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  2. Pyridine - Wikipedia

    en.wikipedia.org/wiki/Pyridine

    Pyridine is colorless, but older or impure samples can appear yellow, due to the formation of extended, unsaturated polymeric chains, which show significant electrical conductivity. [page needed] [17] The pyridine ring occurs in many important compounds, including agrochemicals, pharmaceuticals, and vitamins.

  3. Clar's rule - Wikipedia

    en.wikipedia.org/wiki/Clar's_rule

    Clar's rule states that for a benzenoid polycyclic aromatic hydrocarbon (i.e. one with only hexagonal rings), the resonance structure with the largest number of disjoint aromatic π-sextets is the most important to characterize its chemical and physical properties. Such a resonance structure is called a Clar structure. In other words, a ...

  4. Pyridine-N-oxide - Wikipedia

    en.wikipedia.org/wiki/Pyridine-N-oxide

    Pyridine-N-oxide is the heterocyclic compound with the formula C 5 H 5 NO. This colourless, hygroscopic solid is the product of the oxidation of pyridine . It was originally prepared using peroxyacids as the oxidising agent.

  5. Hückel method - Wikipedia

    en.wikipedia.org/wiki/Hückel_method

    When , and are called the overlap and resonance (or exchange) integrals, respectively, while is called the Coulomb integral, and = simply expresses the fact that the are normalized. The n × n matrices [ S i j ] {\displaystyle [S_{ij}]} and [ H i j ] {\displaystyle [H_{ij}]} are known as the overlap and Hamiltonian matrices , respectively.

  6. Transition metal complexes of pyridine-N-oxides - Wikipedia

    en.wikipedia.org/wiki/Transition_metal_complexes...

    Pyridine-N-oxides bind to metals through the oxygen. According to X-ray crystallography, the M-O-N angle is approximately 130° in many of these complexes. As reflected by the pKa of 0.79 for C 5 H 5 NOH +, pyridine N-oxides are weakly basic ligands. Their complexes are generally high spin, hence they are kinetically labile.

  7. Hückel's rule - Wikipedia

    en.wikipedia.org/wiki/Hückel's_rule

    Hückel's rule can also be applied to molecules containing other atoms such as nitrogen or oxygen. For example, pyridine (C 5 H 5 N) has a ring structure similar to benzene, except that one -CH- group is replaced by a nitrogen atom with no hydrogen. There are still six π electrons and the pyridine molecule is also aromatic and known for its ...

  8. Transition metal pyridine complexes - Wikipedia

    en.wikipedia.org/wiki/Transition_metal_pyridine...

    Transition metal pyridine complexes encompass many coordination complexes that contain pyridine as a ligand. Most examples are mixed-ligand complexes. Most examples are mixed-ligand complexes. Many variants of pyridine are also known to coordinate to metal ions, such as the methylpyridines, quinolines, and more complex rings.

  9. Pyrimidine - Wikipedia

    en.wikipedia.org/wiki/Pyrimidine

    Pyrimidine (C 4 H 4 N 2; / p ɪ ˈ r ɪ. m ɪ ˌ d iː n, p aɪ ˈ r ɪ. m ɪ ˌ d iː n /) is an aromatic, heterocyclic, organic compound similar to pyridine (C 5 H 5 N). [3] One of the three diazines (six-membered heterocyclics with two nitrogen atoms in the ring), it has nitrogen atoms at positions 1 and 3 in the ring.