INDUSTRIAL AND ENGINEERING CHEMISTRY
1488
NOMENCLATURE
a = rate of heat release, B.t.u./hr./cu. ft. b = rate of heat release, B.t.u./hr./cu. f t . / ” F. c = concentration in fluid in spheres, moles/cu. f t . co = initial concentration in fluid in spheres, moles/cu. ft. c = concentration in fluid stream in reactor, moles/cu. ft. co = outlet concentration in fluid stream from reactor, moles/ cu. ft. c, = specific heat of solid, B.t.u./lb./” F. c, = specific heat of fluid, B.t.u./lb./” F. D = diffusivity of reactant in the fluid inside the solid, sq. ft./hr. void volume in bed fG, = = fractional mass rate of flow of solids, Ib./hr./sq. ft. G = mass rate of flow of fluid, lb./hr./sq. ft. hi = heat transfer coefficient at solid-fluid interface, B.t.u./hr./ sq. ft./“ F. h = Laolace transform of t H = Laplace transform of T i
=
3, j(z)
J
Bessel function of order one half Bessel function of order minus one half reaction velocity constant, reciprocal hours thermal conductivity of solid, B.t.u./hr./sq. ft./( F./ft.) mass transfer coefficient at solid-fluid interface, moles/hr./ sq. ft./unit concentration difference D/V transform variable corresponding t o z rate of heat release in solid in B.t.u./hr./cu. ft. radius variable, ft. radius of a sphere, ft. =
--o s(z) =
k = k, = Kj =
m = p = q
=
r
= = = = =
R s
4-1
D/KfR
temperature in the solid, F. initial temperature of osolid, O F. T = temperature of fluid, F. 7 ’ 0 = outlet temperature of fluid, F. U = volume rate of flow of fluid through the bed, cu. ft./hr./ sq. ft. B = velocity of solid, ft./hr. x = distance along exchanger, ft. y = kR2/D 1
tc
O
2 CY
Vol. 42, No. 8
= G,/p,U
= thermal diffusivity = k,/C,p, P = GsC,/GCp Y = h-,/C,P,V A = bR2/k, B = k,/hjR @a = void fraction in solid ps = density of solid, Ib./cu. ft. 0 = time, hr. un = roots of transcendental equations LITERATURE CITED
(1) Arthur, 3. R., and Linnett, J. W., J . Chem. Soc., 1947, 416. ( 2 ) Brinkley, 8.R., Jr., J . Applied Phys., 18, No. 6 , 582 (1947). ( 3 ) Churchill, R. V.,“Modern Operational Mathematics in Engi-
neering,” New York, McGraw-Hill Book Co., Inc., 1944. (4) Damkohler, G., in “Der Chemie-Ingenieur,” Eucken, A , Ed., Vol. 3, Part 1, page 441, Leipaig, Akad. Verlagsges., 1937. (5) Damkohler, G., 2. Elektrochem., 42, 846 (1936), (6) Ebel, R. A., Ph.D. thesis, Vniversity of Minnesota, 1949. ( 7 ) Furnas, C. C., IND. EIFG.CHEM.,22,26 (1930). (8) Furnas, C. C., Trans. Am. Inst. Chem. Engrs., 24, 1942 (1930). (9) Furnas, C. C., U . S . Bur. Mines, Bull. 361 (1932). (IO) Grossman, L. M., Trans. Am. Inst. Chem. Engrs., 42, 535 (1946). (11) Lovell, C. L., and Karnofsky, G., IND.ENG.CHEM.,35, 391 (1943). (12) Marshall, W. R., Jr., and Pigford, R. L., “Application of Differential Equations to Chemical Engineering Problems.” Newark, Univ. of Delaware, 1947. (13) Saunders, 0 . A,, and Ford, H., J . rron SteelInst., 141, 291 (1940). (14) Thiele, E. W., ISD. ENG.CHEM., 38, 563 (1946). (15) Titchmarsh, E. C., ”Theory of Functions,” London, Oxford University Press, 1939. (16) Ton Karman, T., and Biot, M., “l\lathematical Methods in Engineering,” New York, McGraw-Hill Book Co., Inc., 1940. (17) Wilhelm, R. H., Johnson, W.C., and Acton, F. S.,ISD. ENG. CHEM.,35, 562 (1943). (18) Wilhelm, R. H., and Singer, E., preprint for Am. Inst. Chem. Engrs. Regional Meeting, Tulsa, Okla., May 1949. RECEIVED February 20, 1950.
Alfin Catalvsts and t Polymerization of J -
d
AVERY A. 3IORTOiY Mussuchusetts Institute of Technology, Cambridge, Muss. Alfin catalysts are special combinations of sodium salts which cause the rapid catalytic polymerization of butadiene to polymers of unusually high molecular weight. These polymerizations show characteristics which are common to all reactions of organosodium compoundsnamely, the tendency to undergo multiple reactions. The reagents are also insoluble aggregates of ions whose behavior is affected by the ions in the aggregate. The history
of the discover). is review-ed. The catalytic polymerieation show-s no property in common with the conventional sodium process for polymerizing butadiene. The present problems center in the elimination of secondary reactions that are known to occur. The theory by which all the reactions occur, including polymerizations induced by organosodium compounds, is discussed. Progress,toward the practical use of the Alfin polymers is being made.
T
from the fact that the reagents are insoluble aggregates of ions, somen-hat as in the crystal of sodium chloride, and are not fully dispersed in a solvent, so that the ions act separately. An understanding of these points is essential for anyone who works with these eytremely reactive reagents which operate only in hetei ogeneoua processes.
HE Alfin catalysts are special combinations of sodium
salts, one from an alcohol and the other from an olefin, which have uniqiie properties as polymerizing agents for butadiene and similar compounds. In order t o appreciate clearly this account of the discovery, special properties, problems, and possible mechanisms, it is helpful to keep in mind two important principles which apply to all reactions and reagents in the field of organosodium compounds, whether for pol~merizationor for some simpler process. One is the tendency for organosodium reactions to consist of multiple steps which tumble over each other as if in cascades until the end is reached. The other is the control which inorganic components of the reagent and other inorganic salts exert on the process, w circumstance that arises
DISCOVERY OF THE CATALYST
The importance of the two ideas mentioned above is better understood 11-ith a background of the chemistry of the organosodium compounds. For example, in the TYurtz reaction, long held as the most typical activity of sodium in organic chemistry,
August
INDUSTRIAL AND ENGINEERING CHEMISTRY
1950
amyl chloride with metallic sodium yields eit.her decane or the pentane-pentene pair so rapidly that for a long time the majority of chemists regarded the process as the random behavior of free radicals released in the reaction mixture. Now, however, it is known to consist principally of two distinct phases (Equation 1) and can be interrupted after the first one (16, 19, 29) if the amyl 2 l\;a
+ I
+
+ C5HllNa
~
(2)
---+
+
CbHii.C&
or
CBHlO
+ C6H12
Na
With the aid of this amylsodium intermediate and similar ones the second phase (16)of the Wurtz reaction can be 8hou-n to be determined by the inorganic components of the reagents. For instance (Table I), the reactions of ?2roctylsodium with three different methyl halides are different, despite the fact that in each instance the hydrocarbon components are identical. And the reaction of such reagents with alkyl halides in a common disproportionation yields the alkane from the organosodium component and the alkene from the halide [a similar reactton was independently observed by (59) Whitmore and Zookl, aa illustrated in Equation 3 for one of the reactions studied.
+ C&&1
Yields of Different Products _ _Percentage _ _ ~ _____ n-Octylsodium with
Wurtq, nonane 22 21 6
Disproportionation, ootene and octane 18
10 0
Dimerization, hexadecane 7 27 50
(1)
chloride is added dropwise to sodium sand while it is vigorously stirred in pentane. With the high-speed stirring apparatus (14, 21, 28) developed especially for these heterogeneous systems, and with other factors, such as temperature and time, under control, as high as 95% of the chloride can be accounted for as amylsodium, a remarkable yield for such an extremely reactive intermediate. An in-between step is inserted when this process is carried out in toluene. I n seemingly one operation the process cascades through three levels to an alkylated benzene in good yield (Equation 2 ) . Here, too, the prorem can be interrupted a t intermediate steps (17).
CbHllNa
TABLE I. REACTION OF n-OCTYLSODIUM WITH METHYL HALIDES
NaCl
NaCl (1)
CbH11CI
1489
---f
CsH12
+ CeHlz + NaCl
the sodium ion might be in either position without regard to the manner of addition, inasmuch as the system should display allylic isomerism or resonance as shown for the latter case by the formula
However, in any subsequent reaction with carbon dioxide, alkyl halide, or diene the behavior is as if the sodium ion affected a specific carbon. A small amount of acid 1,4 product was indeed isolated and ozonization indicated that the larger amount was 1,2-, but the really important facts were in line with the two principles given above-namely, occurrence of multiple or cascading reactions and control by inorganic components. (Inorganic components refer to all the ions, salts, or atoms present in the aggregate, exclusive of the hydrocarbon components.) One multiple reaction ( 9 , l l )started with addition of amylsodium to butadiene, continued by addition of the adduct t o another molecule of diene, and then followed with metalation, after which repetition of the phases led to products of higher molecular weight. These steps are represented in Equation 5 for a l,P addition to butadiene. A somewhat similar set of formulas could be written for a 1,2process.
(3)
I n all the above, we see a succession of orderly chemical steps which are subject to control by inorganic components rather than let loose to random behavior. With care the separate steps can be sorted and examined separately. In particular, also, we have at hand an extremely active reagent, amylsodium, capable of reactions not found with the more common magnesium and lithium reagents. For the reaction of this organosodium compound with butadiene (86), the technique of dropwise addition of one reagent to a large excess of the other, which had proved so successful in the study of the Wurtz reaction, was applied in the hope that, here too, intermediate early phases could be trapped (26). The process, represented in Equation 4, could be 1,2- or 1,P arid a decision was t o be made by carbonation and subsequent location of the carboxyl group. Ziegler's (40-44) work would cause the prediction that the product would he largely 1,2-. Of course,
Isoprene undergoes similar changes (11) but with grcater case in the metalation step which can occur after phase 1. This metalation was judged (11)t o occur because the carboxyl groups in the dimeric fraction exceeded the number needed for this stage of chain growth. Its likelihood was shown by the metalation of compounds (9-11,26) which had structures similar to units that would be present in a 1,Ppolybutadiene rubber, as illustrated (Table 11) with numerous olefins and their even more numerous products. Dotted vertical CeH13CHCH=CHZ lines emphasize similarities between /CaH1,CH2CHCH=CH, the unit and models. Metalation occurred in each case and very easily C02Na kn coz in diallyl, which is most like the 1,1+ or (4) polybutadiene. Hence polymeriza01' tion by addition converts the ~ C ~ H I ~ C € I ~ C H = -C H C H C ~B H I ~ C H = C H C H ~ monomer to a product extremely susceptible t o &ck by the cataly& + in another way; special attention is h-a C02Na I
I
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
1490
that found in the second phase of the '\Vurta reaction (Table I and Equation 3) where inorganic comnonents were an obvious n a r t of the reagents. The present method 123, 85, SO) of prepwing- the catalvst no longer uses this ether. -4niylsodium is prepared as usual. Alcohol ie added to destroy half or more of the amylsodium, thereby furnishing the nlkoxicie in finely divided state. Propylene is then passed into the mixture. These steps arc shonn 111 Equations 10, 11, and 12.
TABLE11. METALATION OF OLEPINS WITH STRUCTURES SIMILIAR TO PORTIONS OF A RUBBER Compound Polydiene unit
-
Products of Afetalation by Formula Amylsodium (-CI-Is: CH=C! j HCR: CHsjCH=CH ;CHz--)n
/CH*=C/HCH~
DiallJ-1
I-Butene
~
Vol. 42, No. 8
C H ~ = CH / CH~
+ 2Na -+ CjHllSa CjHl1Ya + (CH,),CHOH ---+ CjHllCl
Propylene
/CH~=CIHCH~
Ethylene
ICHz=C\Ilz
Isohutene
;CHz=CkHaa I I CHa
a
Isobutylene is comparable t o
B
T
( CR3)&H0Na
i
CHa=C (CI5)C k d a
CH2=C(CH*N;h unit in a polyisoprene.
called also to the many shifts of cfoiible bonds, a further evample in the multiple hut orderly changes. The consequences to Alfin polymerization or to an\' sodium polymerization are obvious. A more striking example of cascading piocessw occurred with the discovery of the illfin catalyst ($4). Diisopropyl ether was being used as a coordinating agent for the sodium ion somewhat after the way ordinary ether serves the Grignard reagent. A solution of the ether and diene in pentane was added drop%ise (as for Equations 4 and 5 ) t o amylsodium which nas being vigorously stirred in pentane. %thin seconds two distinct steps were inserted before the butadiene R as attacked bg the organosodium reagent, and the full set of reartions yielded a band of rubber completely insoluble and nonswelling in all common solvents and wrapped about the propeller. The multiple equation for this process IS
1 For clarity the separate steps are given in full. CbHnCl f 2K
7CHs)zCH
+
(CHa)&H
0 +( CH3)&HONa
/
+ C5HtlNa +
(3) ( C H 3 ) 2 C H O N a . C H ~ C H C H 2 1 i a nC&
+ CsH12
(7)
+C ~ H I I K+ KCI
(13)
TABLE111. GENERAL AKD SPECIFIC FORMULAS FOR SOME ALFIX CATALYSTS AND VISCOSITIESOF CORRESPONDING POLYBUTADIENES Alcohol
CH2=CHCH2Sa
+
(I 1)
+
CH,=CHCH? (2) CHFCHCH~
+ CbEiI2
prepared in sixu by rmction with an alkyl chloride. A~nyl(22) with the potassium potassium chloride formed during its preparation (Equation 13) has catslytic ilctivity a t -30' C., but a t 0'
-_J
(1) C5HnNa
(IO)
A11 operations are carried out in the highspeed stirring apparatus ( 9 8 ) under an atmosphere of dry nitrogen. Half of the product is sodium chloride, which remains with the cat,alyst. From some preparat,ions ( 1 3 ) gentle centrifuging or decanting will throw out first the traces of sodium metal left by the failure of the first step to be loo?& and secondly, the small amount of blue sodium chloride that often accompanies Wurtz reactions. The remainder is the rnixhre of catalyst and sodium chloridc thaf remains suspended indefinitelg. Many other combinations (23-2.5) have been tried. In general, the alkoxide must come from a secondary alcohol, one branch of which is a methyl group; the olefin must have the essent'ial system -CII=CH-CHz-, which may he part of a ring as in toluene. A few combinations are given in Table 111, together rr-ith ?,lieintrinsic viscosities attained b) their use on but'aiiiene a t room temperature in about, 5 volumes of pentane by common bottle polymerization technique. In addition to these catalysts, a few pairs of salts show soniewhat similar catalytic activity. For example, phenylsodium with sodium chloride ( $ 2 ) is a poor catalyst, and with sodium bromide is a much poorer one,
I
\ '
KaCI
+ C ~ H U(8)
+(C&)n
RCH(CH3)ONa
171
1
H H O 1% E
(9)
Each step was proved by a separate reaction. Separate tests of each salt for catalytic artivity were negative hut the joint action was positive. Sodium isopropoxide is as essential as allylsodium. Although seemingly a pair of unrelated ions, i t s connection with the activity of allylsodium is as specific as
Hydrocarhon CHZ=CHCH(R)Sa or HC=C-CH*Na
(CHs)2CHOSa nCsH7(CH3)CHOPia CeH6(CHa)CHONa (CHsjzCHONa (CHaj2CHONa (CHdzCHOPia ~C~HI(CH~)CI~O
CH2=CHCHzNa CH2=CHCHzKa E€h=CHCHzNa CH~ZCHECHCHJIN~ ~HECI-IZS~ [CH2=CHCHCH&H=CHz1 Na S[C2HsCH~CII': ~ CHzlNa
11-13 12-13
6-7 6-7 6-7 11-12
l
l
AN ALFIN CATALYST
A = ALKOXYL
R = ALKENYL
together. I n Coordination valencies bind the aggregate sodium chloride the coordination number of sodium is 6 (SZ, 33) and the crystal has been called a giant molecule or polymer (S3, 38). Therefore in the Alfin aggregate a coordination valence of 4 or 6 is reasonable. In such environment the sodium ions of the isopropoxide and allyl salts can have equivalent activity through either a linear or cyclic arrangement that might happen t o exist on or in a portion of the aggregate. Simultaneously the allyl ion is bound firmly a t each end. In either structure the sodium ion is not attached solely t o a particular anion. The volume of
Coordination compounds of sodium
Sexicovalent
All reactions with the reactive organosodium salts can occur on the surface of the aggregate, from which no pair of ions, much less a single one, need escape to react in solution. This idea is supported by three facts: The medium, pentane, is the poorwt solvent known for ionic compounds, no solution of the reagent has ever been detected, and the amount of polymer approximately doubles and triples as the catalyst is proportionately increased (SO), whereas no increase should have resulted in a solution already saturated by the reagent. Reactions are clearly dependent on more than the anion or the organosodium salt. A single alkoxide, sodium isopropoxide, accelerates metalation by amylsodium, retards metalation or addition reaction by allylsodium, drastically alters the polymerization induced by allylsodium, and a t first alters and then destroys the polymerization induced by butenylsodium. The related lithium isopropoxide reduces or destroys the unique polymerization created by the presence of sodium isopropoxide on allylsodium, although potassium isopropoxide does not. These changes and numerous others are too diverse to be accounted for by the assumption that the alkoxide is merely an inert surface over which the organosodium reagent is dispersed and made more available. They indicate an actual control of the reaction of an organosodium reagent by another specific ion or salt, The possibilities of control by change of the ion environment in such aggregates are unique, yet fully as diverse as those found in the conventional type of organic reactions which rely on changes in temperature, solvent, pH, etc. These facts m d others related to the chemistry of organo-
INDUSTRIAL AND ENGINEERING CHEMISTRY
August 1950
sodium compounds can be provided for by a simple explanation (25). All processes begin by adsorption of the reagent on the ion aggregate. Coordination takes place by aid of electrons from the adsorbed molecule, which in turn is activated and in part at least becomes a potential anion. The old anion is thus gradually freed for reaction with the polarized adsorbed molecule and the final product results by a few simple electron shifts. This series of changes, illustrated for disproportionation in the Wurtz reaction and for metalation of an olefin, accords nicely with current concepts of valence (32, 33) and the attractive influence (6, 8) of cation for anion.
1495
(The lithium ion which normally has a coordination valence of two obviously could not fit easily in this scheme.) Hence sdsorption of the diene can occur at two points simultaneously rather than one. The diagram (A, B, and C) shows a possibility
H
-No I
- RI - No - RI -NaI I
-
J
(6)
H
ci + -Np
uCHR'
H
H
c,
/* H ~ C - CHR'
1
H R
-cK
!+No-
Disproportionation
b
'CHR' H
-Nf
I
HR
Metalation Manner of reaction w i t h ionic aggregate
As applied to the ordinary or sodium process of polymerizing butadiene, adsorption and activation occur as usual and the old anion adds with simple electron shifts t o give a new anion. The process is repeated over and over to give a large polymer. A definite salt is formed at every step. The process can be called compound polymerization. At all times the growing polymer is an anion. CH*= CH -No I
- CH
- X1 -
= CHI
+&-
Na- 7 - N a - y -
.1
CHI-
CH - CH
- CHI
+
-No
r :
R-
1
GH,= CH - C y - CHa
+
-NY
(c)
Possible combination (A) @f i o n s in aggregate for Alfin catalyst and adsorption of diene to give a pair of carbonium (B)or free radical (C) centers
H
'
R
For Alfin polymerization and the two other fast ones t h a t occur with phenylsodium and amylpotassium, a new factor enters. The anion has reduced reactivity of the ordinary kind-that is, for the concluding phase of the addition reaction. Allylsodium (20) adds t o 1,l-diphenylethylene at a reduced rate, phenylsodium (31)does not add at all (see Table IV), and amylpotassium ( 2 2 )shows its catalytic activity at a low temperature, where the normal addition reaction should be retarded. Hence the adsorbed monomer has a longer period in the activated state. Opportunity is thus provided for reactions with another monomer, possibly similarly activated, instead of the old anion. The process can escape from the vicinity of the anion and become catalytic and can continue at least as long as the old anion remains embedded in the ionic aggregate (the stability factor), or until some specific size is attained. The sodium isopropoxide may help in some way other than by anchoring the organic anion. The sodium ions of the alkoxide and allylsodium might become equivalent through coordination.
for an assumed aggregate that contains all the ions known to be present. Polar bonds (solid lines between ions) and coordinate bonds (dotted lines) obviously are interchangeable. It shows also electron shifts in the adsorbed diene, so as to produce either a pair of carbonium or free radical centers. I n either case a type of polymerization, radically different from the ordinary sodium one, would result. I n summary, all reactions, polymerization or otherwise, with organosodium compounds start by adsorption on the surface. Activation of the adsorbed reagent is then assumed t o occur and the molecule is ripe for a reaction in which the old anion can participate. Usually this phase will pass smoothly to formation of the new anion. If, however, the old anion is rooted in the ion aggregate, or is otherwise unable to complete its role, the activated molecule can follow another course-namely, reaction with monomer. Catalytic polymerization is, thereby, a consequence of an interruption at a phase of an ordinary reaction. This picture is simpler than the assumption of an active anion center which in some unknown way is pried loose from the strongly polar influence of the sodium cation and escapes into solution; and, if such an improbable thing did occur, the anion should then undergo the familiar isomerism or show resonance as it grows, so t h a t the polymer would be largely a 1,2- product, and chain termination would be random. I n general, the idea of separate and sole anion activity is contrary t o the common behavior of organosodium reagents, which are, after all, highly subject to control by inorganic components in the reagents and, as in the case of A l h catalysts, to remarkable control b y seemingly unrelated salts. No fact yet found and no speculation on the reaction encourage the idea t h a t the Alfm process involves a free anion a t any stage of growth or is lacking in the exceedingly high degree of control found, by diligent search, in other organosodium reactions. PROGRESS TOWARD PRACTICAL
USE
The difficulties in the practical use of the interesting A l h polymer lie in its toughness. The polybutadiene does not soften on the mill as does natural rubber. This result might be charged to its very high intrinsic viscosity or perhaps more accurately to the secondary reactions. Attempts t o obtain one of lower viscosity by regulating polymerization in any of the conventional ways are unsuccessful because such catalysts act slowly and the product becomes highly contaminated. The result is an ordinary sodium polymerization, not to mention secondary reactions. This situation has reduced this end of the problem t o one of eliminating all side reactions as far as possible from the fastest acting catalyst, so t h a t the product is as pure an A l h polymer as possible, free from the cross-linking and double bond rearrangements that are the aftermath of metalation.
1496
INDUSTRIAL AND ENGINEERING CHEMISTRY
The achievements in this way have been considerable. The polymer, when first obtained, was insoluble and nonswelling in all common solvents. Hours of extraction in a Soxhlet apparatus had not the slightest effect. By close attention to the quantity of the catalyst and the freedom from organosodium reagent not related to the catalyst, a product was finally obtained which was free from gel and had an intrinsic viscosity of 11 or 13, on a few occasions even as high as 19 with less than 5y0 of gel. Freedom from gel is, however, not enough. Possibly there were enough rearrangements of double bonds to cause structural changes that did not reach the cross-linked state (see Figure 1). At any rate, the milled product for long had the appearance of seersucker cloth, a rough uneven material with hard nodules. Of late more improvements in the catalyst have been made and the polymerization temperature has been lowered in the hope of reducing further the secondary reactions that accompany polymerization. By this means rubbers of high intrinsic viscosity (11 to 13) have been obtained which Taft’s group a t the Government Laboratory a t Akron has been able to mill to plastic sheets on a small tight mill through which not more than twentyfive passes are made. Obviously, progress is being made. An approach has also been made from the use of the copolymer with styrene, which in general can be milled more readily than the polydiene. With the 80/20 copolymer the Goodyear Laboratory was able to obtain enough material for a tire test ( 3 ) . D’Ianni ( 3 ) also reported unusually good abrasion resistance in the lOOyo polybutadiene in spite of the lack of good milling characteristics.) Taft’s group ( 3 7 ) a t the Government Laboratory a t Akron has recently obtained copolymers M ith tensiles of above 4000 and elongation of 500 and above. X-ray diffraction measurements made by the Goodyear (4) and Firestone (5)laboratories on an A l h polymer show a regular growth pattern. The Firestone laboratory has also noted that thr distribution curve is over a very narrow range that begins with a molecular weight of 1,500,000 and extends to 2,000,000 and possibly above. These results are gratifying, but are not measurements on the purest type of polymer possible. Naturally, such a novel arid unusually fast process has numerous problems. Many yeais were required to solve the problems present in the interruption of the TVurtz ieaction. The experience gained in that work is helpful, but the obstacles t o successful interruption in polymerization are possibly greater. Nevertheless real piogress is being made, ACKNOWLEDGMENT
The author is greatly indebted to a large numbcr of students who have helped materially in getting a proper background for this work as well as in making the particular experiments ‘i? ith the catalyst. Their names may Le found in the references cited. Without their splendid coopcration the work would have been impossible. He is also indebted to industrial laboratories for their interest and attention. The Fir estone laboratories have made several measurements of the physical properties. The Goodyear laboratory has cooperated extensively in making the polymer and testing its properties for tires. The government laboratory itt hkroii has been a material help. It has evaluated for processibility over 200 samples of rubber prepared in the author’s laboratory in the course of efforts to improve the catalyst or its use. Without this great help a polymer Tvhich could be milled to a smooth plastic sheet could not have been obtained. The work is supported by the Office of Rubber Reserve, Reconstruction Finance Corporation. The inteirst and help of its officials and staff are gratefully acknowledged. LITERATURE C I T E D
(1) Brady, D. L., and Badger, IT.H., J . Chem. Soc., 1932, 952. 12) Riiese, R. R., and Mcl~:lvain. S. &I., J . Am. Chem. Soc., 5 5 , 1697 (1933).
Vol. 42, No. 8
(3) D’Ianni. J. D., Saples, F. %J.,and Field, 6. E., I N D .ENG.CHWM. 42, 95 (1950).
Dunbrook, R. F., private communication. ( 5 ) Fajans, K. J., “Chemical Forces,” X e w York, hlcGraw*-Hill Book Co., 1931. (6) Farmer, E . H., Trans. Faraday Soc., 42, 228 (1946); J . Soc. (4)
(7) (8) (9) (10) (11)
Chem. Ind., 66, 86 (1947); Rubbe? Chem. and l’echnol., 20, 3ti6 (1947); 21, 27 (1948). McElvain, S. M., J . Am. Chem. SOC.,51, 3124 (1929). hforton, A. A., Chem. Ret., 35, 1 (1944); J . Am. Chem. Snc., 69, 969 (1947). Morton, A. A., and Brown, >I. L., Ibid., 69, 160 (1947). Sforton, A. 9., Brown, M. L. Holden, M. E. T., Lctsinger, R. L., and &Magat.E. E., Ibid., 67, 2224 (1945). Morton, A. A., Brown, M. L., and Magat, E. E., Ihid., 69, 181 (1947).
, Collins, I?. I\-.,and Cluff, E. F., unpublished research. (13) Aforton, .4.9., and Coombs, It. S., unpublished research. (14) Morton, A. h.,Darling, B., and Davidson, J. R., IND. EXG. CHEX.,ANAL.E D . , 14, 734 (1942). (15)
Morton, -4.A . , Davidson, ,J. H., and Hakan, R. L., J . A m . Chem.
Soc., 64, 2242 (1942). (16) Morton, -4.A., Davidson, J. H., and Kewey, H. :I.,Ihid.. 64, 2240 (1942). (17) (18) (19)
Morton, -4. A., and Fallwell, F., Jr., rbid., 60, 1429 (1938). Morton, A. A., and Grovenstein, E., unpublished research. Morton, A. A, and Hechenbleikner, I., J . Am. Clhem. Soc., 58,
(20) (21)
hforton, A. A., and Holden, 11. E. T., Ibid., 69, 1675 (1947). Morton, A. A, and Knott, D. PI.,Ira>.EXG.CHEM..ANAL ED.,
(22)
Morton, A. A., and Letsinger, K. L.,J . A m . Ciiem. Soc., 69, 172
(23) (24)
Morton, A. A., and Little, E. L., Jr., Ibid.,71, 487 (1949). Morton, A. &4., Magat, E. E., and Letsinger, R. L., Ibid., 69, 950
1697 (1936).
13, 649 (1941).
( I947).
(1947). ( 2 5 ) Morton, A. A . , Marsh, F. D., Coombs, R. S., Lyons, A. L.,
Penner, S.E., Ramsden, H. E., Baker, V. B., Little, E. L., Jr., and Letsinger, R. L., Ibid., in press. (26) Morton, 8.A, Patterson, G. H., Donovan, J. .J., and Little, E . L., Jr., Ibid., 68, 93 (1946). (27) AIorton, A. A., and Ramsden, H. E., Ibid., 70,3132 (1948). (28) Morton, .4. A., and Redman, 1,. M., IND. ENG. CHEM.,40. 1190 (1948). (29)
Morton, A. A., and Richardson, G. M., J . Am. Chem. Soc., 62,
(30)
(34)
Morton, A. A., Kelcher, R. P.. Collins, F. W., Penner, 8.E., and Coombs, R. S.,Ibid., 7 1 , 4 8 1 (1949). Morton, A. A., and Wohlers, H. C., Ibid., 69, 167 (1947). I’alnier, W. G., “Valency,” London, Cambridge University Press, 1945. Pauling, L., “Nature of the Chernical Bond,” Ithaca, X’. T., Cornel1 University Press, 1944. Roberts, D. C., and McElvain, 9. >I., J . Am. Chem. SOC.,59,
(35)
Sidgwick, N. V., and Brewer, F. XI., J . Chem.
123 (1940).
(31) (32) (33)
2007 (1937). Soc., 127, 2379
(1925). (36) Sidgwick, N. V., and Plant, S. G. P., Ibid., 127 209 (1925). (37) Taft, W. K., private communication. (38) Van .4rkel, A. E., “Molecules and Crystals,“ tr. by J. C. Ywallow, p. 46, New York, Interscience Publishers, 1949. (39) Whitmore, F. C., and Zook, H. D., J . Am. Ciiern. Soc., 64, 1783 (1942). (40) Ziegler, K., and Baehr, K., Ber., 61, 253 (1928). (41) Ziegler, K., Croessmann, F., Kleiner, H., and Schaefer, O., A v r L . . 473, 1 (1929). (42) Ziegler, K., Dersch, F., and Wollthan, Ibid., 511, 13 (1934). (43) Ziegler, K., and Jacob, L., Ibid.,511, 45 (1934). (44) Ziegler, K., Jacob, L., Wollthan, H., and Wens, A , , Ibid.,511, 6 4 (1934). REOEIVED September 30, 1949. Presented in large part before the Division of Rubber Chemistry at the 116th Meeting of the AMERICAX CHEMICAL SOCIETY,Atlantic City, N. J. A portion is from the paper presented hefore the Division of Physical and Inorganic Chemistry, Syrnposium on C~e\rrOrganometallic Compounds, at the 113th Meeting of the AMERICAN CAI. Q O C I E T P , Chicago, Ill.
