RESEARCH verse effects on the flavor, aroma, and other properties of wines. In this industry, with its long-standing traditions, n e w operating techniques are often accepted only v e r y slowly. In the past few years, ion exchange resins have b e e n improved to make them more suitable for use by the wine industry, Β Ν . Dickinson of Chemical Process told t h e ACS Division of Agri cultural and F o o d Chemistry in San Francisco. I m p r o v e d methods of ap plying these resins and a n increasing knowledge of the precautions to be taken to retain the distinctive quality of wines h a v e helped promote their use. According to several recent stu dies, taste experts frequently find that wines h e a t e d b y ion exchange taste as good as, if not better than, wines treated in t h e conventional way. • Sources of Instability. One of the biggest problems in wine making, espe cially with w h i t e wines, is that, after extended chilling, potassium bitartrate precipitates. T h e wine develops an un sightly haze. T h e conventional way to minimize this is for the wine maker to store the w i n e s for long periods in large refrigerated vats and then filter out the precipitated bitartrate. This requires large storage space, expensive cooling, and also delays production. A simpler procedure is to treat the wine with a cation exchanger such as the Chemical Process's Duolite C-3 or C-25, says Dickinson in a report coauthored with G. F. Stoneman. These resins can b e either in the hydrogen or sodium form a n d may b e used either in a continuous column or batchwise. Sodium cation exchangers of the sul fonic acid t y p e convert the bitartrate salts into t h e relatively soluble sodium form. A sodium exchanger also reduces somewhat t h e acidity of wines. A hydrogen cation exchanger, on the other hand, increases the acidity of wines. It also converts the bitartrate salts into t h e more soluble acid. Some wine treatments call for the combined use of both sodium and hydrogen cat ion exchangers. • Added Problems. Other sources of instability in wines can be partly or completely eliminated by ion exchange. Among these are heavy metals such as copper and iron, which form precipi tates with tannâtes and phosphates. Ion exchange resins or resinous absorbents can also remove proteins, tannins, and oxidized colored material that would otherwise precipitate on chilling.
CH 3 CH 3 I
H3C
CH 3 1
Fe(CO) 5 -+• m -+" H I C C I I CH 3 CH 3
CO
hι/
Fe—CO H3C CO
When iron pentacarbonyl and dimethylacetylene are exposed to sunlight, new carbon-carbon bonds are formed; iron tricarbonyl-duroquinone complex results
N e w Mechanism of Bond Formation Quînone-iron carbonyl complex gives new synthetic route a n d new explanation of some Reppe reactions EVIDENCE
FOR A NEW MECHANISM o f
carbon-carbon b o n d formation, a n e w organometallic complex, a new m e t h o d for preparing quinones and h y d r o quinones, and a simple synthesis for benzene rings labeled in the 1,4 position—these are the outcome of a n experiment involving the action of sunlight on a mixture of iron pentacarbonyl and dimethylacetylene. Heinz W. Sternberg, Raymond Markby, a n d Irving W e n d e r of t h e U. S. Bureau of Mines told the Division of Inorganic Chemistry at the ACS meeting in San Francisco that they tried the experiment in an effort t o d e termine whether t h e reaction of iron pentacarbonyl with acetylenes was analagous to that of cobalt octacarbonyl. Since this iron compound is practically insoluble in organic solvents, they formed it in situ by exposing iron pentacarbonyl to sunlight. An analysis of t h e reaction p r o d u c t showed, to their surprise, that one mole of iron pentacarbonyl reacted with t w o moles of dimethylacetylene. T h e infrared spectrum showed two types of carbonyl groups: terminal carbonyls such as those in iron pentacarbonyl and ketonic carbonyls such as those in quinones. The authors postulate t h a t two moles of dimethylacetylene join under the reaction conditions with t w o carbonyl groups to form a new ligand—
duroquinone. This then forms a complex with iron tricarbonyl. T h e y find strong support for this postulate in their finding that t h e complex, w h e n treated with hydrochloric acid, decomposes to one mole of durohvdroquinone and three moles of carbon monoxide. Furthermore, w h e n the complex is exposed to radioactive carbon monoxide for two weeks and then decomposed, all of the radioactivity is found in the evolved carbon monoxide. T h u s , they reason, only the terminal carbonyl groups can exchange, not those in the quinone ring. W h e n the iron complex is exposed to air, the iron tricarbonyl unit is oxidized, a n d duroquinone is formed in high yield. H e r e , then, is a new synthesis for substituted quinones and hydroquinones. Also, benzene rings labeled in the 1,4 position can be obtained easily in marked contrast to their laborious preparation by other methods. Just expose radioactive iron pentacarbonyl (readily obtainable) and a suitable acetylene to sunlight and acidify the reaction product. W h a t , then, is the structure of the new complex and what is the type of bonding involved? Fortunately, a theory is ready at hand to fit this particular case. T w o years ago, studies based on molecular orbital theory led Longuet-Higgins and Orgel to predict MAY
5,
1958
C&EN
43
You get these added advantages with S&S Analytical Filter Papers
• Lower Ash Content than any filter paper we have tested — less than 0.007% for quantitative grades. • Higher Alpha Cellulose Content than any filter paper we have tested—97-98% for Quantitative and qualitative grades. • No Price Premium. Your company purchasing agent pays no more for the finest. For the chemist who can specify his brand of filter papers, S & S Analytical Filter Papers offer outstanding advantages. These advantages a r e possible because of t h e skill, care and quality control methods used by S & S from selection of raws through to the finished product. Every Lot Pre-tested A substantial test portion of each batch of S & S Analytical Filter Papers is used for quality control determinations in o u r laboratories. This helps assure that you, receive filter papers uniform physically and chemically—lot after lot, month after month, year after year. Specify S&S Analytical Filter Papers for extra advantages to you in your work at no extra cost. Get the "margin of safety" in your analyses that comes with using what many chemists believe to be the finest analytical filter paper in the world. FREE
SAMPLER
Contains assortment of quantitative and qualitative grades. Also, S & S Filtration Chart, Quick Reference Catalog, table of comparative filter paper grades.
Carl Schleicher & Schuell Co. Keene, New Hampshire 44
C&EN
MAY
· 5,
Dept C-58 1958
RESEARCH
the existence of cyclobutadiene as a ligand in transition metal complexes. Sternberg points out that t h e four carbon atoms in the quinone molecule can transform in the s a m e w a y as those in cyclobutadiene and therefore the quinone molecule can form the same kind of bonds. The resulting structure can be visualized as t w o triangular pyramids base-to-base w i t h t h e iron atom at t h e center. A carbonyl group is at each apex a n d a t one of t h e three equatorial corners. The other t w o equatorial corners are occupied by the quinone ring. Quinone formation is not restricted to iron pentacarbonyl. Sternberg's group finds that a cyclopentadienyl cobalt-duroquinone complex can be formed in an entirely analagous manner. This is experimental evidence for a new method of carbon-carbon bond formation. Unsaturated molecules combine to form a conjugated system which is p a r t of a n organometallic complex. Decomposition of the complex gives the synthesized ligand as an organic compound. T h e authors suggest that this mechanism m a y be responsible for many catalytic processes including some of those of the type discovered b y Reppe.
Gamma Is Safe Foods sterilized with g a m m a r a d i a t i o n a r e nontoxic in animal tests T HE
FIRST
COMPREHENSIVE
demon-
stration t h a t gamma irradiated foods are nontoxic should hike interest in radiation sterilization to preserve foods, an Army spokesman believes. Four successive generations of rats were fed a complete diet m a d e u p of nine frozen-stored, irradiated food items, s u p p l e m e n t e d only b y nonirradiated vitamins. The results: no change in growth response, life span, or fertility. This research project's ultimate goal is to preserve food safely for long periods with a minimum of refrigeration, Merrill S. Read, chief of the Irradiated Food Branch of t h e U . S. Army Medical Nutrition Laboratory, Denver, told the American Institute of Nutrition's laboratory members at t h e Federation of American Societies for Experimental Biology's annual meeting in Philadel-
phia. Packaged foods (beef, pork, bacon, haddock, green beans, beets, peaches, powdered milk, and military cereal b a r ) with ingredients approximating a n adequate rat diet are exposed t o gamma rays from nuclear fission wastes. This kills decay-causing bacteria. Over 1600 animals took part in these tests. Half ate irradiated food; the rest ate comparably nonirradiated diets. Moreover, adds Read, t h e irradiation level was 6 million r e p , well above that necessary for sterilization. Extensive studies of six vital enzyme systems, which are believed t o be related to the metabolism of nutrients altered b y radiation, show t h a t only the cytochrome oxidase system (related to essential fatty acid metabolism) is altered. And tins system increased 10 t o 1 5 % over t h e four generations, rather than the expected decrease in activity from malfunction. This effect stems from the meat items in t h e diet, Read learned, but h e believes i t is not a deficiency. The other enzyme systems which show n o change a r e hypotonic endogenous respiration (over-all metabolism of the cell, a n d which with cytochrome oxidase is related t o essential fatty acid metabolism ) , succinic dehydrogenase (sulfhydryl system), a n d serum a n d alkaline phosphatase—both generally related t o fat metabolism in the body. Now, Read a n d his collaborators, H e r m a n Kraybill and William S. W o r t h of t h e Nutrition Laboratory and Norman F . W i t t of Colorado U n i versity, a r e studying 1 5 food items which approximate the master menu fed t o t h e Armed Forces during 1 9 5 6 and 1957. These foods will b e stored at room temperature and then cooked as normally prepared for the table before incorporation into r a t d i e t . No vitamin supplements will b e used. They will also continue studies toward understanding the observed increase in cytochrome oxidase.
"Fingerprinting" Starch A new analytical tool m a y h e l p to develop n e w starches with better properties. T w o Rutgers University (Newark) chemists, Benjamin Carroll and John W. Liskowitz, have come up with a thermogravimetric technique to probe starch mixtures quantitatively. They can determine both amylose (linear) a n d amylopectin (branched) fractions. Before, genetic researchers were hindered in their efforts to u p -
