Question

Give the chemical test to distinguish:

Formaldehyde and acetaldehyde

Answer 1

Formaldehyde and acetaldehyde
Acetaldehyde, when heated with I₂ and NaOH, gives a yellow precipitate of iodoform (Iodoform test) whereas formaldehyde does not give a yellow precipitate of iodoform.

\[\ce{\underset{\text{Acetaldehyde}}{CH3CHO} + 4NaOH + I2 ->[\Delta]\underset{\text{Iodoform}}{CHI3} + HCOONa + 3H2O + 3NaI}\]