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Fig. 1-16. Closed –A and open –B types of cinchonidine conformers. Hydrogens are not shown for clarity. The relative population of these conformers depends on polarity of the solvent and possible chemical interaction (cinchonidine-solvent), in fact as was show by calculations and NMR spectroscopy the open 3 conformer is most abundant in the solvent with low dielectric constant. Fig. 1-17. Dependence of relative abundance of conformer (Open 3) on solvent polarity determined by NMR spectroscopy and calculated using reaction field model [41]. Solvents: (1) benzene, (2) toluene, (e) ethyl ether, (4) tetrahydroguran, (5) aceton, (6) dimethylformamide, (7) dimethyl sulfoxide, (8) water, (9) ethanol. The calculated model, does not take into account specific interaction such as the hydrogen boning between cinchonidine and ethanol. The figure is adapted from review of Baiker [50]. It is important to note, that in the hydrogenation of ketopantolactone over cinchonidinemodified Pt ee decreases with increasing the dielectric constant of a solvent in the very 11
similar way as relative abundance of the Open 3 conformer. Such relation is in agreement with suggestion that the Open 3 plays a crucial role in the mechanism of the enantioselectivity, see below. Fig. 1-18. Combined plot of the enantiomeric excess achieved in the hydrogenation of ketopantolactone over cinchonidine-modified Pt [52, 71] (left axis) and the population of conformer Open(3) as calculated by density functional theory in combination with a reaction field model (P Open(3) , right axis) versus the dielectric constant of the solvent. The axis scale is arbitrarily chosen. The solvents are (1) cyclohexane, (2) hexane, (3) toluene, (4) diethyl ether, (5) tetrahydrofurane, (6) acetic acid, (7) ethanol, (8) water, (9) formamide. The picture is adapted from [70]. Adsorption modes on Pt and Pd macro support Adsorption of quinoline (part of cinchonidine) and dihydrocinchonidine on the surface of Pt (single or polycrystal) was studied by XPS [72, 73], LEED [72], NEXAFS [74], H/D exchange experiments [75] in vacuum. It was found that adsorption of these compounds takes place preferentially in the flat mode through the π-aromatic system at room and lower temperatures, whereas even at 50 °C on average the quinoline ring was considerably tilted with respect to the surface [74]. Since experimental conditions there were far from used in the reactions, Ferri and Bürgi [76] performed ATR studies of the cinchonidine adsorption on solid-liquid interface, where 100 nm layer of Pt was deposited on alumina and cinchonidine in different concentration in dichloromethane was used. It was found that at low concentration (10 -6 M) a predominantly flat adsorption mode prevails (Fig. 1-19-1), at increasing coverage two different tilted species, α-H abstracted (Fig. 1-19-2) and N lone pair bonded (Fig. 1-19-3) cinchonidine were observed, at higher (10 -3 – 10 -4 M) concentrations all three species coexist on the Pt surface, this was also confirmed by the RAIRS experiments of Zaera and et al. [77]. Adsorption of cinchonidine on Pt (111) was also studied by STM in vacuum and with presence of hydrogen, where mobility of cinchonidine was observed at high hydrogen pressure. 12
Page 1 and 2: Preparation and Characterization of
Page 3 and 4: 5.4 Summary 66 Chapter 6 Cinchonidi
Page 5 and 6: Abstract Studies of the interaction
Page 7 and 8: many compounds are biologically act
Page 9 and 10: Fig. 1-7. Hexahelicene [3]. 7. Chir
Page 11 and 12: R H COOH C OH CH 3 H COO - Bricine-
Page 13 and 14: Catalyst activity, expressed in the
Page 15: In fact, there are only two heterog
Page 19 and 20: surface concentration of cinchonidi
Page 21 and 22: site on Pt surface formed by a adso
Page 23 and 24: Chapter 2 Introduction to the nanos
Page 25 and 26: Triangular prism 5 4 Comments: A -
Page 27 and 28: precursors and building-up. This me
Page 29 and 30: 2.3 Preparation of nanoclusters on
Page 31 and 32: Paris Marseille Ljubljana Synphos Q
Page 33 and 34: Chapter 4 Cinchonidine modified Pt
Page 35 and 36: dihydrocinchonidine (355 mg or 1.2
Page 37 and 38: Table 4-1. Comparison between 5 % P
Page 39 and 40: widening can be used in estimation
Page 41 and 42: 1 Absorbance 0.1 2 1600 1400 1200 1
Page 43 and 44: the focus of these prior experiment
Page 45 and 46: Fig. 4-11. Tilted adsorbed cinchoni
Page 47 and 48: sci., QL. comp. 768 (str) 756 (str)
Page 49 and 50: Conversion, % 100 80 60 40 ITP time
Page 51 and 52: 6A c 10 19.5 B, 20 61 0 3 0.18 0.51
Page 53 and 54: pressure, exposing time, cinchonidi
Page 55 and 56: Fig. 4-16. Linear relationship betw
Page 57 and 58: 1 , 1209 cm -1 and 1382 cm -1 remai
Page 59 and 60: Our results are in line with previo
Page 61 and 62: eaction. The stability of the catal
Page 63 and 64: Table 5-1. Ee and reaction rate ind
Page 65 and 66: Enantiomeric excess, % 85 80 75 A2
Page 67 and 68:
35 30 Before After Percent of parti
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catalyst activation seems to indica
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Table 5-3. Assignment of some vibra
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6.2 Experimental Materials Cinchoni
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Fig. 6-3. TEM image of cinchonidine
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From the results of EP and EB hydro
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enhancement. However the exact fact
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Further, this family of man-made li
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Fig. 7-2. TEM of quiphos modified P
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of quiphos adsorbed on Pt and Pd an
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Fig. 7-8 Flat adsorbed quiphos via
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comp., H 11,12,13,14 2 C b., 2 P 11
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Chapter 8 “Quiphos-spider” modi
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flat crystal surface due to the hig
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Chapter 9 Diphos and diop modified
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Table 9-1. Average crystal size of
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Fig. 9-4. Conformation of diphos mo
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ings. Due to these reasons we can n
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Fig. 9-9. Proposed orientation of a
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The model of adsorption of diop on
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The calculation of energy of formin
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For the preparation of synphos modi
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1 2 20 40 60 80 2Θ Fig. 10-3. XRD
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The DRIFT spectra of synphos (Fig.
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peaks which can be used for analysi
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References [1] G.E. Tranter, J. Che
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[64] A. Szabo, N. Kunzle, T. Mallat
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[128] J.D. Aiken III, R.G. Finke, J
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[189] K. Umezawa, T. Ito, M. Asada,
Page 125:
I declare that the current Ph.D. th
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