Patent GB-649641-A (GB)
Title: Improvements in or relating to a process for the preparation of acetylenic alcohols
IPC: C07C29/42
Filed: 1944-11-14
Abstract: Acetylenic alcohols are prepared by a process comprising heating a mixture containing solid potassium hydroxide (pulverized if it contains less than 13 per cent of water), an acetal or polyether, and a primary monohydric alcohol until the potassium hydroxide is at least partially molten and water, if present, is present in an amount less than one mol. per mol. of potassium hydroxide, cooling the heated mixture with agitation to produce a finely-divided suspension of potassium hydroxide, absorbing in the cooled mixture a 1-alkyne having a hydrogen atom in the one-position, thereafter adding to said mixture an aliphatic aldehyde having from four to eight carbon atoms or an aliphatic ketone, hydrolysing the resulting product to the corresponding acetylenic alcohol and separating the latter. Alternatively, an aqueous solution of potassium hydroxide may be utilized; thus, the aqueous solution is heated with the acetal or polyether to distil off the water azeotrope which is collected, the acetal or polyether returned to the distilling mixture and distillation continued until the distilling mixture contains less than one mol. of water per mol. of potassium hydroxide whereupon the primary monohydric alcohol is added, or a mixture of aqueous potassium hydroxide, the primary alcohol and acetal or polyether is similarly heated to distil off a ternary azeotrope of water, primary alcohol and acetal or polyether, the water in which is removed and the organic constituents returned to the distilling mixture until the water content of the mixture is less than one mol. per mol. of hydroxide; with either procedure, after cooling with agitation, there is obtained a suspension of finely-divided potassium hydroxide which is then utilized as above.  The third process is preferred. Azeotropic distillation is continued until no more water distils over, leaving a mixture consisting of two layers, the upper comprising the alcohol and acetal or polyether and the lower essentially potassium hydroxide with 13 per cent water.  This mixture is cooled with agitation to a temperature from slightly above the freezing point of the mixture to 35 DEG  C. and the 1-alkyne then passed in until absorption ceases.  The aldehyde or ketone is next added in an amount about equivalent to the alkyne absorbed at between - 10 DEG  C. and +90 DEG  C. and the potassium derivative of the acetylenic alcohol thus formed is hydrolysed by addition of water. The mixture is subjected to fractional distillation under reduced pressure to remove a water-acetylenic alcohol azeotrope from which the water is removed by azeotropic distillation with, for example, benzene, toluene, xylene or petroleum naphtha.  The primary monohydric alcohols have, preferably, three to eleven carbon atoms and are used generally in an amount of from about 2 to 35 per cent of the total volume of the mixture, an amount of acetal or polyether just high enough to allow formation of a reaction menstruum which is sufficient for satisfactory agitation is normally employed.  In typical examples: (1) a mixture of potassium hydroxide pellets (13 per cent water), butanol and 1,1-dibutoxy-ethane is refluxed for 15 minutes at 188 DEG  C. and then cooled with agitation to - 10 DEG C., and thereafter acetylene and acetone added successively and then water added to hydrolyse the product yielding 2-methyl-3-butyne-2-ol of which is isolated; in comparative tests, the reaction menstruum is prepared by adding powdered potassium hydroxide to 1,1-dibutoxyethane at -10 DEG  C. with agitation and then acetylene and acetone added as before, the yield of final product being smaller; (2) a mixture of 1,1-dibutoxyethane, isoamyl alcohol and aqueous potassium hydroxide is heated and the water removed as its azeotrope with the dibutoxyethane and isoamyl alcohol, the latter two components being separated and returned to the distilling mixture and the residue is cooled with agitation and utilized as in (1).  Other acetylenic alcohols which may be thus prepared are 3-methyl-1-pentyne-3-ol, 2-methyl-3 - pentyne - 2 - ol, 4 - ethyl - 1 - octyne - 3 - ol, 6-ethyl-3-decyne-5-ol, 1-nonyne-3-ol, 1-hexyne-3 - ol, 3 : 5 - dimethyl - 1 - hexyne - 3 - ol and 3-methyl-1-nonyne-3-ol. Additional starting materials mentioned are propyne, 1-pentyne and phenyl-acetylene, and butyraldehyde, hexaldehyde, heptaldehyde and 2-ethylhexaldehyde and ethyl methyl ketone, isobutyl methyl ketone and hexyl methyl ketone.  In preparing the reaction menstruums, there may also be used 1 : 1-diethoxy butane, 1 : 1-dibutoxy-2-ethyhexane, 1 : 1 - dipropoxybutane, dibutoxyphenylmethane, 1 : 2 - diethoxyethane, diethylene glycol diethyl ether, 1 : 2-diethoxypropane, 2 : 3 - dibutoxybutane - 4 : 5 - dimethyl - 2 - propyl - 1 : 3 - dioxolane and dimethoxymethane, and 1-propanol, isobutyl alcohol, methylallyl alcohol, 1-pentanol, 1-octanol, undecanol, diethylene glycol monoethyl ether, ethylene glycol monoethyl ether, 2-phenyl ethyl alcohol, 3-phenyl propyl alcohol and tetrahydrofurfuryl alcohol.  Specifications 544,221 and 627,474 are referred to.  The Specification as open to inspection under Sect. 91 relates to the use of a reaction menstruum, in the synthesis of acetylenic alcohols, comprising a finely-divided suspension of potassium hydroxide in an acetal or polyether and a primary monohydric alcohol, said mixture having been heated and then cooled with agitation.  This subject-matter does not appear in the Specification as accepted.ALSO:In a synthesis of acetylenic alcohols (see Group IV (b)), a reaction menstruum is prepared by a method which includes distilling a mixture of water, potassium hydroxide and an acetal or polyether, with or without a primary monohydric alcohol, to remove an azeotrope consisting of water and acetal or polyether, and primary monohydric alcohol if present in the mixture, the water in the azeotrope being separated and the remainder returned to the distilling mixture until the water content thereof is less than 1 mol. per mol. of potassium hydroxide.  The synthesis yields a reaction mixture containing acetylenic alcohol, water, potassium hydroxide, acetal or polyether and primary monohydric alcohol; this mixture is distilled to remove the acetylenic alcohol in the form of its azeotrope with water and the wet alcohol is subsequently dehydrated by azeotropic distillation with, for example, benzene, toluene, xylene or petroleum naphtha.  Numerous acetals, polyethers, primary monohydric alcohols including such compounds as ethylene glycol monoethyl ether, and acetylene alcohols are mentioned.