Benzene (CAS 71-43-2): The parent aromatic hydrocarbon, C6H6. All six C-C bonds are equal (139 pm) due to delocalized π-electrons. Hückel rule: 4n+2 = 6 π electrons. A known carcinogen — replaced by toluene/xylene in most lab applications. Discovered by Faraday in 1825.
9:57:19 PM · Jul 8, 2026