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
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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
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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
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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
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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.
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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
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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
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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
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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)
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Acoustic pressure Acoustic pressure P (t ) PA sin( 2ft ) 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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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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
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Now, back to….. WORK !!! St. Patrick’s day
March Madness
http://games.espn.go.com/tcmen/en/entry?entryID=2724115&print=true http://consequenceofsound.net/wp‐content/uploads/2008/11/st_patricks_day_graphics_04.gif
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