2022/23 Undergraduate Module Catalogue
CHEM2121 Organic Chemistry: Conformation, Configuration & Reactivity
10 creditsClass Size: 140
Module manager: Prof Steve Marsden
Taught: Semester 1 (Sep to Jan) View Timetable
Year running 2022/23
Pre-requisite qualificationsLevel 1 Chemistry or equivalent
Module replacesCHEM2141 Introduction to Organic Synthesis
This module is not approved as a discovery module
Module summaryThis module will examine how the shapes of organic molecules impact their physical properties and reactivity. This will encompass both the relative and absolute arrangement of the atoms defined by bonding (configuration) as well as the shapes that molecules adopt by rotation/torsion about bonds (conformation).It will also introduce enols/enolates as reactive carbon-centred nucleophiles for the formation of carbon-heteroatom and carbon-carbon bonds, and their applications in the synthesis of complex organic molecules.
Objectives- To understand the meaning and significance of conformation and configuration of organic compounds, and their influence on organic structure/reactivity (stereoelectronic effects);
- To introduce the physical organic concepts that allow the outcome of organic reactions to be rationalised and understood;
- Knowledge of key reactions in organic chemistry including substitution reactions of heterocycles, reactions involving enols and enolates.
Students will be able to:
1. draw appropriate representations of the conformations of cyclic and acyclic molecules and rationalise the relative energies of these in terms of favourable/unfavourable interactions;
2. rationalise the stereochemical and/or regiochemical outcome of reactions (e.g. substitution, elimination, ring-opening, rearrangement) by considering the spatial arrangement of relevant orbitals (stereoelectronics);
3. recognise, identify and correctly label different stereoisomeric molecules (enantiomers, diastereomers);
4. rationalise the relative rates of ring-closure of acyclic molecules in terms of balancing enthalpic and entropic contributions;
5. identify and/or draw enol/enolate forms of carbonyl compounds and to predict equilibrium concentrations of enolates from pKa data;
6. write appropriate mechanisms for the reactions of enols and enolates with appropriate electrophiles and rationalise the outcome of the reactions in terms of kinetic and thermodynamic parameters;
7. rationalise the stereochemical outcome of enolate formation and aldol reactions in terms of well-defined six-membered transition state diagrams.
Students will gain skills in: identification and characterisation of stereoisomeric molecules; understanding and predicting the three-dimensional shape of simple organic molecules; rationalising and predicting reaction outcomes through consideration of the spatial arrangement of reacting orbitals; identifying appropriate conditions for the generation of enols or enolates as reactive carbon-centred nucleophiles for organic synthesis; predicting and rationalising the outcome of chemical reactions of enols/enolates with heteroatom- and carbon-centred electrophiles.
STEREOCHEMISTRY AND CONFORMATIONAL ANALYSIS
The difference between conformation and configuration.
Conformation: Newman projections. Torsional strain. Angle strain and transannular strain in small and medium rings. Chair conformations of 6-rings. 1,3-Diaxial interactions to determine conformation. Conformational analysis of cyclohexenes and cyclohexanonones. Use of NMR in determining favoured conformations. Entropic and enthalpic contributions in thermodynamic control of ring size and (kinetic) ring formation.
Stereochemistry: Enantiomers are non-superimposable mirror image compounds. Types of chirality: stereogenic centres, axial chirality (allenes; biaryl compounds – atropisomers), planar chirality .The difference between enantiomers and diastereoisomers. Alkene geometry. Homotopic, enantiotopic and diastereotopic groups - the substitution test. Diastereotopic groups can be distinguished in NMR spectra.
Revision of SN2 in terms of sigma orbital - the overlap of filled and empty orbitals. Sigma orbitals in other reactions in which a bond is broken; E2. Use of Newman projections. The anomeric effect: kinetic and thermodynamic aspects. Epoxides and iodonium ions etc. have similar conformations to the parent alkenes. Transdiaxial opening of epoxides, iodonium ions etc; iodolactonisation. Suprafacial rearrangements (retention of configuration at the migratory origin, discussion in terms of orbitals). The Wittig reaction: explanation of the stereochemical aspects using Newman projections.
ENOLS AND ENOLATES
Introduction to enols and enolates. Enolisation under base and acidic conditions. Enolate formation; revision of pKa and choice of base. Kinetic and thermodynamic enolate formation. Introduction to enamines. Reactions of enols and enolates: bromination, alkylation, aldol reaction (inter- and intramolecular), Mannich reaction, Claisen condensation/Dieckmann cyclisation, Michael additions. Introduction to six-membered transition states (Zimmerman-Traxler model and enolate formation); diastereomeric enolates give diastereomeric aldol adducts.
|Independent online learning hours
|Private study hours
|Total Contact hours
|Total hours (100hr per 10 credits)
Private study78h (including 15h online study - quizzes, note-taking, additional reading)
Opportunities for Formative FeedbackShort online MCQs. Online workshops with in-class feedback'
Methods of assessment
|% of formal assessment
|Open Book exam
|Total percentage (Assessment Exams)
Normally resits will be assessed by the same methodology as the first attempt, unless otherwise stated
Reading listThe reading list is available from the Library website
Last updated: 07/07/2022 11:10:16
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