CARBOHYDRATE CHEMISTRY both esters or anhydrides are p r e s e n t in mixture. Intensity of color is affected by presence of high concentrations of carbonyls, transition elements, and ions which complex ferric ion. G o d d u said t h a t optimum c o n c e n t r a tion range of technique is 1 0 - 3 t o 10- 2 M. N o n a q u e o u s Titrations. Conductometric titration of sulfuric a n d h y d r o chloric acids a n d their mixtures in a n hydrous acetic acid with alkali acetates show a differentiation in the neutralization end points of the two h y d r o g e n s of sulfuric acid. Takeru Higuchi and Carl R. R e h m also find in work at University of W i s consin t h a t mixtures of sulfuric a n d hydrochloric acid show t h r e e b r e a k s w h e n titrated with lithium a c e t a t e . These occur w h e n the first h y d r o g e n of sulfuric acid is neutralized, w h e n the hydrochloric acid is neutralized, and finally w h e n the second sulfuric hydrogen is neutralized. T h e t h r e e breaks serve as means to estimate q u a n titatively sulfuric and hydrochloric acid in t h e mixture. Bismuth can b e accurately titrated in the presence of other ions i n c l u d i n g large amounts of lead b y use of e t h y l enediaminetetraacetic acid, a c c o r d i n g to James S. Fritz, Iowa State College. In this reaction, disodium ethylenediaminetetraacetate forms a stable soluble complex. Excess thiourea is added, forming a weak complex w i t h bismuth, avoiding any precipitation before or during the procedure. T h e endpoint of titration is m a r k e d by disappearance of last yellow color from complex. This m e t h o d has advantage of avoiding numerous interferences w h i c h d e velop in titrimetric determination of bismuth b y commonly used tests. Tracer S t u d i e s . Of possible application in atomic research is the carrierfree yttrium-90 prepared b y M. L . Salutsky and H . W . Kirby of M o n santo. C o m p o u n d is separated from its parent b y precipitation of strontium 90 with strontium nitrate carrier i n 8 0 % nitric acid. Yttrium-90 has proved its value as a suitable yttrium tracer for fractionation and coprecipitation studies as it has a convenient half life, has no r a d i o active d a u g h t e r , and is a pure b e t a emitter. However, Salutsky said t h a t there has been lack of agreement in reported values for half-life v a l u e . Beta counting at Monsanto shows halflife to b e 64.0 hours.
• Polychromatic X-Ray Studies Although x-ray absorption has b e e n used increasingly for nondestructive testing, it has not been applied t o u s ual type of chemical analyses as widely VOLUME
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as it could be. Information regarding x-ray absorption coefficients for materials in solution is not generally available as the coefficients cannot b e calc u l a t e d accurately. Maurice C. Lambert, Hanford Atomic Product Operation, is investigating absorption of polychromatic xrays b y aqueous solutions of 3 5 comp o u n d s and ions of 2 5 elements widely distributed in t h e periodic chart. K e uses voltages ranging from 25 to 75 p e a k kilovolts. G E scientists are studying absorption as function of several v a r i a b l e s atomic number, concentration, and voltage on x-ray t u b e , which is a measu r e of wave length of x-radiation. Lamb e r t says that for elements between 1 a n d 4 1 a n d over 66, coefficients increase in same order as their atomic n u m b e r s . But for elements 42 to 6 5 , whose K-absorption edges are in range of "effective" w a v e lengths of polychromatic x-rays employed, behavior is anomalous. Lambert has also developed further
applications of the method. A routine precision of 0 . 1 % is possible in some applications of x-ray photometry to rapid analysis of solutions containing both single and mixed solutes. He states t h a t techniques can be used for determination of heavy metals, halogens, hydrocarbons, a n d ash content of coal and tetraethyllead in gasoline. Lithium can b e simply and rapidly separated from other alkali metal ions with dipivaloylmethane, ( C H 3 ) 3 C C O — C H 2 - C O - C ( C H 3 ) , or D P M , according to G. A. Guter and G. S. Hammond, Iowa State College. Earlier use of organic chelating agents have not permitted separation of lithium from other metals except b y tedious procedures which involve stepwise removal of other ions. Separation is possible with D P M as result of formation of a Hthium chelate which is soluble in organic solvents. It is possible to extract lithium efficiently from alkaline aqueous solutions with solutions of 0.1N D P M in diethyl ether.
D I V I S I O N OF CARBOHYDRATE CHEMISTRY
Plotting the Carboxylotion Cycle • C a r b o n d i o x i d e enters photosynthetic cycle by c a r b o x y l a t i o n of five-carbon sugar, not t w o - c a r b o n acceptor • C a r b o h y d r a t e s m a y b e c o m e basic m a t e r i a l f o r synthetic detergents a n d other i n d u s t r i a l products • Research on chemistry of n o n s u g a r constituents of c o m m e r c i a l sugar liquors v i t a l t o s u g a r refiners TN
PHOTOSYNTHESIS
of
sugars
and
-*• carbohydrates t h e r e are very few intermediates b e t w e e n carbon dioxide a n d sugar. Of ideas current o n this subject thirty years ago, this is about t h e only fact still remaining, Melvin Calvin, University of California told t h e Division of Carbohydrate Chemistry. Briefly, tracer methodology, which h a s contributed so much to advancing knowledge of photosynthesis, consists of exposing photosynthesizing plants to carbon dioxide labelled with radioactive carbon-14, and after a short time analyzing products formed b y paper strip chromatography a n d radioautography. Several years ago tracer studies led to t h e conclusion t h a t carbon is incorp o r a t e d into carbohydrate molecules b y a carboxylation reaction leading to t h e three-carbon c o m p o u n d , phosphoglyceric acid w h i c h is then converted b y a series of reactions to six-carbon fructose and glucose phosphates. A
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long search for t h e two-carbon compound supposed to b e the acceptor of carbon dioxide, however, was fruitless. Finally, it was discovered t h a t the seven-carbon carbohydrate, sedoheptulose monophosphate, and the fivecarbon ribulose diphosphate appeared, labelled with radioactive carbon, a short time after exposure. T h e early appearance of five- and seven-carbon sugars led to an idea that perhaps there is no two-carbon compound acting as an acceptor b u t that the two carbons might b e in some way connected with the fact that the difference in n u m b e r of carbon atoms per molecule in sedoheptulose and ribulose is two, a n d also t h a t there is a like difference in n u m b e r between ribulose a n d several three-carbon compounds assigned to the photosynthetic cycle. I n d e e d , this seems to b e the case. N o w t h e cycle Calvin proposes for carbon reduction involves carboxylation of ribulose to two molecules of three3833
126th NATIONAL ACS MEETING carbon c o m p o u n d s . M o s t of the evid e n c e points to phosphoglyeerie acid. In the c y c l e , b o t h s e d o h e p t u l o s e and ribulose diphosphates are formed from triose and h e x o s e p h o s p h a t e s . H e x o s e in turn is s y n t h e s i z e d b y r e d u c i n g 3p h o s p h o g l y eerie acid. Free energy calculations in t h e ribulose earboxylation reaction indicate that it w o u l d p r o c e e d spontaneously if e n z y m a t i c a l l y catalyzed. L a b o r a t o r y S y n t h e s i s . D i s c o v e r y of the importance of the seven-carbon h e p t u l o s e series in photosynthetic and other b i o c h e m i c a l processes has s t i m u lated considerable work on synthesizing m e m b e r s of the series. Of 1 6 possible isomers, only t w o are f o u n d in nature, T>-altro- and D-manno-heptulose. There are n o w only four gaps l e f t in the series and these are so p l a c e d that there is at least one m e m b e r of e a c h possible enantiomorphic pair available, according to J. W . Pratt, N a t i o n a l Institutes of H e a l t h . R e c e n t l y h e and N . K. Richtmyer d e v e l o p e d n e w syntheses for D - a n d L-aZZo-heptulose, as well as D-toZo-heptulose, b y organic chemical methods. A different approach to laboratory sugar synthesis uses e n z y m e s e x t r a c t e d from living material. E n z y m a t i c t e c h n i q u e s are valuable for preparing c o m p o u n d s as w e l l as for s t u d y i n g t h e e n z y m e s t h e m s e l v e s . For e x a m p l e , i t has l o n g b e e n k n o w n that aldolase splits D-fructose l : 6 - d i p h o s p h a t e into d i h y droxyacetone p h o s p h a t e and D-glycera l d e h y d e - 3 - p h o s p h a t e and that this reaction c a n b e reversed to prepare r>fructose. It h a s recently b e e n discovered, says J. K. N . Jones, U n i v e r s i t y of Bristol, E n g l a n d , that a l d o l a s e c a n also synthesize c o m p o u n d s other than D-fructose. B y substituting different
a l d e h y d e s for D-glyceraldehyde p h o s phate, reactions c a n b e carried o u t to p r o d u c e both old a n d n e w sugars. O n e of t h e n e w ones is s e d o h e p t u lose, another, D-xyulose. T h e latter is not a natural c o m p o u n d but is c o n verted enzymatically to D-xylose, a c o m m o n natural sugar. All sugars prod u c e d from e n z y m a t i c c o n d e n s a t i o n of a l d e h y d e s and d i h y d r o x y a c e t o n e p h o s p h a t e can b e considered as derivatives of D-xyulose. A m i n o - s u g a r s . Investigation of the structure of the n e w e r antibiotics s u c h as puromycin, picromycin, erythromycin, a n d carbomycin h a v e turned u p a number of interesting amino-sugars. N o o n e knows just w h a t t h e function of carbohydrate c o m p o n e n t s of antibiotics is, says Peter P. R e g n a , Pfizer, b u t in s o m e cases at least t h e y m u s t b e tied in w i t h antibiotic activity. Erythrom y c i n and picromycin, a n e w antibiotic discovered in E u r o p e , appear t o b e different, but they h a v e a c o m m o n c o n stituent, a d i m e t h y l a m i n o sugar, w h i l e M a g n a m y c i n contains a c l o s e l y related amino-hexose. M a g n a m y c i n h a s b e e n found to contain t h e first k n o w n 3amino sugar, 3-amino-D-ribose. Configuration of carbohydrate c o m p o n e n t s m a y b e critical as far as antibiotic activity is c o n c e r n e d . T h e r> threo isomer of c h l o r a m p h e n i c o l is quite active against Escherichia coli during its early g r o w t h stages w h i l e L - and D-erthyro a n d \,~threo isomers h a v e almost no such activity. T h e 3-amino-3-deoxy-D-ribose m o i e t y of puromycin h a s b e e n s y n t h e s i z e d b y B. R. Baker a n d his c o l l e a g u e s at L e d e r l e Laboratories. T h e c o m p o u n d , prepared b y starting from L-arabinose, is identical w i t h that isolated from puromycin.
Henry B. Hass, Sugar Research Foundation ( l e f t ) , and Sidney M. Cantor discuss carbohydrate raw materials. Hass believes sugar could form basic raw material for a whole series of chemicals
3834
M . L. Wolfrom, Ohio State, says that he has b e e n astonished at the strange sugars b e i n g found, b u t h e b e l i e v e s that unusual sugars are distributed m o r e w i d e l y in nature than is realized. T h e r e is a n e e d to isolate and study more of t h e m . T h e y can p r o b a b l y b e f o u n d e l s e w h e r e than in antibiotics.
• Carbohydrates Raw Materials Carbohydrates are important not o n l y as food but as raw materials for c h e m i cals and other industrial p r o d u c t s . Sucrose, as Henry B . H a s s , Sugar R e search Foundation, pointed out at t h e s y m p o s i u m o n sources of carbohydrate raw materials, is the pure organic chemical produced in greatest q u a n t i t y in t h e world. He s e e s n o reason w h y sucrose should not be the subject of a large long-range research effort s o that it m i g h t some d a y b e c o m e t h e starting material for a w h o l e group of useful chemicals, and perhaps e v e n rival petroleum a s a chemical r a w material. Petroleum is b e i n g u s e d u p more rapidly than it is b e i n g f o r m e d w h i l e sugar production c o u l d e a s i l y b e increased providing there w e r e sufficient d e m a n d . H e says that it s e e m s foolish to g o ( v i a e t h y l e n e oxide) to p e t r o l e u m , w h i c h does not mix w i t h water, to o b tain t h e water-soluble portion of a synthetic detergent molecule. R e s e a r c h n o w b e i n g carried out has p r o d u c e d a promising detergent from sugar. Readiness w i t h which living organisms t a k e u p sugar into their bodies should m a k e sugar an ideal starting substance u p o n w h i c h to build n e w insecticide c o m p o u n d s . Toxic groups might b e a t t a c h e d to the carbohydrate m o l e c u l e , says Hass. By-products of the sugar industry
H. Morita, Canadian Dept. of Agriculture, inserts thermocouple into sample holder of furnace. Temperature differences between starch sample and standard characterize starch varieties
CHEMICAL
AND
ENGINEERING
NEWS
CARBOHYDRATE are already finding many industrial uses, but there is room for research to upgrade these materials. Principal byproducts are bagasse, furfural, molasses, aconitic acid, and monosodium glutamate. Furfural Raw Materials. Furfural is a good example of a commercially successful product prepared from an agricultural waste. Pantosans, from which furfural is derived, are found in stalks, leaves, hulls, and other portions of plants for which there are few uses. Raw material is certainly no problem, according to P. A. Wells, Jr., Quaker Oats. Corncobs alone harvested each year could produce 40 times the present or forseeable market for furfural. Sugar cane bagasse produced annually in the Western Hemisphere could produce 25 times the market as could paper mill wastes. Oat hulls sufficient for 20 times demand and cottonseed hulls (all of which are collected and processed) for four times the demand are available. World market for furfural has grown from nothing in 1922 to about 100 million pounds per year. Plant expansion has taken two different directions. In the U. S. plants have tended to become larger to obtain greater efficiency so that furfural can compete with more chemicals. In Europe, where strenuous efforts are being made in many countries to ensure self-sufficiency and where many special incentives are offered to stimulate new industry, the tendency has been towards smaller plants. Forests. It is almost certain that cellulosic materials will become increasingly important, but it is not clear how quickly they will acquire new importance. It is possible to prepare sugar from wood at present, but it is not economic. In a paper by A. J. Wiley, Sulphite Pulp Manufacturers' Research League, and others at the U. S. Forest Products Laboratory, we should not be too impressed by the negative experience of the past because technology and economic situations change constantly. Periodically it is well to review the part that wood residues can play as a raw material for the carbohydrate using industries. In the past forest operators have been concerned with only one product, wood, and work on individual wood components such as carbohydrates has been discouraged. What is needed is long-range planning by larger operators to achieve integrated operations to recover useful by-products in suitable form. Starch, which is used for industrial purposes to greater extent than it is for food is, of course, a polymeric maVOLUME
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Few "facts" on the photosynthetic cycle remain unknown, states Melvin Calvin, University of California, in review of topic terial. An idea for increasing industrial use of this material is offered by N. F. Kennedy, Corn Industries Research Foundation. He believes it may be possible to develop starch derivatives which take advantage of the fact that the carbohydrate is already polymerized. This does not appear likely in the immediate future, but it is still a possibility. •
Nonsugars in Sugar Liquors "Why should the sugar industry be concerned with the minor and relatively useless components of commercial sugar liquors, such as starch, amino acids, and other organic and inorganic materials?" L. G. Joyner asked the symposium on nonsugar constituents of commercial sugar liquors. One answer might be to recover and sell them. It is true that some day this may be possible, but with the exception of one or two specific compounds it is doubtful whether it will ever be economical to do this because concentrations are so low. Of far greater importance is the effect of these materials on the processing of sugar. If these components were of fixed concentration there would be little difficulty experienced by the sugar refiner because of variations in sucrose content. To someone outside the industry, says Joyner, it must seem strange that if all this "gunk" in sugar liquors is so important, that the sugar refiners do rot know all about it already. However, this type of research is by its very nature slow and tedious and requires highly specialized personnel. As a result of this, the industry has avoided this type of work since it is considered too long-range, even though its ultimate importance may be recognized. Consequently, most of this research has been left to government agencies and nonindustrial laboratories. It may
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CHEMISTRY
be that the time such research becomes of value to industry is not so far away. Starch in Cane. Weather conditions during the harvesting period are the most important factor affecting starch content of sugar cane and its products, aside from the natural varietal differences, according to R. T. Balch, Southern Utilization Research Branch. Any condition which greatly retards or stops normal growth of cane causes starch to be utilized by the plant. Exposure to freezing temperatures is especially effective. Calculations show that about 23% of starch in syrups is taken up by raw sugar crystals and about 70% of that in raw sugar passes into the refinery stream as a constituent of washed sugar melt. All raw sugars so far examined by Balch contain starch in amounts ranging from about 8 to 30 milligrams per hundred grams. Starch in raw juices becomes a highly dispersed colloid as soon as the juices are heated and produce ill-defined effects throughout sugar making operations, including refining. The usual amounts of starch have very little effect on juice clarification. In sugar boiling operations starch may possibly have a retarding action on rate of crystallization. Perhaps greatest harm from unusual amounts of starch comes during filtration. Small amounts drastically reduce fllterability of sugar syrups. Amino Acids. Despite its importance, little information regarding amino acid status of sugar cane is available, says L. F. Wiggins, Imperial College of Tropical Agriculture, Trinidad. There is little qualitative variation of amino acid content of West Indian sugar cane, but there are large quantitative differences, not only between varieties, but also within a single variety, and even within the same plant. There is a steady decrease in amino acid concentration during growth, although there may be important exceptions to this. There is a spectacular rise in amino acid content followed by an equally spectacular drop at eight to nine months of age. Variations in sucrose content follow those of amino acid content, but at an interval of about two months. In artificial drought experiments there is a very sharp rise in amino acid content accompanied by a gradual rise in sucrose content and a fall in reducing sugars. At the onset of irrigation, this process is reversed although response of sucrose again is slower than amino acids. Variations of amino acid content because of drought are of interest, since sugar cane harvested after prolonged dry seasons is difficult to clarify. 3835
