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The structure of pyridine is similar to that of benzene except that a nitrogen atom replaces one carbon atom. Pyridine is used as a flavoring agent. The pyridine ring is part of two B vitamins: niacin and pyridoxine. Niacin, also called nicotinic acid, is found in most organisms.
This difference is partly related to the lower symmetry of the individual pyridine molecule (C 2v vs D 6h for benzene). A trihydrate (pyridine·3H 2 O) is known; it also crystallizes in an orthorhombic system in the space group Pbca, lattice parameters a = 1244 pm, b = 1783 pm, c = 679 pm and eight formula units per unit cell (measured at 223 K).
The pyridine analog is quinoline or isoquinoline, and the class of analogues with two nitrogen atoms is known as the benzodiazines. For azepine, benzazepine is the preferred name. Likewise, the compounds with two benzene rings fused to the central heterocycle are carbazole , acridine , and dibenzoazepine.
Pyrazine is less basic than pyridine, pyridazine and pyrimidine. It is a "deliquescent crystal or wax-like solid with a pungent, sweet, corn-like, nutty odour". [3] Pyrazine and a variety of alkylpyrazines are flavor and aroma compounds found in baked and roasted goods.
Heteroarenes are aromatic compounds, where at least one methine or vinylene (-C= or -CH=CH-) group is replaced by a heteroatom: oxygen, nitrogen, or sulfur. [3] Examples of non-benzene compounds with aromatic properties are furan, a heterocyclic compound with a five-membered ring that includes a single oxygen atom, and pyridine, a heterocyclic compound with a six-membered ring containing one ...
Typical simple aromatic compounds are benzene, indole, and pyridine. [1] [2] Simple aromatic rings can be heterocyclic if they contain non-carbon ring atoms, for example, oxygen, nitrogen, or sulfur. They can be monocyclic as in benzene, bicyclic as in naphthalene, or polycyclic as in anthracene.
Compared to benzene, the rate of electrophilic substitution on pyridine is much slower, due to the higher electronegativity of the nitrogen atom. Additionally, the nitrogen in pyridine easily gets a positive charge either by protonation (from nitration or sulfonation) or Lewis acids (such as AlCl 3) used to catalyze the reaction. This makes the ...
4-Dimethylaminopyridine (DMAP) is a derivative of pyridine with the chemical formula (CH 3) 2 NC 5 H 4 N. This white solid is of interest because it is more basic than pyridine, owing to the resonance stabilisation from the NMe 2 substituent.