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Many nucleophilic substitutions occur more easily not with bare pyridine but with pyridine modified with bromine, chlorine, fluorine, or sulfonic acid fragments that then become a leaving group. So fluorine is the best leaving group for the substitution with organolithium compounds .
Abbe number? Dielectric constant, ε r: 12.3 ε 0 at 25 °C Bond strength? Bond length? Bond angle? Magnetic susceptibility? Surface tension [1] 40.8 dyn/cm at 0 °C 38.0 dyn/cm at 20 °C 26.4 dyn/cm at 100 °C Viscosity [2] 0.974 mPa·s at 20 °C
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.
This reaction mechanism is supported by the observation that addition of pyridine to the reaction leads to inversion. The reasoning behind this finding is that pyridine reacts with the intermediate sulfite replacing chlorine. The dislodged chlorine has to resort to nucleophilic attack from the rear as in a regular nucleophilic substitution. [3]
The direct amination of pyridine with sodium amide can take place in liquid ammonia or an aprotic solvent such as xylene is commonly used. Following the addition elimination mechanism first a nucleophilic NH 2 − is added while a hydride (H −) is leaving. The reaction formally is a nucleophilic substitution of hydrogen S N H.
Other common Lewis bases include pyridine and its derivatives. Some of the main classes of Lewis bases are amines of the formula NH 3−x R x where R = alkyl or aryl. Related to these are pyridine and its derivatives. phosphines of the formula PR 3−x Ar x. compounds of O, S, Se and Te in oxidation state −2, including water, ethers, ketones
Synthesis of nucleosides involves the coupling of a nucleophilic, heterocyclic base with an electrophilic sugar. The silyl-Hilbert-Johnson (or Vorbrüggen) reaction, which employs silylated heterocyclic bases and electrophilic sugar derivatives in the presence of a Lewis acid, is the most common method for forming nucleosides in this manner.
Due to the steric effects of the two methyl groups, 2,6-lutidine is less nucleophilic than pyridine. Protonation of lutidine gives lutidinium , [(CH 3 ) 2 C 5 H 3 NH] + , salts of which are sometimes used as a weak acid because the conjugate base (2,6-lutidine) is so weakly coordinating.