Synthesis and identification of 6,7-epoxy N,N',N'-trichloro derivative of α-bromocinnamaldehyde semicarbazone as an active decontaminating agent for toxic compounds

Article abstract of DOI:10.14233/ajchem.2013.13754

An approach was undertaken to synthesize 6,7-epoxy N,N',N'-trichloro-a- bromo-cinnamaldehyde semicarbazone, by the conversion of a-bromo-cinnamaldehyde semicarbazone into its epoxy derivative and then finally the corresponding N-chloramine. Epoxidation was carried out with hydrogen peroxide and then chlorinated using calcium hypochlorite. The reaction between calcium hypochlorite and compounds containing a nitrogen atom with one or more hydrogen atoms attached to it will form chloramines which have lower disinfection efficiency but possess strong decontamination properties against toxic compounds and warfare agents. Their efficacy has to be tested on toxic compounds of phosphorus and CW agents under suitable conditions in sophisticated laboratory.

Full text of DOI:10.14233/ajchem.2013.13754

Asian Journal of Chemistry; Vol. 25, No. 7 (2013), 4109-4110
http://dx.doi.org/10.14233/ajchem.2013.13754
NOTE
Synthesis and Identification of 6,7-Epoxy N,N′,N′-Trichloro Derivative of α-Bromocinnamaldehyde
Semicarbazone as an Active Decontaminating Agent for Toxic Compounds
*
SORAM IBOMCHA SINGH and SHASHI PRABHA
School of Studies in Chemistry, Jiwaji University, Gwalior-474 011, India
*Corresponding author: E-mail: ibomsoram@yahoo.co.uk
(Received: 19 March 2012;
Accepted: 30 January 2013)
AJC-12769
An approach was undertaken to synthesize 6,7-epoxy N,N′,N′-trichloro-α-bromo-cinnamaldehyde semicarbazone, by the conversion of
α-bromo-cinnamaldehyde semicarbazone into its epoxy derivative and then finally the corresponding N-chloramine. Epoxidation was
carried out with hydrogen peroxide and then chlorinated using calcium hypochlorite. The reaction between calcium hypochlorite and
compounds containing a nitrogen atom with one or more hydrogen atoms attached to it will form chloramines which have lower disinfection
efficiency but possess strong decontamination properties against toxic compounds and warfare agents. Their efficacy has to be tested on
toxic compounds of phosphorus and CW agents under suitable conditions in sophisticated laboratory.
Key Words: Organophosphorus compounds, Chloramines, Decontamination, CW agents.
In general, decontamination of toxic chemicals1 is an
important task required to eliminate the hazard of toxic chemicals
both in laboratories and field conditions. Semicarbazones2 act
as important synthetic intermediates and have been preferably
used for the isolation, purification, characterization3 and even
protection of both aldehydes and ketones. Epoxidations under
acidic conditions were a matter of debate for quite sometime
because it was assumed that the end products were either α-
glycols or their monoacetates when peracetic acid was employed
for olefins. The first report about the formation of an epoxide
successfully from methyl linoleate using peracetic acid came
with the researches done by Boeseken, Smit and Gaster4. Calcium
hypochlorite is one of the commonly used chlorinating agents
for various chemical compounds.Various organic compounds
containing either N-chloro groups or epoxide moiety are reported
as efficient decontamination agents5,6 for chemical warfare
agents7 and various chemical compounds.
derivative using semicarbazide hydrochloride in presence of
sodium acetate in an aqueous-alcoholic medium. The reaction
was carried out with uninterrupted stirring for 1.5 h and
obtained as the light yellow semicarbazone derivative. The
same product was also obtained by refluxing method with
much lesser time period, ca. 22 min. The final product was
recrystallized with alcohol and recorded m.p. of 203-204 ºC.
H2N-NHCONH2 .HCl
C
H
C
C
H
C
H
O
C
N-NHCONH2
C
H
C2H5OH, CH3COONa
Br
Br
-Br-cinnamaldehyde
compound A
H2O2 (30%)
O
O
H
C
H
N
N
C
C
N
H
C
H
Br
H
compound B
During the present study, α-Br-cinnamaldehyde, one of
the important members of α,β-unsaturated aldehyde was
chosen as the starting compound and converted into the corres-
ponding N-chloro compound which is expected to be formed
as an active decontaminating agent in the following crucial
three stepwise synthesis8 (Scheme-I).
CaOCl2
O
O
Cl
C
H
N
N
C
C
N
C
H
Cl
Br
Cl
Synthesis of α-Br-cinnamaldehyde semicarbazone
(compound A): α-Br-cinnamaldehyde, an α,β-unsaturated
aldehyde, was converted9 into the corresponding semicarbazone
compound C
Scheme-I: Stepwise synthesis of 6,7-epoxy N,N',N' -trichloro-α-Br-
cinnamaldehyde semicarbazone

4110 Singh et al.
Asian J. Chem.
Synthesis of 6,7-epoxy α-Br-cinnamaldehyde semicar-
nitrogen nuclei are also observed just like the epoxy derivative
of t-cinnamaldehyde itself.
bazone (compound B): The next step was the epoxidation of
the above semicarbazone derivative under acidic condition
using hydrogen peroxide14 (30 %). α-Br- cinnamaldehyde
semicarbazone (10 g) was dissolved in acetic acid in the presence
of one drop of conc. H2SO4 as catalyst with stirring at room
temperature. It was epoxidized by gradual addition of hydrogen
peroxide keeping the latter in excess. The reaction mixture
was stirred on a magnetic stirrer for 3 h and 45 min and the
pH of the solution was kept as 2.0 with the help of acetic acid.
For this, excess of glacial acetic acid was added at intervals of
time. The light greenish-yellow solution was diluted with
excess of distilled water and extracted with ether. Then, the
ethereal extract on evaporation gave a light-yellow solid, the
epoxy derivative which has a m.p. of 168-170 ºC.
Identification of compound C: 1H NMR spectrum shows
few signals which is due to lesser number of protons as three
protons have been replaced by the chloro-groups. The aromatic
protons are observed at the highest value i.e. 8.5 ppm. The
appearance of a singlet at 2.4 ppm may be assigned to the
proton at C-8. The presence of a doublet at 4.5-4.6 ppm is
assigned to the epoxy ring proton (C-6). It is however, difficult
to account for each and every signal seen in the spectrum. The
above spectral study is able to identify and confirm the forma-
tion of 6,7-epoxy-N,N',N'-trichloro-α-Br-cinnamaldehyde
semicarbazone.
Conclusion
The epoxy compounds was converted into the trichloro-
(N,N',N'-) compound having chloro-substituents at the -NH
and -NH2 hydrogens. Such a class of compound is expected to
bring about chlorination of organic compounds and parti-
cularly the organophosphorus compounds giving positive
chlorine as the reactive species. The introduction of these chlorine
substituents (Cl+) is thus taken to behave quite differently and
may attack13 the organic compounds resulting in the introduction
of the chlorine atom/s at very strategic positions only. Due to
this typical nature of the above chloro- compounds (referred
to as chloramines) organophosphorus compounds may lead
to the formation of their chloro-derivatives, which may possess
a non-toxic character, justifying the role of chloramines as
chemical decontaminants. Such molecules bring about excessive
chlorination with limited oxidation (due to the presence of
epoxy ethereal linkage) and thus are expected to perform as
better decontamination agents than the chloramines alone.
Synthesis of 6,7-epoxy N,N',N'-trichloro-α-Br-cinnam-
aldehyde semicarbazone (compound C): 6,7-Epoxy α-Br-
cinnamaldehyde semicarbazone was dissolved in acetic acid
by stirring on a magnetic stirrer. Then, it was chlorinated by
the addition of (5.739 g) calcium hypochlorite10 (maintaining
the ratio 1:2) in instalments for 3 h with continuous stirring.
During the process there was addition of acetic acid in excess
so as to maintain the pH of the reaction mixture at 2.0 through-
out the stirring. At the end, the reaction mixture was diluted
with water and a creamish precipitate was obtained. It was
then washed again thoroughly with water and kept for drying.
The final product N-chloro-derivative is found to have a m.p.
of 150-154 ºC.
Identification of compoundA: The mass spectral data of
compound A shows the formation of a base peak at m/e 188
(100 %) which is due to the loss of bromine atom (80). Other
prominent peaks are 186 (20 %), 115 (24 %), 89 (2 %, 76 (2 %), etc.
1H NMR data of compound A shows the absence of two
doublets (due to the presence of an α-Br group) for the alkenyl
protons (as seen in case of t-cinnamaldehyde semicarbazone)
clearly indicates its formation. The presence of a multiplet at
δ 7.2 further showed the presence of aromatic protons. The
single olefinic proton appears at δ 6.9 and as expected forms a
doublet in the NMR region. The appearance of a signal at δ
8.8 may be ascribed to the presence of the protons of the amide
(nearly δ 8.5) type.
ACKNOWLEDGEMENTS
The financial support of DRDE, Gwalior (Grant No.
DRDE-P1-2004/Task-27) is gratefully acknowledged.
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