surfactants as catalysts for organic reactions in water atefeh garzan 11/07/07
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Surfactants as Catalysts for Organic Reactions in
Water
Atefeh Garzan
11/07/07
Homogeneous catalysts:
Brønsted acid catalysis:
Lewis acid catalysis:
- Advantages: high activity, selectivity - Disadvantages: separation and recycling problems
Homogeneous catalysis: catalyst is in the same phase as reactants.
+AlCl3H
R
O
R Cl
O
OR
H
H2O+ ROH
O
Heterogeneous catalysts: Heterogeneous catalysis: catalyst is in a different phase than reactants.
- Metals alone
- Metals plus other component
- Advantages: easy separation and recovery- Disadvantages: less activity and selectivity
Other catalysts:
New Methods to combine the benefits:
- high activity, selectivity
- easy separation and recovery
Transfer a homogeneous catalyst into a multi phase system:
- surfactant - phase transfer system- organic or inorganic support:
H. Turkt, W. Ford, J. Org. Chem. 1991, 56, 1253. C. Starks, J. Am. Chem. Soc. 1971, 93, 195.
NaOCl
1
O
N
N
N
N
ClNaO3S
ClSO3Na
ClCl
Cl Cl
ClSO3Na
ClNaO3S
MnII
ClBr + NaCN(n-Bu)4P Cl
CN + NaBr
Surfactant:
surfactant
Surface Active Agent
Surfactants have amphiphilic structure:
HydrophobicHydrophilic
Classification of surfactant:
Anionic
Cationic
Amphoteric
Nonionic
Sodium dodecylsulfate (SDS)
Cetylpyridinium bromide
Dipalmitoylphosphatidylcholine (lecithin)
Polyoxyethylene 4 lauryl ether
N
Br
SO Na
O
O
O
O
O
OP
OCH2CH2N(CH3)3
OO
OO
OO
OH
Behavior of surfactants:
When a molecule with amphiphilic structure is dissolved in aqueous medium, the hydrophobic group distorts the structure of the water.
As a result of this distortion, some of the surfactant molecules are expelled to the surfaces of the system with their hydrophobic groups
oriented to minimize contact with the water molecules.
Nonpolar tail
Polar head
Micelle formation:When the water surface is or begin to be saturated, the overall energy reduction may continue through another mechanism:
Micelle formation
Hunter, Foundations of Colloid Science, p. 572, 1993.
Driving force:Hydrophobic effect
Formation of the micelle No formation of the micelle
Electrostatic repulsion
Critical Micelle Concentration (CMC):
CMC decreases with increasing alkyl chain length CMC increases as the polar head becomes larger. CMC of neutral surfactants lower than ionic
CMC
Hydrophobic effect Electrostatic repulsion
Krafft temperature: For surfactants there exists a critical temperature above which solubility rapidly increases
(equals CMC) and micelles form Krafft point or Krafft temperature (TK )
Krafft point strongly depends on the size of head group and counterion.
Surfactant Tk (oC)
C12H25SO3-Na+
C12H25OSO3-Na+
n-C8F17SO3-Na+
n-C8F17SO3-K+
38
16
75
80
D. Myers, surfactant science and technology, p.111, 2006.
Surfactant aggregates:
Monomers
Spherical Micelles
Polar Solvent
Bilayer Lamella
Cylindrical Micelles
Nonpolar Solvent
Reverse Micelles Inverted Hexagonal Phase
Easy separation and recovery, high activity, selectivity.
Surfactant in organic reaction:
In this system, we can use water as solvent; in water, surfactants can:
- Act as a catalyst
- Help to solubilize the organic compounds in water
In comparison to organic solvents, water is:
- Cheap
- Safe
- Less harmful
Micellar catalysis:
Electrostatic interaction:
M. N. Khan, N. H. Lajis, J. Phys. Org. Chem. 1998, 11, 209.
Additive Conc. (M) 103 Kobs (s-1) - - 1.83
0.01 1.28
0.01 1.78
0.01 2.05
Na ( )11SOO
O
O
N
O
O
OH
Kopen N
OHO
O
N
Br
13
OO
OH99
Micellar catalysis:
N
N
N
N
N
OH
O
OOOH
OBr
Br
Br
Br
Br
Br
Br
OH
OH
OH
OH
OH
OH
N
O
O
OH
Kopen N
OHO
O
Micellar catalysis:
Electrostatic interaction:
M. N. Khan, N. H. Lajis, J. Phys. Org. Chem. 1998, 11, 209.
Additive Conc. (M) 103 Kobs (s-1) - - 1.83
0.01 1.28
0.01 1.78
0.01 2.05
Na ( )11SOO
O
O
N
O
O
OH
Kopen N
OHO
O
N
Br
13
OO
OH99
Micellar catalysis:
A + B A_B
Rate= k [A][B]
The reactants are concentrated through insertion to the micelle.
The TS≠ can be stabilized by interaction of polar head group.
A catalyst is a substance that increases the rate of a chemical reaction
without itself being changed in the process.
A+B
A_B
[A---B] ≠
energy
time
activation energy
activation energy
uncatalyzed reactioncatalyzed reaction
Lewis acid catalysis:
Lewis acid catalysis is generally carried out under strictly
anhydrous conditions because of the water-labile nature of most
Lewis acids.
Some metal salts such as rare earth metal triflates can be used
as water-stable Lewis acids.
PhCHO +
(1 equiv.) (1.5 equiv.)
(0.1 eq)
H2Ort, 4h 88%
OSiMe3
Ph
Sc(OTf)3
SDS (0.2 eq)Ph
OH
Ph
O
S. Kobayashi, T. Wakabayashi, S. Nagayama, H. Oyamada, Tetrahedron Lett. 1997, 38, 4559.
Lewis acid surfactant
K. Manabe, Y. Mori, T. Wakabayashi, S. Nagayama, S. Kobayashi, J. Am. Chem. Soc. 2000, 122, 7202.
“Lewis acid-surfactant-combined catalyst (LASC)”, acts:
-as a Lewis acid to activate the substrate molecules
-as a surfactant to help to solubilize the organic compounds in water
Lewis Acid Surfactant Catalyst:
ScCl3 + SOO
O
O3 Na
H2O
SOO
O
OSc3+
3+3 NaCl
K. Manabe, Y. Mori, T. Wakabayashi, S. Nagayama, S. Kobayashi, J. Am. Chem. Soc. 2000, 122, 7202.
Colloidal Dispersion
Organic Compounds
:
Lewis Acid Surfactant Catalyst:
SOO
O
OSc3+
3
Size of surfactant aggregates:
0.1 1.0 10.0 100.0 1000 10000
SolutionsMicelles
Microemulsion
Colloidal dispersion
Emulsion
size (nm)
So
lub
ilit
y
NaO3SOC12H25
Sc(O3SOC12H25)3
Aldol reaction:
92%
83%
76%
19%
PhCHO +
(1 equiv.) (1.5 equiv.)
(10 mol%)
H2Ort, 4h
OSiMe3
Ph
LASC
Ph
OH
Ph
O
Sc3+ ( )11SOO
O
O
3
Sc3+ ( )11OS
3
O
O
Sc3+( )12O
S3
O
O
Sc3+ ( )13OS
3
O
O
>1.0 µm
0.5-1.0 µm
<0.5 µm
High stability
Medium stability
Low stability
(92%) (83%)
(~1.5 µm) (1.1 µm)
(76%) (0.7 µm)
(19%) (0.4 µm)
CMC decreases as the polar head becomes smaller CMC decreases with increasing alkyl chain length
Stability of colloidal dispersion:
Sc3+ ( )11SOO
O
O
3 Sc3+ ( )11OS
3
O
O
Sc3+( )12O
S3
O
O
Sc3+ ( )13OS
3
O
O
Effect of solvents:
solvent yield (%)
H2O 92
DMF 14
DMSO 9
CH2Cl2 3
PhCHO +
(1 equiv.) (1.5 equiv.)
(10 mol%)
H2Ort, 4h
OSiMe3
Ph
1
Ph
OH
Ph
O
1: Sc(O3SOC12H25)3
K. Manabe, Y. Mori, T. Wakabayashi, S. Nagayama, S. Kobayashi, J. Am. Chem. Soc. 2000, 122, 7202.
0
5
10
15
20
25
30
0 2 4 6 8
Time (h)
Yie
ld (
%)
Series1
Series2
Kinetics for aldol reaction:
Aldol reaction in water was found to
be 130 times higher than that in
CH2Cl2.
in water
in CH2Cl2
K. Manabe, Y. Mori, T. Wakabayashi, S. Nagayama, S. Kobayashi, J. Am. Chem. Soc. 2000, 122, 7202.
Necessity to use water:
solvent yield (%)
none 10
DMF 21
pyridine 23
Et2O 14
H2O 80
S. Kobayashi, I. Hachiya, J. Org. Chem., 1994, 59, 3590.
PhCHO +
(10 mol%)
THF, rt, 19h
OSiMe3Yb(OTf)3
Ph
OH OAdditive (500 mol%)
Mechanism of catalytic reaction:
-
-
-
---
-
-
-
-- -
-Sc3+
Sc3+
Sc3+
Sc3+[Sc(H2O)n]3+
[Sc(H2O)n]3+
[Sc(H2O)n]3+
[Sc(H2O)n]3+
H2O
H2O
OSiMe3
Ph
PhCHO
Ph
OH
Ph
O
Role of water:
Hydrophobic interactions in water lead to increase the local
concentration of substrates, resulting in the higher reaction rate in
water.
Hydration of Sc(III) ion and the counterion by water leads to
dissociation of the LASC salt to form highly Lewis acidic species
such as [Sc(H2O)n]+3.
.Manabe, Y. Mori, T. Wakabayashi, S. Nagayama, S. Kobayashi, J. Am. Chem. Soc. 2000, 122, 7202.
Mechanism of catalytic reaction:
-
-
-
---
-
-
-
-- -
-
[Sc(H2O)n]3+
[Sc(H2O)n]3+
[Sc(H2O)n]3+
[Sc(H2O)n]3+
H2O
H2O
OSiMe3
Ph
PhCHO
Ph
OH
Ph
O
Interface:
The rate of the reaction depends on the total area of the interface.
Stirring of the reaction would increase the total area of the interface.
0
10
20
30
40
50
60
70
80
90
100
0 2 4
Time (h)
Yie
ld (
%)
1400 rmp
0 rmp
LASC-catalyzed Aldol reactions:
Ph Me Ph 92
PhCO Me Ph 86
Ph Me2 SEt 98
PhCH=CH Me Ph 91
R1 R2 R3 yield (%)
K. Manabe, Y. Mori, T. Wakabayashi, S. Nagayama, S. Kobayashi, J. Am. Chem. Soc. 2000, 122, 7202.
1a: Sc(O3SOC12H25)3
R1CHO +OSiMe3
R3
(1 equiv.) (1.5 equiv.)
1a(10 mol%)
H2O, rt, 4hR1
OH O
R3
R2
R2
Workup:
After centrifugation at 3500 rpm for 20 min, the colloidal mixture became a tri-phasic system.
water
LASC
Mixture of organic compounds
Friedlander synthesis of Quinolines:
L. Zhanga, J. Wua, Adv. Synth. Catal. 2007, 349, 1047. M. Zolfigol, P. Salehi, A. Ghaderi, M. Shiri, Z. Tanbakouchian, J. Mol. Cat. A 2006, 259, 253.
LASC (catalyst) yield (%)
Sm(O3SOC12H25)3 82
Ce(O3SOC12H25)3 91
Sc(O3SOC12H25)3 90
Ph
O
NH2
+ H3C OEt
OOcat. (10 mol%)
N CH3
CO2EtPh
Water, rt, air
Rhodium catalyst:
Cationic rhodium catalysts are frequently employed as homogeneous
catalysts for:
- hydrogenation
- hydrosilylation
B. Wang, P. Cao, X. Zhang, Tetrahedron Lett. 2000, 42, 8041.
- hydride transfer
- cycloaddition
Rh(dppb) SbF6
CH2Cl2, 10 minO
Ph
HO
Ph
99%
dppb= diphenylphosphanylbutane
Add surfactant
[{RhCl(cod)}2]-tppts
H2O, 50oC, 12h
O
Ph
O
Ph
H
51%
+ O
Ph
14%
O
Ph
[{RhCl(cod)}2]-tppts
H2O, 50oC, 2hO
Ph
H
32%
Oct3NMeCl(cationic)
[{RhCl(cod)}2]-tppts
H2O, 50oC, 2hO
Ph
H
27%
TritonX-100(nonionic)
[{RhCl(cod)}2]-tppts
H2O, 50oC, 2h
O
Ph
H
91%
Na(O3SOC12H25)3(anionic)
tppts= tris(m-sulfonatophenyl) phosphane cod= cyclooctadiene
D. Motoda, H. Kinoshita, H. Shinokubo, K. Oshima, Angew. Chem. Int. Ed. 2004, 43, 1860.
[4+2] annulation of dienynes:
Decreasing
temperature
The Krafft temperature is strongly dependent on the head group and counterion and increases by increasing the size of counterion.
D. Motoda, H. Kinoshita, H. Shinokubo, K. Oshima, Angew. Chem. Int. Ed. 2004, 43, 1860.
[{RhCl(cod)}2]-tppts
H2O, 50oC, 2h
O
Ph
H
91%
O
Ph
Na(O3SOC12H25)3
[{RhCl(cod)}2]-tppts
H2O, 25oC, 2hO
Ph
H
0%
O
Ph
Na(O3SOC12H25)3
[{RhCl(cod)}2] (2.5 mol%)tppts (20 mol%)
[4+2] annulation of dienynes:
No ligand
D. Motoda, H. Kinoshita, H. Shinokubo, K. Oshima, Angew. Chem. Int. Ed. 2004, 43, 1860.
[{RhCl(cod)}2] (2.5 mol%)tppts (20 mol%)
[{RhCl(cod)}2] (2.5 mol%)
[{RhCl(cod)}2]
H2O, 25oC, 1h
O
Ph
H
96%
O
Ph
Na(O3SOC12H25)3
[{RhCl(cod)}2]-tppts
H2O, 25oC, 2hO
Ph
H
0%
O
Ph
Na(O3SOC12H25)3
Decreasing the amount of catalyst
nbd= norbornadiene
[{RhCl(cod)}2]
H2O, 25oC, 1h
O
Ph
H
96%
O
Ph
Na(O3SOC12H25)3
[{RhCl(cod)}2]
H2O, 25oC, 20min.
O
Ph
H
26%
O
Ph
Na(O3SOC12H25)3
[{RhCl(nbd)}2]
H2O, 25oC, 20 min.O
Ph
H
93%
O
Ph
Na(O3SOC12H25)3
[{RhCl(cod)}2] (2.5 mol%)
[{RhCl(cod)}2] (1.25 mol%)
[{RhCl(nbd)}2] (1.25 mol%)
Formation of micellar catalyst:
Formation of micelle:
Ion-electrode analysis:
- concentration of Cl- (obs.):
2.54 × 10-3 molL-1
- concentration of Cl- (cal.):
2.50 × 10-3 molL-1
D. Motoda, H. Kinoshita, H. Shinokubo, K. Oshima, Angew. Chem. Int. Ed. 2004, 43, 1860.
SDS + [Rh(nbd)(H2O)n]+
Rh+
Rh+
Rh+
Rh+
Rh+
Rh+
Rh+
Rh+
Rh+
Rh+
Rh+
Rh+Rh+
-
-
-
---
-
-
-- -
-
-
[{RhCl(nbd)}2] + H2O [Rh(nbd)(H2O)n]+ + [Cl(H2O)m]-
[4+2] annulation in water:
Dienyne t[min] Product Yield (%)
25 93
10
97
120
(24 h)
95
71
D. Motoda, H. Kinoshita, H. Shinokubo, K. Oshima, Angew. Chem. Int. Ed. 2004, 43, 1860.
O
Ph
NBn
O
OH
Ph
CO2EtCO2Et
O
Ph
H
O
H
HO
NBn
H
Ph
HCO2Et
CO2Et
Brønsted acid catalyst:
The use of a Brønsted acid is one of the more convenient and
environmentally benign methods of catalyzing organic reactions in
water.
The advantage of water over organic solvents in Brønsted-catalyzed
reactions is that the:
- nucleophilicity of the corresponding base may be of less concern
due to extensive solvation of charge by hydrogen-bonding water
molecules.
Brønsted acid surfactant combined catalyst
Dehydration reactions in water:
Remove Water
Add excess amount of substrates
R OH
O
+ R'OH R O
OR' + H2O
R OH
O
+ R'OH R O
OR' + H2O
R OH
O
+ R'OH R O
OR' + H2O
Brønsted acid surfactant Catalyst:
RCO2H
R'OH
: Brønsted acid surfactant catalyst
K. Manabe, S. Iimura, X. Sun, S. Kobayashi, J. Am. Chem. Soc. 2002, 124, 11971.
RCO2R'
H2O
H2O
H2O
Esterification with various catalysts:
NaO3SC6H4C12H252
Sc[O3S(CH2)11CH3]315
H2SO41
TsOH 4
OBSA 39
DBSA 60
Catalyst Yield (%)
catalyst(10 mol %)
H2O40 oC, 24 h
OH
O+ HO Ph
1 : 1
O
O
Ph( )10 ( )10
SO
OOH
SO
OOH
SO
OOH
11
7
TsOH:
OBSA:
DBSA:
K. Manabe, S. Iimura, X. Sun, S. Kobayashi, J. Am. Chem. Soc. 2002, 124, 11971.
0
2
4
6
8
10
12
14
16
18
20
0 20 40 60
Time (h)
Yie
ld (
%) DBSA
OBSA
TsOH
Initial rate of esterification in water:
DBSA catalyzed the reaction 2.3 times faster than OBSA
and 59 times faster than TsOH
SO
OOH
SO
OOH
SO
OOH
11
7
TsOH:
OBSA:
DBSA:
Various amounts of DBSA:
10 84
50 71
100 58
200 32
amount of DBSA (mol %) yield (%)
K. Manabe, S. Iimura, X. Sun, S. Kobayashi, J. Am. Chem. Soc. 2002, 124, 11971.
catalyst(10 mol %)
H2O40 oC, 24 h
OH
O+ HO Ph
1 : 1
O
O
Ph( )10 ( )10
Size of particles:
10 (mol%) 200 (mol%)
K. Manabe, S. Iimura, X. Sun, S. Kobayashi, J. Am. Chem. Soc. 2002, 124, 11971.
10 µm
Effect of substrates:
0 5
2 39
4 72
6
8
10
10a
78
81
84
15
n yield (%)
a: ethanol was used.
DBSA(10 mol %)
H2O, 40 oCOH
O+ HO Ph O
O
Ph( )n ( )n
Esterification of various substrates:
89
92
>99
91
R R` yield (%)
K. Manabe, S. Iimura, X. Sun, S. Kobayashi, J. Am. Chem. Soc. 2002, 124, 11971.
(1:2)
DBSA (10 mol %)
H2O, 40 oC, 48 hR OH
O
+ R'OH R O
OR'
CH2-
( )8
CH2-
( )8
PhCH2-
Ph CH2-
PhCH2
-
CH2-
( )9
CH2-
( )9
BrCH2
-( )9
Etherification:
Williamson ether synthesis:
Lewis acid catalyze:
G. V. M. Sharma, T. Rajendra Prasad, A. K. Mahalingam, Tetrahedron Lett. 2001, 42, 759.
ROH + R'XNaOH
ROR'
X= halides, tosylates
PhOH +
Yb(OTf)3/FeCl3 (10 mol%)
CH2Cl2
PhO Ph
PhPhOH
Ph
Etherification:
DBSA (10 mol%)
H2O, 24hOH + O Ph
Ph
89%
( )9 ( )9PhOH
Ph
OH( )9 + OOH O( )9
O77%
DBSA (10 mol%)
H2O, 24h
DBSA (10 mol%)
H2O, 24hPhOH
Ph+
PhOH
Ph
PhO
Ph
PhPh
91%
K. Manabe, S. Iimura, X. Sun, S. Kobayashi, J. Am. Chem. Soc. 2002, 124, 11971.
0
20
40
60
80
100
120
0 50 100 150
Time (h)
Yie
ld (
%)
benzhydrol
benzhydryldodecyl ether
dibenzhydrylether
Etherification:
Ph
OH
Ph
Ph
PhB
OH( )9
Ph
PhA
PhO
Ph
PhPh
DBSA (10 mol%)
H2O, 24hOH + O Ph
Ph( )9 ( )9Ph
OHPh
+
89% 10%
A B
OH( )9
Ph
PhA
B
PhO
Ph
PhPh
Surfactant, asymmetric organocatalyst:
-
-
-
+ X-Na+
-NaX+
STAO
a)
b) + OH-H+
-H2O+
STAO
+ : Chiral imidazolium cation : Anion of surfactant
S. Luo,X. Mi, S. Liu, H. Xu, J. Cheng, Chem. Commun., 2006, 3687.
-
-
Michael addition of cyclohexanone:
1 12 np — —
2 12 20 nd nd
3 12 93 97 : 3 97
Catalyst t/h yield (%) syn : anti ee (%)
S. Luo,X. Mi, S. Liu, H. Xu, J. Cheng, Chem. Commun., 2006, 3687.
O
+ PhNO2
STAO (20 mol%)
H2O, RT
ONO2
Ph
NH
NN
Bu
3
NH
NN
Bu
2
NH
NN
C8H17-n
Br
1
Br S C12H25
O
OO
STAO= Surfactant-type asymmetric organocatalyst
R Time/h Yield (%) syn : anti ee (%)
Ph 12 93 97 : 3 97
3-NO2Ph
36 83
97 : 3 97
2-ClPh 12 >99
99 : 1 98
4-MePh
12 90
97 : 3 95
4-MeOPh
15 84 99 : 1 94
2-Naphthyl 15 84 97 : 3 96
S. Luo,X. Mi, S. Liu, H. Xu, J. Cheng, Chem. Commun., 2006, 3687.
Michael addition of cyclohexanone:
O
+ RNO2
STAO (20 mol%)
H2O, rt
ONO2
R
Conclusions:
Advantages of using of the surfactant combined catalysts in organic
reaction:
- using of water as a solvent
- high activity
- solve the problem of reagent incompatibility
- easy separation and recovery
Disadvantages of using of the surfactant combined catalysts in
organic reaction:
- substrate limitation
- catalyst limitation
Dr. Borhan
Dr. Smith Dr. Jackson Dr. Baker Dr. Walker
Chrysoula
Marina, Aman, Calvin, Dan, Sing, Mercy, Roozbeh, Stewart, Toyin, Wenjing, Xiaofei,
Xiaoyong
Afra, Maryam, Paramita, Behnaz
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