The Preparation and Infrared and N.M.R. Spectra of Monodeuterated Pyridine and 3-Picoline

Abstract

In connectio~l with other studies it was of interest to get a n estimate of the relative ground-state n-electron densities a t the 2-and 6-positions of 3-picoline and its complex with a simple metallic salt. Smith and Schneider (1) receiltly estimated the charge distribution in pyridiniu~n ion, assuming a simple proportionality between the proton resonance displacement and the electron charge deficiency on the carbon atoll1 t o which the proton is bonded. 3-Picoline-2d, 3-picoline-Gd, and their zinc chloride complexes have been prepared and their n.m.r. and infrared spectra compared.Bal;, Hansen, and Rastrup-Andersen (2) obtained pyridine-2d by the action of zinc dust and sulphuric acid-dz on 2-bromopyridine. I t was prepared more conveniently here from 2-pyridyllithium and deuterium oxide. Preliminary experiments indicated that there was no loss of deuterium when the pyridine-2d was extracted with lnineral acid instead of being isolated as the mercuric chloride complex. This is in agreement with the recent finding by Icatritzky and Ridgewell (3) that pyridine is very resistant t o proton exchange. In the same way, 3-picoline-2d, 3-picoline-Gd, and the corresponding tritiated cornpouilds were obtained (the latter by using tritiated water).The n.1n.r. spectra were run in acetonitrile solutions of the compounds, due t o the limited solubility of the zinc chloride coi~~plexes in carbon tetrachloride and to interference by chloroform when it was used. The results are summarized in Table I. 'The accuracy is f 2 cycles/sec. (4)) and its zinc chloride complex the signals for the 2-and 6-protons overlap and no resolution is possible a t 60 Nc/s. T h e shift between these two protons is seen to be +2.5 cycles/sec fro111 the spectra of 3-picoline-Gd and 3-picoline-2d respectively. From these values, the differences in n-eleciron densities are esti~nated t o be very small. Complexing, as expected, gives rise t o appreciable changes in cl~emical shift, particularly a t the /3-and r-protons. T h e corresponding shift t o lower field of the a-proton is appreciably smaller. This is probably d~~e

Synthesis of 1‐hydroxy‐2‐pyridinethioues, 1‐hydroxy‐2‐pyridones and halopyridine 1‐oxides: Reactions of lithiopyridine 1‐Oxides

“…(YII), h : t i the one formed one would have expected to svv only one 2H peak dut: to ttic: pyridiric: 0-protons and two methyl peaks in the nmr. 111 actual practice, two I H pyriditie 0-proton peaks w m : observed a t T 2.5 and 2.9 and four methyl singlet peaks wert: oliserved at T 7.55, 7.7, 7.75 and 8 , respectively, the: ratio of' tlit: arcas of the latter 1itXc undoubtedly arises l'rorn a nucleopliilic addition of ttir: mouolitliiatt:d product (X111) orientation is consistent witti the knowu effect of a 3-mcttiyl group upon the addition of orgariolithium compounds to pyridines(6).Noneof tht: bimolecular products were obtained in tltt: reactions witti chlorine gas. Pyridine I-oxide gavc: a 4.5%) yield of 2,6-dichloropyridine 1-oxide, m.p.…”

E.P.R. of free radicals in an adamantane matrix

“…In addition, 2-bromo-3-picoline was prepared from 2-amino-3-picoline (Aldrich) by the method of Case [14]. This was then treated with butyllithium in n-hexane (Alfa Inorganics, Inc.) followed by D~O [15] to yield 3-picoline 100 per cent deuterated in position HI.…”

Aromatic Substitution: Part Viii. Some Aspects of the Mechanism of the Tschitschibabin Reaction

“…The preparation of pyridine-2d and 3-picoline-2d has already been described (36). Pyridine-3d was prepared si~nilarly from 3-bromopyridine and n-butyllithium (15% solution in n-hexane …”