Sodium lauryl sulfate-catalyzed oxidative chlorination of aromatic compounds

Article abstract of DOI:10.1080/00397911.2011.589560

Chlorination of commercially important aromatic compounds using sodium chloride as chlorine source and sodium periodate as oxidant in acidic medium catalyzed by sodium lauryl sulfate (SLS) led to the chloro-substituted aromatics in good yields and purity. Addition of sodium lauryl sulfate led to increased chlorination rate, better yield, excellent purity, and better quality of end product. The advantages of the present method are greater yield, excellent purity, and shorter reaction time at room temperature. Also dichlorinated product can be obtained by increasing the amount of sodium chloride and sodium periodate at slightly higher temperature (40C).

Full text of DOI:10.1080/00397911.2011.589560

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Sodium Lauryl Sulfate–Catalyzed
Oxidative Chlorination of Aromatic
Compounds
Tanu Mahajan a , Lalit Kumar a , K. Dwivedi a & D. D. Agarwal a
a Department of Industrial Chemistry, Jiwaji University, Gwalior,
Madhya Pradesh, India
Accepted author version posted online: 20 Jan 2012. Version of
record first published: 20 Aug 2012
To cite this article: Tanu Mahajan, Lalit Kumar, K. Dwivedi & D. D. Agarwal (2012): Sodium Lauryl
Sulfate–Catalyzed Oxidative Chlorination of Aromatic Compounds, Synthetic Communications: An
International Journal for Rapid Communication of Synthetic Organic Chemistry, 42:24, 3655-3663
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Synthetic Communications1, 42: 3655–3663, 2012
Copyright # Taylor & Francis Group, LLC
ISSN: 0039-7911 print=1532-2432 online
DOI: 10.1080/00397911.2011.589560
SODIUM LAURYL SULFATE–CATALYZED OXIDATIVE
CHLORINATION OF AROMATIC COMPOUNDS
Tanu Mahajan, Lalit Kumar, K. Dwivedi, and D. D. Agarwal
Department of Industrial Chemistry, Jiwaji University, Gwalior,
Madhya Pradesh, India
GRAPHICAL ABSTRACT
Abstract Chlorination of commercially important aromatic compounds using sodium
chloride as chlorine source and sodium periodate as oxidant in acidic medium catalyzed
by sodium lauryl sulfate (SLS) led to the chloro-substituted aromatics in good yields
and purity. Addition of sodium lauryl sulfate led to increased chlorination rate, better yield,
excellent purity, and better quality of end product. The advantages of the present method
are greater yield, excellent purity, and shorter reaction time at room temperature. Also
dichlorinated product can be obtained by increasing the amount of sodium chloride and
sodium periodate at slightly higher temperature (40 ꢀC).
Keywords Chlorination; chloroarenes; regioselectivity; sodium lauryl sulfate; sodium
periodate
INTRODUCTION
Chlorinated organic compounds play very important roles in chemistry; they
are essential in organic syntheses as starting compounds and synthetic intermediates,
designer molecules for material science, industrial chemicals, and bioactive com-
pounds.[1–4] The classical synthetic procedure involves the use of molecular chlorine,
which is hazardous, difficult to store, and hard to handle.[5] A range of new methods
has been published lately, and the development of new chlorination protocols
focused on environmentally acceptable techniques and materials. Although use of
halogenating enzymes[6–8] could be the most effective from an environmental point
of view, large-scale halogenations using enzymes have not been commercialized.
Received February 21, 2011.
Address correspondence to Tanu Mahajan, Department of Industrial Chemistry, Jiwaji University,
Gwalior, Madhya Pradesh 474011, India. E-mail: tmahajan1208@gmail.com
3655

3656
T. MAHAJAN ET AL.
Scheme 1. SLS-catalyzed oxidative chlorination of aromatics using NaCl and NaIO4.
Here we report the chlorination of some commercially important aromatic sub-
strates that are widely used in pharmaceutical, agricultural, and dye industries, for
[9,10]
production of various drugs, insecticides, herbicides, and dyestuffs.
Chlori-
nation reported so far has been extensively described using many reagents such as
KCl=oxone,[11] t-butylhypochlorite,[12] HCl=H2O2,[13] NaCl=H2O2=HNO3,[14]
NCSac,[15] HCl=m-CPBA=DMF,[16] SnCl4=Pb(OAc)4,[17] Cl2=1o,2o,3o amines,[10]
and TBACl3=CH3COOH=CH2Cl2.[18] However, these methods have some draw-
backs such as use of strong,[12] nonselective,[16] toxic, and expensive reagents,[17] poor
yield, and long reaction times.[13,11] Also efforts are being directed toward carrying
out the chlorination of aromatic substrates using alumino-silicate catalyst especially
zeolites.[19] However, a stumbling block to this is damage caused to the zeolites, and
hence industrial applications are still rare.
The present communication reports a versatile reaction for the chlorination of
aromatics, giving good to excellent yields (73–99%) of chlorinated products using
NaIO4 as oxidant and NaCl as chlorine source. A perusal of the literature revealed
that an earlier method reported by Dewkar et al.[20,21] has limitations of long reac-
tion time (6–18 h), high temperature (80 ꢀC), and poor yield (20–83%) as well as
nonselectivity. The present method overcomes all these limitations and method
has advantages of good yield (73–99%), low reaction time (1–2 h), and good selec-
tivity or purity at room temperature. When a solution of substrate (0.01 mol) in
AcOH was stirred at room temperature in the presence of NaIO4 (0.005 mol), NaCl
(0.03 mol), SLS (50 mg), and H2SO4 (1 mL), the chlorinated product was obtained in
excellent yield (Scheme 1) and purity.
RESULTS AND DISCUSSION
To optimize the best reaction conditions, 4-bromoacetanilide was used as a
model substrate. Reaction was performed at room temperature using NaIO4 (0.005
mol), NaCl (0.03 mol), and SLS (50 mg) with respect to the substrate (0.01 mol). A
wide variety of aromatic substrates were subjected to chlorination to test the gener-
ality of this method, and results are summarized in Table 1. The results of Table 1
show that all substrates were chlorinated within 1–2 h, and 4-bromoacetanilide
was chlorinated within 1 h at room temperature, having the maximum yield (99%,
Table 1, entry 1) and excellent purity (99%, Table 6, entry 1) of 4-bromo-2-chloroa-
cetanilide. This compound finds application as an intermediate in research and devel-
opment.[22] In the case of benzanilide (3), para-substituted product was obtained

OXIDATIVE CHLORINATION OF AROMATIC COMPOUNDS
3657
Table 1. Oxidative chlorination of aromatics using NaCl and NaIO4
Entry
Substrate
Time (h)
1
Product
Yield (%)
99a
Mp (ꢀC) (lit.)
1
152 (151–152[28a]
)
2
3
4
1
2
1
98a
98a
95a
145 (143–146[18]
198 (199–201[29]
107 (107–110[24]
)
)
)
5
6
2
1
97b
190 (190–194[9]
)
90a
175 (175–177[25]
)
7
8
1
2
92b
85a
101 (101–103[28b]
)
83 (85–87[28b]
)
9
2
93b
121 (120–125[28b]
)
10
11
2
2
80a
73a
130 (128–132[30]
138 (138–139[31]
)
)
(Continued )

3658
T. MAHAJAN ET AL.
Table 1. Continued
Entry
Substrate
Time (h)
Product
Yield (%)
Mp (ꢀC) (lit.)
12
2
2
85a
172 (171–173[26]
)
13
89b
221 (220–222[28b]
)
aReaction conditions: substrate, 0.01 mol; NaCl, 0.03 mol; NaIO4, 0.005 mol; AcOH, 10 mL; H2SO4,
1.0 mL; SLS, 50 mg; temp 25 ꢀC.
bReaction conditions: substrate, 0.01 mol; NaCl, 0.05 mol; NaIO4, 0.01 mol; AcOH, 10 mL; H2SO4,
1.0 mL; SLS, 50 mg; temp 40 ꢀC.
within 2 h in 98% yield and 96.23% purity (Table 2, entry 2), which is also an indust-
rially important compound.[23] 2-Chloro-4-nitroaniline was synthesized by mono-
chlorination of 4-nitroaniline (4) within 1 h at room temperature (Table 1, entry
4). It is used in organic synthesis and also as a dye intermediate.[24] Another indust-
rially important compound, 2,6-dichloro-4-nitroaniline, was obtained by dichlorina-
tion of 4-nitroaniline (5) in 97% yield and 98.8% purity (Table 2, entry 3) within 2 h
at 40 ꢀC. This compound is known to be active against certain soil, foliar, and fruit
pathogens on ornamental and agricultural crops. Earlier its synthesis has been
reported by Smythe et al.[9] using Cl2 gas. 2-Bromo-6-chloro-4-nitroaniline, which
Table 2. Product selectivity in chlorination of various aromatic substrates
Product purityb (%)
Entry
Substrate
Product
Yielda (%)
Main product
Others
1
2
99c
99.2
0.8
98c
96.23
3.77
3
97d
98.8
1.2
aIsolated yield.
bPurity determined by HPLC.
cReaction conditions: substrate, 0.01 mol; NaCl, 0.03 mol; NaIO4, 0.005 mol; AcOH, 10 mL; H2SO4,
1.0 mL; SLS, 50 mg; temp 25 ꢀC.
dReaction conditions: substrate, 0.01 mol; NaCl, 0.05 mol; NaIO4, 0.01 mol; AcOH, 10 mL; H2SO4,
1.0 mL; SLS, 50 mg; temp 40 ꢀC.

OXIDATIVE CHLORINATION OF AROMATIC COMPOUNDS
3659
Table 3. Effect of amount of NaCl on the yield and melting point of 4-bromo-2-chloroacetanilide in
chlorination of 4-bromoacetanilide (1)
Entry
Moles of NaCl
Yield (%)
Mp (ꢀC) (lit.[28a] 151–152)
Appearance
1
2
3
4
0.01
0.02
0.03
0.04
79.3
92.59
99
148
152
152
152
Yellowish white
White crystals
White crystals
White crystals
98.2
Notes. Reaction conditions: substrate, 0.01 mol; NaIO4, 0.005 mol; AcOH, 10 mL; H2SO4, 1.0 mL; SLS,
50 mg; temp 25 ꢀC.
is used as dye, as well as intermediate for dye,[25] was also synthesized within 1 h
starting from 2-bromo-4-nitroaniline (6). 2,6-Dichloro-4-nitrophenol, which is a
valuable chemical intermediate useful in agrochemistry that can be used as enzyme
inhibitor, was obtained in 93% yield from 4-nitrophenol (9) within 2 h at 40 ꢀC. Ear-
lier this compound was synthesized by Desmurs et al.[10] at high temperature (120 ꢀC)
using molecular chlorine as chlorinating agent. 5-Chlorosalicylic acid[26] (Table 1,
entry 12), which is used in pesticides, medicines, and as dye intermediates was
synthesized in 85% yield within 2 h.
Because chlorination reactions are less selective than bromination and chlorine
has a lower oxidation potential than bromine, in case of chlorination reactions we
needed a 3-fold molar excess of NaCl for each introduced chlorine atom.[27] Results
of Table 3 show that decreasing the concentration of NaCl from 0.03 mol to 0.01 mol
reduced the yield of 4-bromo-2-chloroacetanilide from 99% to 79.3% and also
depressed the melting point. Increasing the concentration from 0.03 to 0.04 mol
makes the yield of the product become static and there is no further increase in yield.
It is quite obvious from Table 4 that the yield and quality of the product is strongly
dependent on the concentration of NaIO4. With the decrease in amount of NaIO4
from 0.005 to 0.0025 mol, the yield of the product drops to 78.1% and the melting
point also lowers to 149 ꢀC (not within the required standards). When we further
increased the amount of NaIO4 from 0.005 to 0.01 mol, there was no effect on yield.
It has also been observed from Table 5 that use of 50 mg of SLS gives the best yield
(99%) and also improves the texture of the product. In the absence of SLS the yield
was 85%, purity was 90.6% (Table 6, entry 1), and yellowish white product was
obtained. As we increased the amount of SLS up to 50 mg, the yield of product
increased from 85 to 99%, purity of product increased from 90.6 to 99.2%
Table 4. Effect of amount of NaIO4 on the yield and melting point of 4-bromo-2-chloroacetanilide in the
chlorination of 4-bromoacetanilide (1)
Entry
Moles of NaIO4
Yield (%)
Mp (ꢀC) (lit.[28a] 151–152)
Appearance
1
2
3
0.0025
0.005
0.01
78.1
99
149
152
152
Yellowish
White shiny crystals
White
98.8
Notes. Reaction conditions: substrate, 0.01 mol; NaCl, 0.03 mol; AcOH, 10 mL; H2SO4, 1.0 mL; SLS,
50 mg; temp 25 ꢀC.

3660
T. MAHAJAN ET AL.
Table 5. Effect of amount of SLS on the yield of 4-bromo-2-chloroacetanilide in chlorination of 4-bro-
moacetanilide (1)
Entry
Amount of SLS (mg)
Yield (%)
Mp (ꢀC) (lit.[28a] 151–152)
Appearance
1
2
3
4
5
6
—
10
85
149
151
152
152
152
152
Yellowish white
Yellowish white
White
94.2
94.6
99
30
50
White shiny crystals
White
White
70
100
97.4
97
Notes. Reaction conditions: substrate, 0.01 mol; NaCl, 0.03 mol; NaIO4, 0.005 mol; AcOH 10 mL;
H2SO4 1.0 mL; temp 25 ꢀC.
Table 6. Effect of addition of SLS on purity of 4-bromo-2-chloroacetanilide in the chlorination of 4-bro-
moacetanilide (1)
Product purityb (%)
Entry
Amount of SLS (mg)
Yielda (%)
Main product
Others
1
2
—
50
85
99
90.6
99.2
9.4
0.08
aIsolated yield.
bPurity determined by HPLC.
Notes. Reaction conditions: substrate, 0.01 mol; NaCl, 0.03 mol; NaIO4, 0.005 mol; AcOH, 10 mL;
H2SO4, 1.0 mL; SLS, 50 mg; temp 25 ꢀC.
(Table 6, entry 2), and also white shiny crystals of 4-bromo-2-chloroacetanilide were
obtained. On further increase in amount of SLS from 50 to 100 mg, there was no
effect on yield. Therefore, it is concluded experimentally that 0.005 mol of NaIO4,
0.03 mol of NaCl, and 50 mg of SLS under acidic conditions (H2SO4, 1 mL) afford
best yield and excellent purity of chlorinated product in acetic acid as solvent.
Dichlorinated product has been obtained by increasing the amounts of NaCl
(0.05 mol) and NaIO4 (0.01 mol) at 40 ꢀC (Table 1, entries 5, 7, 9, and 13).
CONCLUSIONS
It is concluded that chlorination of commercially important aromatics using
NaCl as chlorine source, and NaIO4 as oxidant in acidic medium can be performed
within 1–2 h in AcOH and a small amount of SLS to give good yield and purity of
chlorinated product. Monochlorinated product is obtained at room temperature,
whereas for dichlorination temperature is raised slightly (40 ꢀC) along with increased
amount of NaCl and NaIO4. When the reaction was catalyzed in the presence of a
small amount of SLS, the yield, purity, and reaction rate increased.
EXPERIMENTAL
Starting materials and other reagents were obtained from commercial suppliers
1
and used without further purification. H NMR spectra were recorded on a Bruker

OXIDATIVE CHLORINATION OF AROMATIC COMPOUNDS
3661
Avance II 400-MHZ spectrometer in CDCl3 or dimethylsulfoxide (DMSO) using tet-
ramethylsilane (TMS) as an internal standard. Mass spectra were recorded on
Micromass Quattro Micro API triple quadrupole MS equipped with a standard
APCI ion source. High-performance liquid chromatographic (HPLC) analyses were
conducted using a Waters 2695 instrument with PDA detector, column C18 (250 mm
ꢁ 4.6 mm ꢁ 5 mm), solvent system of 70% CH3OH þ 30% H2O, and flow rate of
1 mL=min. HPLC purity is reported by area %.
Monochlorination: Synthesis of 4-Bromo-2-chloroacetanilide (1)
To a solution of 4-bromoacetanilide (2.141 g, 0.01 mol) in AcOH were added
SLS (50 mg), NaCl (1.753 g, 0.03 mol), and H2SO4 (1 mL), respectively, and the reac-
tion was stirred at room temperature. An aqueous solution of NaIO4 (1.064 g,
0.005 mol) dissolved in 7 mL of water was added dropwise utilizing
a
pressure-equalizing funnel. Yellow color appeared after adding aqueous solution
of NaIO4. Reaction progress was monitored with thin-layer chromatography
(TLC). After completion of the reaction, the mixture was poured into water and fil-
tered. The precipitated mass was washed with water, dried, and recrystallized with
methanol. White shiny crystals of 4-bromo-2-chloroacetanilide were obtained in
2.465 g (99%) yield having 99% purity and melting point 152 ꢀC. 1H NMR
(400 MHz, CDCl3) d 2.23 (s, 3H, CH3), d 7.51 (d, 1H, arom), d 7.39 (dd, 1H, arom),
d 7.59 (br, s, 1H, NH), d 8.27 (d, 1H, arom) ppm. MS: calcd. for C8H7BrClNO [M]þ
249; found 250 [M þ 1]þ.
Dichlorination: Preparation of 2,6-Dichloro-4-nitroaniline (5)
SLS (50 mg), NaCl (2.922 g, 0.05 mol), and H2SO4 (1 mL) were added to a sol-
ution of 4-nitroaniline (1.381 g, 0.01 mol) in AcOH and stirred at 40 ꢀC. Dark yellow
color appeared on dropwise addition of aqueous solution of NaIO4 (2.132 g,
0.01 mol) in 7 mL water. Reaction progress was monitored using TLC. After com-
pletion of reaction, the reaction mixture was cooled at room temperature and poured
into water. The product was filtered, washed with water, and dried in an oven. Yel-
low powder of 2,6-dichloro-4-nitroaniline was obtained in 2.015 g (97%) yield having
1
98.8% purity and melting point 190 ꢀC. H NMR (400 MHz; DMSO) d 8.1 (d, 2H,
arom), d 6.08 (s, 2H, NH2) ppm. MS (APCI): calcd. for C6H4Cl2N2O2 [M]þ
207.0; found, 205.0 [M ꢂ 2]þ.
Spectroscopic Data of Some Chlorinated Aromatic Compounds
1
2,4-Dichloroacetanilide (2). White needles; H NMR (400 MHz; CDCl3) d
2.23 (s, 3H, CH3), d 7.36 (d, 1H, arom), d 7.25 (dd, 1H, arom), d 7.64 (br, s, 1H,
NH), d 8.29 (d, 1H, arom) ppm. MS: calcd. for C8H7Cl2NO [M]þ 204.06; found,
206.0 [M þ 2]þ.
4-Chlorobezanilide (3). White powder; 1H NMR (400 MHz, CDCl3) d
7.19-7.80 (m, 9H, arom) ppm. MS (APCI): calcd for C13H10ClNO [M]þ 231; found
232 [M þ 1]þ.

3662
T. MAHAJAN ET AL.
2-Bromo-6-chloro-4-nitroaniline (6). Yellowish powder; 1H NMR
(400 MHz, DMSO) d 7.26 (s, 2H, NH2), d 8.31 (d, 1H arom), d 8.19 (d, 1H, arom)
ppm. MS (APCI): calcd. for C6H4BrClN2O2 [M]þ 251.45; found, 252.5 [M þ 1]þ.
1
2,6-Dichloro-4-nitrophenol (9). Light yellow crystals; HNMR (400 MHz,
DMSO) d 8.22 (d, 2H, arom), d 6.6 (br, s, 1H, OH) ppm. MS: calcd. for
C6H3Cl2NO3 [M]þ 208; found, 207 [M ꢂ 1]þ.
3-Chloro-4-hydroxybenzaldehyde (10). Light brown powder; 1H NMR
(400 MHz; DMSO) d 9.78 (s, 1H, CHO), d 7.81 (d, 1H, arom), d 7.64 (dd, 1H, arom),
d 7.12 (d, 1H, arom) ppm. MS: calcd. for C7H5ClO2 [M]þ 156.5; found, 157.5
[M þ 1]þ.
2-Chloro-4-nitroacetanilide (11). Yellow powder; 1H NMR (400 MHz,
CDCl3) d 2.24 (s, 3H, CH3), d 8.68 (d, 1H, arom), d 8.29 (d, 1H, arom), d 8.16
(dd, 1H, arom), d 7.91 (br, s, 1H, NH) ppm. MS: calcd. for C8H7ClN2O3 [M]þ
214.61; found, 216.8 [M þ 2]þ.
1
5-Chlorosalicylic acid (12). White crystals; H NMR (400 MHz; DMSO) d
9.05 (s, 1H, OH), d 7.79 (d, 1H, arom), d 7.38 (dd, 1H, arom), d 6.91 (d, 1H, arom)
ppm. MS: calcd. for C7H5ClO3 [M]þ 172; found, 173 [M þ 1]þ.
ACKNOWLEDGMENTS
The authors express their thanks to Kapil Kumar, SRF Ltd., and the director,
Sophisticated Analytical Instrumentation Facility, Punjab University, Chandigarh,
for carrying out the spectral analysis of the compounds.
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