2,6-DI-TERT-BUTYLPYRIDINE

Overview

2,6-Di-tert-butylpyridine is a weak base used in the preparation of 2, 6-di-tert-butylpyridine hydrotriflate. It is used as a proton scavenger to check the progress of the living polymerization of isobutylene. It is associated with cerric ammonium nitrate and used in the alfa-enolation of aldehydes. It is involved in the preparation of vinyl triflate using polymer-bound 2,6-di-tert-butylpyridine. Since it was first synthesized by Brown and Kanner^[1], 2,6-di-tert-butylpyridine has attracted the interest of many researchers because of its unusually low basicity: with its two-alkyl substituents, DTBP is nevertheless a weaker base than unsubstituted pyridine in aqueous solution. Brown and Kanner^[1] and others^[2] proposed that the abnormally low basicity of DTBP was caused by steric hindrance to hydration of DTBPH+. Recent determinations of gas-phase proton affinities of DTBP and other alkyl-substituted pyridines showed that the basicity of DTBP in the gas phase was normal^{[2, 3]}, which confirmed that its weak basicity in water was due to solvent effects on DTBP and (or) DTBPH+. A complete analysis of the thermodynamic cycles linking the protonation processes of DTBP and other pyridines in the gas phase and in aqueous solution led Arnett and Chawla^[2] to conclude that there was indeed some hindrance to the hydration of DTBPH+ as reflected in its abnormally low enthalpy of hydration. However, more recently Hopkins et al.^[3], after investigating the protonation of additional tertbutylpyridines and repeating the thermodynamic determinations of Amett and Chawla^[2] of DTBP, concluded from their new data that the hydration enthalpy of DTBPH+ was normal but that the corresponding entropy was abnormal; they suggested that the rotation of the water molecule attached to DTBPH+ and of -CMe3 was restricted. These results and conclusions were in agreement with the gas phase studies of Moet-Ner and Sieck^[4] on the attachment of one water molecule to a series of pyridinium cations including DTBPH+.

Reference

1. H. C. BROWN and B. KANNERJ. Am. Chem. Soc. 75, 3865 (1953).
2. E. M. ARNETT and B. CHAWLAJ. Am. Chem. Soc. 101, 7141 (1979).
3. H.P.HOPKINSD,.V.JAHAGIRDAP.RS,.MOULIKD,.H.AUE, H. M. WEBB,W. R. DAVIDSON and M. D. PEDLEY. J.. Am. Chem. Soc. 106,4341 (1984).
4. M. MEOT-NEaRnd L. W. SIECK J. Am. Chem. Soc. 105, 2956 (1983) 

Chemical Properties

dark brown liquid

Uses

2,6-Di-tert-butylpyridine was used as proton trapping agent to investigate the living polymerization of isobutylene. It was also used with cerric ammonium nitrate in the α-enolation of aldehydes leading to 1,4-dicarbonyl systems.

Uses

2,6-Di-tert-butylpyridine is used in the preparation of 2, 6-di-tert-butylpyridine hydrotriflate. It is used as a proton scavenger to check the progress of the living polymerization of isobutylene. It is associated with cerric ammonium nitrate and used in the alfa-enolation of aldehydes. It is involved in the preparation of vinyl triflate using polymer-bound 2,6-di-tert-butylpyridine.

Definition

ChEBI: 2,6-di-tert-butylpyridine is a member of pyridines.

General Description

Reactivity of 2,6-di-tert-butylpyridine with iron(III) tetraphenylporphyrin pi-cation radical has been examined by proton NMR spectroscopy. Reaction of 2,6-di-tert-butylpyridine with methyl iodide and methyl fluorosulfonate under high pressure has been reported.

Purification Methods

Redistil it from KOH pellets. [Beilstein 20 III/IV 2868.]