How can aldehydes and ketones be prepared by: i) ozonolysis of alkenes ii) hydration of alkynes

 i) ozonolysis of alkenes

 

Overall transformation :  C=C to 2 x C=O Ozonolysis implies that ozone causes the alkene to break (-lysis) Reagents : ozone followed by : a reducing work-up, either Zn in acetic acid or dimethyl sulfide, (CH3)2S  an oxidising work-up, usually H2O2 (under these conditions, carboxylic acids are obtained instead of aldehydes) It is convenient to view the process as cleaving the alkene into two carbonyls The substituents on the C=O depend on the substituents on the original C=C. The work-up determines the oxidation state of the products
	REDUCTIVE work-up			OXIDATIVE work-up

 

ii) hydration of alkynes