Influence of Starting Materials

The properties of the products depend on the starting materials used and on the composition of copolymers and blends (cf also Sect. 4.1). 

A series of terthiophenes substituted with an aryl group at the central thiophene ring (3 position) were polymerized, and the properties of the monomers and the polymers were studied [523, 524], An improvement of the properties compared with the unsubstituted PTT is achieved. The best results are obtained with electron-withdrawing substituents, especially with a 4-cy-anophenyl substituent [524], The redox potentials of PBT derivatives decrease the order poly(3,3 -dibromo-2,2 -bithiophene) poly(3,3 -dichloro-2,2 - 

Poly(4,4 -dibutoxy-2,2 -bithiophene) and poly(3,3 -dibutoxy-2-2 -bithio-phene) are only partially soluble in common organic solvents, in contrast to asymmetrically disubstituted PBTs like poly(3-butoxy-3 -decyl-2,2 -bi-thiophene) and poly(4-butoxy-4 -decyl-2,2 -bithiophene), which are completely soluble in chloroform. The properties of these asymmetrically disubstituted PBTs are intermediate between those of PAT and poly(dialkyloxy-2,2 -bi-thiophene) [526, 528]. Poly(3-styrylthiophene) films deposited on the anode surface by electropolymerization have conductivites of the order of 10 S cm and are redox inactive [529]. 

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Fig. 8.8. The influence of starting material ratio on shock conditioning has been investigated for coarse powders in ratios of nickel to aluminum of 3 1, 2 1, and 1 1. The data show a strong influence of the ratio of the potential reactants consistent with the concept of mechanical mixing. [91D01],...

Influence of Starting Materials Particle Size on Anode... 

Tabic I. Influence of starting material on the choice of a grainforming process. 

Song HS, Kim WH, Hyun SH, and Moon J. Influences of starting particulate materials on micro structural evolution and electrochemical activity of LSM-YSZ composite cathode for SOFC. J. Electroceram. 2006 17 759-764. 

PEG proves to be an efficient reaction medium for the reaction of vicinal halohydrin with carbon dioxide in the presence of a base to synthesize cyclic carbonates (Scheme 5.9) [42], Notably, PEG400 (MW = 400) as an environmentally friendly solvent exhibits a unique influence on reactivity compared with conventional organic solvents. Various cyclic carbonates can be prepared in high yield employing this protocol. The process presented here has potential applications in the industrial production of cyclic carbonates because of its simplicity, cost benefits, ready availability of starting materials, and mild reaction conditions. 

Figure 2. Influence of the pH and the presence of phosphate on rate of conversion of starting materials in the first hour of the reaction...

Although many early synthetic studies employed HMPA as a cosolvent, its mechanistic role remained unclear. Its role was later clarified by Molander, who studied the influence of HMPA concentration on the product distributions from the Sml2-mediated reductive cyclisations of unactivated olefinic ketones.16 The addition of HMPA was required to promote efficient ketyl-alkene cyclisation, and correlations between the concentration of HMPA, product ratios and diastereoselectivities were apparent (Scheme 2.6). In the absence of HMPA, attempted cyclisations led to the recovery of starting material 1, reduced side-product 3 and desired cyclisation product 2. Addition of 2 equiv of HMPA provided 2 and only a small fraction of 3. Further addition of HMPA (3-8 equiv) provided 2 exclusively (Scheme 2.6). 

Corrosion phenomena in remote parts of the system can adversely affect the electrode performance. This is a real threat to processes in which solvents, intermediates, or supporting electrolytes have to be returned to the electrolysis. This danger can influence the decision between batchwise processing with total conversion of starting materials or continuous alternatives in which the starting material has to be recycled. 

Figure 4 Influence of starting Si/Al ratio, time, agitation and seeding on FER- and TON-type materials crystallization Hith n-butylamine template.

In what way are different batches of starting material influencing the result of a synthetic reaction Useful descriptors would be analytical data for the different batches, and the classes would be the different batches. 

The grade of starting material influences both the smoothness of the procedure and the yield. A high-grade ilmenite analyzing ca. 57% Ti02 or better is recommended. 

Attempts to influence the simple diastereoselectivity of a given pair of starting materials by a change in the catalyst employed was, for a long time, a fruitless matter of trial and error15- 17 97. An example is the cyclopropanation of cyclohexene with ethyl diazoacetate under the influence of various catalysts. 

Maintenance and repair work may not have an unfavorable influence on the quality of starting material, packaging materials and products. 

Transport of starting materials, packaging materials and products must be performed in such a manner that the quality will not be unfavorably influenced. 

With the aid of the kinetics, dimensioning of the reactor can be performed. Other important quantities that influence the economics of the entire process are the selectivity and the conversion. If the kinetics are known, both quantities can be optimized and thus the yield (= selectivity x conversion) maximized. First we must define these quantities. Consider the reaction of starting materials A and B to give product P (Equation 3.1.4-1) ... 

Advances in the development of modem chromatography materials and modem equipment have turned scale-up into a less critical issue than it was in the past. Usually, nonchromatographic parameters such as consistency of starting material or limited stability create problems. The scale-up of purification is usually aligned with the scale-up of fermentation. Different reactor types are often used for small and large scale, which may lead to a different composition of the impurities, product concentration, and even molecular structure. Maiorella et al. [90] demonstrated that bioreactor types and culture conditions influence the isoelectric pattern of a monoclonal antibody. This has a big impact on purification because different isoelectric patterns may lead to different solubilities and binding behavior to ion exchangers or other sorbents affected by ionic interactions. 

Allyl acetates 1/ent-l that possess identical R groups undergo aUyUc substitution via an achiral intermediate 2. Both enantiomers of starting material proceed via the same intermediate. In the absence of any controlling influence, approach of the nucleophile via pathways a and b is equally likely, and a racemic product 3/ent-3 will be formed (Scheme 1). However, the opportunity for an asymmetric catalytic reaction exists if the reaction can be channeled through one pathway selectively. Overall, the process represents a dynamic resolution, since a racemic starting material is converted into an enan-tiomericaUy emiched product. 

The properties of the cured UP resins can be varied within wide limits to meet specific requirements, by the choice of specific dicarboxylic (both unsaturated and saturated) acids and diols and by dissolving them in different reactive monomers. Using die appropriate combination of starting materials, it is possible to influence many properties of die resin, such as ... 

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