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A plot illustrating the dependence on temperature of the rates of chemical reactions and various biological processes, for several different Q 10 temperature coefficients. The rate ratio at a temperature increase of 10 degrees (marked by points) is equal to the Q 10 coefficient.
For example, the substituent may determine the mechanism to be an SN1 type reaction over a SN2 type reaction, in which case the resulting Hammett plot will indicate a rate acceleration due to an EDG, thus elucidating the mechanism of the reaction. Another deviation from the regular Hammett equation is explained by the charge of nucleophile.
Functions that maximize or minimize functionals may be found using the Euler–Lagrange equation of the calculus of variations. A simple example of such a problem is to find the curve of shortest length connecting two points. If there are no constraints, the solution is a straight line between the points. However, if the curve is constrained to ...
An individual chemical shift δ is the mole-fraction-weighted average of the shifts δ of nuclei in contributing species. ¯ = Example: the pK a of the hydroxyl group in citric acid has been determined from 13 C chemical shift data to be 14.4.
The Taft equation is often employed in biological chemistry and medicinal chemistry for the development of quantitative structure–activity relationships (QSARs). In a recent example, Sandri and co-workers [13] have used Taft plots in studies of polar effects in the aminolysis of β-lactams.
The Hammett acidity function (H 0) is a measure of acidity that is used for very concentrated solutions of strong acids, including superacids.It was proposed by the physical organic chemist Louis Plack Hammett [1] [2] and is the best-known acidity function used to extend the measure of Brønsted–Lowry acidity beyond the dilute aqueous solutions for which the pH scale is useful.
Conversion and its related terms yield and selectivity are important terms in chemical reaction engineering.They are described as ratios of how much of a reactant has reacted (X — conversion, normally between zero and one), how much of a desired product was formed (Y — yield, normally also between zero and one) and how much desired product was formed in ratio to the undesired product(s) (S ...
For example, if a pilot pushes forward on the stick, speeding up as the plane dives, an uncompensated variometer only indicates that altitude is being lost. But the pilot could pull back on the stick, trading the extra speed for altitude again. A compensated variometer uses both speed and altitude to indicate the change in total energy.