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Pyrrole is an extremely weak base for an amine, with a conjugate acid pK a of −3.8. The most thermodynamically stable pyrrolium cation (C 4 H 6 N +) is formed by protonation at the 2 position. Substitution of pyrrole with alkyl substituents provides a more basic molecule—for example, tetramethylpyrrole has a conjugate acid pK a of +3.7.
with regards to acid-base reactions, electron-rich species have high pKa's and react with weak Lewis acids. [4] with regards to nucleophilic substitution reactions, electron-rich species are relatively strong nucleophiles, as judged by rates of attack by electrophiles. For example, compared to benzene, pyrrole is more rapidly attacked by ...
Examples of non-basic nitrogen-containing aromatic rings are pyrrole and indole. In the oxygen- and sulfur-containing aromatic rings, one of the electron pairs of the heteroatoms contributes to the aromatic system (similar to the non-basic nitrogen-containing rings), whereas the second lone pair extends in the plane of the ring (similar to the ...
Pyrazole is a weak base, with pK b 11.5 (pK a of the conjugate acid 2.49 at 25 °C). [3] According to X-ray crystallography , the compound is planar. The two C-N distances are similar, both near 1.33 Å [ 4 ]
4 PH; it is the phosphorus analog of pyrrole. The term phosphole also refers to substituted derivatives of the parent heterocycle. These compounds are of theoretical interest but also serve as ligands for transition metals and as precursors to more complex organophosphorus compounds. Triphosphole, C 2 H 3 P 3, is a heterocycle with 3 phosphorus ...
Natural bond orbital (NBO) analysis of C 4 H 4 BH has been performed in order to understand the bonding of borole in the familiar Lewis picture. [5] According to the computational results, the occupancy of the two C−C π orbitals is about 1.9, with a tiny amount of electronic charge (an occupancy of 0.13) delocalised on the out-of-plane boron p orbital, illustrated below.
Tetrapyrroles are a class of chemical compounds that contain four pyrrole or pyrrole-like rings. The pyrrole/pyrrole derivatives are linked by (= (CH)-or -CH 2-units), in either a linear or a cyclic fashion. Pyrroles are a five-atom ring with four carbon atoms and one nitrogen atom.
Polypyrrole Pyrrole can be polymerised electrochemically. [1] Polypyrrole (PPy) is an organic polymer obtained by oxidative polymerization of pyrrole. It is a solid with the formula H(C 4 H 2 NH) n H. It is an intrinsically conducting polymer, used in electronics, optical, biological and medical fields. [2] [3]