In ozonolysis with reductive workup, if the alkene is terminal, what is produced as one of the fragments?

• A. Formaldehyde
• B. Carbon dioxide
• C. Methanol
• D. Propyne

Answer: (A)

In ozonolysis with reductive workup, the double bond is cleaved and each carbon becomes a carbonyl. For a terminal alkene, the end carbon that was CH2 becomes formaldehyde (H2C=O) because that terminal carbon carries two hydrogens, which end up as the carbonyl carbon of formaldehyde. The other fragment is the remaining piece attached to the internal carbon, now as an aldehyde or ketone depending on substitution.

So one of the fragments is formaldehyde. Under oxidative workup, that same terminal carbon could be oxidized further to formic acid or CO2, but reductive workup preserves the carbonyls and yields formaldehyde as the fragment from the terminal end. The other choices don’t arise in this standard reductive scenario: carbon dioxide would come from oxidative conditions, methanol would require a different reduction pathway, and propyne isn’t produced from simply cleaving the alkene.