Chemistry · Chapter 11
Study notes aligned to the official NEB syllabus.
Phenols are aromatic compounds in which one or more hydroxyl groups ($\ce{-OH}$) are directly attached to the carbon of a benzene ring. The simplest and most important is phenol (carbolic acid), $\ce{C6H5OH}$. Because the $\ce{-OH}$ is bonded to an $sp^2$ ring carbon, phenols behave very differently from alcohols (in which $\ce{-OH}$ is on an $sp^3$ carbon).
Nomenclature: the parent is phenol; substituted phenols use o-, m-, p- or the cresol names.
| Structure | Name |
|---|---|
| $\ce{C6H5OH}$ | phenol |
| 2-$\ce{CH3-C6H4-OH}$ | o-cresol (2-methylphenol) |
| 1,2-$\ce{C6H4(OH)2}$ | catechol (benzene-1,2-diol) |
| 1,4-$\ce{C6H4(OH)2}$ | quinol / hydroquinone |
$$ \begin{aligned} \ce{C6H5Cl + 2NaOH ->[623,K][300,atm] C6H5ONa + NaCl + H2O} \ \ce{C6H5ONa + HCl -> C6H5OH + NaCl} \end{aligned} $$
$$\ce{C6H5SO3H + 2NaOH ->[fuse] C6H5ONa + Na2SO3 + H2O}$$
$$\ce{C6H5N2+Cl- + H2O ->[\Delta] C6H5OH + N2(g) + HCl}$$
Cumene (isopropylbenzene) is air-oxidised to cumene hydroperoxide, which is decomposed by acid to phenol and propanone (a valuable by-product):
$$\ce{C6H5CH(CH3)2 ->[O2] C6H5C(CH3)2OOH ->[H+] C6H5OH + CH3COCH3}$$
Phenols are aromatic compounds in which one or more hydroxyl groups () are directly attached to the carbon of a benzene ring. The simplest and most important is phenol (carbolic acid), . Because the is bonded to an ring carbon, phenols behave very differently from alcohols (in which is on an carbon).
Nomenclature: the parent is phenol; substituted phenols use o-, m-, p- or the cresol names.
| Structure | Name |
|---|---|
| phenol | |
| 2- | o-cresol (2-methylphenol) |
| 1,2- | catechol (benzene-1,2-diol) |
| 1,4- | quinol / hydroquinone |
Cumene (isopropylbenzene) is air-oxidised to cumene hydroperoxide, which is decomposed by acid to phenol and propanone (a valuable by-product):