of photon absorption ability) as the temperature increases from 234 to 442° K." What this means, he says, is that "fluorocarbons probably have a longer lifetime before breaking down at the temperatures found in the stratosphere than has previously been believed." Ausloos urges other researchers to take temperature into account when measuring absorption cross sections in fluorocarbon experiments. D
chamber at the hyperbaric research laboratory at Texas A&M. Physiologist William P. Fife of Texas A&M and biologist F. Ray Wilson of Baylor had now become involved. Fife had been conducting research with high-pressure breathing mixtures for undersea work for several years. The atmosphere in the test chamber was a mixture of 2.5% oxygen and 97.5% hydrogen at a total pressure of 8.3 atm, an ideal combination, according to the researchers. For one thing, the oxygen percentage in the mixture is outside the explosion limit for oxygen/hydrogen mixtures, eliminating the danger of an explosion. (Hydrogen/oxygen mixtures containing less than 5.3% oxygen will not burn, even with spark ignition.) For another, the partial pressure of oxygen at the pressure in the test chamber is equal to that of As an unexpected result of a theoreti- oxygen in a normal atmosphere, allowcal study in physical chemistry, re- ing the test animals, or humans for searchers in Texas believe they may that matter, to breathe normally— have found a new treatment for cancer. something equally desirable when one The treatment is not foolproof, how- is seeking to cure a patient. In adever, and the scientists are cautious dition, the high hydrogen pressure enabout making predictions about its fu- sures a high concentration of dissolved hydrogen in the test animal, increasing ture. What researchers from Baylor Uni- the chances of obtaining the desired versity, Waco, Tex., and Texas A&M catalytic effect. A soda-lime scrubber University, College Station, have done is also was included in the chamber to to place mice with squamous cell carci- pick up metabolically produced carbon nomas, a form of skin cancer, into a dioxide. The chamber temperature was high-pressure (hyperbaric) hydrogen held at 32° C, to prevent chilling efatmosphere for periods of up to two fects. weeks. After their stay under high Two other groups of mice with squapressure, the mice showed a pro- mous cell carcinomas were used as nounced regression of skin tumors. The controls in the experiments. One group research that led to this experiment, was kept in cages in the laboratory. A oddly enough, grew out of a study of the second group was maintained in a 97% kinetics of the free radical decay in helium/3% oxygen mixture at 8.3 atm irradiated polyethylene. for nine days to see if the effects obFree radicals have been theorized to served were really the result of the hybe part of some cancerous growth pro- drogen and not just high pressure. cesses. Supporters of the controversial After 10 days in hyperbaric hydrofree radical theory of cancer include gen, the test mice showed definite Nobel Laureate Albert Szent-Gyôrgyi. signs of improvement. The tumors had There is, however, little agreement turned black, some had dropped off, among scientists about the validity of some seemed to have shrunk at their this concept of carcinogenesis (C&EN, base and were in the process of being July 28, page 16). pinched off. Moreover, the mice otherMeanwhile, free radicals were being wise were unaffected by the treatment. studied by chemist Malcolm Dole at Maintaining the same mice in the hyBaylor, although not in living tissue perbaric hydrogen for an additional six but in polyethylene. Dole and his co- days produced a continued remission of workers had previously discovered that the skin tumors. Repetition of the exmolecular hydrogen has a pronounced periment with another group of mice catalytic effect on the decay of alkyl with squamous cell carcinomas for 10 radicals, —CH 2 CHCH 2 —, in solid days produced similar results. Meanpolyethylene at room temperature. while, mice in the two control groups They found, for example, that a hydro- continued to show all the symptoms of gen pressure of 400 torr increased the their skin tumors. first-order decay constant of the alkyl The Texas researchers propose one radical by about a factor of 10. Still theory that exposing the mice to a hygreater catalytic effects were achieved perbaric reducing atmosphere retards using single-crystal-thick mats of poly- metabolism and respiration of cancer ethylene and 600-torr hydrogen pres- cells. This allows the host's previously sure, because of the greater solubility of overloaded immuno system to better hydrogen in single-crystalline polyethyl- deal with the cancer cells. The rate-deene. termining step for regression of cancerThis work suggested the animal ex- ous growth, they believe, may be the periments. Hairless albino mice with host's natural ability to cope with the ultraviolet light-induced squamous cell cancer cells. There was some evidence carcinomas were selected for a test of this in their experiment. It took
Pressurized hydrogen may retard cancer
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longer to produce a complete regression in mice with a greater number of the tumors than it did in mice with fewer tumors. In an attempt to repeat the experiment with a different type of tumor, Texas A&M's Dr. Fife used a group of mice with Erlich's ascites carcinoma, an internal cancer. Although the results were somewhat equivocal (one of the three mice in the test chamber drowned in its water bowl) and the hydrogen therapy did not prevent the other mice from dying, it appeared to prolong their lives by about 30%. Other questions remain unanswered. For example, are the effects observed in the mouse experiments a function of the length of time spent in the test chamber, or would an intermittent exposure to hyperbaric hydrogen do as well? Are the effects permanent? Does it work for all types of tumors? And the big question: Will it work for humans? No one knows yet, but Baylor's Wilson has applied to the National Institutes of Health for funds to continue the research, and Fife is conducting additional research. D
Organic heteropoly anion derivatives
HCAGO New complexes that are stable organic derivatives of heteropoly anions have been isolated and characterized by a team of Georgetown University chemists headed by Dr. Michael T. Pope and Dr. Carl O. Quicksall. Graduate student Manja Rajkovic told the Division of Inorganic Chemistry that the new complexes, which are homologs of [(RP) 2 Mo 5 0 2 i] 4 and [R2AsMo 4 Oi4(OH)] 2 _ , offer the possibility of preparing unique materials with the properties of both metal oxides and organic functionalities. The new complexes are not considered to be organometallic compounds in the traditional sense, because they do not contain metal-carbon bonds. Heteropoly anions are clusters of metal and oxygen atoms that generally carry charges of - 3 to - 1 2 , and typically consist of six to 18 metal atoms and 40 to 60 oxygen atoms. Often, they are considered to be fragments of close-packed metal oxide lattices, and indeed, show many of the magnetic and other properties of such lattices. When appropriately combined with positively charged metal ions such as sodium, they are soluble in both water and organic solvents. Similarly, the new organic derivatives of heteropoly anions are soluble in both aqueous and nonaqueous solutions and are stable at pH 2.5 to 5. The tetramolybdo complexes of the dialkyl-
and diaryl arsinates are prepared by stoichiometrically reacting sodium molybdate and methyl, ethyl, or phenyl arsinic acid at pH 4 to 5. Ten crystal line salts containing sodium, potassi um, guanidinium, tetramethy-, or tetrabutylammonium counter ions have been obtained and characterized. The Georgetown team finds two interesting features in these arsinic complexes: an essentially nonacidic oxide proton lo calized on the oxygen atom bridging the four molybdenums, and a surpris ingly low charge ( - 2 ) for a polyanion that remains stable in aqueous solution of pH 2 to 6. The pentamolybdobisphosphonates are prepared by reacting alkyl and aryl phosphonates, R P 0 3 2 ^ (R = H, CH 3 , C 2 H 5 , C 6 H 5 , C2H4NH3+, and p-CH 2 CeH4NH3 + ), with sodium molybdate at pH 4 to 5. Infrared and crystallographic data indicate that their structures are related to that of the P2M05O236" anion, which also shows a 2:5 phosphorus-molybdenum ratio, the chemists observe. The structure is such that the complex cannot undergo facile reduction. However, the Georgetown group believes that by carefully con trolling the acidity of the reaction me dium, and the ratio of reactants, it may be possible to form structural units that allow the polyanions to be reduced and thus serve as electron ex change materials in addition to redox catalysts. According to Pope, the amino deriv atives are the first examples of zwitterionic heteropoly complexes. It is possi ble, he says, to link such zwitterionic molecules together to form organic polymers with metal oxide domains. Such polymers open the possibility for obtaining thermoplastic materials with unique magnetic, semiconductor, or catalytic properties, the Georgetown chemist suggests. Furthermore, Pope adds, if organic derivatives of heteropoly anions can be made that offer an enzyme-substrate type of specificity for certain proteins, it may be possible to utilize the high molecular weight and charge of the an ions to achieve enhanced separations of proteins by electrophoresis and ultracentrifugation. D
New route found to selenium compounds
0H1C/AGQ Organoselenium compounds are useful intermediates in preparing olefins and allyl alcohols. However, their use has been limited, since their α-lithio deriva tives—necessary for reaction with alkyl halides and carbonyl compounds—are difficult to prepare. The attack of organolithium reagents appears to occur
predominantly at the selenium rather than the hydrogen atom. One approach to overcoming this problem has been to prepare α-lithio selenium compounds by reacting butyllithium with selenoacetals and ketals. Now, Dr. Hans J. Reich of the Uni versity of Wisconsin, Madison, has de veloped an alternative method for acidification of a -hydrogens by selenoxide formation. Lithium amide bases, such as lithium diisopropylamide, can then be used without attack on the se lenium, Reich told the Division of Or ganic Chemistry. The facile syn-elimination of selenoxides at or below room temperature necessitates performing the oxidation in situ, Reich notes. Ozone at -78° C and m-chloroperbenzoic acid at -10° C are useful oxidants, he says. Subsequent deprotonation with lithium diisopropyl amide, "occurs cleanly and rapidly at - 7 8 ° C in tetrahydrofuran." The α-lithio selenium compounds thus formed can be reacted with a variety of electrophiles to form products that un dergo elimination upon warming to room temperature. For example, sub stitution on an allyl halide ultimately yields a diene, while reaction with a carbonyl compound is equivalent to re action with a vinyl anion and gives an allyl alcohol. Moreover, Reich observes, the selenoxides can be reduced under mildly acidic conditions at 0° C with sodium iodide to form ^-hydroxy selenides. In an overall transformation equivalent to a Wittig reaction, these hydroxy sele nides can be reacted with sulfene to form olefins. According to Reich, such a reaction is particularly useful for syn thesizing tetrasubstituted olefins, where the Wittig reaction usually fails. Although sulfur analogs are probably less expensive and less toxic than their selenium counterparts, in some cases the selenium reactions have several ad vantages over the corresponding sulfur chemistry, says the Wisconsin chemist. The lithium reagents required for pre paring hydroxy selenides are more gen erally available than related sulfurlithium reagents, and the elimination of β -hydroxy selenides proceeds under milder conditions than those reactions involving β -hydroxy sulfides. Similarly, the allyl alcohol synthesis via a sulfur intermediate would require rather "brutal" conditions, since the sulfoxide syn-elimination occurs at temperatures about 100° C higher than those for the selenoxide reaction, Reich says. Also, the reduction of sulfoxides to sulfides requires more vigorous con ditions than the conversion of selenoxides to selenides. The oxidation of sulfides, however, occurs easily, and their overoxidation to sulfones is another problem with organosulfur compounds. On the other hand, selenoxides convert to selenones slowly, Reich says, so that with organo selenium compounds, inexpensive and convenient oxidants can be used. D
Physiological Effects of Food Carbohydrates ACS Symposium Series No. 15 Aliène Jeanes & John Hodge, Editors A symposium co-sponsored by the Division of Carbohydrate Chemistry and the Division of Agricultural and Food Chemistry of the American Chemical Society. As a scientist or as a general consumer concerned with the dangers of convenience foods, and unrefined sugars and starches, this volume will be an important addition to your company or personal library. Twenty-two papers bring you upto-date on the latest investigations into the underlying causes of carbohydrate-induced diseases such as diabetes, hypoglycemia, and heart disease. Other topics focus on: • intestinal absorption of sugars; dietary fructose as a substitute for glucose; dental caries • lactose intolerance; metabolism of glycogen, maltose, lactose, polyols, pentoses, and uronic acids • alginates and xanthan gum; carrageenan; pectin; dietary fiber; digestibility of food polysaccharides 355 pages (May 1975) $14.50 clothbound (ISBN 0-8412-0246-X). Postpaid in U.S. and Canada, plus 40 cents elsewhere. Order from: Special Issues Sales American Chemical Society 1155 Sixteenth St., N.W. Washington, D.C. 20036 Sept. 1, 1975 C&EN
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