Structural studies by X-ray and electron diffraction with special reference to polymer precursors

• Main Author: Trickey, Peter
• Published: University of Edinburgh 1995
• Subjects: 543.5
• Online Access: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.663040

The gas-phase and solid-phase structures of <I>trans-</I>3,4-dibromotetrahydrothiophene-1,1-dioxide were determined and are compared with the <I>ab initio </I>study in chapter 3, as part of a study into the effect of remote SO<SUB>2</SUB> groups on the bromination of alkenes. The ring puckering parameters show that the in solid phase it adopts an envelope conformation, whilst in the gas phase it adopts a twist conformation. In the solid phase the bromine atoms occupy positions <I>equatorial </I>to the ring, whereas in the gas phase the optimum fit is for a mixture of <I>axial </I>and <I>equatorial </I>conformers. The tetranitriles are poly(ether imide) precursors, and poly(ether imides) are important as new gas separation membranes. Chapter 4 is an introduction to the work carried out on the tetranitriles with a review of the gas permeability data on poly(ether imides) in the literature. The structures of the tetranitriles were studied in an attempt to find a structure-property relationship with the gas-separation properties of the poly(ether imides). Chapter 5 describes the crystal structure determinations of the tetranitriles, whilst chapters 6 and 7 describe the molecular geometries and crystal packing of the tetranitriles. The analysis of the crystal structures of the tetranitriles reveals that the intermolecular interactions between aromatic rings is important in the packing schemes adopted by the tetranitriles. The results show how the packing is affected by the presence and position of various structural features. Chapter 8 is an analysis of the holes found in the crystal structures of the tetranitriles and whether these are related to pores in the poly(ether imides). The results give an insight into the causes of pores within the poly(ether imides). The crystal structures of a series of oxazolidin-2-one chiral auxiliaries based on derivatives of D-fructose are analyzed in chapter 9 to investigate if there is molecular self-recognition by the parent group. Chiral auxiliaries are used in asymmetric synthesis. They impact asymmetry to the diastereomers formed, to aid in their separation by crystallization. The results show that the parent molecule does not recognize itself during crystallization, thus they are likely to be useful chiral auxiliaries.