Xitrite-free water may be prepared from distilled water b y adding one crystal each of potassium permanganate and barium hydroxide, and redistilling from an all-borosilicate glass still. The modified reagent yielded about 50/, less color than the original reagent both with standard nitrite solution and in the midget fritted bubbler with air samples. Thus, the original relationship of 1 mole of nitrogen dioxide pro-
ducing the same color as 0.72 mole of nitrite continues to hold. This standardization factor should be checked for the absorbing column employed, as values u p to 1.0 were reported by Thomas et al. (2) using the original reagent. LITERATURE CITED
(1) Saltaman, B. E., ANAL.CHEM.26, 1949 (1954).
( 2 ) Thomas,
D., McLeod, J. ~4.1 Robbins, R. C., Goettelman, R. C., Eldridge, R. W., Rogers, L. H., Ibid., 28, 1810 (1956).
BERNARD E. SALTZMAN Occupational Health Program Bureau of State Services Public Health Service U. S. Department of Health, Education, and Welfare 1014 Broadway, Cincinnati 2, Ohio
Indirect Method of Determining Optical Rotation of Some Monosaccharides SIR: Recently a number of papers have indicated that the periodate oxidation of aldoses proceeds exclusively b y a stepwise oxidation from the hemiacetal grouping down the molecule ( 1 , 9 ) . If in the reaction between periodic acid and monosaccharides (in either the aldehydo or hemiacetal structure) there is a preferential cleavage between carbon 1 and 2, the monosaccharide will be degraded to the next lower monosaccharide-for example, D-glucose will be degraded to D-arabinose. However, a n y D-arabinose so formed will be subject to further attack b y periodic acid to give D-erythrose. T o overcome this difficulty the amount of D-glucose can be increased so that the reaction will take place primarily between D-glucose and periodic acid. The contribution to the observed rotation b y the excess D-glucose, when subtracted from the observed rotation for the reaction mixture, will give the contribution to the observed rotation made b y the products of the reaction-for example, in one of the following experiments the mole ratio of D-glucose to periodic acid was approximately 40 to 1. If the reaction takes place primarily between carbons 1 and 2, the reaction mixture will contain 39 parts of n-glucose and 1 part of D-arabinose. The contribution to the observed rotation made by the 39 parts of n-glucose, when subtracted from the observed rotation, gives the contribution made by the 1 part of D-arabinose. Because the specific rotation is a function of concentration, i t is necessary to know its value from the literature or to determine it experimentally before calculations can be made. The reaction m-as shown to be complete by using the thiosulfate method (?) and by titration of the formic acid produced ( 3 ) . The conversion of periodate to iodate % as found to be quantitative, and for each mole of periodate consumed 1 mole of formic acid was produced. The time required for the 136
0
ANALYTICAL CHEMISTRY
sugar-periodate mixture to reach constant reading varied with the sugar, but all occurred within 1 to 2 hours. I n one case a control containing the same concentrations of D-glucose, D-arabinose, and iodate ion as that assumed for the products of the reaction gave a n observed rotation agreeing with the experimental to within 0.01".
Starting Material D-Glucose ~-.%rabinose D - x ylose D-Mannose D-Galactose
CONCLUSIONS
When a 40 to 1 excess of monosaccharide is allowed to react with periodic acid in a n aqueous medium, the next lower monosaccharide is produced. Because the cleavage takes place preferentially, i t is possible to calculate the specific rotation of the next lower monosaccharide without isolating the products
Spec. Rotation ' (Lit.)
Expected Product D-Arabinose n-Erythrose D-Threose D-Arabinose D-Lyxose
The values for D-erythrose and Dthreose are in dispute. The literature values for D-erythrose are -14.5' ( l o ) , -19.7' (6),and -23" ( 8 ) ,for D-threose, 19' (4) and -12" ( 5 ) . L-Threose has the value -24.6' ( 2 ) . Because the accuracy depends on the difference in rotation between the starting material and the products, and the observed values are accurate to only 0.01', the error involved nil1 be large for small differences. For the calculated specific rotations given the error varied from h1.5' for D-arabinose to h 7 ' for D-erythrose. EXPERIMENTAL
D-Glucose (anhydrous, 7.20 grams) was dissolved in 30 ml. of distilled water. Periodic acid (H6106,0.272 gram) mas dissolved in 10 ml. of distilled water. The two solutions were mixed in a 50ml. volumetric flask and brought to volume with distilled water. The solution was allowed to stand until a constant rotation was obtained (1 to 2 hours). Using a 2-dni. tube, the observed rotation was 1328'. The calculated rotationois 14.00 . A control run gave 13.99 .
-104 5 -14.5 24.6 -104.5 -13.5
Calcd, Rotation ' - 107 -13 4 26.0 - 106 -14.5
of the reaction. The method might have some value in resolving existing uncertainties as to the specific rotation of certain sugars. LITERATURE CITED (1)
Courtois, J. E., Guernet, hl., Compt.
rend. 245,273 (1957). ( 2 ) Deulofeu. V.. J . Chem. SOC. 225,
.,
2458 (1929). ' (3) Fleury, P., Lange, J., Compt. rend. 195, 1395 (1932); 209, 219 (1939). ( 4 ) Freudenberg, K., Ber. 65, 168 (1932). ( 5 ) Hockett, R. C., Evans, W. L., Jack-
son, E. L., Watters, A. J., J . Am. Chem. SOC.57, 2260 (1935); 60, 278 (1938).
Overend, W.G., Stacey, M., Wiggins, L. F., J . Chent. SOC.1358, 1949. ( 7 ) Pohle, W. D., Mehlenbacher, V. C., Cook, J. H., Oil and Soap 22, 115-19
(6)
(May 1945).
(8) Rappo ort, D. A., Hassid, W. Z., J . Am. $hem SOC.73, 5524 (1953). ( 9 ) Warsi, S. 9., Whelan, S. J., Chem. and Ind. (London) 1958,71. (10) Wohl, -4.) Ber. 32, 3666 (1899).
Syracuse University Syracuse, N. Y. LeMoyne College Syracuse, S. Y.
CLAYTOX C. SPEI~CER CLIFFORD J. ~ ~ C G I W
