1,3-Propanediol model

The second group of studies tries to explain the solvent effects on enantioselectivity by means of the contribution of substrate solvation to the energetics of the reaction [38], For instance, a theoretical model based on the thermodynamics of substrate solvation was developed [39]. However, this model, based on the determination of the desolvated portion of the substrate transition state by molecular modeling and on the calculation of the activity coefficient by UNIFAC, gave contradictory results. In fact, it was successful in predicting solvent effects on the enantio- and prochiral selectivity of y-chymotrypsin with racemic 3-hydroxy-2-phenylpropionate and 2-substituted 1,3-propanediols [39], whereas it failed in the case of subtilisin and racemic sec-phenetyl alcohol and traws-sobrerol [40]. That substrate solvation by the solvent can contribute to enzyme enantioselectivity was also claimed in the case of subtilisin-catalyzed resolution of secondary alcohols [41]. 

It is important that chemical engineers master an understanding of metabolic engineering, which uses genetically modified or selected organisms to manipulate the biochemical pathways in a cell to produce a new product, to eliminate unwanted reactions, or to increase the yield of a desired product. Mathematical models have the potential to enable major advances in metabolic control. An excellent example of industrial application of metabolic engineering is the DuPont process for the conversion of com sugar into 1,3-propanediol,... 

Let us reconsider the hydrogenation of 3-hydroxypropanal (HPA) to 1,3-propanediol (PD) over Ni/Si02/Al203 catalyst powder that used as an example earlier. For the same mathematical model of the system you are asked to regress simultaneously the data provided in Table 16.23 as well as the additional data given here in Table 16.28 for experiments performed at 60°C (333 K) and 80°C (353 K). Obviously an Arrhenius type relationship must be used in this case. Zhu et al. (1997) reported parameters for the above conditions and they are shown in Table 16.28. 

Another route to introduce the 1-[ F]fluoroisopropyl residue into the propanol-amine radioligands is represented by the model radiotracers listed in Table 3. [ F]Fluorometoprolol 6 exemplifies the less affine F-labeled counterpart of the )Si-AR-selective radioligand [ C]metoprolol [103]. 1-[ F]Fluoroisopropyl tosylate is the building block of choice used to prepare (+/ )-p F]fluorometopro-lol 6. 1-[ F]Fluoroisopropyl tosylate itself is accessible via the reaction of 1,2-propanediol di(p-toluenesulfonate) with [ F]K(Kryptofix 2.2.2)F. (+/ )-[ F]Fluorometoprolol 6 was proven to possess a similar Pt-AR selectivity like [ C]metoprolol, but its affinity appeared to be too low to potently visualize p-ARs in the heart with PET. 

If 1 1 complexes are formed (1) in the ground state, then two types of photoreactions will occur parallel to each other, that of the bare and that of the complexed solute, each in its own type of cage. Mixed alcohol/ alkane systems, for example, show an indication of preformed solute-solvent complexes as evidenced by the picosecond experiments of Wang and Eisenthal80 81 on DMABN. Planar model systems like the indolines 3 and 5 (Sec. II.A.l) indicate that an additional channel opens for the B state in alcoholic solvents which increases the nonradiative decay path. This can explain the observed reduction of the fluorescence quantum yield in jirotic solvents about 0.1 in the aprotic polar solvent n-butyl chloride, about 0.01 in 1,2-propanediol, and about 0.001 in water.228... 

Theil, F., Femke, K., Ballschuh, S., Kunath, A., and Schick, H. 1995. Fipase-catalyzed resolution of 3-(aryloxy)-l,2-propanediol derivatives-towards an improved active-site model of Pseudomonas cepacia lipase (Amano PS). Tetrahedron Asymm., 6, 1323-1344. 

We report on the reaction of 2,2-dimethyl-1,3-propanediol catalyzed by various solid acids in the gas phase at temperatures > 250 °C. Originally, we tried to synthesize four membered cyclic ethers since several oxetanes are of synthetic interest [7,8], E g. 3-hydroxy-oxetane can undergo ring opening polymerization, leading to a water soluble polymer Since 3-hydroxy-oxetane is not very stable, we choose 2,2-dimethyl-1,3-propanediol as model substrate. In this communication, we describe the effect of catalyst structure (various zeolites. 

AJ Nonni and CW Dence. The reactions of alkaline hydrogen peroxide with lignin model dimers. Part 3. 1,2-Diaryl-l,3-propanediols. Holzforschung 42 37 6, 1988. 

Toraya et al. [60-63] used B3LYP (with the 6-311G(d) basis set) for calculations on the H-atom transfer steps in diol dehydratase reaction. Both H-atom transfers, i.e., from the substrate and re-abstraction of a hydrogen atom from 5 -deoxyadenosine, were considered. The models used in these studies included the substrate, 1,2-propanediol, a potassium cation found in the active site, and an ethyl radical as a mimic of the dAdo radical (Fig. 19.1). The activation barrier for the abstraction of the pro-S hydrogen atom of substrate by dAdo was calculated to be 9.0 kcal mol while the activation barrier for the reverse reaction between product radical and 5 -deoxyadenosine was 15.7 kcal moUk In the absence of the potassium cation the forward activation barrier is 9.6 kcal moU indicating that coordination of the substrate by the potassium cation has a minimal energetic effect on the H-atom transfer step, but seems to hold the substrate and intermediates in... 

Fig. 2.29. Preferred accommodation of 2- -alkenyl-1,3-propanediol diacetates in an active site model for PPL. Reproduced from J. Org. Chem., 57, 1540 (1992), by permission of the American Chemistry Society.

Sequence of UP model methyl ether of 1,2-propanediol — maleic acid — 1,2-propanediol — orthophthalic acid — methy lether of 1,2-propanediol ... 

Synthesis, Properties, and Mathematical Modeling of Biodegradable Aliphatic Polyesters Based on 1,3-Propanediol and Dicarboxylic Acids... 

Bizukojc M, Dietz D, Sun J, Zeng AP. (2010). Metabolic modelling of syntrophic-Uke growth of a 1,3-propanediol producer, Clostridium butyricum, and amethanogenic archeon, Methanosarcina mazei, under anaerobic conditions. Bioproc Biosyst Eng, 33, 507— 523. 

Papanikolaou S, Aggelis G. (2003). Modelling aspects of the biotechnological valorization of raw glycerol production of citric acid Yarwwia lipolytica and 1,3-propanediol by Clostridium butyricum. J. Chem. Technol. Biotechnol, 78, 542-547. 

Sun YQ, Qi WT, Teng H, Xiu ZL, Zeng AR (2008). Mathematical modeling of glycerol fermentation by Klebsiella pneumoniae concerning enzyme-catalytic reductive pathway and transport of glycerol and 1,3-propanediol across cell membrane. Biochem Eng J, 38, 22-32. 

Hamlet, C. G., and Sadd, P. A. 2005. Effects of yeast stress and pH on 3-monochloro-propanediol (3-MCPD)-producing reactions in model dough systems. Food Additives Contam., 22 616-623. 

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