Describe the following:
(a) Crossed Aldol condensation.

Explanation

When two aldehydes each containing at least one -hydrogen atom are treated with dilute alkali, four different products are obtained of which two are cross-aldol condensation products and the other two are self aldol condensation products as shown:
`CH_(3) - CH_(2) - CHO + CH_(3) CHO overset("OH")to CH_(3)-CH_(2)-CH_(2)-CHO`
Propanal     Ethanal      `underset("3-hydroxypentana"l)(OH)`.
(b) Saponification: When an ester is hydrolysed in a basic medium it is known as saponification.
`CH_(3)underset("Ethyl acetat"e)(COOC_(2))H_(5)+NaOHtoCH_(3)underset("sod acetate")(COO^(-))Na^(+)+C_(2)underset(E"thano"l)(H_(5))OH`