Reppe's Acetylene Chemistry M. H. BIGELOW, Plaskon Division, Libby-0wens-Ford Glass Co., Toledo, Ohio

A s a l i e u t e n a n t c o l o n e l i n t h e C h e m i c a l W a r f a r e S e r v i c e , D r . B i g e l o w s p e n t m a n y m o n t h s i n t e r v i e w i n g W a l t e r R e p p e . H e r e h e d i s ­c u s s e s v a r i o u s n e w s y n t h e s e s d e v e l o p e d b y t h e G e r m a n c h e m i s t w o r k i n g w i t h a c e t y l e n e u n d e r h i g h j i -ressures w i t h v a r i o u s c a t a l y s t s

.F OLLOWING the defeat of Germany, al­lied technical investigators invaded the inner sanctums of the German chemical industry, and learned among other things abou t the fabulous growth of the use of acetylene. Responsible for this growth, and considered by many as the father of acetylene chemistry was J. Walter Reppe, who rose from a position as an obscure chemist to a directorship of I. G. Farben, heading its main research laboratory.

Reppe was born in Goringen, Germany, in 1892. Following his academic training which terminated in 1920 when he received a Ph .D . from the University of Munich, he joined the main laboratory of the Bad-ische Anilin und Sodafabrik. For several years, he was identified with the chemistry of indigo and azo dyestuffs. In 1925 he s tar ted working with acetylene as a raw material for producing butadiene. He developed a process for the preparation of vinyl ether from acetylene and alcohol, under pressure, using alkaline catalysts . This discovery was later recognized as a general method for introducing acetylene into organic compounds containing hy­droxy! groups. On the first of January 1934 he was made director of t he newly founded "intermediate plastics labora­tory" , which within four years developed from an insignificant s ta tus to t he most modern laboratory of the I. G. Farben. Here he was assisted b y scores of expert chemists and developed large-scale con­tinuous processes for t he reaction of acety­lene under pressure. Reppe a t times supervised the work of more t h a n 1,000 of Germany's leading chemists. Three of the men with whom he worked most closely were Ot to Hecht, Hans Triesch-mann, and a D r . Kroeper, who was Reppe 's r ight-hand man on carbon mon­oxide chemistry. Hecht was a physical chemist of exceptional merit. Before em­barking on a long, expansive research program, he would review the reactions involved and could spot instantly whether it could work thermodynamically. If it couldn' t work theoretically, t h e project was sidetracked. Trieschmann was a genius a t p lan t construction. Given a finished research problem he could build a working commercial plant with speed and accuracy.

Reppe 's work falls into three general categories: vinylation, or the additive re­action of acetylene destroying the triple bond; ethynylation, or the reaction of acetylene wi thout loss of the triple bond;

iiaid carboxylation, or the reaction of car­bon monoxide and acetylene. Pe rhaps he is; best known for the fearlessness dis-p[iayed in utilizing high pressures to control Ids acetylene reactions, this in spite of the well-known fact t ha t this gas i s especially sensitive to pressure and will de tona te vio­lently.

Reppe dispelled the fears of explosion associated with the use of acetylene gas a-t high pressures and used th is gas on a commercial scale at pressures of 200 at­mospheres (3,000 p.s.i.). To reduce the hazards involved, he devised some unique appara tus such as the water ring com­pression pump, the single-leg compression pump, and an explosionproof exhaust waive. In addition he used ni trogen gas a s a diluent and stuffed all la rge pipes with small tubing to reduce explosion hazards.

After Germany's capitulation, Reppe was among many top ranking chemists ga thered where they could be readily in­terrogated. I t was obvious t h a t a com­prehensive review of his pet thesis would [be of immediate value to allied industry, B O he was turned over to the chief chemical •officer of t h e United States Forces in the European Theater and charged wi th the :mission of writing a treatise o n acetylene •chemistry. I t became evident t h a t he • could only write on generalities, as he had been top m a n of an extensive research or­ganization. His major contr ibut ion was t o sift through some 20 tons of documents and sor t o u t those worth t ransla t ing into

M. 11. Bigelow

English. Possessed with the idea t h a t he was destined to become the leader of a new era of German industr ia l develop­ment , he had extreme difricult\- in apply­ing himself to the work a t hand . How­ever, with the assistance of certain former collaborators, hundreds of documents were abstracted which are now being compiled and will be published through t h e Office of Technical Service of t h e Commerce De­par tment as a Chemical Corps project.

I t was hoped t h a t Reppe could see fit to accept a W a r Depa r tmen t contract to come to the United States , b u t this he most emphatically declined, and what was more, he made i t clear to his collaborators tha t the}7 also should refuse such offers. This is regret table for t w o reasons. First, it has denied us the services of some capable chemists, and second, it shows tha t our efforts to break u p t h e I . G. com­bine have n o t been entirely successful. The spirit of un i t y and loyal ty which ex­isted among the technical men of tha t organization before and during the war continues with no evidence of weakening.

Wide Applications

Reppe's chemistry covered such a large territory t h a t i t is difficult to find any one German chemical process t h a t did not in one way or o ther relate to his findings. 11 covered the fields of pharmaceuticals, plastics, textiles, detergents, solvents, and a host of others . Natura l ly , much of hi* work related directly to war mater ia l , bul peculiarly enough most of i t could be di­rected into pos twar civilian economy. For example, polyvinylpyrrolidone, or Peris­ton, was developed as a subs t i tu te for blood plasma. However, it could be used equally well as an in termediate from which useful plastics could be made .

Ignoring Reppe ' s self-glorification, which to some extent was justified bul due in no small measure to t h e enormous number of interviews by leading American and British scientists, one could no t fail to discover t w o inherent qualities. First , he had a boundless creative imagination. His mind was fertile soil for fruitful ideas. Secondly, h e was a perfectionist in the efficiency of chemical processes. H e would not tolerate b a t c h processes.

Reppe has a son, a young Nazi if there ever was one, bu t ta lented . I t would be well to keep th is young m a n in mind be­cause he apparen t ly has inherited his father 's qualifications, and given access to a proper education, i t is predicted he too will be a g rea t chemist in his day .

There is no doubt t h a t Reppe is just approaching t h e peak of his creative abilities and i t will be a dist inct loss to the progress of acetylene chemistry if he is not allowed to cont inue his researches. For-

1038 C H E M I C A L A N D E N G I N E E R I N G N E W S

tunately, the war did not decimate the number of his co-workers although at the moment they are scattered throughout the several zones. I t would be a worth­while project to establish an Institute of Acetylene Chemistry headed by Reppe and staffed with his former assistants. The costs involved would be repaid in short order.

Catalysts

Reppe's results largely depended upon the use of proper catalysts which in many cases were not previously commercially used. His success was due largely to the fact that he established the actual role that catalysts played in the reaction. Once knowing the mechanism of the cata­lytic steps, he was then able to pick and choose the proper catalyst and to predict with remarkable accuracy the efficiency of a given process. In this way the discon­certing trial and error method of research was eliminated. For reactions of the vinylation and ethynylation type copper acetylides proved to be efficient. The catalyst must be prepared so that it is highly reactive and wear-resistant. Silicic acid is soaked several times in a strong nitric acid solution of copper nitrate and bismuth nitrate (Cu:Bi = 4:1) until the metal content is equal to 12% copper and 2% bismuth. The silicic acid is in the form of rods 4 to 6 mm. in diameter and 6 to S mm. long, stabilized by glowing at a temperature of S00° C. The soaked catalyst, is heated to 450° C. This ma­terial is packed into the reaction towers and then ''developed''. This is done by circulating dilute formaldehyde (5 to 209c) at 70° C. in the presence of acety­lene through the mass for 12 hours. To­ward the end of the development period the temperature is raised to 90° C. The catalyst is then ready to function.

In the carboxylation reaction iron, co­balt, and nickel carbonyls are employed. An elaborate study was made to deter­mine the mechanism of the reactions. The following will serve to show some of the steps involved.

Preparat ion of Acrylic

H20 -f C,H2 4- y4Ni(CO)4 + V2HCI-

->- HOCH2C=CCH2OH - ^ HOCH2C=CH

J. Walter Tteppe

I inylation Briefly denned, vinylation is the addi­

tion of the l^drogen atom of an organic compound to one side of the acetylene molecule, and the addition of the balance of the compound to the opposite side. This reaction is equally applicable to all organic compounds containing hydroxy 1 groups. Alcohols, amines, acids, phenols, sugars, and glycols are susceptible. A characteristic example involving the re­action of an amine is: Ri

C2H2 + 2HCHO -C2H2 + HCHO -

By changing the conditions of the reaction the yield of propargyl alcohol may be in­creased to 80%.

The side reactions which may be pur­sued in any given synthesis are numerous. For example, in the above reaction, the number of side products obtained in pro­ceeding to Buna rubber are shown in the chart on page 1040.

Ethynylation Perhaps the most interesting reaction

Reppe discovered was ttie addition of or­ganic compounds directly t o acetylene without disturbing the triple bond. This was called ethynylation. The reaction of acetaldehyde with acetylene will illus­trate this form of chemistry.

H

C H 3 C = O 4- H C = C H -CH3CHOH—C= 3-Bufcyn-2-ol

NH + C H s C H \

N-/

R2

-CH=CH 2

acetylene double

mole-bond.

H2 The triple bond of the cule always becomes Pressure and catalysts are required to ob tain commercial yields.

Reactions involving acetylene are versatile. For example, the reaction involving acetylene and formaldehyde to form 2-butene-l,4-diol may be made to yield 96% butenediol and 4% propargyl alcohol.

Acid

=CH

JH2O CHaCHOH—CO—CH3

3-Hydroxy-2-butanone I ^

CH3CHOH—CHOH—OH* 2,3-ZButanediol

Ethynylation proceeds only with the aid of catalysts. For the most part these are the acetylides of copper, silver, gold, and mercury. In addition, the reaction re­quires acetylene underpressure. Ethynyla­tion is also possible with derivatives and substituted products of acetylene. For example, 3-butyn-2-ol will react with diethylaminomethanol to form 5-diethyl-amino-3-pentyn-2-ol which when hydro­gen ated and condensed with 6-methoxy-quinoline forms the drug plasmochin* which is a specific for malaria.

-CH3

2H 2

H2C=CHCOOH 4- lANiCl 4- y4H2

Preparat ion of Nickel Carbonyl NiCl2 4- 2NH3 + H20 -+- 5CO > Ni(CO)4 -f- 2NH4Cl -f- C02

[Xi(NH3)6]Cl3 4- 5CO 4- 2H20 -

C2H5

N—CH2OH -f- H C = C - C H -

C2H5 O H C2H5

N—CHz—C=C—CHC—CH3 3

C2H5

N—CH2—CHLz—CH2-CH

/ • o-

C2H6

-CH3

C2H& H

Ni(CO) 4 4- 2NH4CI 4- (NH 4 ) 2 CO s 4- 2NH»

Preparat ion of Iron Carbonyl Hydride and Iron Pentacarboiiyl

Fe(CO)5 4- H20 >- Fe(CO)4H2 4- COa

Fe(CO)«H2 4- CO >- Fe(CO)6 4- H2

Preparat ion of jx-Propyl Alcohol Fe(CO)4Ho 4- 2CH«>=CH2 4- 4H20 >-

2CH3—CH2—CH2OH 4- Fe(HCOs)2

Preparat ion of Hydroquinone Fe(CO)4H2 4- 4C2H2 4- 2H20 >- 2C6H602 4- Fe(OH)2

or Fe(CO)5 4- 4C2H2 4- 2H20 4- OH" ^ 2C6H602 4- FeCOs 4- OH~

Other typical reactions are shown he-low.

C E = C

HOH2C CH2OH

4- NH 3 > || |J 4- 2H20

H

2HOCH2—C=CH H0CH2—CE=C—C=C—CH2OH 2,4-EEexadiyne-l ,6-diol

HOCH2—(CH^)4^CH2OH

I HNO3

HOOC—(CH^-COOH

V O L U M E 2 5, N O . 1 5 A P R I L 1 4 , 1 9 4 7 1039

1 '

Propiolic acid

Pyruvaldehyde

Lactic acid

1 1 I

2-Aminopyrimidine

Pharmaceuticals

Polymerized products

Alkynol Synthesis with Forma

Acetylene

Propiolaldehyde

Acetol

Chloro-2-propyn-1-ol

Chloro-2-propen-1-ol

Formaldehyde

Propargyl alcohol

Diacetylene

2,4-Hexadiyne-1,6-diol

3,4-Epoxytetra-hydrofuran

Polymerized products

I ^

1,4-Dichloro-2-butyne

Pyrroline

Butyl alcohol

Dihydrofuran

Idehyde

-j Allyl alcohol

H Propionaldchyde

-j Acrolein

H Propyl alcohol

4 2,4-Hcxadiyne-I 1,6-diol

2-Butyne-1,4-diol

Maleic acid esters

Artificial resins Lacquer raw material

. H Diprolyl ethers ch'carbonic acid

Thiodib utyric acid

Artificial resins Plasticizers

Maleic anhydride

Diels-Alder syntheses (e.g. with anthracene)

2-Butene-1/4-diol

Y-Cyanobutyric acid

Glutaric acid

i

r-Cnlorobutyric acid

r-Aminobutyric acid

Pyrrolidone

* 1 - Vinylpyrrolidone

t

Periston

v-Butyrolactone

•

r

1,4-Butanediol

Pyrrol

jS-Naphthyl-pyrrolidine

Polyamides

Tetrabutylene glycol

-*-1 Pyrrolidine

^S'-Dichlorobutyl ethers

PolytetrahydFofuran k

Phenanthrene

Tetrahydrofuran

i 1,3-Butadiene

. I Buna

1-Hydroxy-3-H buten-2-one

1,4-Dihydroxy-2--j butanone

-iBenzenehexamethanol

J Racemic or meso-erythritol

J 1,4-Dichloro-j 2-butene

J 1,4-Dicyano-2-butene

-JAcetal (withHCHO)

n Polyurethanes

•j Succinic acid

'

Glycerin

2-Methyl-1,3-butanediol

Artificial resins

1,6-Hexanediol •

Adipic acid

2,4-Hexadiene-1,6-diol

•

Hexose

1,2-Butanediol

1,2,4-Butanetriol

Mellitic acid

Tetrahydro-3,4-furandiol

Isoprene

1 Polymerized products

6-Caprolactone

* cT -Caprolactam

•

Polyamides

Tetrahydro-3-furanol

—

Hydromuconic acid

Polymerized products Factice

r-Oxopimclic acid

Maleic acid

, _.̂ _ , , . Malleic acid

Tartaric acid

* Artificial resins

Pimelic acid

•

Polyamides i

A Adipic acid

-j 1,4-Dichlorobutane

H 4-Chloro-1-butanol

"j 4-Chloro-1-butanol J esters

A 2,3-Dichloro-I tetrahydrofuran

Adiponitrile

Dodecahydro-triphenylene

- 1,6-Hexanediamine

j 2-Alkoxy-3-chloro-tetrahydrofurans

Chart illustrating side products obtained in synthesis of Buna

1 040 C H E M I C A L A N D E N G I N E E R I N G N E W S

Carboxylation

Another major contr ibut ion made by Reppe was the detailed s tudy of the re­action of carbon monoxide with acetylene, a process referred to as carboxylation. This field of synthesis became exceedingly impor t an t because carbon monoxide was available in lar^e quant i t ies as a by­product of the quenching process for gen­era t ing acetylene. T h e calcium carbide method for producing acetylene proved costly, part icular ly when the German military absorbed railroad transportation for t he movement of w a r material, thus reducing the available supply of coal and limestone. T h e new process for making acetylene consisted of burning the lower order of hydrocarbons, and by proper quenching of the flame with a spray of water, both acetylene and carbon mon­oxide were obtained.

Carboxylat ion opened a fertile field for producing both al iphat ic and aromatic organic compounds. A typical reaction for t he prepara t ion of hydroquinone il-lusti-ates carboxylntion.

O II c

G H ,

Type I S~%

v_y Type I I Type I I I

Cyclooctatetraene H 2 ( /

l,2-4,5-Dimethyleiie-2,5-cycloliexadiene

A large number of derivatives of cyclooetatraene have been m a d e and identified.

Bicyclo [4.2.0]-2,4,7-octatriene

Typical reactions are il lustrated in the following figures.

CI

+ C—COOR

C—COOR

Acetylenedicarboxylic acid ester

COOR 200-240 c

COOR

•CI

+ 3 H a .

N^OOR Phthalic acid ester

CI

3,4-Dichloro-cyclobuteno

Cyclobutane

11-

II-

-C III

-c c

C—II III C—H

II \

-f- O -h CO /

H

H / I

H C

OH

a

2C2H2 -}- 3CO -f H 2 0 C 6H 60 2 + C0 2

C H

Cyclooctane p-Xylene

Dehydrogenation of cyclooctane according to Rxizicka.

React ions involving carbon monoxide are unl imi ted and for t h e mos t part pro­duce raw mater ials of in teres t t o the plas­tics indus t ry . A few typical reactions are as follows:

Cycloocta te t r aene

CH2

H2C

HOCL

CHO

O H C Tercph. thalaldehy d e

C r 0 3

COOH

C 6 H 5 C = C — C H 3 + C O + R O H • C6Hi

COOR

, C = C H - -CH3 a-Phenylcrotonic acid ester

H O O C / N

Terephthalic acid

C2H2 + CO -f- H 2 0 ^ H 2 C = C H C O O H Acrylic acid

C>H2 + CO + R O H ^ H 2 C = = C H C O O R Acrylic ester

T h e reaction of carbon monoxide with acetylene proceeds on ly th rough the aid of specific ca ta lys ts of t he carbonyl type. These cata lys ts have been described under the heading of ca ta lys t s .

Cyclooctatetraene

R e p p e found t h a t acetylene could be polymerized into a series of cycloolefins, much after the classic reaction of Berthe-lot for the formation of benzene. I n this field, however, Reppe succeeded in form­ing wi th reasonable yields an eight-mem-bered ring, cycloocta te t raene; a ten-membered ring, cyclodecapentaene; and a twelve-membered ring, cyclododecahex-aene.

Cyclooctatetraene appears to exist in th ree isomeric forms:

The Cover . . .

Ralph Herbert Allee O C I E N C E and Agriculture in Inter-

American Affairs'' is the topic of Ralph Herbert Allee's address to be delivered before the ACS general meeting a t Atlantic City. Agriculture is the pri­mary interest of Mr. Allee, bu t he has long been an advocate of scientific meth­ods in agriculture. As director of the Inter-American Inst i tute of Agricultural Sciences located a t Turrialba, Costa Rica, he is engaged in introducing modern agricultural methods and the value of scientific research to the more backward regions of Central and South America. Previous to assuming the directorship a t Turrialba in May 1946 he was active in organizing United

States collaboration in agricultural re­search and extension with the other American republics. H e litis also served in international capacities with the Food and Agriculture Organization of the UN. For agricultural achievement Albania has made him a Commander of the Order of Skenderbeg, arid Ecuador has awarded him t h e Order of Agri­cultural Merit.

He received his B . S . from Pomona College in 1937, and studied agricul ture a t the University of California and Cornell University, receiving an M.S. degree from the l a t t e r in 1940. His major fields of study were agronomy and agricultural educa/tion.

V O L U M E 2 5, N O . 1 5 A P R I L 1 4 , 1 9 4 7 1041

HgS0 4 CH3COOH

<f\ ococri: ^ > ' - C H 2 - C H

OCOCH;

^Phenylacetaldehyde

OC2H5

OC2H5

Phenylethylidene diacetate Phenylacetaldehyde diethyl acetal

In spite of the enormous amount of work done by Reppe and his fellow work­ers, the surface of acetylene chemistry has only been scratched. In addition t o the expansion and improvements of pres­ent processes, Reppe was planning to i n ­vestigate several definite projects before the termination of the war interrupted riis work. Among these were the considera­tion of supersonic waves to promote chemi-

HEN Herman Dorn leaves the labora­tory at Owens-Illinois Glass Co. a n d returns home, he knows a full-time job is waiting for him there too. In the labora­tory he has built in the basement of his Toledo home, Dr . Dorn is producing small quantities of Sogenate, a drug which holds a promise for thousands of heart disease sufferers.

The result of ten years' work and the in­vestment of §14,000, Sogenate is now being used in several U. S. hospitals.

To tell the story of Sogenate is to tell the story of the man who developed -the drug. When Herman Dorn was 18 his eyes were injured in an explosion. During the two years he spent in the hospital re­covering, he became interested in research on digitalis drugs. Following his gradua­tion from Clark University a t Worcester, Mass., his home town, Dorn began work on glycosides, used as cardiac stimulants. By the time he had received his doctorate in chemistry he had put in two years' work on the problem.

With William Parker, a pharmacologist friend in Worcester, he formed a corpora­tion, Parker-Dorn, Inc., to protect any discoveries made. This arrangement per­mitted both members of the firm to work at their usual occupations without giving up the results of their work. A»s progress was made, Parker acted as business con­tact man, visiting the clinics periodically to learn of their needs, while Dorn worked on new compounds and strived to maintain

cal reactivity and polymerizat ion; the cyclization of 1,4-butynediol to hexa(hy-droxymethyl)benzene; preparat ion of qua terna iy vinyl ammonium compounds, such as neurine from tr imethylamine, water, and acetylene; and s tudy of the reaction of carbon monoxide with phenolic com­pounds. These are bu t a few of many ideas lie wants to test .

I t is interesting to note tha t many of the

Herman, Dorn

t h e needed production. During this pe­riod neither of the men received any in­come for his work.

Dr. Dorn 's problem was t h a t of modify­i n g glycosides and digitalis compounds used in the t r ea tment of hear t disease. Pie wanted to change the drugs so t h a t they would no longer have the effect of con­str ict ing the blood vessels. While useful in slowing down the hear t beat t o allow t h e muscle t o rest, use of available drugs often brought on an a t tack much like angina pectoris because of the vasocon­str ictor effect. Also, t h e toxic dose of the drugs, which Dr. Dorn terms ' a poison under control", was so near to t he thera-

nevver plants built in late 1943 were pri­marily for the manufacture of war chemi­cals, and in most cases the equipment could be used for the preparation of plastics and resins. Consequently the equipment was made of excellent materials and set up with the characteristic of German precision.

I t is hoped t h a t in t he demilitarization of these German plants this well con­structed equipment will be left intact for postwar economy.

With our great natural gas reserve, the work of Reppe should be of direct benefit to our industries manufacturing plastics, pharmaceuticals, and textiles. With leather as scarce as it is, our interest in certain plastic subst i tutes should be keen. Germans preferred plastic belts over leather for power transmission. I tems tha t should be investigated, all of which in one way or another relate to Reppe 's work, include: low temperature lubri­cants (esters of adipic acid), water repel­lents (ethyienimines), synthet ic deter­gents, diisocyanate resins for paper t reat­ing, plastic magnetic recording tapes, plastic foams for acoustical and thermal insulation.

peutic dose, t h a t underdosing was ab­solutely necessary. In the impure form in which many were made available, the drugs were rapidly decomposed by the enzymes and other catalytic substances present.

The purpose of any compound used in treating a diseased heart , one which beats too rapidly bu t with insufficient power to carry the blood to the extremities, is to slow down the beat, add power to it, and so allow the overworked heart to rest and recover.

Mixtures of glycosides with vasodila­tors, agents t h a t cause expansion of blood vessels, were tried in the hope t ha t the vasodilators would conteract the danger­ous constrictive action of the hear t drugs. The experiments were unsuccessful be­cause the two effects did not occur simul­taneously.

Extract ing his own supply of drugs di­rectly from dried plants, Dr. Dorn suc­ceeded in chemically compounding them with suitable vasodilators such as caffeine. The resulting compounds are somewhat less potent t han the original glycosides, but they may be given in large doses with­out danger of causing fatal constrictions of the blood vessels.

Dr . Dorn is now striving to produce enough Sogenate to fill the needs of the clinics at the medical schools of Harvard , New York University, Minnesota, and a clinic a t Santiago, Chile.

Dr . Dorn, 35, went to Owens-Illinois Glass Co. in 1945 as a supervisor in the biochemistry laboratory of process and product research. During the war he did research work on a rmy emergency food rations at Iowa State Universit}'.

Chemist Develops Drugs in Home Laboratory

1042 C H E M I C A L A N D E N G I N E E R I N G N E W S