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This document contains information affecting the National Defense of the United States within the meaning of the Espionage Act, 50 U.S.C., 31 and 32, as amended.  Its transmission or the revelation of its contents in any manner to an unauthorized person is prohibited by law.

T.A.C. Report SnMc-6

(T.O.M. Report No. 12)

Report on Interview with Dr. J. W. Reppe, I.G. Farbenindustrie, A.G. at Gendorf, Germany

Interviewed May 19 & 20, 1945

Reported by

E. B. Peck, U.S.A
Irvin H. Jones, U.S.A.

Information Supplied by the U.S. Government Technical Oil Mission

Submitted for Distribution by the Petroleum Administration for War

to the Technical Advisory Committee
(A Subcommittee for the Technical Committee)

of the

Petroleum Industry War Council

Report on Interview With Dr. J. W. Reppe

at

Gendorf, Germany

Reported by Dr. E. B. Peck, Irvin H. Jones.

on behalf of 

U.S. Intelligence Committee

CIOS Target No. 30/Opportunity

Fuels and Lubricants.

Combined Intelligence Objectives Sub-Committee
G-2 Division, SHAEF (Rear), APO 413.

Table of Contents

Personnel of Team:

Dr. E. B. Peck - U.S. Petr. Admin. for War.
Irvin H. Jones - U.S. Bureau of Mines.

Dr. J. Reppe, director of I.G. Farbenidustrie and head of the Hauptlaboratorium at Ludwigshafen, was interviewed with respect to his contribution to the German war effort.  He played an important part in the last war (1914-1918) in developing the German process for making mustard gas but has had nothing to do with war gases in this war.

His principal contributions to this war were stated to be:

    a.  Synthesis of a substitute for blood plasma called Periston;
    b.  An adhesive that makes Buna adhere to fabric and is called Korosin - it formed an essential part of the German synthetic rubber program;
    c.  New reactions in the synthesis of butadiene.

Dr. Reppe and his co-workers have developed new processes that involve novel reactions of the acetylenes, olefines and reactions of metallic carbonyls; these developments will probably be of future industrial importance and are discussed below along with other reactions described by Dr. Reppe.

The industrial success of the above acetylene chemistry depended first on the development of safe method and means of handling acetylene (C₂H₂) under pressure, and for some of its reactions, and the safe use of large quantities of metallic acetylides - more especially that of copper.  Reppe's laboratory has C₂H₂ piped at 30 atm. pressure and plans are made to use it at pressures of 150 atm.  Basic investigations of explosions in compressed acetylene in the absence of oxygen in small bombs showed that the pressures developed to 10 times its initial partial pressure in a mixture and that the large scale application depended (1) on the provision of equipment to withstand such possible pressure increases and (2) restricting possible explosions to rather small volumes.  This latter requirement was met in small-scale apparatus by using for a required delivery of acetylene instead of a single pipe a plurality of smaller pipes about one inch in diameter through which more than a given output of acetylene was continuously circulated by ? the lines back to the suction-side of the large capacity compressor and by using one-way bicycle-tire valves at spaced intervals in the lines.  In larger installations, the 4-6 inch pipelines were completely filled throughout their length with pipes of small diameter (about 5-10 mm.) to form a sort of honeycomb structure throughout their extent.  The latter has worked so well that, in the large plant for manufacturing about 4500 tons per month of butindiol from acetylene and formaldehyde at Ludwigshafen, of the three explosions experienced, only the lines were burnt through in a very small area without further trouble.  After these explosions, the tubes were carefully cleaned and reassembled.

Explosions are prevented in large masses of metal-acetylide catalyst by keeping them wet.  They are formed in situ by depositing a salt of the required metal, for example the nitrate, on silica-gel pellets and heating the same for conversion of the nitrate to the oxide and thereafter treating them with acetylene under pressure.  The only acetylide catalyst in commercial plants is made by reacting copper oxide with acetylene in situ (see butindiol process).

Acetylene Chemistry.

Reactions of Alcohols and Acetylenes.

Dr. Reppe discussed the well-known reaction between acetylene and alcohols and stated that the reaction was quite general for both aliphatic and aromatic alcohols including primary and secondary alcohols, mercaptans and phenols.  Potassium hydroxide is employed as the catalyst.  Ethers and esters and secondary amines also react with acetylene under pressure.  For example, the reaction between methyl alcohol and acetylene goes very smoothly at about 200º C. to give methyl vinyl ether in the presence of KOH:

CH₃OH + HC = CH → CH₃O - C = CH₂

Methyl vinyl ether is hydrolyzable at 180º C. with water to give acetaldehyde and methyl alcohol and the latter can be returned to the process.

This production of acetaldehyde without a mercury catalyst was considered important for German industry because 2 kgs of mercury are lost in the production of a ton of Buna; however, a plant was never built.

Another important reaction of acetylene and an alcohol is that with phenol, also employing KOH as the catalyst, which gives first phenyl vinyl ether that can convert to vinyl phenol.  Depending upon the amount of acetyle substituted on the benzene nucleus, will depend the characteristics of the polymer made from the resultant oxystyrenes wherein the vinyl groups are normally in the ortho and para position to the hydroxy group.  To make a resin of the Bakelite type, phenol is reacted with acetylene at a pressure of 10 atm.

Organic zinc salts, for example the naphthenate, are goos catalysts for the phenol-acetylene reaction and they can give substituted oxy-styrenes that are solids.

Although the mercaptans, as above mentioned, react with acetylene to give products analogous to those derived from the oxygen alcohols, the products are malodorous and are not of particularly practical value.

Korosin, the adhesive for synthetic rubber, is made by reacting isobutylphenol with acetylene.  This was considered an indispensable development in the German synthetic rubber program as this material bound the synthetic rubber to the fabric.  It also assists in producing a tire that does not get hot in use.  In this case, the acetylene does not form an ether but substitutes for hydrogen on the benzene ring under the influence of zinc naphthenate as the catalyst.  The reaction takes place in the liquid phase (Rieselverfahren) forming the hypothetical monomer shown below which, however, polymerized as formed:

At Lugwigshafen, the I.G. Farbenindustrie has a small plant for the production of vinyl ether especially from methyl alcohol and acetylene.  The reaction was carried on in liquid phase at 15 to 20 atm. pressure of acetylene which was delivered to the reaction vessel as a 50-50 mixture with nitrogen; the total pressure in the system was thus about 30-40 atm.  The compressors were of the vertically-reciprocating piston type and the connecting rods were enclosed in a transparent case to prevent ingress of dust as a precaution against friction and possible explosion that the presence of dust in the cylinder would cause.  The compressors were of the usual type and were capable of delivering 100 and 180 m³ per hour.

Reactions of Aldehydes with Acetylene

Such aldehydes as formaldehydes, acetaldehyde, propionaldehyde etc. can be reacted with acetylene under pressure in the presence of metallic acetylides to form unsaturated alcohols.  Either one or two molecules of the employed aldehyde can react with the acetylene and the so-formed alcohols have as many carbon atoms as are present in the reacted reagents, for example with acetylene and formaldehyde, there can be prepared both

(1) Propargyl alcohol     HC = C - CH₂OH
(2) Butine 3 diol 1,4        HOCH₂  - C = C - CH₂OH

The reaction is one of the most promising developments of Dr. Reppe and his co-workers.  The above alcohols are made by introducing a mixture of reaction products with sufficient of a 35% aqueous solution of formaldehyde to provide a 10% solution of the latter in concurrent flow into a tower that is packed with copper acetylide (10-12%) deposited on baked silica gel pellets.  The catalyst is prepared by depositing CuO (Cu(NO₃)₂ and roasting - it may contain some Bismuth also - and treating with acetylene in situ in the contact vessels in the presence of water at 60-70º C.  The reaction may be controlled to make up to 70-80% of the product as propargyl alcohol, but the usual procedure makes 92% of said butinediol and 4% propargyl alcohol.  The latter is recycled when only the diol is wanted.  The reaction conditions employed are 5 atm. pressure and 100º C.  The acetylene is employed in excess and in dry upon entering the process; it therefore evaporates water sufficiently to remove the exothermic heat of reaction.  The outlet gaseous mixture from the reactor should be water-vapor and acetylene in the ratio of respectively about 4 to 1.

A plant has been running at Ludwigshafen for two years at a capacity of 4500 metric tons per month of butinediol.  In this plant the acetylene is compressed in 2 stages to 5-6 atm. with ring-water centrifugal compressors and the compressed gas (without dilution by N₂) is piped to the honeycomb pipes described above.  There are 6 reactors (1.5x18 m.) designed for 50 atm. pressure which however operate at the above 5 atm. only.  They are lined with stainless steel (V₄A) and have each a volumetric capacity of 20 m³ of catalyst containing 2000kg. of copper acetylide.  The inlet solution of formaldehyde is dripped (Diesel verfahren) through the tower at the rate of 10 m³ per hour concurrent to a stream of acetylene of 1 m³ per hour.  The reaction being highly exothermic, the only heating employed is heat exchange in the formaldehyde feed lines.  The Leistung is 1 ton of butinediol per cubic meter catalyst per day.  The outlet solution from the reactor is distilled to recover 10% unreacted formaldehyde and produced propargyl alcohol which were overcome by diluting the formaldehyde solutions, as above described.  There have been acetylene explosions in the pipes near the control valve to the reactor, but the only damage was to burn a small hole in the pipe.

The reaction solution contains abour 30% butindiol.  By evaporation and crystallization from ethyl acetate, the butindiol can be recovered in crystallization form; the butindiol as prepared about in aqueous solution can be hydrogenated while still in such solution to butenediol 1,4 and also to butanediol 1,4 by means of a nickel or copper catalyst at 200-300 atm. by means of circulated hydrogen.  The conversion of butindiol 1,4 to Butanediol 1,4 by hydrogenation is 96%.

The butanediol 1,4 (n-butylene glycol) can be recovered from the acqueous solution and be dehydrated in one step to butadiene over a phosphate catalyst as developed by I.G. Farben in 1926.  The butanediol is now made at Ludwigstafen for 60 pfg. per kilo and it is expected to reduce this to 40-50 pfg per kilo.

However, it is preferable because of higher yields and for other reasons according to Dr. Reppe, to dehydrate the butaanediol to butandiene in two steps:  that is, first to tetrahydrofurane and then the latter to butadiene.

Tetrahydrofuran appears to be an important new building block in synthetic chemistry.  It is a good solvent for many types of compounds including also such high polymers as polyvinylchloride, polyvinyl carbazol, natural rubber and Buna.  It enters many reactions.  Adipic acid can be made therefrom (see below).  In the above aqueous solution of 30-35% butanediol 1,4, obtained by hydrogenation of the reaction product of formaldehyde and acetylene, the former can be dehydrated to tetrahydrofuran in said solution by the addition of a small amount of H₃PO₄ and maintaining the pH at at least 2 and distilling the mixture at a temperature of about 260-300º  C. and a pressure of 60-100 atm; the THF (tetrahydrofuran) is easily volatilized under these conditions and is quantitatively produced.  The Na and Ca ions in the solution added for control of the pH value are substituted by H ions and by ion-exchange media (Volfatite). 

The THI can then be converted at 260-280º C. to butadiene by means of a phosphate catalyst; it can also be treated with metallic carbonyls and converted to adipic acid.

Butanediol 1,4 is also the starting product for the new blood plasma substitute.  By oxydation of its hydroxy-groups to aldehydes by simple spraying over a Cu catalyst at 200º C. by well-known Cannizzaro reaction, there is produced gamma hydroxybutyric acid and butyrolactone by reaction with liquid ammonia at 250º C. gives alpha pyrroliden, as described by Prof. Späth of Vienna, and in accordance with the following equation:

Conversion of pyrrolidon to its potassium salt and the latter's reaction with acetylene, similarly to the known preparation of vinyl carbazole, gives a N-vinyl-pyrrolidon which is the monomer of Periston.

Vinyl Pyrrolidone can be polymerized to Periston by aqueous solution of NaHSO₃ or by oxidation with H₂O₂ at a temperature of 70-80º C.; the H₂O₂ is the catalyst and is employed in amounts of 0.05 to 1% plus NH₃ to the extent of 1/2 to 1/2 of the employed H₂O₂ which determines the degree of polymerization.  Periston is neutral, has a high viscosity and is broken down in and eliminated by the human body.  It has been used in thousands of German soldiers, but the Allied medical experts have not accepted its use.

By reaction of NH₃ or amines with THF, it is converted to Pyrrollidine and its N- substituted products; these products are valuable in insecticides and in vulcanization acceleration.  The dehydrogenation of pyrrollidine gives pyrrol.  The reaction between THF and NH₃ is:

Propargyl alcohol which is made when one mole of formaledhyde adds to acetylene has promising uses.  When oxidized with air at 30º C. in the presence of copper chloride, it forms the following:

This latter compound, on incomplete hydrogenation, yields two isomers of hexdienol -

a) Hexadienediol, 2,4 diene, 1,5 diol -

b) Hexadienediol, 2.4 diene, 1,6 diol -

No use is known for the compound (a), but the compound (b) can be converted to either of two Nylon building blocks.  It is hydrogenated to hexanediol 1,6 and it then can be oxidized with nitric acid to adipic acid on the one hand, or said diol can be partially oxidized to give epsilon hydroxy caproic acid that easily dehydrates to caprolactone; reaction of the latter with NH₃ gives epsilon caprolactam which has the following structural formula:

Propargyl alcohol can be partially hydrogenated to give allyl alcohol and further n-propyl alcohol in neutral or alkaline solution; in acid solution by hydrogenation the propargyl alcohol converts to propionaldehyde.  Allyl alcohol can be converted to glycerine either by treatment with hydrogen peroxide (or persalts) or by conventional method with chlorine and water.  For the hydrogenation step Fe can serve as the catalyst and for the H₂O₂ oxidation to glycerine selenic acid is employed.

Carbonylation.

Carbonylation is the name given to reactions wherein carbon monoxide is added to another compound, for example to acetylene, olefine, cyclic oxide, and the like, along with such a hydrogen-containing compound as H₂, H₂O, ROH, NH₃, RSH, etc.  These reactions include the OXO reaction (olefines - CO- H₂) as a special case.  In this reaction, olefines in liquid phase are reacted with CO - H₂ in the presence of the Fischer-Tropsch cobalt catalyst to give a mixture of aldehydes, having more carbon atoms than the employed olefines; the aldehydes are thereafter hydrogenated to alcohols for separation by distillation.  A characteristic of this process resides in the fact that, due to the shift of olefinic double bond along the hydrocarbon chain during the reaction (isomerization), a multiplicity of isomers of the produced branched and normal alcohols is formed.  Separation of a single compound in pure form is difficult if not impossible even when a single olefine is that starting material.  This result seems to be a property of the cobalt catalyst.

Dr. Reppe prefers to use as the catalyst Nickel Carbonyl (Ni(CO)₄) or Iron Carbonyl (Fe(CO)₅) and H₂) instead of H₂ when the desired end-product is alcohols; by means of this advance, Reppe produces from a given olefine, or the like, a mixture of two isomeric carboxy acids having each one more carbon atom then the employed starting material, the acids can then be reduced to corresponding alcohols or aldehydes if they are the desired products.  The said acid isomers are usually straight chain and alpha substituted acids if the employed olefine is a straight-chained compound.

The nickel carbonyl can be formed outside the reaction vessel and be added to this reaction mixture or it can be formed in situ from a nickel salt, for example NiCl₂, that forms Ni(CO)₄ but in any even it must be present in a stoichiometric relationship to the product formed.  NiCl₂ in the presence of excess NH₃, reacts readily with CO at 150-180º C. to give the Nickel Carbonyl, as follows:

The NH₄Cl is regenerated with CaO.

As an example of the above reaction, the following synthesis of acrylic acid from acetylene was given, the reaction taking place at 40-42º C;

Cobalt and iron catalyst do not react as well in the above reaction.

Similarly also to acetylene, the olefines react with CO and H₂O and form saturated acids in the presence of Ni(CO)₄ ; for instance, ethylene yields propionic acid at 270º C. and 200 atm. pressure, as follows:

C₂H₄ - CO

and if an acid is used instead of water in the above reaction, it is possible to go directly from ethylene to propionic anhydride in the reaction -

If alcohol, ammonia, or amine is used instead of water, the corresponding ester or amide of the corresponding acid is obtained. 

If the employed acetylene or olefine lacks symmetry in respect of the unsaturated bond, two isomers of the formed acid, or the like, are formed; this is consonant with Dr. Reppe's theory that during the reaction CO unites at the unsaturated bond of the hydrocarbon to form the propenons ring because there thus exists the possibility of severing the ring at either carbon valence of its CO-group; for example, when reacting phenyl acetylene with CO-H₂O, the reaction may progress as follows:

Oleic olefine reacts as above to give corresponding fatty acids.

As aforementioned, these carbonylations can be carried out with Ni(CO)₄ added to the reactor or it may be formed in situ from such soluble nickel salt as nickel chloride activated with sodium iodid - said carbonyl being formed under the pressure conditions of reaction.

In the preparation of propionic acid from C₂H₄, CO and H₂O, said acid is formed as follows:  into a reactor maintained at about 235º C. - 280º C. and at a pressure of 250-300 atm., Co, C₂H₄ and H₂O are introduced at the bottom thereof, said reactor also containing elemental nickel and nickel acetate.  Ni(CO)₄ is formed from said nickel or its compound by reactions with the inflowing CO.  In the case of ethylene, as the unsaturated hydrocarbon, no solvent or liquid phase is necessarily present in the reactor although it is of advantage.  The reactor can be made with a lining of absolutely pure copper; idodine or other halogens are not necessary but they have an advantage if apparatus resistant to them are developed - which copper is not.  The use of the halogens has the advantage that they must be eliminated from the product.

The propionic acid formed in the reactor upon removal therefore contains some Ni(CO)₄ which can be removed therefrom by volitization - it is very poisonous and boils at 45º C. and decomposed in the air.  Fractional condensation has been found effective in performing the separation - the separated Ni(CO)₄ can be returned to the process.

When the employed unsaturated hydrocarbon is propylene or butylene, it is necessary to employ a solvent, such as the formed acid in the reactor; in the case of the higher olefines (such as produce fatty acids) the use of a solvent is not necessary probably because of their high boiling points.

From ethylene up to 95 yield of propionic acid is obtained.

Not only can monocarboxylic acids be made from olefines but also from alcohols, and polycarboxylic acids are preparable from CO and the glycols as well as from cyclic ethers of the latter.  For example, Hexandiol 1,6 smoothly reacts to Suberic acid; and Tetrahydrofuren with CO - H₂O converts to Apidic acid in the presence of the above metal carbonyls as follows:

Although not specifically so-stated by Dr. Reppe, it may be assumed, from his above statement, that methyl acetate can be formed from methyl ether -

The above carbonylation of the THF is carried out in continuous operation in the liquid phase with NiCl₂ and NaI as catalyst at 200 atm. and 270º C.  In an 8 liter reactor, 40 liters/hour of CO, measured at 200 ats. is passed counter-current to a downward flow of 300-600 cc/hour of a 10% aqueous solution of THF containing 1% of Nal, the CO being recycled; the conversion of THF to adipic acid is better than 90%.

The diolefin, butadiene, reacts with CO and H₂O in the presence of Ni(CO)₄, giving a 70%-90% yield of fatty acids at 200 atm. pressure and about 270º C.  The reaction is good for the manufacture of poly-amides to make high polymers of the Nylon-type.  The reaction proceeds along rather complicated courses giving a multiplicity of closely-related products.  Firstly, under the conditions of reaction, butadiene condenses with itself to form vinyl cyclohexene which then carbonylates at the unsaturated bonds to give carboxy-acids, as shown on the next page.

The commercial development of these carbonylations was held up for lack of acid-resisting materials of construction that were not available in Germany during the war.

Synthesis of Alcohols from ater and Olefines.

At a pressure from 200-300 atm. and a temperature of 300º C. for ethylene and about 250º C. for propylene, these unsaturateds can be converted directly to alcohols by reaction with water in the presence of tungsten oxide supported on silica gel.  The tungsten oxide forms about 20% of the catalyst by weight.  The higher the pressure employed, the better.  Tungsten Trioxide (WO₃) is inoperative but must be reduced at 600º C. to W₂C₅ before starting; about 5% ZnC in methylamine solution promotes the catalyst.

In practicing the above process, C₂H₄, for example, and H₂O are introduced at the above pressure into the top of a reactor tower containing the catalyst which is maintained at the above required temperature.  From the bottom of the reactor tower, there is withdrawn into an expansion vessel, about a 20% aqueous solution of the formed alcohol.  Molybdenum is also operative for the same purpose, but is not as good as the tungsten.

When propylene or butylene are used in the above reactions, the secondary alcohols are produced.

Cyclopolyolefines.

Dr. Reppe discussed his recent developments in the field of cyclopolyolefines, a development that may have only scientific interest, but may have wide future application.  He had done extensive research to establish the structural formula of especially C₈H₈ - cyclooctatetraen, which is the counterpart of C₆H₆ in the benzene series of compounds.  It is now indisputably established that this compound had the structure -

In the preparation of these compounds, acetylene, at a pressure of 10 to 20 atm using nitrogen as a diluent and such neutral solvent as especially tetrahydrofurane, is converted at temperature of from 60-70º C. and up to 130-140º C. in the presence of such nickel compounds as its cyanide, thicyanate, or halide into the cyclopolyolefines by condensation with itself.  The yield of product from acetylene is aobut 90%.  The formed cyclopolyolefines are predomitely C₈H₈ with minor amounts of C₁₀H₁₀, C₁₂H₁₂, and some soluble resins, and azulene.  The C₁₀H₁₀ and C₁₂H₁₂ are monocyclic compounds where as the azulene is dicyclic; the latter is an isomer of naphthalene and is formed by the dehydrogenation and rearrangement of cyclododecapentaen.

The inert solvent used is preferably tetrahydrofuran (THF).  The actual catalyst is assumed to be a very labile nickel - acetylene compound that is just made from the nickel halide, or the like, by reaction of C₂H₂ under pressure.  The formation of nickel acetylide can be promoted by the addition of a cyclic oxide such as ethylene oxide.

The portion of the condensed acetylene that converts to C₁₀H₁₀ and C₁₂H₁₂ can be considerably increased by variation of the temperature of reaction.  At 60-70º C., there is a preponderance of cyclooctatetraen formed.  The optimum temperature for C₁₀H₁₀ is 80-90º C. whereas that for C₁₂H₁₂ is 130-140º C.  The most azulen (intense blue color) is formed by a by product of reaction at 120º C.  Azulen is a dicyclic hydrocarbon having a C₇ and a C₅ ring with 5 olefine bonds as follows:

Azulen has a m.p. of 99.5º  in the absolutely pure form in which Dr. Reppe has prepared it.

Physical Properties of the Cyclopolyolefines.

The constitution of the latter two compounds has not been definitely established.

These compounds have no practical value; they have been investigated pharmacologically and no essential action established by their use.  However, Prof. Aohn at Heidelberg in the case of the C₁₂H₁₂ fraction (b.p. 230º C. to 235º C. and colored deep-blue with some azulen - about 3%) determined that the increases of certain pathological bacteria were completely suppressed in dilution of said fraction of 1:100,000.

Dr. Reppe said that the C₁₀H₁₀ fraction called cyclodecapetaene did not yield an oxidation sebacic acid and he believes that the compound may be instead vinyl cyclooctatetraene.

Samples of the above three fractions and of the refined azulen prepared by Dr. Reppe were obtained by members of CIOS Trip No. 215 - Ministry of Supply.

In consequence of its olefinic character, cyclooctatetraene is very reactive in the presence of various reagents.  It is -

Recent Advances in Carbonylation Chemistry.

The latest development in the carbonylation chemistry is the use of the metallic hydro carbonyls which are strong acids and react quite differently than do the above simple carbonyls.  Dr. Reppe had worked with both the nickel and cobalt hydrocarbonyls.

Dr. Reppe developed new methods of preparing the above compounds, H Co(CO)₄, in large quantities and studied their physical constants and chemical behavior.  This work showed that H Co(CO)₄ belonged to the group of strongest acids (about the HCl) and that H₂ Fe(CO)₄ behaved like an average mono basic acid.  These compounds were reacted with acetylene and olefine in the presence of water and the reaction products in the case of the olefines proved to be aliphatic alcohol, and in the case of the acetylene to be hydroquinone, or the like.  The empirical equation for the reaction with the iron compound can be the following;

The reaction progresses at about 100-110º C. and needs no Iodine, but there should be present an organic base that does not react with CO (amines), to form the H₂Fe (CO)₄ , as follows:

In contrast to Ni(CO)₄, the iron hydrocarbonyl can react at ordinary pressure but has the disadvantage that for each CO taken up to form product, two CO₂ molecules are lost.  The relation between ethylene, carbon monoxide, and water to give ether propionic acid or its anhydride is recognizable.

If a portion of the water is in the above empirical equation is substituted by NH₃, propylamine is produced, as well as the di- and tri- propylamine.

By extension of this olefinic reaction with metallic hydrocarbonyls, Dr. Reppe thought to arrive at unsaturated alcohols but, instead, with substituted acetylene arrived at hydroquinone derivatives in a yield of about 30% as far as his investigations have been conducted; empirically it seems to progress about as follows:

Stoichiometrically, the reagents react in the following ratio:

When employed substituted acetylenes and H₂Fe(CO)₄, benzene derivatives are formed; for example CH₃ - C = CH yields trimethylbenzene.

The success of this new carbon-monoxide chemistry is attributable to this first use of these hitherto unusable catalysts or their substitution products, i.e. metal carbonyls or metal hydrocarbonyls, as is also the similar situation in the use of the heavy metal acetylides and their first employment as catalysts in the ethylenetion reactions.

(The metallic hydrocarbonyls are not new chemical compounds.  They have been extensively investigated by W. Hieber and his colleagues.  In 1932, he and others published method of preparation and certain reactions of Fe(CO₄)H₂ in the Z. anorg. allgem. chemie, Vol. 204, pages 145-64.  Hieber therein describes the preparation of Fe(CO)₄ H₂ according to the following reaction:

Heiber also states that alkaline solutions of iron hydrocarbonyl have a strongly reducing action on organic substances such as nitrobenzene, quinene and dyes - for example indigo.  Although stable in alkaline solution, the hydrocarbonyl easily decomposes in the free state or in the presence of acids because of the initial reaction 2 Fe(CO)₄H₂ → Fe(CO)₅ + Fe(CO)₃ + H₂ which proceeds further leading to indefinite results).