scholarly journals Study of the Variation of the Electronic Distribution and Motional Dynamics of Two Independent Molecules of an Asymmetric Unit of Atorvastatin Calcium by Solid-State NMR Measurements

ACS Omega ◽  
2021 ◽  
Vol 6 (35) ◽  
pp. 22752-22764
Author(s):  
Krishna Kishor Dey ◽  
Lekhan Lodhi ◽  
Manasi Ghosh
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Asymmetric Unit ◽  
Atorvastatin Calcium ◽  
Electronic Distribution ◽  
Motional Dynamics ◽  
Independent Molecules

Topochemically controlled solid-state methyl rearrangement in thiocyanurates

2001 ◽  
Vol 57 (3) ◽  
pp. 428-434 ◽  
Author(s):  
Mark Greenberg ◽  
Vitaly Shteiman ◽  
Menahem Kaftory
Keyword(s):  
Solid State ◽  
Driving Force ◽  
Mirror Plane ◽  
Energy Calculation ◽  
Asymmetric Unit ◽  
Methyl Transfer ◽  
Plate Shape ◽  
Polymorphic Forms ◽  
Independent Molecules ◽  
The Difference

4,6-Dimethoxy-3-methyl-1,3,5-triazine-2(3H)-thione crystallizes in two polymorphic forms, needles and plates. In the needle-shaped crystals (9a) the molecules occupy the crystallographic mirror plane, thus the layers are stacked along the b axis. The molecules of the other polymorph [plate-shape crystals, (9b)] are packed in a herringbone packing mode. Upon heating, (9b) undergoes a phase transition to form (9a). At 378 K the needles undergo O → S topochemically controlled methyl transfer in the solid state to produce 1-methyl-4-methoxy-6-methylthio-1,3,5-triazine-2(1H)-one in 75% yield. The enthalpy of the rearrangement is estimated to be −39.1 kJ mol−1. 1-Methyl-6-methoxy-4-methylthio-1,3,5-triazine-2(1H)-thione crystallizes in space group P21 with two crystallographically independent molecules in the asymmetric unit. Compound (9b) undergoes O → S methyl transfer in the solid state at 373 K. The rearrangement is topochemically assisted and the product, 1-methyl-2,4-bismethylthio-1,3,5-triazine-6(1H)-one, is obtained in quantitative yield. The enthalpy of the rearrangement is estimated to be −58.8 kJ mol−1. The crystal structures of the compounds as well as their DSC thermographs are described and discussed. Energy calculation by ab initio methods shows that the driving force for the reactions is the difference between the molecular energies of the pre-rearranged compounds and their products, 54.2 and 59.3 kJ mol−1 in the two cases, respectively.

Cooperative Effects in Aminothiols: Acid-Base Equilibria and the Molecular Structure of 2-(N, N-Dimethylaminomethyl)thiophenol

2008 ◽  
Vol 63 (10) ◽  
pp. 1199-1203
Author(s):  
Holger Fleischer ◽  
Dieter Schollmeyer
Keyword(s):  
Molecular Structure ◽  
Aqueous Solution ◽  
Hydrogen Bond ◽  
Solid State ◽  
Ab Initio ◽  
Ab Initio Methods ◽  
Asymmetric Unit ◽  
Acid Base ◽  
Cooperative Effects ◽  
Independent Molecules

Abstract2-(N,N-Dimethylaminomethyl)thiophenol, (1, HL), is present as a non-zwitterionic aminothiol in the solid state, exhibiting an intramolecular S-H···N hydrogen bond. The S···N distances of the two independent molecules in the asymmetric unit are 2.929(10) and 3.050(10) Å. This structural feature is also present in an ab initio (MP2/6-31G*) optimized molecular structure. The investigation of the hydrogen bond by ab initio methods supports an n(N)-σ *(S-H) interaction as the reason for this bond type. On the basis of data from potentiometric acid-base titrations of a 0.01 M aqueous solution of [H2L]Cl with a 0.1 M aqueous solution of sodium hydroxide, values of 4.09±0.01 and 11.50±0.01 were obtained for pKa1 and pKa2 of [H2L]+. pKa1 is much smaller than pKa of thiophenol while pKa2 is bigger than pKa of benzyldimethylamine. The increased difference between pKa1 and pKa2 is attributed to the stabilization of HL by the intramolecular S-H···N hydrogen bond.

3-Oxoandrosta-4,6-dien-17β-yl 2-methyl-1H-imidazole-1-carboxylate and 3-oxo-5α-androst-17β-yl 2-methyl-1H-imidazole-1-carboxylate: C—H...π and π–π intermolecular interactions

2009 ◽  
Vol 65 (3) ◽  
pp. o88-o91
Author(s):  
Manuela Ramos Silva ◽  
Vânia M. Moreira ◽  
Cláudia Cardoso ◽  
Ana Matos Beja ◽  
Jorge A. R. Salvador
Keyword(s):  
Solid State ◽  
Ab Initio ◽  
Torsion Angle ◽  
Molecular Conformation ◽  
Asymmetric Unit ◽  
Compound I ◽  
The Mean ◽  
Independent Molecules ◽  
Compound Ii ◽  
Supramolecular Aggregation

The title compounds, C24H30N2O3, (I), and C24H34N2O3, (II), both contain an androstane backbone and a 2-methylimidazole-1-carboxylate moiety at the 17-position. Compound (I) contains two symmetry-independent molecules (denoted 1 and 2), while compound (II) contains just one molecule in the asymmetric unit. The C—C—O—C torsion angle that reflects the twisting of the 2-methylimidazole-1-carboxylate moiety from the mean steroid plane is 143.1 (2)° for molecule 1 of (I), 73.1 (3)° for molecule 2 of (I) and 86.63 (17)° for (II). The significance of this study lies in its observation of significant differences in both molecular conformation and supramolecular aggregation between the molecules of the title compounds. The solid-state conformations compared with those obtained theoretically fromab initiomethods for the isolated molecules show large differences, especially in the orientation of the methylimidazole substituent.

scholarly journals (Z)-5-(4-Bromophenyl)-3-{[(3,5-dichlorophenyl)amino]methylidene}furan-2(3H)-one

IUCrData ◽  
2020 ◽  
Vol 5 (7) ◽  
Author(s):  
Oksana A. Mayorova ◽  
Vyacheslav S. Grinev ◽  
Alevtina Yu. Yegorova
Keyword(s):  
Solid State ◽  
Title Compound ◽  
Crystal Packing ◽  
Large Cell ◽  
Monoclinic Space Group ◽  
Stacking Interactions ◽  
Asymmetric Unit ◽  
Compound C ◽  
Benzene Rings ◽  
Independent Molecules

The title compound, C17H10BrCl2NO2, crystallizes in the monoclinic space group C2/c with a large cell volume of 6207 (3) Å3. The asymmetric unit of the title compound investigated at 120 K contains two crystallographically independent molecules (Z′ = 2). Each molecule demonstrates slight non-planarity in the solid state and a Z-configuration for the exocyclic C=C bond. The crystal packing reveals the presence of π-π stacking interactions between the substituted benzene rings [centroid–centroid distances of 3.836 (5) Å, shift distances in the range 1.272–1.843 Å].

Solid State and Solution Structures of an Adenine Analogue of the Antiviral Acyclonucleoside 9-(1,3-Dihydroxy-2-propoxymethyl)guanine

1990 ◽  
Vol 45 (7-8) ◽  
pp. 915-921 ◽  
Author(s):  
Joachim Granzin ◽  
Wolfram Saenger
Keyword(s):  
Solid State ◽  
Biological Activities ◽  
Monoclinic Space Group ◽  
Asymmetric Unit ◽  
Extended Form ◽  
Solution Structures ◽  
Cell Dimensions ◽  
Independent Molecules ◽  
Unit Cell Dimensions ◽  
C Nmr

Abstract The title compound. 9-(1,3-dihydroxy-2-propoxymethyl)adenine (DHP-Ade). an analogue of the antiviral acyclonucleoside 9-(1,3-dihydroxy-2-propoxymethyl)guanine (DHPG), crystallizes in the monoclinic space group P21. with unit cell dimensions of a = 10.848(4), b = 8.765(3), c = 11.432(4) Å. β = 102.14(3)° . with two independent molecules in the asymmetric unit. The crystal structure of DHP-Ade was determined and compared with that for DHPG. The solution conformations of both acyclonucleosides were also determined with the aid of 1H and ,13C NMR spectroscopy. In the solid state the acyclic chain may adopt a “folded” form, i.e. gauche about the C(1′)-O(1′) bond (as in DHP-Ade), or an “extended” form (as in DHPG), results which corre- spond to the rotations about this bond in solution. A general discussion is presented of the conformations of the acyclic chains of various acyclonucleosides, from the antiviral 9-(2-hydroxyethoxymethyl)guanine (Acyclovir, ACV) through to 2′,3′-seco-nucleosides, both in the solid state and in solution, and the relevance of these to biological activities.

Solid-State NMR Studies of Form I of Atorvastatin Calcium

2012 ◽  
Vol 116 (11) ◽  
pp. 3641-3649 ◽  
Author(s):  
Wei David Wang ◽  
Xudong Gao ◽  
Mark Strohmeier ◽  
Wei Wang ◽  
Shi Bai ◽  
...  
Keyword(s):  
Solid State ◽  
Solid State Nmr ◽  
Nmr Studies ◽  
Atorvastatin Calcium

Intramolecular and intermolecular geometry of thiophenes with oxygen-containing substituents

1999 ◽  
Vol 55 (6) ◽  
pp. 963-974 ◽  
Author(s):  
Alexander J. Blake ◽  
Bernard A. J. Clark ◽  
Hedi Gierens ◽  
Robert O. Gould ◽  
Gordon A. Hunter ◽  
...  
Keyword(s):  
Hydrogen Bonding ◽  
Solid State ◽  
Methoxy Group ◽  
Tautomeric Form ◽  
Nitrile Group ◽  
Two Dimensional ◽  
Asymmetric Unit ◽  
Liquid Samples ◽  
Independent Molecules

The intramolecular and intermolecular geometries of six thiophenes carrying oxygen-containing substituents have been determined. Crystals of 2-methoxythiophene and 3-methoxythiophene were grown in situ on a diffractometer from liquid samples. The 2-methoxy group introduces significant distortions to the thiophene nucleus and each molecule participates in four S...O contacts leading to an infinite bilayer. The extended structure of 3-methoxythiophene comprises zigzag chains of molecules linked by S...O contacts. Molecules of 2-acetyl-3-methoxythiophene are arranged in pairs about inversion centres, with ring centroids 3.835 Å apart. 5-Cyano-3-hydroxythiophene adopts the hydroxythiophene tautomeric form which allows conjugation between the S atom and the nitrile group: O—H...N hydrogen bonding leads to chains which are cross-linked by S...O contacts to give infinite two-dimensional layers. 5-(Methylthio)thiophen-3(2H)-one exists exclusively as the thiophen-3(2H)-one form in the solid state, allowing maximum conjugative interaction of both the ring heteroatom and the substituent with the carbonyl group: each molecule is linked to two of its neighbours through pairwise C—H...O interactions, forming ribbons. Spiro[cyclohexane-1,2′-2′,3′-dihydrothiophen]-3′-one crystallizes with four independent molecules in the asymmetric unit with only minor differences between these: the five- and six-membered rings in each molecule are approximately orthogonal and C—H...O hydrogen bonding generates chains. The last two structures differ from the others in that they lack a fully aromatic thiophene system.

scholarly journals 4-Chloro-3-ethylphenol

2014 ◽  
Vol 70 (7) ◽  
pp. o801-o801
Author(s):  
Sean H. Majer ◽  
Joseph M. Tanski
Keyword(s):  
Solid State ◽  
Title Compound ◽  
Side Chain ◽  
Asymmetric Unit ◽  
Torsion Angles ◽  
Face To Face ◽  
Compound C ◽  
Centroid Distance ◽  
Π Stacking Interaction ◽  
Independent Molecules

The title compound, C8H9ClO, packs with two independent molecules in the asymmetric unit, without significant differences in corresponding bond lengths and angles, with the ethyl group in each oriented nearly perpendicular to the aromatic ring having ring-to-side chain torsion angles of 81.14 (18) and −81.06 (19)°. In the crystal, molecules form an O—H...O hydrogen-bonded chain extending along theb-axis direction, through the phenol groups in which the H atoms are disordered. These chains pack together in the solid state, giving a sheet lying parallel to (001),viaan offset face-to-face π-stacking interaction characterized by a centroid–centroid distance of 3.580 (1) Å, together with a short intermolecular Cl...Cl contact [3.412 (1) Å].

4-Acetamidobenzenesulfonyl azide

2006 ◽  
Vol 62 (5) ◽  
pp. o1751-o1753 ◽  
Author(s):  
Monica L. Vicarel ◽  
Peter Norris ◽  
Matthias Zeller
Keyword(s):  
Solid State ◽  
Hydrogen Bonds ◽  
Title Compound ◽  
Unit Cell ◽  
Asymmetric Unit ◽  
The Third ◽  
Compound C ◽  
Independent Molecules ◽  
Partial Inversion

The title compound, C8H8N4O3S, is planar chiral in the solid state. It crystallizes with three independent molecules in the asymmetric unit, two of which have the same chirality and the third is the opposite enantiomer. Partial inversion twinning is present in the crystal which was examined. All three molecules are connected via hydrogen bonds between the amide groups, forming a helix around the b axis of the unit cell.

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