Supplement, p. 239, Julius Springer, Berlin, 1930; Chem. Zentr. Part 1, p. 1511, R. Friedlander & Son, Berlin, 1911. (4) Braun, J. von, Ann. 472,25 (1929). . , raun, J. von, Blessing, G., Ber. 56, 2154 (1923). (7) Corson. B. B.. Heintzelman. W. J.. Schwartzman. L. H.. Tiefenthal, H. E., Lokken, R. J., Nickeis, J. E., Atwood, G. R.; Pavlik, F. J., J . Org. Chem. 23, 544 (1958). (8) Dixon, J. K., Saunders, K. W., Znd. Eng. Chem. 46, 652 (1954). (9) Dokukina, A. F., Koton, M. M., Kryukova, K. N., Mineeva, 0. K.. Paribok. V. A.. Zh. Fir. Khim. 30. 190 (19561. (10) Flood, S. A:, Nieuwland, J. A., J . A m . Chem.’Soc. 50, 2566 (1928). (11) Hoffenberg, D. S., Smolin, E. M., Matsuda, Ken, J . Chem. Eng. Data 9, l-06 (1964). (12) Klages, A., Bey. 35, 2249 (1902). (13) Klages. A.. Keil. R.. Zbid.. 36. 1633 (1903). (14j KoGppa, G., Zbid., 26, 677 (1893). (15) Kuhn, R., Dann, O., Ann. 547, 293 (1941). (16) Kunckell, F., Ber. 36, 2235 (1903). (17) Marvel, C. S., Allen, R. E., Overberger, C. G., J . A m . Chem. SOC.68, 1088 (1946). \
I
’
.
,
118) Marvel. C. S.. Hein. D. W.. Zbid.. 70. 1895 (1948). (19) Marvel; C. S:, Inskeep, G: E., Deinin, R:,Hein, D. W., Smith, P. V., Young, J. D., Znd. Eng. Chem. 40, 2371 (1948). (20) Marvel, C. S., Overberger, C. G.. Allen. R. E.. Saunders. . J. H.. J . A m . Chem. SOC.68. ?-36.11946).’ (21) M’arvel, C. S., Saundkrs, J: H.,‘ Overberger, C. G., Zbid., 68, 1085 (1946). (22) May, D. R., Saunders, K. W., Kropa, E. L., Dixon, J. K., Discussions Faradav SOC.8. 290 (1950). (23) Mowry, D. T:, Rendl, M.; Huber, W. F., J . A m . Chem. SOC. 68.1106 (19461. (24) ‘Overderge; C. G., Saunders, J. H., Org. Syn. 28, 31 (1948). (25) Rupe, H., Burgin, J., Ber. 44, 1220 (1911). (26) Schildknecht. C. E., “Vinvl and Related Polymers,” . p. - 148, ’ Wiley, New York, 1952. (27) Schmid, H., Karrer, P., Helu. Chim. Acta 28,722 (1945). (28) Walling, C., Wolfstirn, K. D., J . A m . Chem. SOC.69, 852 (1947). RECEIVED for review August 26, 1963 ACCEPTED December 18, 1963
A NOVEL SYNTHESIS OF HIGHER
ALUMINUM ALKYLS C . M . S T A R K S , D.
D. K R E H B I E L , M. T. ATWOOD, A N D G. C. F E I G H N E R
Research and Development Department, Continental Oil Co., Ponca City, Okla. Addition of diethylaluminum hydride to higher alpha-olefins gives alkyldiethylaluminum, which disproportionates to higher aluminum alkyls and triethylaluminum. Triethylaluminum i s removed b y use of a wiped(less film distillation apparatus to yield higher aluminum alkyls. The product retains ca. 15 to 25 mole than 10 weight %) ethylaluminum groups. The method i s economically superior to the diisobutylaluminum hydride method if by-product triethylaluminum values can be recovered and ethylaluminurn groups in product can be tolerated.
70
method for the synthesis of higher aluminum alkyls has been devised, beginning with the addition of diethylaluminum hydride to alpha-olefins.
A
NOVEL
RCH=CH2
+
(C2Hj)ZAlH
+
RCH2CHzAI(CzHs)z
(1)
As the product from this reaction equilibrates (4)to a mixture of dial kylethylaluminum and triethylaluminum, and thence to trialk>-laluminumand triethylaluminum,
+ +
2 RCI-12CH2Al(C2H5)2$ ( R C H ~ C H Z ) Z A ~ C ~ A1(C2H$3 HS 3 (RCHzCH2)zAlCgHj 2 Al(CHZCHzR)3 Al(CZHj)3 (2) the equilibria are forced to the right by distillation of trie thylaluminum. Experimental
Alpha-olefins and diethylaluminum hydride in equimolar amounts were mixed without solvent a t room temperature in a n atmosphere of nitrogen or argon. Careful heating of the mixture to 95’ C. over a period of 1 hour resulted in quantitative addition of the hydride to the olefin. Triethylaluminum was distilled from the addition product a t 80’ to 100’ C. (wall temperature) and 2 mm. of H g pressure by passage through a wiped-film distillation apparatus (Arthur Smith Co. 2-inch Rota-Film molecular still, Model 50-2).
Results
This procedure was employed for the synthesis of higher aluminum alkyls from a variety of alpha-olefins and a n alphaolefin mixture, and for removal of olefins from mixtures of olefins and aluminum alkyls, such as are encountered in the reaction of triethylaluminum with ethylene (4). Olefins as low as 1-hexene may be used without loss to overhead products.
Table 1.
Analysis of Higher Aluminum Alkyls Prepared from Olefins and Diethylaluminum Hydride Ratio of Moles Higher Theor. Alkyl-Al A1 in W t . yo C2Hs-Al Groups to Product, A1 in Groups, Et-A1 OleJn W t . q b a A l R 8 Mole yoc Groups 1-Dodecene 6.70 5.06 11-15 5.7-8.1 I-Decene 10.34 6.00 25 3 2-Butyl-1-octene 7.82 5.06 15 5.7 Mixture containing 35.5 mole % 1-octene 1 35.5 mole % 1-decene 8,76 6,21 15 5.7 29.0 mole 70 l-dodecene J a By titration (2). b AIRB = pure higher aluminum alkyl. By N M R and hydrolysis.
1
VOL 3
NO. 1 M A R C H 1 9 6 4
19
Because of the practical limitations inherent in the equilibria represented by Equation 2, the higher aluminum alkyls obtained by the present procedure contain small amounts of ethylaluminum groups, as shown in Table I. Aluminum alkyls prepared by the present method have been air-oxidized according to the procedure of Ziegler ( 3 ) . Hydrolysis of the resulting aluminum alkoxides gave the corresponding alcohols in excellent yields, based on starting olefin.
realized with the diisobutylaluminum hydride method. In commercial use this problem may be minimized by regeneration of diethylaluminum hydride from triethylaluminurn by the Ziegler synthesis ( 5 ) ,
4 Al(C2Hs)a
+ 2 A1 + 3 Hz
+6
Al(CzHs)?H
(6)
+ CZHB
(7)
or by hydrogenation ( 7 ) . Al(CzHs)s
+ Hz
+
(CzH6)zAlH
Conclusions Discussion The present method for the preparation of higher aluminum alkyls has the advantage of a mild temperature and short reaction time. Under these conditions alkyl dimerization (Equation 4) is prevented. (RCHzCHz)sAl*
RCHCHz-AI-H
I
I
(4)
RCHzCHz CHzCHzR This is in contrast to the diisobutylaluminum hydride method ( 6 ) ,
3 RCH=CH?
+ [(CH~)ZCHCH~]~AIH
Higher aluminum alkyls may be rapidly and conveniently prepared from higher olefins and diethylaluminum hydride, although the aluminum alkyl product is contaminated with ca. 15 to 25 mole % ethylaluminum groups. The diisobutylaluminum hydride method for the preparation of higher aluminum alkyls requires about three times as much processing time but gives a product substantially free of lower alkyl groups. The economic feasibility of the diethyIaluminum hydride method is critically dependent on the extent to which ethylaluminum groups in the product may be tolerated and the availability of facilities for the use or re-use of by-product trie thylaluminum.
+
(RCHzCH2)aAl
+ 2 (CHJzC=CHz
(5)
which we have often observed to give ca. 5 to 10 mole % of alkyl dimer. Two primary disadvantages are inherent in the present method. The retention of ethylaluminum groups in the product precludes the preparation of pure higher aluminum alkyls. Secondly, the present method uses directly only one third of the available organoaluminum groups, while the other two thirds are recovered as triethylaluminum. In contrast, almost complete utilization of all organoaluminum groups is
literature Cited (1) Podall, H. E., Petree, H. E., Zietz, J. R., J. Org. Chem. 24, 1222 (1959). ( 2 ) Wanninen, E., Ringbom, A., Anal. Chim. Acta 12, 308 (1955). (3) Ziegler, K., Experientia, Suppl. 2, 14‘ Congr. intern. chim. pure appl., Zurich, 274 (1955). (4) Ziegler, K., “Organometallic Chemistry,” H. Zeiss, ed., pp. 194-269, Reinhold, New York, 1960. (5) Ziegler, K., Gellert, H.-G., Lehmkuhl, H., Pfohl, W., Zosel, K., Ann. 629, 1 (1960). (6) Ziegler, K., Martin, H., Krupp, F., Ibid., p. 14. RECEIVED for review September 20, 1963 ACCEPTED December 23, 1963
RECYCLING PROCESS FOR THE COMMERCIAL PREPARATION OF 1=METHY LPYRI D I N I U M= 2-ALDOXIME CHLORIDE R 0 B E R T I . E L L I N , Physiological Chemistry Branch, Physiology Division, Edgewood Arsenal, M d . A process has been developed for the preparation of 1 -methylpyridinium-2-aldoxime chloride (2-PAM-CI) b y simply heating the corresponding iodide salt (2-PAM-I) with methanolic hydrogen chloride. The yields are high, and the resulting product is white and does not require recrystallization. Methyl iodide, recovered as a by-product in 80y0 yields, may be made to react with pyridine-2-aldoxime to prepare additional starting product for the reaction. OmmATIoNs
of 1-methylpyridinium-2-aldoxime chloride
C (2-PAM-C1) and atropine have proved to
be effective as antidotes when administered to animals and humans exposed to organophosphorus cholinesterase inhibitors. If the oxime is to be stockpiled for service or civilian use, a process for its large scale manufacture is required. Three procedures are known for the preparation of 2PAM-Cl : (A) 1-methylpyridinium-2-aldoximeiodide (220
I & E C PRODUCT RESEARCH A N D DEVELOPMENT
PAM-I) is made to react with a suspension of silver chloride in water ( 6 ) ; (B) 2-PAM-I may be passed over a chloride exchange resin (6) ; (C) pyridine-2-aldoxime (P-2-A) is made to react with methyl chloride in dimethylformamide (DMF) in a closed reaction vessel ( 3 ) . The cost of the silver chloride makes Procedure A expensive. Furthermore, the resulting white 2 - P A M 4 1 crystals turn gray on storage, probably because of traces of silver ion. Because
