Molecular association in low-temperature and high-pressure polymorphs of 1,1,1,2-tetrachloroethane
Interactions and aggregation of 1,1,1,2-tetrachloroethane molecules, Cl3CCH2Cl, have been investigated at low temperature and high pressure. Isobaric and isochoric crystallizations led to two polymorphs, characterized by single-crystal X-ray diffraction. The low-temperature polymorph α is monoclinic, space group C2/c, with molecules orientationally disordered in two sites at the temperature independent 70:30 rate. In isothermal conditions (295 K) 1,1,1,2-tetrachloroethane freezes at 0.73 GPa. The high-pressure polymorph β is monoclinic, space group P21/c, with the molecules fully ordered. The molecular aggregation at varied thermodynamic conditions results from the interplay of halogen inte…
Relations between compression and thermal contraction in 1,2,4-trichlorobenzene and melting of trichlorobenzene isomers
The compression and thermal expansion of crystalline 1,2,4-trichlorobenzene, C6H3Cl3, 124TCB, investigated under isobaric and isothermal conditions, are in reverse relation, as for most of crystals, however, the isochoric strain along direction c is clearly different from those along a and b. Single crystals of 124TCB have been in situ grown under isochoric and isobaric conditions, at 270 K/0.1 MPa and 295 K/0.16 GPa, and also at 100 K/0.1 MPa and 295 K/0.64 GPa, when the unit-cell volume is similar. All crystallizations yielded the same phase, of monoclinic space group P21/n, with two symmetry-independent molecules (Z′ = 2). The structure is governed by Cl⋯Cl and Cl⋯H interactions and the …
High-pressurein-situcrystallization, structure and phase transitions in 1,2-dichloroethane
AbstractThe single crystal of 1,2-dichloroethane, C2H4Cl2wasin-situcrystallized in a Merrill-Bassett diamond-anvil cell, and its structure determined at 0.7 GPa and 280 K. The crystals are monoclinic, space groupP21/c. The C2H4Cl2molecules in thes-transconformation are located at the inversion centers. The —H2C—CH2—ethylene group is disordered in two sites, with equal occupancies, one rotated by 180° to the other about the Cl⋯Cl axis of the molecule. The crystal cohesion forces have been attributed mainly to Cl⋯Cl intermolecular interactions, and their role in the mechanism of the phase transition at 177 K has been analysed. It was found that the order-disorder phase transition in the struc…
Crystalline gas of 1,1,1-trichloroethane
Isobaric freezing of 1,1,1-trichloroethane yields crystals where all the intermolecular contacts are much longer than the sums of the van der Waals radii and only in the structure compressed to ca. 1.2 GPa do the first Cl⋯Cl contacts become commensurate with this sum. This sheds new light on the range of intermolecular interactions that are capable of controlling molecular re-orientation and arrangement.
Chemistry of density : extension and structural origin of Carnelley's rule in chloroethanes
Low-density liquids and solids, with all intermolecular contacts longer than the sum of van der Waals radii, are formed by all ethanes chlorinated at one locant: CH2ClCH3, CHCl2CH3 and CCl3CH3. The concepts of molecular symmetry described by Carnelley and that of point groups have been compared. Carnelley's rule, when applied to liquid and solid chloroethanes clearly reveals the density dependence on the presence of intermolecular Cl⋯Cl and H⋯Cl short contacts, or their absence due to steric hindrances of overcrowded substituents. At 2.62 GPa, CH2ClCH3 freezes directly into phase II, with molecules arranged into layers with short Cl⋯Cl, H⋯Cl and H⋯H contacts. Only for CH2ClCH3, both the low…
Halogen...halogen interactions in pressure-frozen ortho- and meta-dichlorobenzene isomers.
Isomers 1,2-dichlorobenzene (o-DCB) and 1,3-dichlorobenzene (m-DCB) were high-pressure frozen in-situ in a Merrill–Bassett diamond–anvil cell and their structures determined at room temperature and at 0.18 (5) GPa for o-DCB, and 0.17 (5) GPa for m-DCB by single-crystal X-ray diffraction. The patterns of halogen...halogen intermolecular interactions in these structures can be considered to be the main cohesive forces responsible for the molecular arrangements in these crystals. The molecular packing of dichlorobenzene isomers, including three polymorphs of 1,4-dichlorobenzene (p-DCB), have been compared and relations between their molecular symmetry, packing arrangements, intermolecular inte…
In-situ pressure crystallization and X-ray diffraction study of 1,1,2,2-tetrachloroethane at 0.5 GPa
Abstract 1,1,2,2-Tetrachloroethane, C2H2Cl4 (denoted TCE, m.p. 230 K) has been in-situ pressure crystallized in a Merrill-Bassett diamond-anvil cell, and its structure has been determined at 0.5 GPa and 295 K from the single-crystal X-ray diffraction data. TCE crystallizes in the monoclinic space group P21 /c with the molecules located at the inversion centers. The molecules are in the s-trans conformation, while they assume the gauche conformation in the crystal obtained by cooling. This implies that a phase transition may exist between the low-temperature and high-pressure phases of TCE. In the high-pressure phase the HC–CH moiety of the C2H2Cl4 molecule is disordered in two sites, one re…
1,1-Dichloroethane: a molecular crystal structure without van der Waals contacts?
Isochoric and isobaric freezing of 1,1-dichloroethane, CH3CHCl2, mp = 176.19 K, yielded the orthorhombic structure, space group Pnma, with the fully ordered molecules, in the staggered conformation, located on mirror planes. The CH3CHCl2 ambient-pressure (0.1 MPa) structures were determined at 160 and 100 K, whereas the 295 K high-pressure structures were determined at 0.59 and 1.51 GPa. At 0.1 MPa, all intermolecular distances are considerably longer than the sums of the van der Waals radii, and only a pressure of about 1.5 GPa squeezed the Cl···Cl and Cl···H contacts to distances commensurate with these sums. The exceptionally large difference between the melting points of isomeric 1,1- a…
Pressure-Stabilized Solvates of Xylazine Hydrochloride
High pressure strongly favors the highest-density polymorph Z of active pharmaceutical ingredient 2-(2,6-xylidino)-5,6-dihydro-4H-1,3-thiazine hydrochloride (xylazine hydrochloride, XylHCl) up to about 0.1 GPa only, but still higher pressure destabilizes this structure. Above 0.1 GPa, XylHCl preferentially crystallizes as solvates with CH2Cl2, CHCl3, or (CH3)2CHOH depending on the solvent used. However, when XylHCl·H2O is dissolved in any of these solvents, the high-pressure crystallizations yield the hydrate XylHCl·H2O only. The single crystals of the CH2Cl2, CHCl3, and (CH3)2CHOH solvates could be grown in situ in a diamond anvil cell, which allowed their structure determination from the …
Halogen and hydrogen bonds in compressed pentachloroethane
In pentachloroethane, C2HCl5, high pressure initially strongly compresses the C–H⋯Cl bonds in phase I; however, in phase II which is stable above 0.62 GPa the role of hydrogen bonds is diminished and molecular aggregation is dominated by halogen bonds Cl⋯Cl. Both phases have been determined by X-ray diffraction and the phase diagram of C2HCl5 has been outlined. The transition between phases I and II retains some relation between their structures and reduces the symmetry from class mmm (space group Pnma) to 2/m (space group P21/n11). The discontinuous transition, with the shear strain exceeding 21°, is so strong that its progress can be visually observed even for powdered samples. The single…
Conformational polymorphs of 1,1,2,2-tetrachloroethane: pressure vs. temperature.
Directional Cl···Cl type I and II interactions govern the low-density aggregation of 1,1,2,2-tetrachloroethane molecules in synclinal conformation in the crystalline state at low temperature, whereas the dense molecular packing in high-pressure is achieved for the antiperiplanar conformers and electrostatically less favored Cl···Cl contacts. The mechanism of transformation between loose and dense associations involves the collapse of Cl···Cl contacts and conformational conversion.
Energetics of conformational conversion between 1,1,2-trichloroethane polymorphs
Pressure-induced transformations between gauche-, gauche+ and transoid conformations have been evidenced by X-ray single-crystal diffraction for 1,1,2-trichloroethane, and the energies of intermolecular interactions, conformational conversion, and the latent heat have been determined.
Properties and interactions – melting point of tribromobenzene isomers
The melting points of tribromobenzene isomers are correlated with the number, nature and distribution of intermolecular interactions in their structures.
Loose crystals engineered by mismatched halogen bonds in hexachloroethane
Distortions of the directional requirements in halogen⋯halogen contacts between hexachloroethane (HCE), C2Cl6, molecules lead to a loose crystal under ambient conditions. Single-crystal X-ray diffraction shows that the orthorhombic HCE phase of space group Pnma, with the molecules in the staggered conformation, extends at least from 85 to 305 K and from 0.1 MPa to 5.42 GPa. At ambient pressure, all intermolecular distances are longer than the sum of van der Waals radii, reached only at the pressure of ca. 1.2 GPa.
CCDC 1454091: Experimental Crystal Structure Determination
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CCDC 1454081: Experimental Crystal Structure Determination
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CCDC 1582519: Experimental Crystal Structure Determination
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CCDC 1028850: Experimental Crystal Structure Determination
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CCDC 1582517: Experimental Crystal Structure Determination
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CCDC 1477289: Experimental Crystal Structure Determination
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CCDC 1582518: Experimental Crystal Structure Determination
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CCDC 1028853: Experimental Crystal Structure Determination
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CCDC 1454078: Experimental Crystal Structure Determination
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CCDC 1454087: Experimental Crystal Structure Determination
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CCDC 1582515: Experimental Crystal Structure Determination
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CCDC 1477285: Experimental Crystal Structure Determination
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CCDC 1454090: Experimental Crystal Structure Determination
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CCDC 1028851: Experimental Crystal Structure Determination
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CCDC 1454088: Experimental Crystal Structure Determination
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CCDC 1454089: Experimental Crystal Structure Determination
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CCDC 1582521: Experimental Crystal Structure Determination
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CCDC 1454079: Experimental Crystal Structure Determination
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CCDC 1454080: Experimental Crystal Structure Determination
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CCDC 1477287: Experimental Crystal Structure Determination
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CCDC 1582516: Experimental Crystal Structure Determination
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CCDC 1454085: Experimental Crystal Structure Determination
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CCDC 1454086: Experimental Crystal Structure Determination
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CCDC 1454084: Experimental Crystal Structure Determination
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CCDC 1582520: Experimental Crystal Structure Determination
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CCDC 1477286: Experimental Crystal Structure Determination
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CCDC 1028852: Experimental Crystal Structure Determination
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CCDC 1477284: Experimental Crystal Structure Determination
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CCDC 1454082: Experimental Crystal Structure Determination
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CCDC 1477288: Experimental Crystal Structure Determination
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CCDC 1454083: Experimental Crystal Structure Determination
Related Article: Anna Olejniczak, Kristine Krukle-Berzina, Andrzej Katrusiak|2016|Cryst.Growth Des.|16|3756|doi:10.1021/acs.cgd.6b00264