Hydrogenation pyridine

Metaldehyde [9002-91-9] a cycHc tetramer of acetaldehyde, is formed at temperatures below 0°C in the presence of dry hydrogen chloride or pyridine—hydrogen bromide. The metaldehyde crystallizes from solution and is separated from the paraldehyde by filtration (48). Metaldehyde melts in a sealed tube at 246.2°C and sublimes at 115°C with partial depolymerization. 

In contrast to pyridine-hydrogen fluoride, which is acidic and acts as a protonating agent, in alkylamine-hydrogen fluoride complexes, fluorine is a nucleophile. The difference of the nature of these two types of reagents has been... 

Reductive alkylation by alcohol solvents may occur as an unwanted side reaction 22,39), and it is to avoid this reaction that Freifelder (20) recom mends ruthenium instead of nickel in pyridine hydrogenation. Alkylation by alcohols may occur with surprising ease 67). Reduction of 18 in ethanol over 10% palladium-on carbon to an amino acid, followed bycyclization with /V,/V-dicyclohexylcarbodiimide gave a mixture of 19 and 20 wiih the major product being the /V-ethyl derivative 49,50). By carrying out the reduction in acetic acid, 20 was obtained as the sole cyclized product 40). 

Fig. 24. A portion of the hydrogen-bonded chain formed by the 1 2 complex between l,l,5,5-tetraphenyl-3,3,7,7-tetrahydroxycyclotetrasiloxane and pyridine. Hydrogen atoms have been omitted for clarity. Drawn using coordinates taken from the Cambridge Crystallographic Database. 

Figure 11. Crystal structure of morellic add, 15 in its 1 1 complex with pyridine. Hydrogen bonds a (strong) and b through g (weak) are marked. The pyridine molecule assists in assembling the structure.

Solubility in non-aqueous solvents.—Hydrogen chloride dissolves in many other solvents besides water—e.g. it dissolves in hydrocarbons, alcohols, aldehydes, ketones, ethers, esters, formic acid, nitrobenzene, aniline, pyridine, hydrogen... 

The regioselective DoM effects can be rationalized in terms of kinetic and thermodynamic control of the reaction (83T2009). The relative thermodynamic acidity (NaNH2/NH3/-25°C) of pyridine hydrogens... 

A behavior similar to that of pyridine and pyrazine N-oxides is exhibited by complexes of pyridines with hexafluoroacetone. Such complexes are expected to enhance the acidity of the pyridine hydrogens by oxygen-lithium chelating effects and therefore direct 2-deprotonation. In fact, treatment of f-butylpyridine (495) with LiTMP/THF-Et20/- 107°C generated, via the known complex 507, the stable 2-lithio species 508 which, upon reaction with electrophiles, furnished 2-substituted pyridines 509 (Scheme 154) (83JOC4156). 

The catalytic activities for pyridine hydrogenation (HDN) were evaluated at 4.5MPa in a fixed bed reactor packed with 30ml of catalyst. The catalyst first were sulfided with a H2S/H2 (92/8) mixture gas at flow rate of 60 ml/min at 300°C for 3 hr at 4.5Mpa. After cooling down to 270 °C, the mixture of pyridine and Hexane was introduced into reactor, at constant pressure (4.5MPa). The reaction products were analyzed by gas chromatography. 

T.R. Shattock, K.K. Arora, P. Vishweshwar, M.J. Zaworotko, Hierarchy of supramolecular synthons persistent carboxylic acid pyridine hydrogen bonds in cocrystals that also contain a hydroxyl moiety, Cryst. Growth Des. 8 (2008) 4533M545. 

Acetylhydrazino)pyridine Hydrogen bromide 2-Bromopropiophenone Bromine... 

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