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In this type of substitution reaction, one group of the substrate participates initially in the reaction and thereby affects the reaction. A classic example of NGP is the reaction of a sulfur or nitrogen mustard with a nucleophile, the rate of reaction is much higher for the sulfur mustard and a nucleophile than it would be for a primary or secondary alkyl chloride without a heteroatom.
The HC5 is the concentration at which five percent of the species in the SSD exhibit an effect. [10] The HC5 is typically divided by an assessment factor of 1-5. [6] In many cases, SSDs may not exist due to the lack of data on a large number of species. In these cases, the assessment factor approach to derivation of a PNEC should be used. [1] [6]
In chemistry, solvent effects are the influence of a solvent on chemical reactivity or molecular associations. Solvents can have an effect on solubility , stability and reaction rates and choosing the appropriate solvent allows for thermodynamic and kinetic control over a chemical reaction.
The primary objective of chemical thermodynamics is the establishment of a criterion for determination of the feasibility or spontaneity of a given transformation. [3] In this manner, chemical thermodynamics is typically used to predict the energy exchanges that occur in the following processes: Chemical reactions; Phase changes; The formation ...
The relative activity of a species i, denoted a i, is defined [4] [5] as: = where μ i is the (molar) chemical potential of the species i under the conditions of interest, μ o i is the (molar) chemical potential of that species under some defined set of standard conditions, R is the gas constant, T is the thermodynamic temperature and e is the exponential constant.
Relation between chemical reaction conversion selectivity and yield. In chemical reaction engineering, "yield", "conversion" and "selectivity" are terms used to describe ratios of how much of a reactant has reacted—conversion, how much of a desired product was formed—yield, and how much desired product was formed in ratio to the undesired product—selectivity, represented as X, S, and Y.
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 ...
An illustrative example is the effect of catalysts to speed the decomposition of hydrogen peroxide into water and oxygen: . 2 H 2 O 2 → 2 H 2 O + O 2. This reaction proceeds because the reaction products are more stable than the starting compound, but this decomposition is so slow that hydrogen peroxide solutions are commercially available.