Germine chemical reactions

The concept of electronic delocalization has germinated in the pre-electron period to Kekule s structural theory and its application to benzene as a prototype of a family of compounds so-called aromatics . Kekule had to address two major properties of benzene revealed from substitution experiments. The first was the empirical equivalence of all positions of benzene, what is called today the Dfjh symmetry of both geometry and electronic structure, and second the persistence of the aromatic essence in chemical reactions, what we recognize today as aromatic stability . Thus, Kekule postulated that there is a Ce nucleus and the four valences of the carbons are distributed to give two oscillating structures, which when cast in our contemporary molecular drawings look like part a in Scheme 2.39-44 One of the many alternative hypotheses on the nature of... 

In drying of some materials, which requires careful hygienic attention, e.g., food, availability of water for growth of microorganisms, germination of spores, and participation in several types of chemical reactions becomes an important issue. This availability, which depends on relative pressure or water activity is defined as fhe ratio of the partial pressure p of water over the wet solid system to the equilibrium vapor pressure of water at the same temperature. Thus, which is also equal to the relative humidity of the surrounding humid air, is defined as... 

The development of a plant consists of the formation of a succession of characters a seed germinates, puts forth a root and seed leaves, forms shoots that unfurl their leaves, blossoms and, finally, bears fruit and seeds. (Fig. 1) The formation of each character, in turn, consists of the intricate interlocking of many sequences of chemical reactions. All of these reaction sequences, and thus the formation of the characters, are genetically controlled. For that reason, let us inquire first into which substances form the genetic material and how they are involved in the formation of characters. 

This work describes the application to soil of compounds of a previous study (11) which dealt primarily with organic synthesis and physical properties of reaction products of pure fatty acids with BETA. In this study derivatives were prepared from various industrial fatty materials. In addition, water infiltration studies on sand, sandy soil, and clay soils were carried out on the previously prepared and new compounds. Finally, an investigation was initiated to determine the biological effects of one water-repelling chemical, the partially hydrogenated tallow-fatty acid-DETA reaction product, on seed germination and plant growth. 

Light absorption is usually quite fast (time scale = 1-10 femtoseconds), and various physical measurements can be used to characterize the properties of intermediates that are formed along the reaction coordinate. This strategy was introduced by Porter who later shared the Nobel Prize in Chemistry with Eigen and Norrish for their germinal contributions to fast reaction kinetics. See Chemical Kinetics... 

The patent filed in 1991 by the United States Air Force (Anon, 1991) comes close to the concept which allowed the subject of this study to germinate. The USAF proposed a hollow gas turbine rotor blade with a catalyst coated on the inner surface. The cooling would be effected by vaporisation and decomposition of an endothermic fuel introduced into the hollow blade. The concept is illustrated in Figure 8.13. The endothermic fuel is defined as one which is liquid and which decomposes in the presence of a catalyst into two or more gaseous compounds different chemically from the liquid. At least one of the gaseous compounds is, of course, combustible in this case. The liquid fuels covered in the patent include methylcyclohexane, methanol, n-heptane or JP7 (kerosene fuel). An additional feature of using a liquid fuel as the feedstock is that latent heat of vaporisation contributes to cooUng, in addition to the endothermic reaction. 

Plotnikov had been somewhat hasty in judging that photochemistry had become a mature science in 1930. In fact, many seeds were close to germinate, the paradigms of photochemistry had been not yet formulated, the number of known photochemical reactions was too small for reaching generalizations, and apart from the fact that in many cases it was difficult to recognize which chemical change occurred upon irradiation, key instruments that were able to afford a more detailed view of excited states had yet to be devised and assembled. 

Many biochemical reactions can be induced by temperature increase in foods Maillard reactions, vitamin degradation, fat oxidation, denaturation of thermally unstable proteins (resulting in variation of solubility or of the germinating power of grains, for example), enzyme reactions (which can either be promoted or inhibited), and so on. Some of these biochemical reactions generate components suitable, for example, for their sensory properties (flavor development) others may be more or less undesirable for nutritional or potential toxicity reasons (vitamin losses, changes in color, taste or aroma, formation of toxic compounds). All the reactions are linked to the simultaneous evolution of product composition, temperature and water content (or chemical potential, or water activity), these factors varying diflferently from one point to another, from the center to the surface of the products. 

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