Sonochemical and Mechanochemical Applications in Organic Synthesis
Hovig Kouyoumdjian
Wednesday, March 17, 2010
Energy sources of chemical reactions
Energy sources of chemical reactions
Microwaves
Heat
Pressure
Electricity
https://www.kintera.com/accounttempfiles/account105257/images/heat_thermometer.jpg
2
http://www.mdpi.org/ecsoc/ecsoc‐6/Papers/E001/E001_files/208_files/Micro.gif
http://wpcontent.answers.com/wikipedia/commons/thumb/3/39/ElectrochemCell.png/250px‐ElectrochemCell.png
http://www.americanairworks.com/images/dial_a_pressure.gif
Ultrasound: Alternative source of energy
Ultrasound: Alternative source of energy
• Nanomaterials
• Sonoelectrochemistry
S
l t h it
• Organic synthesis
Organic synthesis
• Glassware cleaning
Ultrasound baths
http://www.bransonic.com/pdf/Bransonic%20Brochure.pdf
3
Outline
•
Ultrasound (US)
– Definition and background
Definition and background
•
Cavitation phenomenon
– Characteristics and influencing factors
•
A sample of sonochemical reactions in organic synthesis
–
–
–
–
•
Kornblum‐Russell reaction
Hetero Michael reaction
Hetero‐Michael reaction
Preparation of Grignard reagent
Suzuki coupling
Cavitation induced mechanochemistry
– Cleavage of azo‐linkages
– Reconfiguration of atropisomers
g
p
– Electrocyclic opening of benzocyclobutene
4
Outline
•
Ultrasound (US)
– Definition and background
Definition and background
•
Cavitation phenomenon
– Characteristics and influencing factors
•
A sample of sonochemical reactions in organic synthesis
–
–
–
–
•
Kornblum‐Russell reaction
Hetero Michael reaction
Hetero‐Michael reaction
Preparation of Grignard reagent
Suzuki coupling
Cavitation induced mechanochemistry
– Cleavage of azo‐linkages
– Reconfiguration of atropisomers
g
p
– Electrocyclic opening of benzocyclobutene
5
Electromagnetic and sound spectrum
Electromagnetic and sound spectrum
Radio
Microwaves
3GHz
Infrared
430THz 750THz
3THz
Earthquake monitoring
Earthquake monitoring
Human speech
Human speech
Low bass notes
Infrasound
Ultraviolet
SONAR
Animals
Acoustic
20Hz
X‐rays
300PHz
Gamma
30EHz
Medical diagnosis
Medical diagnosis
Sonochemistry
Ultrasound
20KHz
2MHz
200MHz
6
Definition of sonochemistry
Definition of sonochemistry
Sonochemistry: A branch of chemical research dealing y
g
with the chemical effects and applications of ultrasonic waves, that is, sound with frequencies above 20 kHz th t li b
that lie beyond the upper limit of human hearing.
d th
li it f h
h i
Luche, J. L. Synthetic Organic Sonochemistry, Plenum Press, New York, 1998, pp. 1–19
7
Best known uses of ultrasound
Best known uses of ultrasound
• Target detection using SONAR
(SOund NAvigation and Ranging)
and Ranging)
• Medical applications:
pp
– Medicalsonography (ultrasonography)
– Acoustic targeted drug delivery
– Cleaning teeth in
Cleaning teeth in dental hygiene
dental hygiene
• Industrial Applications:
– Ultrasonic testing (non‐destructive)
– Ultrasonic cleaning
http://www.personal.psu.edu/users/k/g/kgc5007/Project%203%20Active%20Sonar.gif
http://www.advanceusa.org/blog/content/binary/Ultrasound%202.jpg
http://media.noria.com/sites/archive_images/Backup_200411_Tech‐Ultrasound1.jpg
8
Ultrasound instruments for organic chemistry
h i
Cup‐horn sonicator $1 200‐$1
$1,200
$1,600
600
http://www.nano‐lab.com/ultrasonic‐probe‐dispersion‐equipment.html
Probe sonicator $2 300‐$5
$2,300
$5,000
000
9
Ultrasound reactors in process chemistry
Ultrasound reactors in process chemistry
UIP16000
UIP16000 reactor
Ultrasonic reactor
http://www.hielscher.com/image/7xuip1000hd_flowcell_p0500.jpg
http://www.hielscher.com/image/uip1000_uip16000_p0500.jpg
10
Development of ultrasound in organic synthesis
Development of ultrasound in organic synthesis
1930
Richards and Loomis applied ultrasound (100‐500KHz) in organic synthesis for the first time (1927)
1950
Renaud reported that certain organometallics could be prepared in shorter reaction times using ultrasound bath (1950) 1980
Luche reported metal activation reactions using ultrasound probes (1980)
1990
Mason reported switching reactions using ultrasound Cup‐horn instruments (1995)
2005
Wilson and Moore reported biasing chemical reaction pathways using ultrasound (2007)
Richards, W. T.; Loomis, A. L. J. Am. Chem. Soc. 1927, 49, 3086‐3088
Renaud, P. Bull. Soc. Chim. Fr. 1950, 1044‐1048
Luche, J.‐L.; Damiano, J. C. J. Am. Chem. Soc. 1980, 102, 7926‐7927.
11
Outline
•
Ultrasound (US)
– Definition and background
Definition and background
•
Cavitation phenomenon
– Characteristics and influencing factors
•
A sample of sonochemical reactions in organic synthesis
–
–
–
–
•
Kornblum‐Russell reaction
Hetero Michael reaction
Hetero‐Michael reaction
Preparation of Grignard reagent
Suzuki coupling
Cavitation induced mechanochemistry
– Cleavage of azo‐linkages
– Reconfiguration of atropisomers
g
p
– Electrocyclic opening of benzocyclobutene
12
Ultrasound effects
Ultrasound effects
• Direct effects:
– Ultrasound waves have low Energies (20KHz – 500MHz)
(too low to alter electronic, vibrational, or rotational molecular states)
• Indirect effects:
– Ultrasound waves cause cavitation phenomenon which generates higher energy
(enough energy to alter vibrational and rotational molecular states)
(enough energy to alter vibrational and rotational molecular states)
20KHz‐500KHz Ultrasound waves
Cavitation Phenomenon
X
Rotational and Rotational
and
vibrational alterations
Luche, J. L. Synthetic Organic Sonochemistry, Plenum Press, New York, 1998, pp. 1–19
13
Cavitation phenomenon
Cavitation phenomenon
At sufficiently high power:
‐ Pressure wave cycle exceeds the Pressure wave cycle exceeds the
attractive forces of the molecules ‐ Cavitation bubbles forms
‐ Bubbles grow over a few cycles ‐ Bubbles suffer sudden expansion p
‐ Bubbles collapse violently
(energy generation)
14
Another way of bubble collapse: Microjet
i j formation
f
i
S lid f
Solid surface
• Cavitation bubble is trapped between solid surface and liquid flow
)))) ))))
Sound waves
Cavitation bubble
15
Another way of bubble collapse: Microjet
i j formation
f
i
• Cavitation bubble is trapped between solid surface and liquid flow
Mi j
Microjet
• liquid jet forms (100 m.s
liquid jet forms (100 m s‐1)
)))) ))))
Sound waves
• Violent non‐symmetric bubble collapse
Cavitation bubble
• Microjetting is the reason why ultrasound is effective in cleaning is the reason why ultrasound is effective in cleaning
• Activates surface catalysis
• Increases mass and heat transfer
16
The example of propeller blades
The example of propeller blades
Negative pressure originate microbubbles
Negative pressure originate microbubbles
When collapsing near the metal, they release enough energy to cause erosion to the blade
http://www.tecplot.com/images/showcase/contours/issue_19/01_propeller.jpg
http://www.fractureinvestigations.com/images/prop.jpg
17
Cavitation bubble
Cavitation bubble
H2O  .OH  .H
.
Bulk: Intense shear forces
H  O2  .OOH
OH  .OOH  H 2O  O2
.
OH  .OH  H 2O 2
.
.
Interface:
Shear forces
H  .OH  H 2O
Cavity: extreme condition
18
Factors impacting sonochemistry
Factors impacting sonochemistry
• Acidity, basicity, dipole moment, etc… do not have significant role in sonochemistry
• Volatility, viscosity, dissolved gases, and surface tension are directly involved
directly involved
• These factors can be manipulated via two parameters: These factors can be manipulated via two parameters:
– Acoustic Pressure (P)
– Acoustic Intensity (I)
19
Acoustic pressure
Acoustic pressure
P (t )  PA sin( 2ft   )
P(t) = pressure at any point of an elastic medium (Pa)
PA = acoustic pressure amplitude (Pa) f
= frequency of the alternating pressure wave (Hz)
t
= time (s)
Frequency (KHz scale) 
Frequency (KHz scale) amplitude of irradiation 
amplitude of irradiation 
constant cavitation
constant cavitation
1
Frequency (MHz scale) compression and rarefaction cycles’ duration

If compression and rarefaction cycle duration is short, cavitation might be difficult to achieve
Luche, J. L. Synthetic Organic Sonochemistry, Plenum Press, New York, 1998, pp. 1–19
20
Frequency time relation
Frequency time relation
•
•
Frequency influences the time Frequency
influences the time
taken by a bubble to collapse
High frequency (500 KHz)
High frequency (500 KHz) – Collapse time is 400 ns
– Less than the lifetime of most radicals
radicals (radical reaction will be initiated)
•
H2O  .OH  .H
Low frequency (20 KHz)
Low frequency (20 KHz) .
H  O2  .OOH
OH  .OOH  H 2O  O2
.
OH  .OH  H 2O 2
.
.
H  .OH  H 2O
– Collapse time 10 μs
– Enough time for radicals to recombine
Luche, J. L. Synthetic Organic Sonochemistry, Plenum Press, New York, 1998, pp. 1–19
21
Acoustic pressure and frequency effect
Acoustic pressure and frequency effect Sono‐oxidation of 2,2,6,6‐tetramethylpiperidin‐4‐one 1
O
O2 or Ar
2
N
O2
3
4
Frequency
Gas present
Rate of nitroxide
formation
.OH form
520KHz
O2
3.6 x 10‐6 M/min
Free
520KHz
Ar
No nitroxide
Free
20KHz
O2
0.083 x 10‐6 M/min
recombined 20KHz
Ar
1.08 x 10‐6 M/min
recombined Petrier, C.; Jeunet, A.; Luche, J.‐L.; Reverdy, G. J. Am. Chem. Soc. 1992, 114, 3148‐3152
22
Sono‐oxidation of 2,2,6,6‐tetramethylpiperidin‐4‐one h l i idi
High Frequency 520KHz
Low Frequency 20KHz
Presence of Ar
Presence of Ar
H 2O  OH  H
))))
.
.
OH  .OH  H 2O  O
.
2O  O2
Petrier, C.; Jeunet, A.; Luche, J.‐L.; Reverdy, G. J. Am. Chem. Soc. 1992, 114, 3148‐3152
23
Acoustic intensity
Acoustic intensity
I  PA2 / 2 c
I = acoustic intensity (sound strength)
PA = acoustic pressure amplitude
= acoustic pressure amplitude
ρ = density of the fluid
C = speed of transmission • Acoustic intensity sonochemical
effect

• Minimal intensity is required to reach cavitation threshold
Luche, J. L. Synthetic Organic Sonochemistry, Plenum Press, New York, 1998, pp. 1–19
24
Intensity effect
Intensity effect Ph
O
Ph
O
O
KOH
TBAB
Ph
Chalcone
O
O
Ph
Ph
O
Ph
O
Pentane‐2,4‐dione
A
Conditions
A (%)
B(%)
Stirring
52
0
)))), Cup‐horn
69
0
)))), Probe
72
12
O
B
Sound Intensity
Probe >> Cup‐horn 100W 10W
Mason, T. J.; Berlan, J. Current Trends in Sonochemistry, G. J. Price, Royal Society of Chemistry, Cambridge, 1992, pp. 148–157
25
Summary (Cavitation)
Summary (Cavitation)
• Ultrasound waves indirectly affect chemical reaction through cavitation phenomenon
• Cavitation
Cavitation generates a vacuum, form bubbles which grow over a generates a vacuum form bubbles which grow over a
few cycles and collapse violently
• The energy generated by the collapse manipulates the reaction • High frequency (500KHz), radical mechanism might be favored
High frequency (500KHz) radical mechanism might be favored
26
Outline
•
Ultrasound (US)
– Definition and background
Definition and background
•
Cavitation phenomenon
– Characteristics and influencing factors
•
Sample sonochemical reactions in organic synthesis
–
–
–
–
•
Kornblum‐Russell reaction
Hetero Michael reaction
Hetero‐Michael reaction
Preparation of Grignard reagent
Suzuki coupling
Cavitation induced mechanochemistry
– Cleavage of azo‐linkages
– Reconfiguration of atropisomers
g
p
– Electrocyclic opening of benzocyclobutene
27
Sonochemichal reactions
•
Switching reactions
Switching reactions
– Kornblum‐Russell reaction
•
Homogeneous reactions
Homogeneous reactions
– Hetero Michael reaction
•
Heterogeneous reactions
– Metal activation reactions
• Grignard reagent preparation
– Palladium catalyzed coupling reactions
• Suzuki coupling
28
Ultrasound‐assisted Kornblum‐Russell reaction
i
5
6
7
5
6
8
Dickens, M. J.;Luche, J. L. Tetrahedron Lett. 1991, 32, 4709‐4712
29
Kornblum‐Russell
Kornblum
Russell reaction mechanism
reaction mechanism
Polar pathway
Polar pathway
Br
O2N
5
O
N
O
Li
7
6
SET pathway
8
5
Dickens, M. J.;Luche, J. L. Tetrahedron Lett. 1991, 32, 4709‐4712
30
Ultrasound‐assisted Hetero‐Michael reaction
i
H3C
H3C
HO
9
R=
O
R NH2
OEt
H2O
, r.t., 2 h
R
HN
O
O
H3C
CH3
90%
10
91%
11
9
12
Arcadi, A.; Alfonsi, M.; Marinelli, F. Tetrahedron Lett. 2009, 50, 2060–2064
Tejedor, D.; Santos‐Expósito, A.; García‐Tellado, F. Synlett 2006, 1607‐1609
31
Ultrasound‐assisted Grignard Reagent preparation
i
• Traditional:
d
l
• Ultrasonication:
l
– Oxide free Magnesium
– Periodic crushing of metal
g
SiMe3
Mg, THF,
)))), 45oC, 1 h
90%
Br
13
SiMe3
Br
– Any grade of Magnesium
– Crushing not
g
required
q
SiMe3
MgBr
14
Mg, THF,
X
45oC, 1 h
13
Yamaguchi, R.; Kawasaki, H; Kawanisi, M. Synth. Commun. 1982, 12, 1027‐1037
32
Ultrasound‐assisted
Ultrasound
assisted Suzuki coupling
Suzuki coupling
Ph
I
16
15
Ph
15
Ph B(OH)2
I
Ph B(OH)2
16
1 mol% Pd(OAc)2
Ar, NaOAc
[bbim]+BF4-/MeOH
, r.t., 20 min
Ph Ph
92%
17
1 mol% Pd(OAc)2
Ar, NaOAc
[bbim]+BF4-/MeOH
30oC, 10 h
Deshmukh, R. R.; Jarikote, D. V.; Srinivasan, K. V. Chem. Commun. 2002, 616–617
Ph Ph
25%
17
33
Summary (Sonochemistry)
Summary (Sonochemistry)
• Sonochemistry is utilized in organic synthesis in many areas (switching homogeneous and heterogeneous reactions)
(switching, homogeneous and heterogeneous reactions)
• Sonochemistry might lead to better yields, faster rates and might lead to better yields faster rates and
milder temperatures
34
Outline
•
Ultrasound (US)
– Definition and background
Definition and background
•
Cavitation phenomenon
– Characteristics and influencing factors
•
Sample sonochemical reactions in organic synthesis
–
–
–
–
•
Kornblum‐Russell reaction
Hetero Michael reaction
Hetero‐Michael reaction
Preparation of Grignard reagent
Suzuki coupling
Cavitation induced mechanochemistry
– Cleavage of azo‐linkages
– Reconfiguration of atropisomers
g
p
– Electrocyclic opening of benzocyclobutene
35
Mechanochemistry definition definition
• Mechanochemistry
ec a oc e s y is the molecular‐scale coupling of the s e o ecu a sca e coup g o e
mechanical force and the chemical reaction
– Mechanical breakage
– Chemical behavior of mechanically‐stressed solids – Cavitation‐related phenomena
C it ti
l t d h
– Shockwave chemistry and physics
chemistry and physics
36
Cavitation bubble revisited
Cavitation bubble revisited
Bulk: shear forces
Mechanochemistry
Interface:
shear forces
Cavity: extreme condition
37
Cavitation induces shear forces
Cavitation induces shear forces
polymer
38
Mechanophores
•
Possess strategically weakened bonds
•
Force transfered to the mechanophore from the polymer chain segments
•
Undergo bond breakage or deformation
Undergo bond breakage or deformation •
Many examples for mechanically‐induced chemical processes:
– Cleavage of azo‐linkages
Cl
f
li k
– Reconfiguration of atropisomers
– Electrocyclic opening of benzocyclobutene
= Mechanophore
= Polymer
39
Ultrasound‐induced
Ultrasound
induced cleavage of azo
cleavage of azo‐linkages
linkages
))))
. .
N2
|||
Frequency = 20 kHz
q
y
Intensity = 8.7 W/cm2
Temperature = 6‐9 °C
18
Berkowski, K. L.; Potisek, S.L.; Hickenboth,C.R.; Moore, J.S. Macromolecules 2005, 38, 8975-8978
40
Specific chain scission
Specific chain scission
40KDa
18
40KDa
20KDa
20KDa
19
Berkowski, K. L.; Potisek, S.L.; Hickenboth,C.R.; Moore, J.S. Macromolecules 2005, 38, 8975-8978
41
Control experiment of non‐specific
Control experiment of non
specific scission
scission
40KDa
40KDa
20KDa
18
8
20
0
Berkowski, K. L.; Potisek, S.L.; Hickenboth,C.R.; Moore, J.S. Macromolecules 2005, 38, 8975-8978
42
Differentiation from thermolysis product
Differentiation from thermolysis
Th
e
CH rmol
y
3C
N, sis
82 o
C
Berkowski, K. L.; Potisek, S.L.; Hickenboth,C.R.; Moore, J.S. Macromolecules 2005, 38, 8975-8978
43
13C NMR characterization
C NMR characterization
19
22
21
Black = after sonication for 47 min
Red = after thermolysis for 24 h
Blue = before thermolysis
18
Berkowski, K. L.; Potisek, S.L.; Hickenboth,C.R.; Moore, J.S. Macromolecules 2005, 38, 8975-8978
44
Mechanical reconfiguration of atropisomers*
i
*
S BINOL
S‐BINOL
S‐BINAP
Isomerization barrier
>30kcal mol‐1
R BINOL
R‐BINOL
R‐BINAP
*Atropisomers: chiral molecules whose asymmetric structures are derived from hindered rotations about sterically congested bonds
about sterically
congested bonds
Wiggins,K. M.; Hudnall,T. W.; Shen, Q.; Kryger, M. J.; Moore, J. S.; Bielawski, C. W. J. Am. Chem. Soc.
2010, 132, 3256–3257
45
Mechanochemistry is involved is involved
))))
))))
S‐polymer
R‐polymer
≡
23
Wiggins,K. M.; Hudnall,T. W.; Shen, Q.; Kryger, M. J.; Moore, J. S.; Bielawski, C. W. J. Am. Chem. Soc.
2010, 132, 3256–3257
46
Isomerization monitoring by Circular Dichroism
i l
i h i (CD) ( )
Before sonication
After sonication
After sonication
Br
n
O
O
O
O
CO2CH3
CO2CH3
nBr
))))
> 95% undergoes racimization
23
Aliquots removed at 0, 2, 4, 8, 12 and 24h
Wiggins,K. M.; Hudnall,T. W.; Shen, Q.; Kryger, M. J.; Moore, J. S.; Bielawski, C. W. J. Am. Chem. Soc.
2010, 132, 3256–3257
47
Isomerization monitoring by Circular Dichroism
i l
i h i (CD) ( )
Before sonication
After sonication
After sonication
))))
> 95% undergoes racemization
23
Aliquots removed at 0, 2, 4, 8, 12 and 24h
Wiggins,K. M.; Hudnall,T. W.; Shen, Q.; Kryger, M. J.; Moore, J. S.; Bielawski, C. W. J. Am. Chem. Soc.
2010, 132, 3256–3257
48
Attempts at thermal racemization
Attempts at thermal racemization
Before heating
After heating
270oC
72h
Thermal Gravimetric Analysis (TGA) Wiggins,K. M.; Hudnall,T. W.; Shen, Q.; Kryger, M. J.; Moore, J. S.; Bielawski, C. W. J. Am. Chem. Soc.
2010, 132, 3256–3257
49
Importance of polymer incorporation
Importance of polymer incorporation
))))
26
Br
27
O
O
O
O
O
+
))))
O
25
Br
O
28
O
O
O
O
+
))))
O
25
Wiggins,K. M.; Hudnall,T. W.; Shen, Q.; Kryger, M. J.; Moore, J. S.; Bielawski, C. W. J. Am. Chem. Soc.
2010, 132, 3256–3257
50
Electrocyclic opening of benzocyclobutene
opening of benzocyclobutene
PEG
HN
O
))))
O
O
))))
cis
LFP O
O
O
HN
= Mechanophore
29
PEG
30
= Polymer
PEG = Poly ethylene glycol
l kf
l d l
LFP = link‐functionalized polymer
Hickenboth, C. R.; Moore, J. S.; White, S. R.; Sottos, N. R.; Baudry, J; Wilson, S. R. Nature 2007, 446, 423‐427
51
Unexpected results for ring opening?
Unexpected results for ring opening?
PEG
HN
HO
O
O
O
O
O
O
mPEG-NH2
DCC, DMAP
CH2Cl2
O
O
O
))))
O
OH
O
32
HN
))))
LFP = link‐functionalized polymer
(E, Z)
Violation of Woodward‐Hoffmann rules
cis
LFP 30
(E, E)
PEG
Heat
29
(E, E)
trans
LFP O
31
Heat
(E E)
(E, E)
52
Woodward‐Hoffmann
Woodward
Hoffmann rules
rules
Conrotatory
H
Conrotatory
H3C
CH3
Heat
H3C
H
trans-compound
CH3
H
H
(E,E)
Disrotatory
Disrotatory
Woodward, R. B.; Hoffmann, R. Angew. Chem. Int. Ed. 1969, 8, 781‐853
53
Ultrasound conditions
Ultrasound conditions
H
H3C
CH3
H
Heat
H3C
CH3
H
H
(2E,4E)-hexa-2,4-diene
(3R,4S)-3,4-dimethylcyclobut-1-ene
X
54
Ultrasound conditions
Ultrasound conditions
H
H3C
CH3
H
Heat
H3C
CH3
H
H
(2E,4E)-hexa-2,4-diene
(3R,4S)-3,4-dimethylcyclobut-1-ene
55
Mechanical effect on configuration
Mechanical effect on configuration ≡
trans
( )
(E,E)
Violation of Woodward‐Hoffmann rules
≡
cis
(E,E)
Hickenboth, C. R.; Moore, J. S.; White, S. R.; Sottos, N. R.; Baudry, J; Wilson, S. R. Nature 2007, 446, 423‐427
56
Do modeling calculations agree?
Do modeling calculations agree?
• Minimal
Minimal energy pathway energy pathway
(MEP) calculations
• B3LYP density functional theory (DFT)
• 6‐31G** basis set
Ong, M. T.; Leiding, J.; Tao, H.; Virshup, A.M.; Martinez, T. J. J. Am. Chem. Soc. 2009, 131, 6377–6379
57
Minimal energy pathways
Minimal energy pathways
Disrotatory
Conrotatory
Disrotatory
Conrotatory
Pdt.
S.M.
Pdt.
S.M.
cis
trans
Pdt.
Pdt.
Conrotatory and disrotatory pathways become equivalent at an applied force of 1.5nN
Ong, M. T.; Leiding, J.; Tao, H.; Virshup, A.M.; Martinez, T. J. J. Am. Chem. Soc. 2009, 131, 6377–6379
58
Trapping the intermediate
Trapping the intermediate
PEG
HN
HO
O
O
O
O
O
O
mPEG-NH2
DCC, DMAP
CH2Cl2
O
O
O
trans
LFP )))) O
O
O
OH
31
HN
32
PEG
33
N‐(1‐pyrene)‐maleimide
(Dienophile)
PEG
HN
HO
O
O
O
O
O
mPEG-NH2
DCC, DMAP
CH2Cl2
O
cis
LFP O
O
29
34
O
))))
One product
O
O
OH
30
O
HN
PEG
LFP = link‐functionalized polymer
59
Control experiments
Control experiments
LFP 3 reaction with the pyrene‐labeled
LFP 3 reaction with the pyrene
labeled dienophile, without sonication
dienophile, without sonication
Hickenboth, C. R.; Moore, J. S.; White, S. R.; Sottos, N. R.; Baudry, J; Wilson, S. R. Nature 2007, 446, 423‐427
60
Proof of incorporation
Proof of incorporation
• trans polymer product
• cis polymer product
• PEG polymer
This indicates that pyrene‐labeled dienophiles are incorporated to polymers
61
13C labeling experiments
C labeling experiments
PEG
HN
O
O
O
O
trans
LFP Heat or US
O
*
O
O
32
HN
N
*O
PEG
PEG
HN
O
O
O
O
*
33
O
O
N
*O
PEG
HN
O
HN
O
PEG
O
O
cis
LFP O
30
34
US
O
O
HN
PEG
62
35
13C NMR analysis
C NMR analysis
Control compound
Control compound
Thermal, cis (decomposes)
Thermal, trans
N‐pyrene‐2,3‐naphthimide
Sonication, cis
Sonication, trans
Sonication, trans
Arnold, B. J.; Sammes, P. G..; Wallace, T. W. J. Chem. Soc. Perkin Trans. I 1974, 415
63
Chain length factor
Chain length factor
4 kDa S.M.
cis
40 kDa
Sonicated
4 kDa
Sonicated
32
13C NMR
4 kD S.M.
4 kDa
SM
trans
40 kDa
Sonicated
4 kDa
Sonicated
13C NMR
30
Amide carbonyl (red) in the starting material
Ester carbonyl (blue) in the starting material
Amide carbonyl (green) in Diels‐Alder adduct 64
Summary (Mechanochemistry)
Summary (Mechanochemistry)
• Ultrasound
Ultrasound can be applied to polymer based reagents to break can be applied to polymer based reagents to break
or reconfigure bonds in chemical reactions
• The mechanical effects can be clearly differentiated from the thermal effects in the presence of polymeric chains
• Shear forces generated by cavitation, represent the most accepted explanation for the observed mechanochemical effects 65
Conclusion
• Although low in energy, ultrasound waves can indirectly effect chemical reactions ia a high energ e ent referred to as the
chemical reactions, via a high energy event referred to as the cavitation phenomenon
• Recent advances in mechanochemistry show a considerable potential in the fields of polymer and organic chemistry
• Additional research needs to be conducted to better understand the physical repercussions of the cavitation phenomenon, as well as, to explore the potentials of ultrasound technology
l
th
t ti l f lt
dt h l
gy
p
,
g
• Ultrasound technology has more potentials, other than glassware cleaning application
66
Acknowledgment
•
•
•
•
•
•
•
Prof. Xuefei
o ue e Huang
ua g
Prof. Babak Borhan
Prof James E Jackson
Prof. James E. Jackson
Labmates
Allison Aman D., Monica, Gina, Luis Q., Anil Allison, Aman
D Monica Gina Luis Q Anil
My family
Audience
67
Now, back to…..
WORK !!!
St. Patrick’s day
March Madness
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http://consequenceofsound.net/wp‐content/uploads/2008/11/st_patricks_day_graphics_04.gif
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