Abstract
The crystal structures of two alditol acetates, D-glucitol hexaacetate and xylitol pentaacetate, have been determined by diffraction methods with Mo-K$\alpha$radiation, using direct methods for phase determinations. The crystal data are: for D-glucitol hexaacetate, P2$_1$, with a = 10.275 (2), b = 8.363 (1), c = 12.560 (5) $\AA;\beta$ = 95.97 $(2)^{\circ}$, Z = 2; for xylitol pentaacetate, P2$_1$/C with a = 18.126 (1), b = 11.422 (2), c = 8.649 (1) $\AA$, $\beta = 95.03 (1)^{\circ}$, Z = 4. Both molecules have extended zigzag carbon chain conformations which differ from previous studies of the structures of D-glucitol and xylitol and also differ from NMR studies on alditol acetates. The bond lengths and angles are normal, with mean values over both structures of C($sp^3)-C(sp^3): 1.514 (10),\; C(sp^3)-O: 1.444 (6),\; C(sp^2)-O: 1.347 (9),\; C(sp^2)=O: 1.197 (6),\; C(sp^2)-C(sp^3): 1.479(9){\AA},\; C(sp^3)-C(sp^3)-C(sp^3): 114.6 (17),\; O-C(sp^3)-C(sp^3): 109.4 (23),\; C(sp^2)-O-C(sp^3): 117.4 (6),\; O=C(sp^2)-O: 122.6 (6),\; C(sp^3)-C(sp^2)-O: 111.8 (7),\; C(sp^3)-C(sp^2)=O: 125.5 (4)^{\circ}$. The atoms of acetate groups are in coplanar. There are no particularly short intermolecular contacts and the molecules are held together by van der Waals force only.
D-glucitol hexaacetate 와 xylitol pentaacetate의 결정구조를 단결정 X-선 회절법으로 연구하였다. D-glucitol hexaacetate 는 공간군 P2$_1$, 단위세포 상수는 a = 10.275 (2), b = 8.363 (1), c = 12.560 (5) $\AA$, $\beta$= 95.97 $(2)^{\circ}$; Z = 2이고, xylitol pentaacetate는 공간군이 P2$_1$/C이고, a = 18.126 (1), b = 11.422 (2), c = 8.649 (1) $\AA$, $\beta$ = 95.03 $(1)^{\circ}$이며 Z = 4이다. 회절세기는 diffractomerer로 얻었고, 분자구조는 직접법으로 밝혔으며, 최소자승법으로 정밀화하였다. 두 분자에 결쳐 결합의 평균길이는 C($sp^3)-C(sp^3$)가 1.514 (10), C($sp^3)-O: 1.444 (6),\; C(sp^2)-O: 1.347 (9),\; C(sp^2)=O: 1.197 (6),\; C(sp^2)-C(sp^3): 1.479(9){\AA}$이고, 평균 결합각도는 C($sp^3)-C(sp^3)-C(sp^3): 114.6 (17),\; O-C(sp^3)-C(sp^3): 109.4 (23),\; C(sp^2)-O-C(sp^3): 117.4 (6),\; O=C(sp^2)-O: 122.6 (6),\; C(sp^3)-C(sp^2)-O: 111.8 (7), C(sp^3)-C(sp^2)=O: 125.5 (4)${\circ}$이다. 두 분자내의 탄소 사슬들은 extended zigzag chain으로 되어 있어 D-glucitol과 xylitol 분자들의 conformation과는 다르다. Acetate group들의 각 원자들은 모두 한 평편상에 놓여있다.
