Dynamic thermodynamic

Additionally, a personal objective was to provide the information contained within this book in such a way that it could be used regularly in the field rather than be relegated to a bookshelf with other works of occasional reference. As such, although this book is essentially concerned with applied chemistry, I found it necessary to devote several of the initial chapters to a discussion on some basic but practical engineering aspects. Subjects covered include fluid dynamics, thermodynamics, the various types and designs of boilers to be found, and the function of all the critical system auxiliaries and components. The subject of boiler water chemistry is so inextricably bound up with the mechanical operation of boiler plants and all their various systems and subsystems that it is impossible to discuss one topic without the other. 

Dynamic thermodynamic resolution in a lithiation substitution reaction sequence was used to provide access to the amino ester 48 which could then be converted, via 49 and 50, into the chiral substituted 1-benzazepine derivative 51 <06OL2667>. 

The model includes a dynamic thermodynamic sea ice model. The dynamics of sea ice are formulated using viscous-plastic rheology [Hibler (1979)]. The thermodynamics relate changes in sea ice thickness to a balance of radiant, turbulent, and oceanic heat fluxes. The effect of snow accumulation on sea ice is included, along... 

If kepi, k-epi are much larger than the rates k, ki of substitution, the enantiomeric ratio Hepi-1 is similar to kxjk (path C, dynamic kinetic resolution . Both mechanisms are performing when the rates of the two steps are similar. Since rates and equilibrium are temperature-dependent, enhancement of stereoselectivities can be achieved by sophisticated protocols (see Section m.E). The equilibrium 6/epi-6 is determined by the difference of free energy A AG. This effective energy difference is enlarged if it can be coupled with a second order transformation such as the selective crystallization of one diastere-omer dynamic thermodynamic resolution ). In fact, this applies to the first successful (—)-sparteine-mediated deprotonation (Section FV.C.l). 

An efficient resolntion of the racemic lithinm tert-bntylphosphine-borane complex 203 dnring deprotonation by n-BnLi/(—)-sparteine (11) and alkylation was reported by Liv-inghonse and Wolfe (eqnation 47) . One of the epimers 204/cp/-204 on warming to 0 °C crystallizes during a dynamic thermodynamic resolntion, and reaction with alkyl halides fnmishes the alkylation prodncts 205 with high ee values. Applying dihalides, essentially enantiomerically pure diphosphines snch as 206, besides few of the mcio-diastereomer, were obtained. Borane is removed by treatment with diethylamine to yield the free tertiary phosphines 207. 

The closely related a-(pyrid-2-ylthio)benzyllithium (257) has a higher configurational stability, and equilibration with the chiral ligand prior to the substitution step is required , indicating that a dynamic thermodynamic resolution is important (equation 61). Depending on the method of calculation, (7 )-257 255b was found to be by 1.42 to 1.92 kcalmoD ... 

Dilithiation of Af-methyl-3-phenylpropaneamide (261) and subsequent addition of a slight excess of (—)-sparteine (11) form a mixture of epimeric ion pairs 262/epi-262, which is substituted by electrophiles to give the -substitution products 263 with good ee values (equation 63) . The intermediates are not configurationally stable, but at low temperature one epimer 262 or epi-262 dominates due to the higher thermodynamic stability. Consequently, Beak and coworkers propose on the basis of a detailed mechanistic investigation the pathway of dynamic thermodynamic resolution . 

Repeated deprotonation of 278 removed due to a high H/D kinetic isotope effect the 1-proton, forming the dideuterio compound 279 with low diastereoselectivity . It is quite likely that a dynamic thermodynamic resolution is the origin. Intermediate 277 is configurationally labile, enabling an equilibration of the diastereomeric ion pairs 277 and epi-211. Similar studies were undertaken with 1-phenyl-l-pyrid-2-ylethane (280) and l-(4-chlorophenyl)-l-(pyrid-2-yl)-3-(dimethylamino)propane (281) (50% eef. An improvement of the achieved enantiomeric excesses resulted when external chiral proton sources, such as 282 or 283, were applied (84% ee for 280 with 283 and 75% ee for 281). 

The lithium-(—)-sparteine complexes, derived from primary 2-alkenyl carbamates, are usually configurationally labile even at —78 °C. During the investigation of the (ii)-crotyl carbamate 301, the (—)-sparteine complex (5 )-302 crystallized in a dynamic thermodynamic resolution process (equation 76) and stereospecific substitutions could be performed with the slurry An incorrect assignment of the configuration of the lithium inter-... 

Plrret, D., Si ille, P., Shields, G., Crovisier, J.-L. Madlr, U. 2000. Long-Term Stability of HT Materials Report 4. SAEFL, Section Wastes, Switzerland. The CD-ROM Long-Term Stability of HT Materials. A Compendium of the Static, Dynamic, Thermodynamic Pictures of Products from the High-Temperature Treatment of Municipal Solid Wastes and Associated Residues contains the technical report and the complete set of... 

An asymmetric synthesis of 3,4,5-trisubstituted-tetrahydro-l-benzazepines has been reported based on a type a ring construction process mediated by triethylaluminium with a chiral amino ester followed by lactam reduction with borane <2006OL2667>. Dynamic thermodynamic resolution in a lithiation-substitution sequence was integral to the preparation of the amino ester. An acid-catalyzed ring construction approach to the asymmetric synthesis of 4,5,6-trisubstituted- and 3,4,5,6-tetrasubstituted azepanes based on chiral acyclic precursors has also been described <2006JA2178>. 

Scheme 6.2.2 Asymmetric substitution by dynamic thermodynamic resolution.

In some cases, crystallisation of the intermediate organolithium-(-)-sparteine complexes is necessary to force their equilibration to the major diastereoisomer.54 This type of dynamic thermodynamic resolution was involved in one of the very first effective uses of (-)-sparteine in organolithium chemistry. Hoppe showed in 1988 that the carbamate 82 could be deprotonated in the presence of (-)-sparteine, and that when the product 83 was transmetallated with titanium and then added to an aldehyde, a homoaldol product 85 was formed in 83% ee. It became apparent that acceptable enantiomeric excesses were obtained only when the intermediate organolithium-(-)-sparteine complex was allowed to crystallise the complexes 83a and 83b interconvert in solution, but one diastereoisomer crystallises preferentially, leading to a dynamic resolution of the organolithium. 

Constrained Dynamics, Thermodynamic Integration, and Free-energy Barriers... 

In Fig. 11, at high concentrations of ethylene carbonate, the rate constants ks[EC] and kR[EC] for insertion into the EBTHI zirconaaziridine 17q are much greater than kSSR and ksss and insertion occurs more rapidly than the equilibrium can be maintained. The product ratio reflects the equilibrium of 17q, where Keq is 17.2 (Eq. 32) [21]. Beak has called this limit a dynamic thermodynamic resolution pathway [66]. In contrast, at the lowest concentration of ethylene carbonate in Fig. 10, the first-order rate constants kSSR and ksss for diastereomer interconversion are comparable to the effective first-order rate constants for insertion. As Keq is known to be 17.2, ks/kR can be calculated the 53% ee of (S)-amino acid ester 19q (Scheme 9) implies that kslkR<0.19 (Eq. 33) and that the rate constant for insertion kR[EC] into the minor diastereomer is at least five times faster than ks[EC] into the major diastereomer. 

More elaborate models, including the rheology, and the drift of sea ice have to be applied to describe the formation of different ice classes, transports of sea ice, and a forecast potential for ship navigation. Dynamic-thermodynamic sea ice is applied in three-dimensional models of the Baltic Sea by Haapala and Lepparanta (1996), Meier et al., (1999,2(X)2a,b), Lehmann and Hinrichsen (2000), and Schrum et al. (2003). A comprehensive overview of the theory and application of sea ice drift is given by Lepparanta (2005). Models based on the Flexible Model System (FMS), including the Modular Ocean Model (version 4), may also apply a dynamical ice module (Griffies et al., 2004 Balaji, 2004). 

In Chapter 22 we saw resolution with racemisation applied to the synthesis of L-364,718. That could have been described as a dynamic resolution or possibly even a dynamic thermodynamic resolution but not a dynamic kinetic resolution as it did not depend on one enantiomer reacting faster than the other. Rather it depended on the thermodynamic stability of one crystalline form over the other. 

McCreary, J.P., Kundu, P.K. and Molinari, R.L. (1993) A numerical investigation of dynamics, thermodynamics and mixed-layer processes in the Indian Ocean. Progress in Oceanography, 31, 181-244. 

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