ANS:D - Pyroles

Among the options provided, Pyroles is not a sulfur compound present in petroleum. Here's a breakdown of each term:

1. Thiophenes: Thiophenes are organic compounds containing a five-membered ring structure with a sulfur atom. They are commonly found in crude oil and refined petroleum products.
2. Mercaptans (Thiols): Mercaptans, also known as thiols, are organic compounds containing a sulfur atom bonded to a hydrogen atom and an alkyl or aryl group. They are characterized by their foul odor and are found in petroleum products.
3. Sulphones: Sulphones are organic compounds that contain a sulfonyl group (-SO2-). They can be formed as oxidation products of other sulfur compounds present in petroleum, but they are not typically native components of crude oil.
4. Pyroles: Pyroles (or pyrroles) are heterocyclic aromatic compounds containing a five-membered ring structure with one nitrogen atom. They are not sulfur compounds and are generally not present in significant quantities in petroleum.