Organic paper on sulfates

1. Adv. Org. Chem. 2009
Synthesis of Sulfa Drugs from Acetylation of Amines
Assay of Sulfanilamide
Ashley Cothran, Zan Messer, Diane C. Starrantino
Department of Chemistry, 5400 Ramsey Street, Fayetteville, NC, Methodist University
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Sulfanilamide, sulfapyridine, sulfathiazole, and sulfaguanidine studied by numerous
scientists to determine methods for assay, differentiation, and identification provide
useful synthesis techniques and methods of sulfa drug identification. Sulfanilamide
remains primary standard of nitrite solution in assay of sulfa drugs due to ease of
purification and stability in air1. This experiment sought to assay adequate amounts of
sulfanilamide to identify product as sulfa drug using aniline synthetic scheme.
Introduction
Sulfonamide drugs were the first
antimicrobial drugs. Bayer AG engineered the
first sulfonamide, trade named Prontosil, in
1932. Sulfur is not an isolated element in the
body, but part of complex molecules, as in
sulfur-containing amino acids. Sulfa antibiotics
generally work in one of five ways: inhibition
of nucleic acid synthesis and/or protein
synthesis, action on cell membrane and/or cell
wall, and interference with enzyme
cascade/system. Sulfa Drugs are synthesized
by acetylating amines, often with the use of
acetic anhydride, acetyl chloride, or glacial
acetic acid. Acetic anhydride is preferred for
laboratory synthesis due to its low rate of
hydrolysis allowing the acetylation of amines
in aqueous solutions. Acetylation is used to
‘protect’ primary or secondary amine
functional groups, which are less susceptible to
oxidation, less reactive in aromatic substitution
reactions, and less prone to reactions of typical
free amines due to their high pH2.
Despite new developments in
antimicrobial drugs, sulfa drugs prove valuable
in that they can provide a detailed picture of
their mechanism. Thus, allowing theoretical
hypothesis of how other therapeutic agents
carry out their medicinal activity. IR
spectroscopy, sulfanilamide preparations in
potassium bromide, is used rather than color
tests to identify sulfanilamide due to similar
chemical structures between the other sulfa
drugs3. Sulfa drugs continue to provide
medicinal benefits by simple synthesis from
available raw materials, specific microbial
degradation, and historical effectiveness.
(1) Calamari, J.A.; Hubata, Robert; Roth, P.B. Ind.Eng.
Chem. Anal. Ed. 1942, 14 (7), 534-535.
(2) Fields, John. Procedural handout. Adv. Org. Spr.
2009.
(3) Trius, N.V. Pharm. Chem. Journ. 1979, 13(11),
1200-1204.

2. Experimental
Stage 1 DCS-001: 2.0 g of aniline
weighed into 125-mL EF. 15mL water added
to EF. Swirled EF gently added (2.5 mL)
acetic anhydride slowly. Noted whitish, froth-
like formation, hot to the touch as precipitation
occurred. Sealed with parafilm over several
days in order to allow hardening of acetanilide
product.
Stage 2 DCA-002: Under Hood!
Assembled trap apparatus. Placed 12g dry
acetanilide in dry 250-mL EF. Melted the
acetanilide by gently heating with flame,
keeping separation on lower wall and bottom of
EF. Cooled EF in ice bath. Added 33mL of
chlorosulfonic acid to solidify product and
attached trap. Once removed from ice bath, as
swirled, hydrogen chloride gas evolved, leaving
small amount of acetanilide left behind. After
10 minutes, the reaction subsided, heated EF on
steam bath to completed reaction (within trap).
Removed trap and cooled flask in ice bath.
Slowly poured cooled mixture while vigorously
stirring into beaker with 200mL crushed ice.
Stirred the precipitate to break up chunks and
vacuumed filtered. Dissolved solids in 150 mL
boiling methylene chloride. Transferred
mixture to warm 500-mL separatory funnel,
drained lower methylene chloride layer rapidly.
Cooled mixture in ice bath. Obtained
crystalline p-acetamidobenzenesulfonyl
chloride by vacuum filtration used Buchner
funnel.
Stage 3 DCS-003: Under Hood!
Placed 5g p-acetamidobenzenesulfonyl chloride
in 125-mL EF added 15mL concentrated
ammonium hydroxide. Stirred mixture and
reaction immediately began, as EF got hot.
Heated mixture on steam bath for 15minutes,
stirred frequently. Material became pasty
suspension. Removed and placed in ice bath.
After cooled, added 10mL HCl/10mL H2O
until mixture indicated acidic on litmus paper.
Continued to cool mixture in ice bath. Filtered
on Buchner funnel with vacuum. Washed
product with 70mL cold H2O.
Stage 4 DCS-004: Transferred crude
product to small round-bottomed flask, added
3mL concentrated hydrochloric acid, 6mL H2O,
and boiling salts. Attached reflux condenser
until solid dispersed. *Note: in our trial solid
would not disperse even after 45 minutes of
reflux. Cooled mixture to room temperature.
Filtrated again using 4g sodium bicarbonate
(dissolved in H2O), stirred until indicated
neutral on litmus paper. Foaming occurred
after each addition of sodium bicarbonate
(release –CO2). Sulfanilamide precipitated,
filtrated through Buchner funnel. Attempted to
dry product as much as possible.
Recrystallization minimal as stated under trial
conditions.
Discussion and Results
The melting point obtained from the
final crystals and further IR spectroscopy in
potassium bromide can confirm the purity of
the sulfanilamide obtained during this
experiment. The literature states melting point
range of 164.5-166.5ºC. The very low yield of
<1% can be explained by a variety of factors.
When working in molecular scale, any small
loss can affect the results considerable. The
first source of loss can come from handling of
the products. Inevitably, some crystal product
will stay behind on the filter papers after
filtrations. After numerous filtrations, a
significant amount of product/precursors may
have been left behind. It is also possible that
some of the synthesis steps did not go to
completion; therefore, fewer products could be
obtained. In addition, water was used as a
solvent in many of the steps; some of the
products are insoluble in water, dissolved, then
discarded. The last source of water-caused loss
is found in the final recrystallization step;
recrystallizations are never 100% efficient
because not all to the dissolved product can be
precipitated back out of solution. Further,
during DCS-003, we did not calculate percent
yield or weight of p-acetamidobenzenesulfonyl
chloride.

3. Figure 1. Sulfanilamide reaction once acetanilide
formed during stage 1 DCS-001
Compound Molecular
Formula
Boiling
Point
(ºC)
Melting
Point
(ºC)
Density Solubility
in H2O
(g/ml) g/100ml
at 25ºC
Acetanilide C8H9NO 304 114.3 1.219 0.1
Chlorosulfonic
acid
ClHO3S 152 -80 1.753
Water H2O 100 0 0.995 N/A
Ammonium
hydroxide
NH4OH 36 -77 0.895 soluble
Hydrochloric
acid
HCl -85.06 -114.2 0.909 62
Sulfanilamide C6H8N2O2
S
164.5 -
166.5
1.08 7.5
Sodium
carbonate
Na2CO3 1600 851 2.532
Figure 2. Physical properties of chemicals used
Compound Molecular
Weight
(g./mol)
Moles Mass
(g)
Volume
(ml)
Acetanilide 135.1652 7.4X10-3 2
Chlorosulfonic acid 116.5191 0.04513 3
Water 18.0152 N/A Liberal
use
Ammonium hydroxide 35.0456 0.102 15
Hydrochloric acid 36.4609 N/A 10-May
Sulfanilamide 172.2014 3.77X10-
4
0.065
Sodium carbonate 105.98874 N/A 4
Acetic Anhydride 2.5
p-
acetamidobenzenesulfonyl
chloride 5
Figure 3. Quantitative properties of chemicals used
Conclusion
Experimental synthesis of sulfa drug,
sulfanilamide, did not produce expected yields
as stated in the findings. The probable causes
are infinite and require further, continual
calibration of techniques used during this
experiment. The findings regard the chemical
synthesis likely on human error. After careful
review of previous synthesis of sulfanilamide,
we discerned that different techniques provide
differing yields. The scientific processes used
allowed for development and future
experiments will yield more fruitful findings.