Condensation Reactions

Aldol condensation (Reactions involving hydrogen):- it is a chemical reaction in which two or more molecules of same or different carbonyl compounds containing hydrogen atom unite together in the presence of dilute base such as NaOH,Ba(OH)₂ or K₂CO₃, etc,. to from compounds calle aldols. The term aldol is derived from the combination of words aldehyde and alcohol, the two functional groups present in the product. In such condensation, the hydrogen of one molecule in alfa-position with respect to the carbonyl group enters into combination with the oxygen of the carbonyl group of the other molecule forming a hydroxyl group.

Characteristics of Aldol Condensation

(i)This reaction may take place between (a) same or different aldehydes, (b)an aldehyde and a ketone and (c) same or different ketones. The carbonyl compound must contain an alfa-hydgogen atom which is involved in aldol condensation. However, formaldehyde though contains no alfa-hydrogen atom yet undergoes aldol condensation.

(ii) New carbon to carbon linkage is formed.

(iii) The condensation product, i.e., aldol, loses a molecule of water to form unsaturated aldehyde or keton.