New microsoft word documentDiscuss Phenols and their derivatives as Antiseptics
MSA University, Faculty of Pharmacy Organic Chemistry Department.
1- NAME OF THE ASSIGN : Discuss Phenols and their
derivatives as Antiseptics
2- Course Code, PC 112
NAME : MOHMAEDADEL AFIFI ABDO ID:142311
FOR DR : NADIA
Phenol is the original antiseptic, old name carbolic acid. This was used
by Lister, who discovered antiseptics. It works well but is rather toxic.
If you react phenol with chlorine, then you get a Trichlorophenol, called
TCP. This is pretty non-toxic and TCP is the most widely used phenol
derivative used as an antiseptic today.
There are many other halogenated phenol derivatives in use and these
Phenol was first extracted from coal tar, but today is produced on a
large scale (about 7 billion kg/year) from petroleum.
It is an important industrial commodity as a precursor to many
materials and useful compounds. Its major uses involve its
conversion to plastics or related materials. Phenol and its chemical
derivatives are key for building polycarbonates,epoxies, Bakelite,
nylon, detergents, herbicides such as phenoxy herbicides, and
numerous pharmaceutical drugs.
Although similar to alcohols, phenols have unique distinguishing
properties. Unlike in alcohols where the hydroxyl group is bound to
a saturated carbon atom, in phenols the hydroxyl group is
attached to an unsaturated ring such as benzene or other arene
ring. Consequently, phenols have greater acidity than alcohols
due to stabilization of the conjugate base through resonance in the
Phenol is appreciably soluble in water, with about 84.2 g dissolving
in 1000 mL (0.88 M). Homogeneous mixtures of phenol and water
at phenol to water mass ratios of ~2.6 and higher are also possible.
The sodium salt of phenol, sodium phenoxide, is far more water
Phenol is weakly acidic and at high pHs gives the phenolate anion
C6H5O− (also called phenoxide):
PhOH ⇌ PhO− + H+ (K = 10−10)
One explanation for the increased acidity over alcohols is
resonance stabilization of the phenoxide anion by the aromatic ring.
In this way, the negative charge on oxygen is delocalized on to the
ortho and para carbon atoms. In another explanation, increased
acidity is the result of orbital overlap between the oxygen's lone
pairs and the aromatic system. In a third, the dominant effect is
the induction from the 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
The phenoxide anion has a similar nucleophilicityto free amines,
with the further advantage that its conjugate acid (neutral phenol)
does not become entirely deactivated as a nucleophile even in
moderately acidic conditions. Phenols are sometimes used in
peptide synthesis to "activate" carboxylic acids or esters to form
activated esters. Phenolate esters are more stable toward
hydrolysis than acid anhydrides and acyl halides but are sufficiently
reactive under mild conditions to facilitate the formation of amide
Phenol is highly reactive toward electrophilic aromatic substitution
as the oxygen atom's pi electrons donate electron density into the
ring. By this general approach, many groups can be appended to
the ring, via halogenation, acylation,sulfonation, and other
processes. However, phenol's ring is so strongly
activated—second only to aniline—that bromination or chlorination
of phenol leads to substitution on all carbons ortho and para to the
hydroxy group, not only on one carbon.
When a mixture of phenol and benzoyl chloride when shaken in
presence of dilute sodium hydroxide solution, phenyl benzoate is
formed. This is an example of Schotten-Baumann reaction:
C6H5OH + C6H5COCl → C6H5OCOC6H5 + HCl
Phenol is reduced to benzene when it is distilled with zinc dust or its
vapour is passed over granules of zinc at 400 °C:
C6H5OH + Zn → C6H6 + ZnO
Because of phenol's commercial importance, many methods have
been developed for its production. The dominant current route,
accounting for 95% of production (2003), involves the partial
oxidation of cumene (isopropylbenzene) via the Hock
C6H5CH(CH3)2 + O2 → C6H5OH + (CH3)2CO
Compared to most other processes, the cumene-hydroperoxide
process uses relatively mild synthesis conditions, and relatively
inexpensive raw materials.
However, to operate economically, there must be demand for both
phenol, and the acetone by-product.
An early commercial route, developed by Bayer and Monsanto in
the early 1900s, begins with the reaction of a strong base with
C6H5SO3H + 2 NaOH → C6H5OH + Na2SO3 + H2O
Other methods under consideration involve:
hydrolysis of chlorobenzene, using base or steam
C6H5Cl + H2O → C6H5OH + HCl
The major uses of phenol, consuming two thirds of its production,
involve its conversion to precursors to plastics. Condensation with
acetone gives bisphenol-A, a key precursor to polycarbonates and
epoxide resins. Condensation of phenol, alkylphenols, or diphenols
with formaldehyde gives phenolic resins, a famous example of
which is Bakelite.
Partial hydrogenation of phenol gives cyclohexanone, a precursor
to nylon. Nonionic detergents are produced by alkylation of phenol
to give thealkylphenols, e.g., nonylphenol, which are then
subjected to ethoxylation.
Phenol is also a versatile precursor to a large collection of drugs
Phenol and its vapors are corrosive to the eyes, the skin, and the
respiratory tract. 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. The
substance may cause harmful effects on the central nervous
system and heart, resulting in dysrhythmia, seizures, and coma.
The kidneys may be affected as well. Long-term or repeated
exposure of the substance may have harmful effects on the liver
and kidneys. There is no evidence that phenol causes cancer in
humans. Besides its hydrophobic effects, another mechanism for
the toxicity of phenol may be the formation of phenoxyl radicals.