Difference between revisions of "Phenol"
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The industrial method relies on the oxidation of cumene with air at 90-130°C in the presence of alkali additives (Udris-Sergeev process), resulting in cumene hydroperoxide, followed by cleavage with sulfuric acid into phenol and acetone: | The industrial method relies on the oxidation of cumene with air at 90-130°C in the presence of alkali additives (Udris-Sergeev process), resulting in cumene hydroperoxide, followed by cleavage with sulfuric acid into phenol and acetone: | ||
| − | :C<sub>6</sub>H<sub>5</sub>CH(CH<sub>3</sub>)<sub>2</sub> + O<sub>2</sub> | + | :C<sub>6</sub>H<sub>5</sub>CH(CH<sub>3</sub>)<sub>2</sub> + O<sub>2</sub> → C<sub>6</sub>H<sub>5</sub>C(CH<sub>3</sub>)<sub>2</sub>OOH → C<sub>6</sub>H<sub>5</sub>OH + CH<sub>3</sub>COCH<sub>3</sub> |
Other methods involve the hydrolysis of chlorobenzene, using a base (Dow's Process) or steam (Raschig–Hooker process), direct oxidation of [[benzene]] with [[nitrous oxide]], oxidation of toluene with air or the reaction of a strong base with benzenesulfonate. | Other methods involve the hydrolysis of chlorobenzene, using a base (Dow's Process) or steam (Raschig–Hooker process), direct oxidation of [[benzene]] with [[nitrous oxide]], oxidation of toluene with air or the reaction of a strong base with benzenesulfonate. | ||
| − | The most cheap and accessible method involves the thermal decomposition of [[salicylic acid]], that can either be purchased from the pharmacy or obtained from [[sodium salicylate]] by adding a strong acid. Gently heating salicylic acid in a tube yields molten phenol, giving off carbon dioxide and phenol vapors. A condenser can be used to recover the resulting phenol vapor, to increase the yield. The resulting impure phenol is dissolved in [[dichloromethane]], and filtered. The DCM is removed by gently heating the solution at 40°C. The resulting phenol has a purity between 95-98%.<ref>[https://books.google.ro/books?id=y5mZrW1KB_AC&pg=PA129&lpg=PA129&dq=phenol+from+salicylic+acid&source=bl&ots=IfPZNCSYJv&sig=i6RYWa1Hi8oSl0YyR_QV-iBBWKE&hl=en&sa=X&ei=h4xkUaiwN4rMiQKu14GoAQ#v=onepage&q=phenol%20from%20salicylic%20acid&f=false Kings Chem Guide, Edition 2, Jared Ledgard, 2010, p. 129]</ref> | + | The most cheap and accessible method involves the thermal decomposition of [[salicylic acid]], that can either be purchased from the pharmacy or obtained from [[sodium salicylate]] by adding a strong acid. Gently heating salicylic acid in a tube yields molten phenol, giving off carbon dioxide and phenol vapors. A condenser can be used to recover the resulting phenol vapor, to increase the yield. The resulting impure phenol is dissolved in [[dichloromethane]], and filtered. The DCM is removed by gently heating the solution at 40°C. The resulting phenol has a purity between 95-98%.<ref>[https://books.google.ro/books?id=y5mZrW1KB_AC&pg=PA129&lpg=PA129&dq=phenol+from+salicylic+acid&source=bl&ots=IfPZNCSYJv&sig=i6RYWa1Hi8oSl0YyR_QV-iBBWKE&hl=en&sa=X&ei=h4xkUaiwN4rMiQKu14GoAQ#v=onepage&q=phenol%20from%20salicylic%20acid&f=false Kings Chem Guide, Edition 2, Jared Ledgard, 2010, p. 129]</ref> |
==Projects== | ==Projects== | ||
Revision as of 16:28, 11 January 2016
Phenol, also known as carbolic acid, is an aromatic organic compound with the molecular formula C6H5OH.
Contents
Properties
Chemical
Phenol is weakly acidic, though still more acidic than aliphatic alcohols (about one million times more acidic), and at high pH gives the phenoxide (or phenolite) anion, C6H5O−.
- PhOH ⇌ PhO− + H+; (K = 10−10)
It will react with sodium metal or sodium hydroxide to yield sodium phenoxide. However, as it is weaker than carbonic acid, phenol does not react with carbonates or bicarbonates.
Phenol is reduced to benzene when it is distilled with zinc dust or its vapour is passed over granules of zinc at 400°C:[1]
- C6H5OH + Zn → C6H6 + ZnO
Physical
Phenol is a volatile white crystalline solid, with a distinct sweet and tarry odor. It is sparingly soluble in water (8.3 g/100 mL at 20 °C), but soluble in most organic solvents, such as ethanol, methanol, diethyl ether, acetone, chloroform. Phenol has a melting point of 40.5 °C and a boiling point of 181.7 °C. Its density is 1.07 g/cm3.
Availability
Phenol is sold by chemical suppliers.
Preparation
There are several ways to prepare phenol.
Historically, phenol was obtained from the pyrolysis of coal tar.
The industrial method relies on the oxidation of cumene with air at 90-130°C in the presence of alkali additives (Udris-Sergeev process), resulting in cumene hydroperoxide, followed by cleavage with sulfuric acid into phenol and acetone:
- C6H5CH(CH3)2 + O2 → C6H5C(CH3)2OOH → C6H5OH + CH3COCH3
Other methods involve the hydrolysis of chlorobenzene, using a base (Dow's Process) or steam (Raschig–Hooker process), direct oxidation of benzene with nitrous oxide, oxidation of toluene with air or the reaction of a strong base with benzenesulfonate.
The most cheap and accessible method involves the thermal decomposition of salicylic acid, that can either be purchased from the pharmacy or obtained from sodium salicylate by adding a strong acid. Gently heating salicylic acid in a tube yields molten phenol, giving off carbon dioxide and phenol vapors. A condenser can be used to recover the resulting phenol vapor, to increase the yield. The resulting impure phenol is dissolved in dichloromethane, and filtered. The DCM is removed by gently heating the solution at 40°C. The resulting phenol has a purity between 95-98%.[2]
Projects
- Nucleic acid extraction
- Carbolic soap
- Mono-, di- and trinitrophenol (picric acid) sinthesis
- Cyclohexanone synthesis
- Phenolphthalein synthesis
- Make benzene
Handling
Safety
Phenol and its vapors are corrosive to the eyes, the skin, and the respiratory tract. Its corrosive effect on skin and mucous membranes is due to a protein-degenerating effect. Repeated or prolonged skin contact with phenol may cause dermatitis, or even second and third-degree burns. Inhalation of phenol vapor may cause lung edema. It may cause harmful effects on the central nervous system, heart, resulting in dysrhythmia, seizures, and coma. Long-term or repeated exposure of the substance may have harmful effects on the liver and kidneys.
Storage
Phenol should be stored in closed bottles, to reduce the smell.
Disposal
Phenol can be destroyed by either burning it, or neutralizing it with Fenton's reagent.
References
- ↑ A Treatise on Chemistry, Volume 3, Part 3, Henry Enfield Roscoe, Macmillan & Company, 1891, p. 21
- ↑ Kings Chem Guide, Edition 2, Jared Ledgard, 2010, p. 129
