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In chemistry, initiation is a chemical reaction that triggers one or more secondary reactions. Initiation creates a reactive centre on a molecule which produces a chain reaction . [ 1 ] The reactive centre generated by initiation is usually a radical , but can also be cations or anions . [ 2 ]
A summary of the pathophysiology of a type 1 hypersensitivity reaction. Type I hypersensitivity can be further classified into immediate and late-phase reactions. Within minutes of exposure to an antigen, the immediate hypersensitivity occurs, releasing histamines and lipid mediators which are responsible for the initial allergic reaction response.
The activation energy (E a) of a reaction is measured in kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol). [2] Activation energy can be thought of as the magnitude of the potential barrier (sometimes called the energy barrier) separating minima of the potential energy surface pertaining to the initial and final thermodynamic ...
Also acid ionization constant or acidity constant. A quantitative measure of the strength of an acid in solution expressed as an equilibrium constant for a chemical dissociation reaction in the context of acid-base reactions. It is often given as its base-10 cologarithm, p K a. acid–base extraction A chemical reaction in which chemical species are separated from other acids and bases. acid ...
Chemical reactions are usually characterized by a chemical change, and they yield one or more products, which usually have properties different from the reactants. Reactions often consist of a sequence of individual sub-steps, the so-called elementary reactions, and the information on the precise course of action is part of the reaction mechanism.
The reaction begins in the amygdala, which triggers a neural response in the hypothalamus. The initial reaction is followed by activation of the pituitary gland and secretion of the hormone ACTH. [19] The adrenal gland is activated almost simultaneously, via the sympathetic nervous system, and releases the hormone epinephrine.
When t = 0 to 50, the rate of reaction is low. Thereafter, the reaction accelerates, until almost all reactants have been consumed. At that point, the reaction rate tapers off. An induction period in chemical kinetics is an initial slow stage of a chemical reaction; after the induction period, the reaction accelerates. [1]
Whether a reaction actually will go in the arbitrarily selected forward direction or not depends on the amounts of the substances present at any given time, which determines the kinetics and thermodynamics, i.e., whether equilibrium lies to the right or the left of the initial state, In reaction mechanisms, stoichiometric coefficients for each ...