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The nitrogen center of pyridine features a basic lone pair of electrons. This lone pair does not overlap with the aromatic π-system ring, consequently pyridine is basic, having chemical properties similar to those of tertiary amines. Protonation gives pyridinium, C 5 H 5 NH +.The pK a of the conjugate acid (the pyridinium cation) is 5.25.
Solid properties Std enthalpy change of formation, ... log 10 of Pyridine vapor pressure. Uses formula: ...
In the solid state the dimeric form is not present; the 2-pyridones form a helical structure over hydrogen bonds. Some substituted 2-pyridones form the dimer in solid state, for example the 5-methyl-3-carbonitrile-2-pyridone. The determination of all these structures was done by X-ray crystallography. In the solid state the hydrogen is located ...
This white solid is of interest because it is more basic than pyridine, owing to the resonance stabilisation from the NMe 2 substituent. Because of its basicity, DMAP is a useful nucleophilic catalyst for a variety of reactions such as esterifications with anhydrides , the Baylis-Hillman reaction , hydrosilylations , tritylation, the Steglich ...
In fact, the addition of acid (H+) or hydroxide (OH-) acts to attenuate protodeboronation by shifting the speciation away from the reactive zwitterion. It is important to note that not all basic heteroaromatic boronic acids are reactive through a zwitterionic intermediate. Scheme for the speciation of 2-pyridine boronic acid in aqueous solution
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Bases are proton acceptors; a base will receive a hydrogen ion from water, H 2 O, and the remaining H + concentration in the solution determines pH. A weak base will have a higher H + concentration than a stronger base because it is less completely protonated than a stronger base and, therefore, more hydrogen ions remain in its solution.