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Crystal Structures and Phase Transitions of 3-Chloro-2,2-bis(chloromethyl)propionic Acid-1 and 1,3-Dichloro-2,2-dimethylpropane

Astrid Götze ; Department of Materials Science, Fachgebiet Strukturforschung, University of Technology Darmstadt, Petersenstr. 23, 64287 Darmstadt, Germany
Claudia Buhrmester ; Department of Materials Science, Fachgebiet Strukturforschung, University of Technology Darmstadt, Petersenstr. 23, 64287 Darmstadt, Germany
Ingrid Svoboda ; Department of Materials Science, Fachgebiet Strukturforschung, University of Technology Darmstadt, Petersenstr. 23, 64287 Darmstadt, Germany
Hartmut Fuess ; Department of Materials Science, Fachgebiet Strukturforschung, University of Technology Darmstadt, Petersenstr. 23, 64287 Darmstadt, Germany

Sažetak

The crystal structure of 3-chloro-2,2-bis(chloromethyl)propionic acid-1 was determined from single crystal data. The compound crystallizes in the acentric monoclinic space group P21. Lattice constants at T = 304 K are a = 6.961(1) Å, b = 9.979(2) Å, c = 12.0569(3) Å, b = 94.01(2)°. Structure refinement on 1736 independent reflections yielded R = 0.041. Two molecules are interconnected by hydrogen bridges to form dimers. Thermal analysis and temperature dependent X-ray and IR-measurements gave no indication of a phase transition in the range 150 K < T < 384 K. An order-disorder phase transition was detected for 1,3-dichloro-2,2-dimethylpropane at T_I→II = 194.3 K, with a plastic cubic phase in the range 194.3 K < T < 259.1 K. The lattice constant in space group Fm3m is a = 9.24 Å at 220 K with a thermal expansion coefficient a(200 K) = 2.6769 x 10–4 K–1. The entropy at the melting point Tm = 259.1 K and at the solid-solid phase transition T_I→II = 194.3 K is rather low giving strong evidence of a plastic phase. Powder X-ray diffraction pattern in the ordered phase at T = 160 K gave indication of monoclinic symmetry with a = 12.27 Å, b = 10.86 Å, c = 10.68 Å, b = 111.8°. Temperature dependent infrared measurements revealed the conformation of the molecule.

Ključne riječi

ODIC phases; order-disorder; thermoanalysis; crystal structure; pivalic acid

Hrčak ID:

132183

URI

https://hrcak.srce.hr/132183

Datum izdavanja:

1.9.1999.

Posjeta: 1.252 *