Linear dimerization Difficult any other way
truly remarkable/' in Dr. Smutny's opinion, "because some change in structure, be it branching or cyclization, usually accompanies oligomerization of conjugated dienes by other routes." He points to these other unusual as pects of the reaction: • It's simple, fast, and takes place equally well in the presence or ab sence of solvents. • Changes in temperature or pres sure don't affect it. • Yields are high and essentially free of by-products. • Complexes of other Group VIII metals catalyze the reaction equally well. The catalysts aren't afiFected by oxygen, water, and other common "poisons." • Nucleophiles such as alcohols, amines, and organic acids also enter into the reaction with butadiene. Like phenols, these add to the terminal car bon atom of the dimer. In a typical experiment, Dr. Smutny and his collaborators, Harold Chung, Dr. Kenneth C. Dewhirst, Dr. Willi Keim, and Dr. Thomas M. Shryne, mix phenol (1.0 mole) and butadiene (4.0 moles) together at 0° C. for several hours in the presence of 7r-allyl pal ladium chloride and sodium phenoxide. A 96% conversion of phenol to phenoxyoctadiene takes place in the process. The reaction product consists of 95% l-phenoxy-2,7-octadiene and 5% 3-phenoxy-2,7-octadiene. Vacuum distillation of this mixture in the pres ence of triphenylphosphine yields high-purity 1,3,7-octatriene and phe nol. The Shell Development team believes that the role of triphenylphos phine is to stabilize and prolong the catalyst life. If triphenylphosphine isn't added, palladium metal sepa rates out and catalytic decomposition 22 C&EN DEC. 11, 1967
to octatriene stops, Dr. Smutny notes. In practically all cases, the reaction stops at the dimer stage. Conversion to dimer can be carried out continu ously by recycling the phenol and re acting it with additional fresh diene monomer. The findings of Dr. S. Takahashi, Dr. T. Shibano, and Dr. N. Hagihara of Osaka University substantiate Shell Development's discovery. Using a soluble palladium catalyst system, the Japanese workers have dimerized bu tadiene to 1,3,7-octatriene [Tetrahed ron Letters, 2451 (1967)]. What probably happens is that the diene first dimerizes around the cat alyst, Dr. Smutny conjectures. The nucleophile then interacts with the re sulting complex in the presence of excess diene. The result, in effect, is an anti-Markovnikov addition of nu cleophile to the linear dimer, he points out.
Other investigators have prepared solutions that probably contain various sulfenium ions but under conditions that are not amenable to organic syn theses, Dr. Helmkamp points out. He and his students—Dennis Owsley, Wayne Barnes, and Howard Cassey— were interested in using the reactive ions in organic reactions. One obvious application, for example, would be to react them with olefins as an alter nate route to the alkylated episulfides. Sulfenium ions, Dr. Helmkamp ex plains, have long been postulated in polar additions of sulfenyl halides to olefins and acetylenes, and in disulfide exchanges in acid solutions and in bio logical systems. In the system devised by the UC group, methanesulfenyl bromide, RSBr, was reacted with silver 2,4,6-trinitrobenzenesulfonate (TNBS) in a mixture of nitromethane and dichloromethane. In some runs, acetonitrile was also present. When acetonitrile was present, the resulting solution was conductive. Without it, the solution was a weak conductor. In either case, whatever species was present was able to transfer its sulfenium portion in a reaction with an olefin. The conductivity data, along with Ν MR spectra, lead Dr. Helmkamp to theorize that the methanesulfenyl ion reacts with acetonitrile to form an other ion, RS-N=C-CH 3 , and it is this ion that reacts in subsequent re actions rather than free sulfenyl ions. Without acetonitrile, he believes, the sulfenyl ions react with the trinitrobenzenesulfonate ions to give the nonconducting species RS-OS0 2 -trinitrophenyl. When acetonitrile is added to this, the conductivity of the solution goes up, indicating that the ionic com pound is being formed. Thus, Dr. Helmkamp has tentatively concluded that he is not dealing with free sulfen-
Organic solutions may yield ions that behave like sulfenium ions It is possible in organic solutions to get reactive ions that behave like sulfen ium ions, RS+, but they are probably not free sulfenium ions, according to Dr. George K. Helmkamp of the Uni versity of California, Riverside. Speak ing at the Symposium on Sulfenyl Chemistry, sponsored by the IntraScience Research Foundation in Santa Monica, Calif., Dr. Helmkamp said evidence indicates that the reactive RS+ is very likely bonded to another compound that can be displaced easily by nucleophilic reactants. He also described an interesting outgrowth of his research in this area—an organic reaction that appears to fix molecular nitrogen.
Dr. Helmkamp (left) and Owsley Transfer agents
ium ions, but with sulfenium ion transfer agents. It was in recent work on the preparation of benzenesulfenium ion that Dr. Helmkamp's group discovered the ion's ability to react with molecular nitrogen. Although transition metal complexes are known to fix nitrogen, C e H 5 S+ appears to be the first reported organic species to do so. Dr. Helmkamp does not yet know the structure of the reaction product with nitrogen, however, and describes it only as [C 6 H 5 -SN 2 ]+. Infrared data indicate that the nitrogen is probably in a linear array, as in a diazonium salt, and that is probably attached to sulfur rather than to the benzene ring. The compound couples with anything a diazonium salt couples with, but Dr. Helmkamp has not been able to purify any of the products enough to do structure studies because they are unstable. The reaction product with azulene explodes on warming to produce nitrogen. He is still looking for a stable, solid product to characterize. In an extension of the work, he plans to react the benzenesulfenium ion with carbon monoxide, which has an electronic structure like nitrogen's.
Electrode system may be able to operate heart pacemaker While much attention centered on the first human heart transplant in Cape Town, South Africa, last week, another development in heart research appeared. By inserting inert electrodes in a dog's heart and blood stream, University of Maryland scientists have produced electric power—more than enough to operate a human heart pacemaker. If the electrode system can be developed for use in humans, it could supplant the battery systems currently powering the pacemakers. Moreover, it could eliminate the periodic surgery needed to replace these batteries, according to Dr. R. Adam Cowley and Dr. Mostafa E. Talaat. The electrode system would eliminate periodic surgery by providing a more permanent and reliable power supply for the pacemakers, devices implanted in certain heart patients to control heart rate. The batteries used now "are just not adequate," Dr. Cowley says. The surgeon at the university's school of medicine in Baltimore, Md., adds that the batteries "are supposed to be good for five years, but most don't last two years and are unreliable before then." To find another energy source, the Maryland scientists tried inserting in-
Dow vetoes Distillers' plan to unload its share of Distrene
Dr. Cowley, Dr. Talaat, and electrode Possibly like a fuel cell
ert, platinum-black electrodes into the blood stream and heart of rabbits, and later dogs. Varying electrode geometries were tried with one electrode placed inside and the other electrode placed on the outer wall of the left atrium, the right atrium, or the right ventricle of the heart. The output ranged from 0.1 to 0.65 volt depending upon where the electrode was placed on the outer wall. In each case, a sustained power level of 49 to 114 microwatts resulted. This power level is two to four times that needed to power a pacemaker [IEEE Trans. Biomed. Eng., 14, 263 (1967)]. The Maryland research is in an early stage and precisely how the electrode system works is still unknown. It is definitely not a galvanic process, Dr. Talaat says, because the electrodes are nonreactive. One possible mechanism is that the electrode system acts like a fuel cell and the body, perhaps the blood, supplies the fuel and oxidant. Another is that a concentration gradient between the electrodes produces the power. One of the next steps in the research effort at College Park, Md., will be to quantitatively determine what produces the electric power. Then, before the inert electrode system can be tested in humans, the Maryland scientists must determine the best electrode type and geometry as well as the long-term reliability of the power output. Thus far, the longest implant was for about half an hour and was not sutured. When a final choice of electrode configuration is made, Dr. Cowley will attempt longer implants. Besides studying the reliability of long-term implants, there are several other medical problems to be solved. A simple and fast surgical method of implanting electrodes in the heart must be found, Dr. Cowley says. And clots may form during long-term use.
Distillers Co., Ltd., has run into difficulties again in its plans for selling its chemical interests to British Petroleum. Dow Chemical International, A.G., has turned thumbs down on the transfer to BP of Distillers* share of Distrene, Ltd., a polystyrene maker in which each has half interest. Last summer Union Carbide balked at the transfer of Distillers' half of Bakélite Xylonite, one of Europe's largest integrated plastics groups, to BP (C&EN, July 17, page 2 6 ) . The reason for its veto, Dow says, is that "basically there was no real interest on the part of Dow or on the part of BP in the proposed transfer of ownership." As for Distillers, Dow's blocking of the transfer knocks about $5.8 million off the value of Distillers' deal with BP. The original package price was $240 million in cash and BP stock. Adding the $5.8 million to the sum lost through Carbide's refusal, the total cut is more than $27 million. Distrene, one of the U.K.'s largest producers of polystyrene, was formed in 1954 to take advantage of Dow's technical know-how and Distillers' knowledge of the U.K. market. It has a plant at Barry in South Wales with a polystyrene capacity of 26,000 long tons per year. This is to be increased to 40,000 long tons next year. Had the transfer of Distillers' half of Distrene to BP gone through, BP would have become a formidable factor in the U.K. polystyrene picture. Current capacity of BP Plastics, Ltd., is 7000 long tons of polystyrene. The U.K.'s biggest polystyrene producers now are Shell Chemicals (U.K.), Ltd. and Monsanto Chemicals, Ltd., each with a capacity of 35,000 long tons annually. Next is Distrene, followed by Bakélite Xylonite, Sterling Moulding Materials, BP Plastics, and Kaylis Chemicals. Total polystyrene capacity (rigid and expandable) at present is about 137,000 long tons. U.K. production of polystyrene (excluding expandable) in 1966 was about 106,000 long tons. Expansions now in the works will boost capacity to 166,000 long tons. For the time being at least, Distrene will continue as a 50-50 venture of Distillers and Dow, which has made an informal offer for Distillers' share. But so far the offer has been neither accepted nor rejected. Distillers' partner headaches are not over. Still to be obtained is agreement by its partners to the sale of Distillers' interests in Herdillia Chemical in India, Distugil, S.A., in France, and Hedon Monomers in the U.K. DEC.
11, 1967 C&EN
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