Organic Syntheses, Coll. Vol. 4, p.451 (1963); Vol. 30, p.41 (1950).
Two hundred and sixty-seven grams (296 ml., 4.38 moles) of 28% aqueous ammonium hydroxide
, 207.5 g. (209 ml., 1.57 moles) of paraldehyde
, and 5.0 g. (0.065 mole) of ammonium acetate
are heated to 230° with continuous agitation in a 2-l. steel reaction vessel (Note 1)
, and the temperature is maintained at 230° for 1 hour (Note 2)
. The autoclave
is then allowed to cool, and the two layers of the reaction mixture are separated (Note 3)
. To the non-aqueous layer is added 60 ml. of chloroform
, causing separation of water which is combined with the aqueous layer. The aqueous layer is extracted with three 50-ml. portions of chloroform
, and the extracts are combined with the main portion of the chloroform
solution. After removal of the chloroform
by distillation at atmospheric pressure, fractional distillation under reduced pressure through a 30-cm. Fenske-type column3
gives a fore-run of water, paraldehyde, and α-picoline
, b.p. 40–60°/17 mm.
, followed by 72–76 g.
) of 5-ethyl-2-methylpyridine
, b.p. 65–66°/17 mm.
1.4971 (Note 4)
A steel reaction vessel of the type used for high-pressure catalytic hydrogenations is satisfactory. The pressure of the reaction mixture ranges from 800 to 3000 lb. A larger volume of reactants should not be used in a 2-l. reaction vessel.
The reaction is exothermic and in some reaction vessels may cause the temperature to rise above 230° for a short period. This has no apparent effect on the yield of product. The temperature measured is that of a thermocouple inserted in a well in the cover of the autoclave and corresponds to about 250° if the thermocouple is in the wall of the autoclave.
The mixture contains a small amount of solid material, apparently due to slight corrosion of the steel reaction vessel. If the solid causes the formation of an emulsion, it can be removed by filtration.
The yield may be increased to 60–70%
by use of an 8:1 molar ratio of ammonium hydroxide
, but this is generally inconvenient because of the greatly increased volume of the reaction mixture.
(also known as "aldehyde-collidine") has been prepared by heating aldehyde-ammonia
and phosphorus pentoxide15 ethylene glycol
and ammonium chloride
;16 ethylidene chloride17,18 or bromide19
; ethylidene chloride
, or n-amylamine
;16 crotonic acid
and a calcium chloride-ammonia complex
and by passage of acetylene21
and other catalysts.
A study has been made of catalysts for the present reaction,23
and a mechanism for the synthesis of pyridine
and its derivatives by the Beyer-Chichibabin method has been published.24
Copyright © 1921-, Organic Syntheses, Inc. All Rights Reserved