Crystal structure of polysulfonamides

Structures of poly(alkylene-1,3-benzenedisulfonamide)s [? HN(CH₂)_mNH? O₂SC₆H₄SO₂? ]_n (PMm: 2 ≤ m ≤ 6) were studied by x-ray diffraction and infrared spectroscopy. The crystal structure of PB6 is monoclinic, space group C2/m? C_2h³, with a = 7.70 Å, b = 7.76 Å, c (molecular axis) = 14.1 Å, and β = 117°. Two mirror-image molecules repeating with two monomeric units in an identity period 28.2 Å occupy the same lattice site with equal probability. The alkylene chains assume the planar zigzag conformation, which is the structure isomorphous with PB4. An intermolecular hydrogen bond is formed between each NH group and one of the two O = S groups of the corresponding SO₂ unit. The c axis tends to tilt from the fiber axis by an inclination angle of about 3° around the b axis.     

Crystal structure of acrylamide

The crystal structure of acrylamide is re-determined by single crystal X-ray diffraction (133(1) K, BRUKER SMART 1000 CCD, a = 8.228(1) Å, b = 5.759(1) Å, c = 9.760(1) Å, β = 120.04(1)°, V = 400.3(1) Å,³, space group P2₁/c, Z = 4, R = 0.0543 for 867 reflections). In the structure strong hydrogen bonds N-H...O join the molecules of C₃H₅NO into bi-molecular layers that make C...C molecular contacts. It is demonstrated that the process of solid phase polymerization of acrylamide should proceed through the cleavage of double bonds C(1)=C(2) in the monomers and formation of bonds C(1)-C(1) and C(2)-C(2) between the closest carbon atoms of different layers.     

Crystal structure of amikacin

Amikacin is one of the important aminoglycoside antibiotics used against gram-negative bacteria. Here we report the crystal structure of amikacin that has been crystallized by vapor diffusion against polyethylene glycol. The molecule exists in a long, extended conformation, with all three six-membered rings in chair conformations and connected together by -glycosidic linkages. The orientation between the A, B and C rings of the molecule is maintained by intramolecular hydrogen bonds involving the O₅ hydroxyl group and the amide NH group.     

Crystal structure of polyisobutylene

The crystal structure of polyisobutylene was determined by x-ray analysis. The orthorhombic cell, with a = 6.88 Å, b = 11.91 Å, c (fiber axis) = 18.60 Å (space group: P2₁2₁2₁ ? D), contains two molecular chains each consisting of eight monomeric units in the fiber identity period. The chain conformation is essentially an (8/3) helix, but deviates appreciably from the exact (8/3) helix symmetry. The symmetry of the molecular chain is only a twofold screw axis in exact sense, and a crystallographic asymmetric unit consists of four monomeric units. The torsional angles are where M denotes the methyl group. The averaged skeletal C? CH₂? C and C? CM₂? C bond angles are 128° and 110°, respectively. The large C? CH₂? C bond angles may be due to steric respulsion between the adjacent methyl groups, giving intramolecular distances larger than 3.09 Å.