Exercise 9: PHENOLS Flashcards
organic aromatic compounds
wherein the hydroxyl group is
attached to a benzene ring
considered as alcohols due to
their OH group, however,
differ in their chemical
behavior
PHENOLS
PHENOLS difference with alcohols
technically is due to the
phenyl ring
PHENOLS
also known as
hydroxybenzene or carbolic acid
PHENOLS is
toxic, colorless crystalline solid with sweet tarry odor
Phenols usually employed as an
antiseptic and disinfectant
also used in cosmetic formulations and manufacture of some
drugs (precursor)
PHENOLS
generally have higher boiling points as compared to hydrocarbons
having the same molecular masses
mainly due to the intermolecular H-bonding in between the OH
groups
BOILING POINT
boiling point = number of C atoms increase
Increase
governed by its ability to perform intermolecular H-bonding with
polar solvents
SOLUBILITY
H-bonds make it possible for the phenol to be - to the
water
however, an - attached to the
hydroxyl group decrease its solubility in water
slightly soluble
increase in the size of the aryl group
ACIDITY
acidic in nature due to its reactivity with active metals (e.g. sodium, potassium,
etc.) to form corresponding
sp2 hybridized C of the benzene ring attached to the OH group functions as an
(decreases the electron density on the oxygen)
phenoxides
electron withdrawing group
due to the, phenoxide ions are more stable (phenols are more, than alcohols)
delocalization of the electrons in the benzene ring, acidic
in substituted phenols, its acidity - if an electron donating group is
attached to the ring and vice versa
decreases
diazotization of primary aromatic amines
SYNTHESIS OF PHENOLS
when a primary aromatic amine with nitrous acid (NaNO2 + HCl) at ~5°C,
is formed
these diazonium salts are highly reactive and upon warming with water, will be
hydrolyzed in to
benzene diazonium chloride
phenol
primary aromatic amine with at
benzene diazonium chloride is formed
nitrous acid (NaNO2 + HCl) , ~5°C,
SOLUBILITY TEST results
phenol in 5% NaOH
soluble; clear dark brown to black solution
Identify solubility
of phenols
SOLUBILITY TEST
principle: phenols react with
dilute aqueous sodium hydroxide
to form (more soluble with water compared to
phenol due to its phenyl ring)
sodium phenoxide
Solubility Test
phenols react with
to form Na phenoxide (more soluble with water compared to
phenol due to its phenyl ring)
dilute aqueous sodium hydroxide
REACTION WITH FERRIC CHLORIDE results
1% phenol
purple soln
REACTION WITH FERRIC CHLORIDE results
1% cathecol
clear colorless solution
REACTION WITH FERRIC CHLORIDE results
1% thymol
Clear pale green soln
REACTION WITH FERRIC CHLORIDE results
1% α-naphthol
Dark red sol
function of test: can detect the presence of
phenolic compounds
REACTION WITH FERRIC CHLORIDE
reagent: ferric chloride
REACTION WITH FERRIC CHLORIDE
Rxn with Ferric Chloride
principle: formation of that
absorbs visible light to give an excited state
in which electrons are delocalized over both
the iron atom and the conjugated organic
system
ferric phenoxide
BROMINE WATER TEST results
1% phenol
clear colorless solution with white precipitate
BROMINE WATER TEST results
salicylic acid
clear colorless solution with white precipitate
function of test: can be used to identify phenolics (however, other
compounds may also yield positive results)
BROMINE WATER TEST
reagent: bromine water
BROMINE WATER TEST
positive result: bromine water test
clear colorless solution with white precipitate
Bromine Water Test
principle: bromination of phenol results to product which
appears as white precipitate while
the results to decolorization of the solution with an odor of an antiseptic
2,4,6-tribromophenol
side product of hydrobromic acid
FORMATION OF PHENOLPHTHALEIN results
5% HCl
clear colorless solution
FORMATION OF PHENOLPHTHALEIN results
5% NaOH
pink soln
can also be used as precursor in the synthesis of several organic
compounds
one of which is an, used in acid-base titration
phenol
organic indicator phenolphthalein
Formation with phenolphthalein
phenol reacts with - under an
acid catalyst using an electrophilic aromatic
substitution reaction
the resulting solution can be further tested for its
indicator property:
in acidic solutions
in basic solutions
phthalic anhydride
colorless
pink to magenta
phenol reacts with phthalic anhydride under an
acid catalyst using an
electrophilic aromatic
substitution reaction
MILLON’S TEST results
1% phenol
clear golden brown solution
MILLON’S TEST results
5% albumin
clear yellowish solution with red precipitate
determine the presence of
phenolic compounds in amino acids
MILLON’S TEST
reagent: Millon’s reagent
(mercurous nitrate HgNO3 and mercuric nitrate Hg(NO3)2 in nitric acid
HNO3)
positive result: millons test
red precipitate
(is the only amino acid with phenol in its
structure)
tyrosine
principle: react with Millon’s reagent to form red colored complexes
amino acids and proteins with phenol radicals
principle: amino acids and proteins with phenol radicals react with Millon’s reagent to form
red colored complexes
positive result: rxn with ferric chloride
colored complexes
