Optical and Crystallographic Properties of D-Fructose Hemihydrate F. T.JONES, F. E. YOUNG, AND DALE R. BLACK Western Regional Research Laboratory, Albany, Calif. HE refractive indices, crystal morphology, and x-ray powder T d e t a . are given for D-fructose hemihydrate. 8-D-FUlctose often crystallises from concentrated (ahout 83%) aqueous solutions as spheruliies of very fine needles. During an investigation of the fructosewater phase diagram ( 6 ) crystals of the needle type were isolated and analyzed. The analysis shows that this phase is pD-frUctose hemihydrate (C6Hm0c1/zHa0). Needles of the hemihydrate will change slowly ahove 20" C. into prismatic cry8tals of the stable anhydrous form if the solution is seeded with it. Figure 1 shows both of these forms. It seems likely that erroneous descriptions of anhydrous Dfructose as needles, found in several widely used handbooks (S-4) are the result of mistaking the hemihydrate for anhydrous D-fructose. Observations in this lahoboratory on anhydrous Dfructose agree with those given by Bates (I) and R'inehell ( 5 ) . Crystals such as those shown in Figure 1 can he grown under 5 cover glass on a slido. Slow growth from solutions not highly supersaturated or growth by slow evaporation through the crust formed a t the edge of the cover glass will sometimes produce
larger crystals of theneedle type. Thegrowingendsof thecrystala tend to splinter into new clusters of needles during rapid growth, but in a solution a t equilibrium the ends are irregular, and a tubular cavity often extends into the crystal. A slit may extend part way down the side. Fimre 2 shows such cavities in an end view of a bundle of crystals. OPTICAL AND CRYSTALLOGRAPHIC PROPERTIES
Between crossed Nicols the needles show sharp parallel extinction and low birefringence. The slaw m y is always lengthwise. Refractive indices were measured in sodium light by immersion on crystals broken out of a loose ma86 which had dried very slowly in 8. vial. The siaa of these crystals can he judged from Figure 2. This view was obtained b y supporting a bundle of crystals in the hole of a thin cross section cut from 8. capillary tube. The end view gives a positive uniaxial interference figure which, together with the six-sided shape, indicates that the crystal system is hexagonal. A dry nuas of the needles of n-fructose hemihydrate can he melted a t about 68' C. under a cover glass to a colorless liquid which becomes viscous when cooled. The crystals will grow back into the melt during a day or two if remnants are left for seed. Tahle I gives the optical and crystdographie properties. X-ray powder data are given in Tahle 11.
Table I. Optical and Crystallographic Properties of D-Fructose H e m i h y d r a t e
Table 11. X-Ray Diffraction Powder D a t a of D-Fructose Hemihydrate (Radiation. CuKol = 1.5418 A,) d Estd. d Estd. Int.' Line No. 1 13.71 M 18 2.991 MS 2 2.863 MW 7.90 W 19 3 6.87 2,799 M YW 20 4 6.29 YW 21 2.685 VW 5 MS 2.637 MW 5.60 22 6 5.39 2,505 MW vw 23 7 5.1s 2.469 VW vs 24 8 4.85 MS 25 2.387 M 9 2.284 MW 4.57 MS 26 10 4.43 w 27 2.194 W 11 4.29 VW 28 2.146 w 12 3.96 2.004 VW S 29 13 3.81 1.979 W w 30 1.921 W 14 3.66 W 31 15 3.32 1.822 VW M 32 16 3.24 1.815 W W 33 17 3.15 1.783 W 34 vs = verystron 6 = strong. h4S = mediumstrong: M = mndium: M W = mediumwea,&i W = w e d ; Y W = veryweak. Line No.
Figure 1.
D-Fructose Hemihydrate F i l a m e n t s a n d Anhydrous n-Fruotose Prisms lOOX
vw
LITERATURE CITED
(1) Bates, F. J., and Associates, Natl. Bur. Standards (US.).C i x . C440,543 (1942). (2) Grent, Julius, ed., "Haokh's Chemieel Diotionary." 3rd ed., P. 358,Philadelphia. Blakiston Co.. 1944. (3) Hodp-man, C. D.. ed.. "Handbook of Chemistry and Physics." 31st ed., P.846. Cleveland, Ohio, Chemical Rubber Publishing Co.. 1949. (4)Lawe. N. A., ed., "Handbook of Chemistry." 7th ed., p.' 536, Sandusky. Ohio. Handbook Publishers, Inc., 1949. (5) Winchell, A. N.,"Optioal Properties of Organic Compounds." P. 186, Madison. Wis.. University of Wisconsin Press. 1943. (6) Young. F. E., Jones. F. T., and Lewis, H. J., J . Phys. Chem., 56, 738 (1952). REOEmED for review June 2, 1952. Acoeoted November 12. lS52.
I Figure 2.
n-Fructose Hemihydrate, E n d view 6nn x
649
