Hov Ho i v g i Ko Kouyo uyoumdji j a i n

Sonochemical and Mechanochemical Applications in  Organic Synthesis Hovig Kouyoumdjian Wednesday, March 17, 2010 Energy sources of chemical reactio...
Author: Raymond Ray
0 downloads 2 Views 4MB Size
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

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

68