Formaldehyde to acetaldehyde
`underset("Formaldehyde")(HCHO)overset(CH_(3)MgBr)rarrunderset(["Addition compound"])(CH_(3)CH_(2)OMgBr)overset(H_(2)O)rarrunderset("Ethyl alcohol")(CH_(3)CH_(2)OH) underset(K_(2)Cr_(2)O_(7)//H_(2)SO_(4))overset("Oxidation")rarrunderset("Acetaldehyde")(CH_(3)CHO)`