Phenol (systematically named Benzenol, also called carbolic acid or phenolic acid) is an aromatic organic compound with the molecular formula . It is a white crystalline solid that is volatile. The molecule consists of a phenyl group () bonded to a hydroxy group (). Mildly acidic, it requires careful handling because it can cause chemical burns. Phenol was first extracted from coal tar, but today is produced on a large scale (about 7 billion kg/year) from petroleum-derived feedstocks. It is an important industrial commodity as a precursor to many materials and useful compounds. It is primarily used to synthesize plastics and related materials. Phenol and its chemical derivatives are essential for production of polycarbonates, epoxies, Bakelite, nylon, detergents, herbicides such as phenoxy herbicides, and numerous pharmaceutical drugs. Properties Phenol is an organic compound appreciably soluble in water, with about 84.2 g dissolving in 1000 mL (0.895 M). Homogeneous mixtures of phenol and water at phenol to water mass ratios of ~2.6 and higher are possible. The sodium salt of phenol, sodium phenoxide, is far more water-soluble. Acidity Phenol is a weak acid. In aqueous solution in the pH range ca. 8 - 12 it is in equilibrium with the phenolate anion (also called phenoxide or carbolate): C6H5OH <=> C6H5O- + H+ Phenol is more acidic than aliphatic alcohols. The differing pKa is attributed to resonance stabilization of the phenoxide anion. In this way, the negative charge on oxygen is delocalized on to the ortho and para carbon atoms through the pi system. An alternative explanation involves the sigma framework, postulating that the dominant effect is the induction from the more electronegative sp2 hybridised carbons; the comparatively more powerful inductive withdrawal of electron density that is provided by the sp2 system compared to an sp3 system allows for great stabilization of the oxyanion. In support of the second explanation, the pKa of the enol of acetone in water is 10.9, making it only slightly less acidic than phenol (pKa 10.0). Thus, the greater number of resonance structures available to phenoxide compared to acetone enolate seems to contribute very little to its stabilization. However, the situation changes when solvation effects are excluded. A recent in silico comparison of the gas phase acidities of the vinylogues of phenol and cyclohexanol in conformations that allow for or exclude resonance stabilization leads to the inference that about of the increased acidity of phenol is attributable