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Gustation is a chemical sense that, along with olfaction (smell), contributes to our perception of taste. It starts with the activation of receptors by chemical compounds (tastants) dissolved in the saliva. The saliva and filiform papillae on the tongue distribute the tastants and increase their exposure to the taste receptors.
Taste receptors are found on the surface of the tongue as well as on the soft palate, the pharynx, and the upper esophagus. On the tongue, taste receptors are contained...
Just like β-keto acids—which upon thermal decarboxylation form ketones—β-dicarboxylic acids undergo decarboxylation to generate monocarboxylic acids with the liberation of carbon dioxide.
The mechanism initiates with an internal electronic redistribution, resulting in a cyclic six-membered transition state. This is followed by a C–C bond cleavage to produce an enol by releasing carbon dioxide gas. Next, the enol rapidly tautomerizes under the acidic conditions to yield a more stable...
The Arrhenius equation,
relates the activation energy and the rate constant, k, for many chemical reactions.
In this equation, R is the ideal gas constant, which has a value 8.314 J/mol·K, T is the temperature in kelvin, Ea is the activation energy in joules per mole, e is the constant 2.7183, and A is a constant called the frequency factor, which is related to the frequency of collisions and the orientation of the reacting molecules.
The frequency factor, A, reflects how well the...
Sigmatropic rearrangements are a class of pericyclic reactions in which a σ bond migrates from one part of a π system to another. These are intramolecular rearrangements where the total number of σ and π bonds remain unchanged.
Sigmatropic shifts are classified based on an order term [i, j ], where i and j indicate the number of atoms across which each end of the σ bond migrates. Below are examples of a [3,3] sigmatropic shift in...
Baeyer–Villiger oxidation converts aldehydes to carboxylic acids and ketones to esters. The reaction uses peroxy acids or peracids and is often catalyzed by acid. The reaction is named after its pioneers, Adolf von Baeyer and Victor Villiger. The reaction is achieved by a wide range of peracids such as m-chloroperoxybenzoic acid (mCPBA), perbenzoic acid (C6H5COOOH), peracetic acid (CH3COOOH), hydrogen peroxide (H2O2), and tert-butyl hydroperoxide (t-BuOOH).
The carbonyl center is...
Entropy is a state function, so the standard entropy change for a chemical reaction (ΔS°rxn) can be calculated from the difference in standard entropy between the products and the reactants.
where np and nr represent the stoichiometric coefficients in the balanced equation of the products and reactants, respectively.
For example, ΔS°rxn for the following reaction at room temperature
is computed as follows:
A partial listing of standard entropies is provided in the table.
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