BENZOCAINE
EXPERIMENT
SIX
A
topical medication
is a
medication
that is applied
to
body surfaces
such as the
skin
or
mucous
membranes
to treat ailments via a large range of
classes including but not limited to
creams
,
foams
,
gels
,
lotions
and
ointments
.
Anesthesia
, or
anaesthesia
(from
Greek
αν-,
an-
,
"without"; and αἴσθησις,
aisthēsis
,
"sensation") traditionally meant the condition of
having
sensation
(including the feeling of
pain
) blocked
or temporarily taken away.
Local anesthesia is drug induced reversible local
blockade of pain sensation in specific part of the body
that doesn't alter consciousness or block sensation in
other part
An ester is fragrant
organic
compound
where
the
hydrogen
in the compound's
carboxyl group
is replaced with a
hydrocarbon
group
Benzocaine is one of the widely used local
anesthetics that act by preventing the impulse
transmission along the nerve fibers.
Benzocaine is the common name of ethyl
aminobenzoate, normally prepared by acid
catalyzed esterification.
Benzocaine is a local anesthetic commonly used as a
topical pain reliever. It is the active ingredient in many
over-the-counter analgesic ointments.
It is also indicated for general use as a lubricant and
topical anesthetic on intratracheal catheters and
pharyngeal and nasal airways to obtund the pharyngeal
and tracheal reflexes; on nasogastric and endoscopic
tubes; urinary catheters; laryngoscopes; proctoscopes;
sigmoidoscopes and vaginal specula.
It is also used to suppress gag reflex.
[gag: a surgical device for holding the mouth open.or to
strive to vomit.]
Benzocaine
is a
local anesthetic
commonly used as a
topical
pain
reliever or in cough drops. It is the active ingredient in many over-
the-counter
anesthetic
ointments such as products for
oral ulcers
.
It is also combined with
antipyrine
to form
A/B Otic Drops
to relieve
ear pain and remove
earwax
.
Benzocaine is used as a key ingredient in numerous
pharmaceuticals:
Over the counter throat lozenges such as
Anbesol
and
Cepacol
.
Some glycerol-based ear medications for use in removing excess
wax as well as relieving ear conditions such as
Otitis
Media
and
swimmers ear
.
Some previous diet products such as
Ayds
.
Some
condoms
designed to prevent
premature ejaculation
.
Benzocaine acts to desensitize the
penis
, and theoretically allows
an
erection
to be maintained.
Benzocaine binds to sodium channel and reversibly stabilizes the
neuronal membrane which decreases its permeability to sodium ions.
Depolarization of the neuronal membrane is inhibited thereby blocking
the initiation and conduction of nerve impulses.
A surface anesthetic that acts by preventing transmission of impulses
along nerve fibers and at nerve endings.
Benzocaine products—which are sold as gels,
liquids, sprays and lozenges ….
But the use of benzocaine gels and liquids for
mouth and gum pain can lead to a rare but
serious—and sometimes fatal—condition called
methemoglobinemia, a disorder in which the
amount of oxygen carried through the blood
stream is greatly reduced.
And children under 2 years old appear to be at
particular risk.
What parents do?
Advise your adult patients “ Do not use them more
than 4 times a day”.
Description:
white, crystalline powder.
Sparingly soluble in water.
Mwt = 165.2 g/mole
Melting point = 92 °C
[between 88and 92,but the range between
beginning and end of melting does not exceed
2], so
Melting range.
88-92°C
In a100 mL round bottom flask, add 2.5 mg of 4-aminobenzoic acid (often called
PABA for Para aminobenzoic acid), 20 mL of
absolute
ethanol and 3 boiling chips.
Heat this mixture on a sand bath until all the solid dissolves. Cool in ice and then
add 2 mL of concentrated sulfuric acid drop wise. A large amount of precipitate will
form when the sulfuric acid is added, but this will dissolve during the reflux that
follows.
Attach an air condenser and reflux gently for 60 min. Check periodically to be sure
that the mixture is refluxing gently.
Allow the reaction mixture to cool to room
temperature. Transfer the reaction solution
to an Erlenmeyer flask and
add 40 mL of distilled water.
Drop wise, add saturated sodium bicarbonate to neutralize the excess sulfuric acid
and the ammonium sulfate salt form of the amino ester (making it neutral and
insoluble in water). Extensive CO2 evolution (gas) and frothing will be observed until
the
mixture is nearly neutralized. As the pH increases, a white precipitate of
benzocaine is produced.
Collect the benzocaine by vacuum filtration. Use three 1-mL portions of cold water to
wash the product crystals from the flask onto the funnel.
Dried thoroughly by leaving it in an open container until the next lab, weigh it,
calculate the % yield, and determine its melting point. The m.p. of pure benzocaine is
92°C.
steam bath
hot water bath
sand bath
oil bath
hot plate
heating mantle
What other equipment you can add?
Drying agent is a chemical used to remove
water from an organic compound that is in
solution.
Drying agents should be insoluble in the
solvent to be dried as well as unreactive toward
both the solvent and the solute.
Drying agents should also remove water
quickly and be easily removed by filtration.
Class of compounds: Recommended drying agent
Alkane, alkyl halides: MgSO4, CaCl2, CaSO4,
H2SO4, P4O10
Aromatic hydrocarbons, ethers: MgSO4, CaCl2,
CaSO4, P4O10, Na-metal
Aldehydes, ketones, esters: Na2SO4, MgSO4,
K2CO3, CaSO4
Alcohols: MgSO4, K2CO3, CaSO4, CaO, BaO
Amines: KOH, K2CO3
Acidic compounds: Na2SO4, MgSO4, CaSO4
Mwt of benzocaine = 165.2 g/mole
Mwt of p-aminobenzoic acid=137.14 g/mole
Mwt of ethanol=46.07 g/mole
Density of ethanol=0.789 g/ml
Note : flaky crunchy bowtie crystals.
A:
Infrared Absorption
á197Kñ:previously dried over phosphorus pentoxide
for 3hours.
B:
Ultraviolet Absorption
á197Uñ
—
Solution:
5µg per mL.
Medium:
chloroform.
Absorptivities at 278nm,calculated on the dried basis,do not differ by more
than 3.0%.
C:
Dissolve about 20mg in 10mLof water with the aid of a few drops of
3Nhydrochloric acid,and add 5drops of a solution of sodium nitrite (1in
10),followed by 2mLof a solution of 100mg of 2-naphthol in 5mLof
1Nsodium hydroxide:an orange-red precipitate is formed.
NMR
Gas chromatography–mass spectrometry
(
GC-MS
) is a method that
combines the features of
gas-liquid chromatography
and
mass
spectrometry
to identify different substances within a test sample.
NMR
Nitrite titration
,. Each ml of sodium nitrite (0.1
mol/l) VS is equivalent to 16.52 mg of
C
9
H
11
NO
2
.
chromatography
Benzocaine,dried over phosphorus pentoxide
for 3hours,contains not less than 98.0percent
and not more than 101.0percent of C
9
H
11
NO
2
.
For lozenges:85-120%
Write the name of reactants & products of our
today experiment.
Write 4 informations about drying agent with
examples.
This experiment focuses on the synthesis and purification process of benzocaine. The detailed steps and methods used in the experiment help in understanding the chemical properties and purification techniques involved in producing pure benzocaine.
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Presentation Transcript
EXPERIMENT EXPERIMENT SIX SIX SYNTHESIS AND SYNTHESIS AND PURIFICATION BENZOCAINE BENZOCAINE PURIFICATION OF OF http://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Benzocaine-from-xtal-3D-balls.png/220px-Benzocaine-from-xtal-3D-balls.png http://upload.wikimedia.org/wikipedia/commons/thumb/b/bb/Benzocaine.svg/220px-Benzocaine.svg.png
Key concepts A topical medication topical medication is a medication that is applied to body surfaces such as the skin or mucous membranes to treat ailments via a large range of classes including but not limited to creams, foams, gels, lotions and ointments. Anesthesia Anesthesia, or anaesthesia "without"; and , aisth sis, "sensation") traditionally meant the condition of having sensation (including the feeling of pain) blocked or temporarily taken away. anaesthesia (from Greek -, an-, Local anesthesia is drug induced reversible local blockade of pain sensation in specific part of the body that doesn't alter consciousness or block sensation in other part
ESTERS ESTERS DEFINITION DEFINITION An ester is fragrant organic compound where the hydrogen in the compound's carboxyl group is replaced with a hydrocarbon group
INTRODUCTION: INTRODUCTION: Benzocaine is one of the widely used local anesthetics that act by preventing the impulse transmission along the nerve fibers. Benzocaine is the common name of ethyl aminobenzoate, normally prepared by acid catalyzed esterification.
PHARMACOLOGY AND USE PHARMACOLOGY AND USE: Benzocaine is a local anesthetic commonly used as a topical pain reliever. It is the active ingredient in many over-the-counter analgesic ointments. It is also indicated for general use as a lubricant and topical anesthetic on intratracheal catheters and pharyngeal and nasal airways to obtund the pharyngeal and tracheal reflexes; on nasogastric and endoscopic tubes; urinary catheters; laryngoscopes; proctoscopes; sigmoidoscopes and vaginal specula. It is also used to suppress gag reflex. [gag: a surgical device for holding the mouth open.or to strive to vomit.]
Benzocaine Benzocaine is a local anesthetic commonly used as a topical pain reliever or in cough drops. It is the active ingredient in many over- the-counter anesthetic ointments such as products for oral ulcers. It is also combined with antipyrine to form A/B Otic Drops to relieve ear pain and remove earwax. Benzocaine is used as a key ingredient in numerous pharmaceuticals: Over the counter throat lozenges such as Anbesol and Cepacol. Some glycerol-based ear medications for use in removing excess wax as well as relieving ear conditions such as Otitis Media and swimmers ear. Some previous diet products such as Ayds. Some condoms designed to prevent premature ejaculation. Benzocaine acts to desensitize the penis, and theoretically allows an erection to be maintained.
MECHANISM OF ACTION A surface anesthetic that acts by preventing transmission of impulses along nerve fibers and at nerve endings. Benzocaine binds to sodium channel and reversibly stabilizes the neuronal membrane which decreases its permeability to sodium ions. Depolarization of the neuronal membrane is inhibited thereby blocking the initiation and conduction of nerve impulses.
DOSAGE FORMS Benzocaine products which are sold as gels, liquids, sprays and lozenges .
Precausions But the use of benzocaine gels and liquids for mouth and gum pain can lead to a rare but serious and sometimes fatal condition called methemoglobinemia, a disorder in which the amount of oxygen carried through the blood stream is greatly reduced. And children under 2 years old appear to be at particular risk. What parents do? Advise your adult patients Do not use them more than 4 times a day .
PHYSICOCHEMICAL PROPERTIES PHYSICOCHEMICAL PROPERTIES: : Description: Description: white, crystalline powder. Sparingly soluble in water. Mwt = 165.2 g/mole Melting point = 92 C [between 88and 92,but the range between beginning and end of melting does not exceed 2], so Melting range. Melting range. 88-92 C http://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Benzocaine-from-xtal-3D-balls.png/220px-Benzocaine-from-xtal-3D-balls.png
SYNTHETIC PROCEDURE: SYNTHETIC PROCEDURE: In a100 mL round bottom flask, add 2.5 mg of 4-aminobenzoic acid (often called PABA for Para aminobenzoic acid), 20 mL of absolute Heat this mixture on a sand bath until all the solid dissolves. Cool in ice and then add 2 mL of concentrated sulfuric acid drop wise. A large amount of precipitate will form when the sulfuric acid is added, but this will dissolve during the reflux that follows. Attach an air condenser and reflux gently for 60 min. Check periodically to be sure that the mixture is refluxing gently. Allow the reaction mixture to cool to room temperature. Transfer the reaction solution to an Erlenmeyer flask and add 40 mL of distilled water. Drop wise, add saturated sodium bicarbonate to neutralize the excess sulfuric acid and the ammonium sulfate salt form of the amino ester (making it neutral and insoluble in water). Extensive CO2 evolution (gas) and frothing will be observed until the mixture is nearly neutralized. As the pH increases, a white precipitate of benzocaine is produced. Collect the benzocaine by vacuum filtration. Use three 1-mL portions of cold water to wash the product crystals from the flask onto the funnel. Dried thoroughly by leaving it in an open container until the next lab, weigh it, calculate the % yield, and determine its melting point. The m.p. of pure benzocaine is 92 C. absolute ethanol and 3 boiling chips.
Mechanism of reaction Fischer esterification mechanism
HEATING METHODS steam bath hot water bath hot water bath sand sand bath bath oil bath oil bath hot hot plate plate heating heating mantle mantle What other equipment you can add? What other equipment you can add?
DRYING AGENTS Drying agent is a chemical used to remove water from an organic compound that is in solution. Drying agents should be insoluble in the solvent to be dried as well as unreactive toward both the solvent and the solute. Drying agents should also remove water quickly and be easily removed by filtration.
EXAMPLES OF DRYING AGENTS Class of compounds: Recommended drying agent Alkane, alkyl halides: MgSO4, CaCl2, CaSO4, H2SO4, P4O10 Aromatic hydrocarbons, ethers: MgSO4, CaCl2, CaSO4, P4O10, Na-metal Aldehydes, ketones, esters: Na2SO4, MgSO4, K2CO3, CaSO4 Alcohols: MgSO4, K2CO3, CaSO4, CaO, BaO Amines: KOH, K2CO3 Acidic compounds: Na2SO4, MgSO4, CaSO4
CALCULATIONS: Mwt of benzocaine = 165.2 g/mole Mwt of p-aminobenzoic acid=137.14 g/mole Mwt of ethanol=46.07 g/mole Density of ethanol=0.789 g/ml Note : flaky crunchy bowtie crystals.
IDENTIFICATION IDENTIFICATION A: A: Infrared Absorption 197K :previously dried over phosphorus pentoxide for 3hours. B: B: Ultraviolet Absorption 197U Solution: 5 g per mL. Medium: chloroform. Absorptivities at 278nm,calculated on the dried basis,do not differ by more than 3.0%. C: C: Dissolve about 20mg in 10mLof water with the aid of a few drops of 3Nhydrochloric acid,and add 5drops of a solution of sodium nitrite (1in 10),followed by 2mLof a solution of 100mg of 2-naphthol in 5mLof 1Nsodium hydroxide:an orange-red precipitate is formed. NMR Gas chromatography Gas chromatography mass spectrometry mass spectrometry (GC combines the features of gas-liquid chromatography and mass spectrometry to identify different substances within a test sample. NMR GC- -MS MS) is a method that
Assay Assay Nitrite titration,. Each ml of sodium nitrite (0.1 mol/l) VS is equivalent to 16.52 mg of C9H11NO2. chromatography
Accepted Ranges Benzocaine,dried over phosphorus pentoxide for 3hours,contains not less than 98.0percent and not more than 101.0percent of C9H11NO2. For lozenges:85-120%
Quiz Write the name of reactants & products of our today experiment. Write 4 informations about drying agent with examples.
