Phenol

Phenol, also known as carbolic acid, is an aromatic organic compound with the molecular formula C6H5OH. It is a white crystalline solid that is volatile. The molecule consists of a phenyl group (−C6H5) bonded to a hydroxyl group (−OH). It is mildly acidic and requires careful handling due to its propensity to cause chemical burns.

Quotes

 * Phenols and their ethers are ubiquitous in nature; some derivatives have medicinal and herbicidal applications, whereas others are important industrial materials. (...) phenols are stronger acids because of the neighboring aromatic ring.
 * K. Peter C. Vollhardt, Neil E. Schore (2011) Organic chemistry : structure and function 6th ed. Ch. 22 : Chemistry of Benzene Substituents


 * When a benzene ring bears enough strongly electron-withdrawing substituents, nucleophilic addition to give an intermediate anion with delocalized charge becomes feasible, followed by elimination of the leaving group (nucleophilic aromatic ipso substitution). Phenols result when the nucleophile is hydroxide ion, arenamines (anilines) when it  is ammonia, and alkoxyarenes when alkoxides are employed. Very strong bases are capable  of eliminating HX from haloarenes to form the reactive intermediate benzynes, which are  subject to nucleophilic attack to give substitution products. Phenols may also be prepared  by decomposition of arenediazonium salts in water and by Pd-catalyzed hydroxylations of  haloarenes.
 * K. Peter C. Vollhardt, Neil E. Schore (2011) Organic chemistry : structure and function 6th ed. Ch. 22 : Chemistry of Benzene Substituents