| Unit 1: Aromaticity and the planarity of benzene |
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| To investigate the structural requirements for aromaticity. To understand the stability of benzene in terms of its molecular orbital description. To apply Huckels rule to predict whether or not certain compounds are aromatic. |
Visualize a series of benzene and cyclooctatetraene derivatives, measure and compare the carbon–carbon bond lengths and planarity of the structures. Relate structural characteristics to the number of π electrons. Use findings to predict whether or not certain compounds are aromatic. |
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| Unit 2: Ring strain and conformation |
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| To understand that angle strain can occur in cycloalkanes as a result of deviation from the ideal sp3 geometry and when neighbouring bonds are forced to be eclipsed (Pitzer strain). To be able to account for the conformations of three- to six-membered carbocycles in terms of the strain present. To explain why cyclohexane is essentially strain free. |
Calculate angle strain for a series of fully saturated planar carbocycles. Measure the actual angle strain in cyclohexane by analysing structural data. Plot and compare calculated angle strain for planar rings with that measured in actual compounds. Visualize three- to six-membered carbocycles and account for the observed conformations. |
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| Unit 3: Stereochemistry and chirality |
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| To recognize a stereogenic (chiral) centre in a molecule. To assign R and S configurations. To predict, identify and distinguish between enantiomers and diastereomers. To recognize a meso compound. To recognize other structural features that can give rise to chirality. |
Compare two crystal structures of alanine and describe their relationship. Identify basic structural features that give rise to chirality. Describe the configuration of chiral centres in given molecules. Visualize and understand the relationship between the structures of threonine, ephedrine and tartaric acid. Examine further structures and recognize other features that can give rise to chirality, e.g. quadrivalent and tervalent chiral atoms, restricted rotation, and helicity. |
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| Unit 4: VSEPR |
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| To investigate three-dimensional molecular shape. To understand factors that determine the preferred three-dimensional shape of specific molecules. To use the VSEPR model to predict three-dimensional molecular shape. |
Examine the structures of di-, tri- and tetrachloromercury; determine the main factors that control the geometry adopted. Observe effects of lone pairs on geometry by examining [XeF5]−, water and dibromodimethylselenium. Apply the VSEPR model to predict the geometry of given molecules. Compare predictions with crystal structures and comment on how closely the observed bond angles agree with the expected ideal values. |
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| Unit 5: Hapticity |
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| To investigate the concept of hapticity and learn its nomenclature. To examine the structural perturbations of ligands as a function of their hapticity. |
Visualize given CSD structures and investigate the different modes of metal–carbon bonding. Relate nomenclature to structural features. Examine a series of structures and identify the hapticity of the organometallic ligands. |
