Cellulose organic solvents: V. Conformational aspects of N,N-dimethyl ethanolamine N-oxide in its crystalline and diluted states

1984 ◽  
Vol 62 (1) ◽  
pp. 6-10 ◽  
Author(s):  
E. R. Maia ◽  
A. Péguy ◽  
S. Pérez
Keyword(s):  
Tertiary Amine ◽  
Amine Oxide ◽  
Direct Methods ◽  
Monoclinic Space Group ◽  
Cyclic Form ◽  
Asymmetric Unit ◽  
Ir And Nmr Spectroscopy ◽  
Conformational Investigation ◽  
Intramolecular Hydrogen ◽  
Strong Intramolecular Hydrogen Bond

N,N-Dimethyl ethanolamine N-oxide (DMEAO) belongs to the class of tertiary amine oxide molecules that are good solvents for cellulose, although not being cyclic. Crystallographic investigation shows that anhydrous DMEAO is monoclinic, space group Cc, a = 25.725(9), b = 7.023(4), c = 9.483(5) Å, β = 101.16(10)°, Z = 12. The crystal structure has been solved by direct methods and refined to a final R value of 0.063 for 575 observed reflexions. Three independent molecules are found within the asymmetric unit; one of these displays a pseudo-cyclic form dictated by the occurrence of a strong intramolecular hydrogen bond. Conformational investigation of DMEAO in solution, using ir and nmr spectroscopy shows that this pseudo-cyclic form is more likely to occur in diluted states. These findings are related to the ability of this tertiary amine oxide to act as a good solvent, up to a water content of one water molecule per DMEAO molecule.

Crystal structure of N,N '-Ethylenebis(1,1,1-Trifluoro-4-iminopentan-2-one)

1984 ◽  
Vol 37 (4) ◽  
pp. 879 ◽  
Author(s):  
R Cea-Olivares ◽  
I Rodriguez ◽  
MJ Rosales ◽  
A Toscano
Keyword(s):  
Crystal Structure ◽  
Direct Methods ◽  
Monoclinic Space Group ◽  
Enamino Ketone ◽  
Space Group ◽  
R Value ◽  
Intramolecular Hydrogen

The crystal structure of N,N'-ethylenebis(1,1,1-trifluoro-4-iminopentan-2-one) (tfaen) was determined: C12H14F6N2O2, M 342.04, monoclinic, space group P21/n, a 6.939(2), b 20.529(5), c 10.662(2) �, V 1507.84 �3 β 96.87(2)�, p(calc.) 1.506 g cm-3 (Z = 4), F(000)680, �(Cu Kα) 13.15 cm-1. The structure was solved by direct methods and refined to a final R value of 0.073 for 1198 unique reflections. Discrete molecules in the crystal are characterized by a conjugated enamino ketone structure with intramolecular hydrogen bridges.

The halotrichite group: the crystal structure of apjohnite

1976 ◽  
Vol 40 (314) ◽  
pp. 599-608 ◽  
Author(s):  
S. Menchetti ◽  
C. Sabelli
Keyword(s):  
Crystal Structure ◽  
Least Squares Method ◽  
Direct Methods ◽  
Water Molecules ◽  
Monoclinic Space Group ◽  
Direct Connection ◽  
Asymmetric Unit ◽  
X Ray ◽  
Bonding System ◽  
Hydrogen Bonding System

SummaryApjohnite, MnAl2(SO4)4·22H2O, is monoclinic, space group P21/c, a 6·198 (2), b 24·347 (4), c 21·266 (4) Å, β 100·28 (3)° and Z = 4. The crystal structure was determined by means of direct methods applied to X-ray data collected with a single-crystal diffractometer. At the end of the refinement, performed with least-squares method, the R index was 0·039.The SO4 tetrahedra, Al(H2O)5 octahedra, and MnO(H2O)5 octahedra are connected by a hydrogen bonding system; the only direct connection between polyhedra is by sharing of an oxygen between S(4) and Mn. In the asymmetric unit there are twenty-two water molecules, five of which lie in channels of the structure and are not linked to the cations but only to ligand water oxygens by means of hydrogen bonds.Powder data indicate a close structural relationship between apjohnite, halotrichite, and pickeringite.

Two polymorphs ofN-(2-methoxyphenyl)-4-oxo-4H-chromone-3-carboxamide

2013 ◽  
Vol 69 (8) ◽  
pp. 927-933 ◽  
Author(s):  
Ligia R. Gomes ◽  
John Nicolson Low ◽  
Fernanda Borges ◽  
Fernando Cagide
Keyword(s):  
Hydrogen Bonds ◽  
Molecular Conformation ◽  
Three Dimensional ◽  
Amide Group ◽  
Monoclinic Space Group ◽  
Asymmetric Unit ◽  
Intramolecular Hydrogen Bonds ◽  
Compound C ◽  
Dimensional Network ◽  
Intramolecular Hydrogen

The title compound, C17H13NO4, crystallizes in two polymorphic forms, each with two molecules in the asymmetric unit and in the monoclinic space groupP21/c. All of the molecules have intramolecular hydrogen bonds involving the amide group. The amide N atoms act as donors to the carbonyl group of the pyrone and also to the methoxy group of the benzene ring. The carbonyl O atom of the amide group acts as an acceptor of the β and β′ C atoms belonging to the aromatic rings. These intramolecular hydrogen bonds have a profound effect on the molecular conformation. In one polymorph, the molecules in the asymmetric unit are linked to form dimers by weak C—H...O interactions. In the other, the molecules in the asymmetric unit are linked by a single weak C—H...O hydrogen bond. Two of these units are linked to form centrosymmetric tetramers by a second weak C—H...O interaction. Further interactions of this type link the molecules into chains, so forming a three-dimensional network. These interactions in both polymorphs are supplemented by π–π interactions between the chromone rings and between the chromone and methoxyphenyl rings.

The Crystal Structure of cis-Inositol Monohydrate—Un Objet Retrouvé

1996 ◽  
Vol 49 (3) ◽  
pp. 413 ◽  
Author(s):  
HC Freeman ◽  
DA Langs ◽  
CE Nockolds ◽  
YL Oh
Keyword(s):  
Crystal Structure ◽  
Least Squares ◽  
Direct Methods ◽  
Monoclinic Space Group ◽  
High Symmetry ◽  
Asymmetric Unit ◽  
Fourier Methods ◽  
Full Matrix ◽  
Structure Factors ◽  
Independent Molecules

cis-Inositol monohydrate, C6H12O6.H2O, crystallizes in the monoclinic space group P 21/n [a 9.900(8), b 9.296(8), c 17.795(15) Ǻ, β 90.5(1)°, Z 8]. The normalized structure factors Eh have an atypical statistical distribution, and attempts to solve the structure by direct methods (triplet relationships) were unsuccessful. The structure was ultimately solved by Patterson and Fourier methods, and was refined by full-matrix least squares [Rw = 0.047 for 1665 independent reflections ≥2σ(Imin)]. The cis-inositol molecules have approximately trigonal symmetry, as expected. The difficulties encountered during the structure analysis are explained by the presence of two nearly identical molecules of high symmetry in the asymmetric unit. The independent molecules are related by translational pseudosymmetry, and their orientations are such that all the C-C and C-O bonds in the structure are approximately parallel to a small number of directions.

scholarly journals 5-Amino-1-(2′,3′-O-isopropylidene-D-ribityl)-1H-imidazole-4-carboxamide: a crystal structure withZ′ = 4

2017 ◽  
Vol 73 (2) ◽  
pp. 183-187 ◽  
Author(s):  
Vincenzo Piccialli ◽  
Nicola Borbone ◽  
Giorgia Oliviero ◽  
Gennaro Piccialli ◽  
Stefano D'Errico ◽  
...  
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Title Compound ◽  
Monoclinic Space Group ◽  
Intermolecular Hydrogen Bonding ◽  
Asymmetric Unit ◽  
Compound C ◽  
Independent Molecules ◽  
Intramolecular Hydrogen ◽  
Similar Conformation

The title compound, C12H20N4O5, crystallizes in the monoclinic space groupP21, with four crystallographically independent molecules in the asymmetric unit. The four molecules have a very similar conformation that is basically determined by the formation of two intramolecular hydrogen bonds between the amino NH2donors and the carbonyl and ring O-atom acceptors, forming, respectively,R(6) andR(7) ring motifs.. In the crystal, intermolecular hydrogen bonding leads to the formation ofR22(10) ring patterns, involving one amide CONH2donor and an imidazole N-atom acceptor. The cluster of the four independent molecules has approximate non-crystallographicC2point symmetry. The structural analysis also shows that during the synthesis of the title compound, the reductive cleavage of the D-ribose ring of the inosine precursor proceeds stereoselectively, with retention of configuration.

Determination of the structure of p-methylbenzamidinium formate monohydrate

1988 ◽  
Vol 53 (12) ◽  
pp. 3131-3137
Author(s):  
Bohumil Kratochvíl ◽  
Jan Ondráček ◽  
Jindřich Hašek ◽  
László Csordás
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Three Dimensional ◽  
Direct Methods ◽  
Monoclinic Space Group ◽  
Hydrogen Atoms ◽  
Intermolecular Hydrogen Bonds ◽  
Dimensional Network ◽  
Intramolecular Hydrogen

The molecular and crystal structure of p-methylbenzamidinium formate monohydrate, C9H14N2O3, was solved by direct methods. The positions of all the atoms were localized and the structure was refined anisotropically. The final value of the R factor equalled 0·043 for 1 150 observed reflections (I > 1·96σ(I)). The substance crystallizes in the P21/c monoclinic space group with lattice parameters a = 1 038·9(4), b = 1 146·1(5), c = 912·4(3) pm, β = 94·77(3)0, Z = 4. The molecule contains an amidinium-carboxylate bond, formed by two intramolecular hydrogen bridges of the N-H···O type. Intermolecular hydrogen bonds are formed by the side hydrogen atoms of the amidine and the hydrogen atoms of the water molecule and are of the N-H···O and O-H···O types; they form a three-dimensional network in the crystal structure. In this, the structure of p-methylbenzamidinium formate monohydrate differs from the related structures of benzamidinium pyruvate and benzamidinium bromoacetate, characterized by infinite intermolecular chains formed through hydrogen bonding.

scholarly journals The crystal structure of 1-(4-chlorophenyl)-3-(4-methylbenzoyl)thiourea

2005 ◽  
Vol 3 (4) ◽  
pp. 780-791 ◽  
Author(s):  
Aamer Saeed ◽  
Masood Parvez
Keyword(s):  
Crystal Structure ◽  
Monoclinic Space Group ◽  
Fragmentation Pattern ◽  
X Ray Diffraction ◽  
1H And 13C Nmr ◽  
X Ray ◽  
Cell Dimensions ◽  
Intramolecular Hydrogen ◽  
Unit Cell Dimensions ◽  
Strong Intramolecular Hydrogen Bond

Abstract1-(4-Chlorophenyl)-3-(4-methylbenzoyl)thiourea was synthesized and characterized by IR,1H and 13C NMR, mass spectroscopy and the elemental analysis. The crystal structure was confirmed from single crystal X-ray diffraction data. It crystallizes in the monoclinic space group P21/c with unit cell dimensions a=12.038(3), b=6.330(6), c=18.912(5) Å and β=100.32(3)°. There is a strong intramolecular hydrogen bond of the type N−H...O, with distance N1...O1=2.659(3) Å. The structure is composed of dimers related by inversion centers. The dimers are formed by intermolecular interactions of the type N−H...S with N...S separation of 3.440(2) Å. The mass fragmentation pattern has also been discussed.

Structure Investigations of Agonists of the Natural Neurotransmitter Acetylcholine, III [1] X-Ray Structure Analysis of (2-Ethoxyethyl)trimethyl- ammonium Chloride

1982 ◽  
Vol 37 (10) ◽  
pp. 977-984 ◽  
Author(s):  
Alfred Gieren ◽  
Michail Kokkinidis
Keyword(s):  
Structure Analysis ◽  
Direct Methods ◽  
Monoclinic Space Group ◽  
Muscarinic Agonist ◽  
Asymmetric Unit ◽  
Muscarinic Agonists ◽  
X Ray ◽  
Ether Oxygen ◽  
Quaternary Ammonium Group ◽  
Structure Investigations

Abstract To elucidate the structure-activity correlations we have performed an X-ray structure analysis of the title compound (1), which is a muscarinic agonist of the natural neurotransmitter acetyl­ choline. 1 crystallizes in the monoclinic space group P 21/n with 2 molecules per asymmetric unit. Lattice parameters are: a = 10.375(6), b = 12.468(5), c = 15.274(17) Å; β= 95.32(7)°. The structure was solved by direct methods and refined to an R-value of 0.14 for 1828 observed reflections. Both cations in the asymmetric unit are disordered. In the crystal structure at least four conformations of the cation occur, indicating a pronounced conformational flexibility of the neurotransmitter cation. The anions are arranged stereospecifically with respect to the quaternary trimethylammonio methyl group. The geometry of triangles which are defined by a nitrogen of the quaternary ammonium group and an ether oxygen on one hand and an anion occupying a specific type of tetrahedral faces of a (CH3)3N+-CH2 group on the other hand, is characteristic for muscarinic agonists if they contain an ether or ester oxygen in the analogous position to the ester oxygen of acetylcholine.

Ab initiostructure determination of sulfathiazole polymorph V from synchrotron X-ray powder diffraction data

1999 ◽  
Vol 32 (3) ◽  
pp. 436-441 ◽  
Author(s):  
Fung Choy Chan ◽  
Jamshed Anwar ◽  
Robert Cernik ◽  
Paul Barnes ◽  
Rory McHardy Wilson
Keyword(s):  
Powder Diffraction ◽  
Diffraction Data ◽  
Computational Modelling ◽  
Direct Methods ◽  
Polymorphic Form ◽  
Monoclinic Space Group ◽  
Powder Diffraction Data ◽  
Asymmetric Unit ◽  
X Ray ◽  
Unit Cell Dimensions

The crystal structure of sulfathiazole [4-amino-N-(2,3-dihydro-2-thiazolylidene)benzenesulfonamide, C9H9N3O2S] polymorphic form V has been determined from high-resolution synchrotron X-ray powder diffraction data. The structure is monoclinic, space groupP21/n,Z= 8, with two molecules in the asymmetric unit. The unit-cell dimensions area= 14.3296 (3),b= 15.2733 (2),c= 10.4428 (2) Å and β = 91.052 (1)° with cell volumeV= 2285.13 (8) Å3. The structure has been solved by direct methods without recourse to any computational modelling techniques for generating possible structures. The unrefined structure obtained from direct methods gave anRwpvalue of 36.5%. Refinement of atomic and displacement parameters yielded a finalRwpof 12.54% (Rp= 9.37%). The conformations of the two molecules in the asymmetric unit are nearly identical and very similar to that found in other forms of sulfathiazole. The molecular packing is characterized by molecular sheets lying perpendicular to theaaxis. Each sheet is two molecules thick, being integrated by hydrogen bonding. With 16 non-H atoms in the molecule and two molecules in the asymmetric unit, this structure represents a further advance in terms of the complexity of an organic structure solved from X-ray powder diffraction data.

The crystal structure of 4,7-oxido-7-methyl-7-hydroxymethyl-2,2,6,6-tetramethylpiperidin-1-oxyl

1982 ◽  
Vol 60 (18) ◽  
pp. 2392-2397 ◽  
Author(s):  
M. Cygler
Keyword(s):  
Direct Methods ◽  
Chair Conformation ◽  
Hydroxyl Group ◽  
Piperidine Ring ◽  
Monoclinic Space Group ◽  
Intensity Data ◽  
Asymmetric Unit ◽  
Torsion Angles ◽  
Cell Dimensions ◽  
Unit Cell Dimensions

4,7-Oxido-7-methyl-7-hydroxymethyl-2,2,6,6-tetramethylpiperidin-1-oxyl, C12H22NO3, crystallizes in the monoclinic space group P21/m with unit cell dimensions a = 8.041(1), b = 13.348(1), c = 5.945(1) Å, β = 95.90(1)°, Z = 2. Intensity data were measured on a diffractometer and the structure solved by direct methods. The least-squares refinement converged at R = 0.039 for 1304 reflections. Two enantiomeric molecules, differing in the position of the OH group, occupy the same site in the asymmetric unit (each with a probability of 0.5) giving rise to a disorder of the hydroxyl group. The piperidine ring adopts the usual chair conformation, with C—C—C—C torsion angles being intermediate between those observed for C(4) mono- and for bisubstituted nitroxypiperidine derivatives. The N—O bond is 1.282(2) Å long, and it makes an angle of 18.5(2)° with the CNC plane. Molecules are connected by O—H … O hydrogen bonds. The influence of the degree of substitution at C(4) on ring geometry is discussed.

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