the stability of the state. carbon with electron withdrawing groups > carbonyl carbons > no. of alpha hydrogens.

Enol content is the number of structures formed after taking one H from its alpha position to carbonyl oxygen. The compound which makes the highest number of enol structure possible, will have the highest enol content.