Advanced Organic Chemistry/ Organic Synthesis – CH 621 .

Advanced Organic Chemistry/Organic Synthesis – CH 621Ultrasound Assisted OrganicSynthesis (Sonochemistry)Bela TorokDepartment of ChemistryUniversity of Massachusetts BostonBoston, MA1

Ultrasonics/Sonochemistry - Historical OverwievUltrasonics- Ultrasounds (20-10 000 kHz)- 1880 Piezoelectricity (Curie brothers)- 1893 Galton- 1912 TITANIC- 1912 Behm (Echo technique)- 1917 Langevin (Ultrasonic variation,Icebergs, Submarines)- 1945 Application in chemistry2

Ultrasonics/Sonochemistry – BasicsFrequency ranges of sound3

Ultrasonics/Sonochemistry – BasicsSound transmission through a medium4

Ultrasonics/Sonochemistry – Acoustic CavitationBubble size and cavitationdynamicsFormation of an acoustic bubbleTransient cavitation5

Ultrasonics/Sonochemistry – Acoustic CavitationAcoustic cavitation in a homogeneous liquidSuslick - 4-5000 K6

Ultrasonics/Sonochemistry – Acoustic CavitationAcoustic cavitation in solid/liquid system7

Ultrasonics/Sonochemistry – Acoustic CavitationAcoustic cavitation in solid/liquid system8

Ultrasonics/Sonochemistry – Acoustic CavitationAcoustic cavitation in liquid/liquid system9

Ultrasonics/Sonochemistry – Sonochemical EffectSpecific ultrasonic effect ?Yes and NoNo - another internal heating approachYes - The temperature dependence of EA of different reactionscould be significantly different – change in selectivities- Very effective mixing- Cavitation- Surface cleaning10

Ultrasonics/Sonochemistry – ExperimentalParameters1. Acoustic frequencyIncreasing frequency – increasing energyTheory - usually higher reaction rateReal life – optimum frequency as we have to balancereactivity/selectivityThe effect is different for every reaction and general rule can not bemade.11

Ultrasonics/Sonochemistry – Sonochemical Effect2. Acoustic powerSimilar as frequency, however, the extent of increase is limitedOptimum12

Ultrasonics/Sonochemistry – Sonochemical Effect3. TemperatureCavitation bubbles – energy of collapsePressure inside the bubbleIn general lower temperature is better, but again there is an optimumas higher temperature increases the probability of the cavitation13

Ultrasonics/Sonochemistry – Sonochemical Effect4. External (static) pressureNot quite clear, but in general higher pressure is better.Role of particles (ultrafiltration)14

Ultrasonics/Sonochemistry – Sonochemical Effect5. GasPolytrop ratio (γ Cp/Cv), thermal conductivity, and solubilityUsually inert gases are the best (noble gases)15

Ultrasonics/Sonochemistry – Sonochemical Effect6. SolventShould be as inert as possible, and stable toward ultrasoundsSonolysis of the solventUsually high bioling point is preferred, but it is controversialas diethylether is a good solvent in many applications.16

Ultrasonics/Sonochemistry – ExperimentalParametersExperimental parameterPhysical parameterEffectAcoustic frequencyPeriod of bubble collapseChange in the size of the bubblesAcoustic powerSize of the reaction zoneThe number of cavitationphenomena in a unit volumeTemperatureVapor pressure of liquidThemal activationThe content of bubbles, theintensity of collapseSecondary reactionsStatic pressureTotal pressureSolubility of gasIntesity of collapseThe content of bubblesGasPolitrop ratioThermal conductivityChemical reactivitysolubilityIntesity of collapsePrimer and secondary reactionsThe content of bubblesSolventVapor pressureSurface tensionViscosityChemical reactivityIntesity of collapseLimit of transient cavitationPrimer and secondary reactions17

Ultrasonics/Sonochemistry – TransducersGalton whistle (physical)Liquid whistle (physical)Piezoelectric sandwich transcducerMagnetostrictive transcducer18

Ultrasonics/Sonochemistry – Reactors19

Ultrasonics/Sonochemistry – Applications- Electronics industry (coating with metals)- Therapy (surgery with ultrasounds), diagnostics- Food industry- Materials (metallurgy)- Synthesis- Environmental applications20

Ultrasonics/Sonochemistry – SynthesisApplications in Organic Synthesis1. Homogeneous Sonochemistry- Aqueous medium- Non-aqueous media2. Heterogeneous Sonochemitsry- Phase Transfer Catalysis- Reactions with metals- Heterogeneous Catalysis3. Enzyme reactions21

Ultrasonics/Sonochemistry – Synthesis1. Homogeneous sonochemistry1.1. Aqueous sonochemistryCOOHH2OH OH2H2 OH2 OH2O0,5 O2 2 HH OHH2OH2H2O2O H2OO2H2O2 BrBr2) ))COOHHOOC(2.8)COOHCOOHCOOH(2.9)) ))OH22

Ultrasonics/Sonochemistry – Synthesis1. Homogeneous sonochemistry1.2. Non-Aqueous sonochemistry23

Ultrasonics/Sonochemistry – Synthesis1.2. Non-Aqueous sonochemistryRCl3CCOONa, CH3CN NCCl3R) ))I- CCl3NR'R (2.14)NR'R'70-100 %RRR(2.15)tBuOK))) N-IMeNNOtBuOMeMe85-98 %OC CH3CH2RRCH3COCH3, NaOH NMe-I)))R (2.16) NMeOCH2NCMeCH391 - 98 %24

Ultrasonics/Sonochemistry – Synthesis1.2. Non-Aqueous sonochemistryOH P OEtEtOo90 C, toluene stirringsonicationOEtO PEtONHMeNMe15 min012Yield (%)30 min60 min0 53267120 min378225

Ultrasonics/Sonochemistry – Synthesis1.2. Non-Aqueous sonochemistryOOOOR R' R" R R' R"OOR R' R"Yield (%)stirringsonication10-5357-9326

Ultrasonics/Sonochemistry – Synthesis1.2. Non-Aqueous sonochemistry)))OO O2OOOOHOOH HMo(CO)6OH O27

Ultrasonics/Sonochemistry – Synthesis2. Heterogeneous sonochemistry2.1. Phase transfer catalysis28

Ultrasonics/Sonochemistry – Synthesis2.1. Phase transfer catalysisClNaOH CHCl3:CCl2Cl0.7-5h74-99%NaOH CHCl3TEBAHCCl2H4.3HCCl2H1stirring 9 h15%sonication, 3h 83%29

Ultrasonics/Sonochemistry – Synthesis2.1. Phase transfer catalysis30

Ultrasonics/Sonochemistry – Synthesis2.2. Reactions with metalsRO R"-ClRLi)))R'R'R"OH10-40 min 68-99%OR R'-ClOLiLi, THF)))ROR'72-99%31

Ultrasonics/Sonochemistry – Synthesis2.2. Reactions with metalsCOOEtEtOOCCOOEtK, tolueneO))), 5 min83%RF-X CO2Zn, DMF)))R F COOH35-77%Me C 8H 17MeMe C 8H 17Zn, AcOHMe))), 10 minOHH32

Ultrasonics/Sonochemistry – Synthesis2.3. Heterogeneous catalysis33

Ultrasonics/Sonochemistry – Synthesis2.3. Heterogeneous catalysis34

Ultrasonics/Sonochemistry – Synthesis2.3.Heterogeneouscatalysis35

Microwaves/Sonochemistry – References- tml- Luche, J. L., Synthetic Organic Sonochemistry, Plenum Press, 2001- Suslick, K. S., Ultrasound: Its Chemical, Physical, and Biological Effects;VCH, 1988.- Mason, T. J., Sonochemistry: Current Uses and Future Prospect in Chemicaland Industrial Processing, RSC, 199936

Advanced Organic Chemistry/ Organic Synthesis – CH 621 Ultrasound Assisted Organic Synthesis (Sonochemistry) Bela Torok Department of Chemistry