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Pyridine N-oxide is five orders of magnitude less basic than pyridine: the pK a of protonated pyridine-N-oxide is 0.8. [7] Protonated derivatives are isolable, e.g., [C 5 H 5 NOH]Cl. [3] Further demonstrating its (feeble) basicity, pyridine-N-oxide also serves as a ligand in coordination chemistry.
Structure of pyridine N-oxide. Oxidation of pyridine occurs at nitrogen to give pyridine N-oxide. The oxidation can be achieved with peracids: [94] C 5 H 5 N + RCO 3 H → C 5 H 5 NO + RCO 2 H. Some electrophilic substitutions on the pyridine are usefully effected using pyridine N-oxide followed by deoxygenation. Addition of oxygen suppresses ...
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.
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 ...
Pyridine forms an N-oxide with some oxidation agents such as hydrogen peroxide. This pyridine-N-oxide undergoes a rearrangement reaction to 2-pyridone in acetic anhydride: [21] [22] [23] In the Guareschi-Thorpe condensation cyanoacetamide reacts with a 1,3-diketone to a 2-pyridone. [12] [13] The reaction is named after Icilio Guareschi and ...
Nitrosylation results in a molecule "R" adducted with the group N=O. Nitrosation and nitrosylation are two names for the process of converting organic compounds or metal complexes [1] into nitroso derivatives, i.e., compounds containing the R−NO functionality. The synonymy arises because the R-NO functionality can be interpreted two different ...
Today's NYT Connections puzzle for Friday, December 13, 2024The New York Times
The phrase ipso nitration was first used by Perrin and Skinner in 1971, in an investigation into chloroanisole nitration. [18] In one protocol, 4-chloro- n -butylbenzene is reacted with sodium nitrite in t -butanol in the presence of 0.5 mol% Pd 2 (dba) 3 , a biarylphosphine ligand and a phase-transfer catalyst to provide 4-nitro- n -butylbenzene.