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Acta Cryst. (2014). A70, C964
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The study of multi-component crystals, as well as the phenomenon of polymorphism, both have relevance to crystal engineering. Obtaining a specific polymorph is crucial as different polymorphs usually exhibit different physical and chemical properties and often the origin of this behaviour is unknown. This is especially important in the pharmaceutical industry. Herein, we present results of comparative studies of an analgesic drug, ethenzamide and its co-crystals with saccharin. The co-crystalisation of ethenzamide (2-ethoxybenzamide, EA) with saccharin (1,1-dioxo-,1,2-benzothiazol-3-one, SAC) with a 1:1 stoichiometric ratio resulted in two polymorphic forms of the co-crystal. Form I crystallises in the triclinic P-1 space group, whereas form II crystallises in monoclinic space group P21/n. Previous crystal structure analyses on forms I and II revealed that in both polymorphs the primary carboxy-amide-imide heterosynthon is the same, however the secondary level of interactions which extends the hydrogen bond network is different. Form I consists of extended linear tapes via N-H···O hydrogen bonds, whereas form II is composed of stacks of tetrameric motifs including N-H···O hydrogen bonds and C-H···O interactions. These two forms of EA-SAC can be classified as synthon polymorphs at a secondary level of hydrogen bonding [1]. In our approach an accurate, high resolution charge density distribution analysis has been carried out to obtain greater insight into the electronic structures of both types of the EA-SAC co-crystals and relate differences in electronic distribution with their polymorphic behaviour. To describe the nature and role of inter and intra-molecular interactions in a quantitative manner, the Hansen-Coppens formalism [2] and Bader's AIM theory [3] approach have been applied.

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Acta Cryst. (2014). A70, C1276
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Teaching of laboratory-based chemistry in universities has barely evolved since its inception. Practical work is generally conducted in a highly structured, dedicated teaching laboratory environment or on a `student-as-apprentice' basis in an active research laboratory. Exposure to crystallography as an undergraduate is generally limited to theoretical lecture-based courses, with little or no practical experience, despite the fact that training in the use of expensive research-based instruments is becoming a necessity of modern science. We present a course based around the solid-state structural chemistry of a molecular polymorphic system, delivered to third year undergraduates (70 students) at the University of Southampton which contains numerous novel features: 1) Students work in pairs (maximum group size of 8). 2) It is a `hands-on' experience for every participant, involving single crystal and powder diffractometers (Rigaku XtaLab mini and MiniFlex benchtop systems) dedicated to educational activities. 3) It is a student-led activity, designed as an `advanced practical' providing a taste of the research experience. 4) Laboratory manuals are available to students via an Electronic Laboratory Notebook (ELN) system. 5) Plans, experimental enactments, observations and conclusions are recorded by students in the ELN (directly linked to the manual sections). 6) Feedback and assessment is delivered through the ELN by directly linking instructor comments to the student ELN record. The experiment comprises about 15 manual sections in the LabTrove ELN system, which has a similar design to a blog, enabling student comments and assessor feedback to be linked to these sections. This talk will outline the design of the experiment and instruments involved, the mode and logistics of delivery, and will discuss the evaluation of its impact on student learning by analysis of feedback questionnaires.
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