In Wacker process, alkene is oxidised into aldehyde. CH2=CH2+
1
2
O2
PdCl2⋅CuCl2
───────▶
H2O
CH3CHO
(B)
Since on ozonolysis, only alkenes produce aldehydes, 'A' must be an alkene. To decide the structure of alkene that undergoes ozonolysis, bring the products together in such a way that O atoms are face to face and, replace O by double (=) bond. Thus,