Final answer:
To convert an alkyne to a ketone or aldehyde, oxidative cleavage with ozone and reductive workup or selective hydrogenation using a Lindlar catalyst and subsequent mild oxidation can be used.
Step-by-step explanation:
To convert an alkyne to a ketone or aldehyde, you can use a process called oxidative cleavage. One method involves the use of ozone (O3) in ozonolysis, followed by a reductive workup, typically with zinc (Zn) and acetic acid (HOAc), which cleaves the triple bond to form the corresponding carbonyl compounds. Alternatively, if only a partial oxidation is desired, such as in the conversion of a terminal alkyne to an aldehyde, the use of less harsh reagents like the Lindlar catalyst (a specially prepared palladium on calcium carbonate, treated with various forms of lead) along with hydrogen gas (H2) can selectively hydrogenate a triple bond to a cis-double bond. A subsequent mild oxidation (e.g., with PCC — Pyridinium chlorochromate) can yield the aldehyde. For internal alkynes leading to ketones, one can use hydrogenation with a poisoned catalyst like the Lindlar catalyst, followed by oxidation with reagents such as PCC.