Answered by Shaykh Faraz Rabbani
Question: Is it permissible to buy alcohol with the intention of turning it into vinegar?
Answer: In the Name of Allah, Most Merciful & Compassionate
It would not be valid to buy wine with the intention of making vinegar. Rather, such a sale would be invalid (batil), because wine is in itself haram (haram li `aynihi) and not an item of considered value (mal mutaqawwim) for Muslims. [Ibn Abidin, Radd al-Muhtar; Marghinani, Hidaya, with al-`Inaya and Fath al-Qadir]
And Allah alone gives success.
Faraz Rabbani
(Originally answered on the SeekersGuidance Academy’s Islamic Law for Seekers: Transactions Course Forum)