Factors influencing product formation

Several factors influence product formation in triazoline thermolysis. The stereochemistry of the triazoline adducts from cis- and trans-cyclooctene has been found to play a role in aziridine or imine formation aziridines predominate in the trans and imines in the cis isomers.86 However, the relative product ratios depend on the reaction temperature, and thermolysis of the cis-triazoline at 310°C leads to 78% aziridine as against 5% at 80°C.87... 

The regioselectivity in palladium-catalyzed alkylations has been attributed to the dynamic behavior of trihapto pentadienyl metal complexes60. For example, competing electronic and steric effects influence product formation in dienyl epoxides, but in palladium-catalyzed reactions steric factors were often found to be more important. Thus, alkylation of dienyl epoxide 76 with bulky nucleophiles such as bis(benzenesulfonyl)me-thane in the presence of (Ph3P)4Pd occurred exclusively at the terminal carbon of the dienyl system producing allyl alcohol 77 (equation 39). However, the steric factors could be overcome by electronic effects when one of the terminal vinylic protons was replaced with an electron-withdrawing group. Thus, alkylation of dienyl epoxide 78 affords homoal-lylic alcohol 79 as the major product (equation 40). 

The study of indoor organic chemistry improves our understanding of personal exposure to both reactants and products. At present, our ability to make predictions or estimate past exposure is rudimentary. To improve, we need a more comprehensive evaluation of the mechanisms, rates and mediating factors in indoor environments. For example, it is well established that humidity tends to enhance ozone uptake on indoor surfaces, but how does this influence product formation Do C02 or NH3 influence transformative product yields as well as influencing the sorptive capacity of surfaces To what extent do occupants contribute to this chemistry through their choice of products, smoking or cooking ... 

It Is generally recognised that In fruit and vegetable production more attention should be given to the hidden sensory quality parameters, such as flavor and texture. These quality attributes are the result of a number of pre- and post-harvest factors and are closely related with fruit ripening. Palllard distinguishes external and Internal factors Influencing aroma formation In fruits (U. The... 

Many factors influence acid corrosion. Metallurgy, temperature, water turbulence, surface geometry, dissolved oxygen concentration, metal-ion concentration, surface fouling, corrosion-product formation, chemical treatment, and, of course, the kind of acid (oxidizing or nonoxidizing, strong or weak) may markedly alter corrosion. 

We have seen that both the maintenance energy requirement and the P/O quotient of the process micro-organism influences the rate of product formation. In the following sections we will consider how these two factors can be determined, together with the maximum biomass yield. 

Xiang, Y., Larsen, S.C. and Grassian, V.H. (1999). Photooxidation of 1-alkenes in zeolites a study of the factors that influence product selectivity and formation. J. Am. Chem. Soc. 121, 5063-5072... 

Terminal RCH—CH2 1-Hexene C4H9CH=CH2 is isomerized by complex 1 in accordance with the factors influencing the thermodynamic stability of cis- and trans-2 -hexene [15], At the end of the reaction, the alkyne complex 1 was recovered almost quantitatively. No alkene complexes or coupling products were obtained. The corresponding zirconocene complex 2a did not show any isomerization activity. Propene CH3CH=CH2 reacts with complex 6 with substitution of the alkyne and the formation of zirconacydopentanes as coupling products, the structures of which are non-uniform [16]. 

While we are not aware of any systematic investigation of the conditions and structural factors that influence diketopiperazine formation, the literature contains a number of examples of such reactions. Thus, cyclo(His-Trp), a degradation products of LHRH (Fig. 6.16, Reaction c), is a secondary product formed after cleavage of the Glp-His bond. After an incubation of 90 d at neutral pH, cyclo(His-Trp), represented 4 and 10% of the breakdown products obtained at 37° and 50°, respectively [74],... 

Because amine formation in fish muscle and other foods usually results from bacterial growth with concomitant production of a bacterial decarboxylase, this paper will concentrate on the mechanisms of bacterial decarboxylation and factors influencing the production and activity of the enzymes. Also, because of the overall scope of the subject, the availability of excellent reviews on bacterial decarboxylation (2, 3) and the public health importance of histamine in fish and fishery products, this paper will primarily be limited to a discussion of histidine decarboxylase (EC 4.1.1.22) and the formation of histamine in fish muscle. 

Relationship of Bacterial Histidine Decarboxylase Production to Histamine Formation. Many studies have been completed with the objective of understanding factors such as storage time and temperature that influence production of histamine in fish. The majority of the investigations have considered only the histamine content of the product, and, consequently, only limited information is available concerning the relationship of histidine decarboxylase formation by the microflora to histamine build-up. 

Kf., while not quantified experimentally, was recently introduced by Kirby and coworkers on the basis of product formation from O-attack at electrophilic P and C centers, as well as MO calculations incorporating the novel species, ammonia oxide, NH3+-0 . In common with other ambident nucleophiles, factors such as electronic, steric, kinetic and thermodynamic effects will determine actual extant pathways in a given system. Af-substituted hydroxylamines (see Scheme 1) can in principle partake of the equilibria shown in Scheme 2. Again, actual outcomes will be influenced by the aforementioned criteria. 

From the discussion in the foregoing section, it should be clear that the structure of the product(s) from the cycloaddition reactions is dependent on the nature of the reactants as well as reaction conditions. In this section an attempt will be made to look at the general factors influencing the selectivity and reactivity of the nonclassical A,B-diheteropentalenes. In simple terms, cycloaddition or bond formation between terminal carbon atoms occurs when the topology and symmetry of the orbitals of the reacting ylide system and the dipolarophile allow parallel approach (Figure 2). 

We here review the factors that control the kinetics of product formation through reaction at an active surface. This includes consideration of the availability of those adsorbed intermediates which participate in the rate-limiting step (this term is analogous to concentration in a homogeneous reaction) and the mobility of the same species, which may determine, or at least influence, the frequency of occurrence of the reaction situation. The discussion is given under three broadly interpreted general headings, between which there is considerable overlap. 

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