CHEM2018 Intermediate Organic Chemistry I
The aim of this module is to provide a basis for future studies in chemistry and allied subjects. Students select two areas of Chemistry from Inorganic, Organic, and Physical Chemistry according to the needs of their programme of study. Please consult with the leader of your programme or your personal academic tutor in deciding which two modules to follow. Note that this module is not available for students enrolled in any of the Chemistry degree programmes.
Aims and Objectives
The aim of this component of the course is to provide students with the tools to describe and work out reaction mechanisms using the ‘curly arrow’ notation. Appreciation of the relative stabilities and reactivities of the reactive intermediates (Carbenium ions, Carbanions, Radicals and Carbenes) are important. The SN2, SN1, E1, E2 and E1CB mechanisms are reinforced including solvent effects, basicity and nucleophilicity, and steric and electronc effects of substrate structure on rates of reaction. Neighbouring group participation and rearrangements are introduced together woth basic radical and carbene chemisty. Stability of carbanions is particualry developed in the context of enolate chemistry including condensation and cyclisation reactions. Electrophilic addition to alkenes and aromatic sytems is developed, alongside nucleophilic addition to alkenes and aromatic substitution.
Having successfully completed this module you will be able to:
- Use curly arrow reaction mechanisms and a knowledge of the relative stability of intermediates to predict and / or account for the products of reactions.
- Design experiments to probe mechanisms, particularly using stereochemistry or isotopic labelling.
- Recognise neighboring group participation and rearrangement reactions.
- Use spectroscopic information to assign or confirm structures.
- Combine reactions to achieve simple synthesis of target molecules.
- Predict the reactivity and regiochemistry of electrohilic addition to alkenes and aromatic systems.
- Predict outcomes and draw mechanisms for reactions of carbonyl compounds (condensations, additions, cyclisations).
- Predict outcomes and draw mechanisms for nucleophilic addition to alkenes and nucleophilic aromatic substitution reactions.
- Appreciate the scope and limitations of nucleophilic additions to pi-systems.
Spectroscopy. • Proton NMR: Chemical shifts and how they arise. Inductive and anisotropic effects. • Use and limitations of prediction equations. Sizes of coupling constants including • Karplus relationship, long range couplings, and how they arise. • Carbon-13 chemical shifts and DEPT. Mechanisms and reactive intermediates • SN2 mechanism. Orbital picture. Transition state. Inversion of configuration. Leaving groups. Nucleophiles. Steric hindrance. Activation by adjacent pi-systems; Dipolar aprotic solvents. • SN1 mechanism. Carbenium ions – relative stability of a wide range (delocalisation, stabilisation by lone pairs on adjacent heteroatoms; ‘hyperconjugation’, stabilisation of tertiary carbenium ions by release of steric strain). Importance of polar protic solvents. Loss of stereochemistry. • Neighbouring Group participation. Rearrangements (Wagner Meerwein; Pinacol; Baeyer-Villiger; Beckmann; Benzylic acid and semi-benzylic) with particular emphasis on steric requirements. • E1, E2, and E1CB elimination mechanisms. Kinetic isotope effect. • Neutral reactive intermediates: Carbenes and Radicals (brief introduction) Electrophilic Addition to p-Systems • Electrophilic addition to alkenes, regioselectivity and stereoselectivity issues of typical reactions including hydrogen halide addition (Markovnikov), halogen addition, bromolactonisation and epoxidation. Hydrogen halide addition to 1,3-dienes, including kinetic vs thermodynamic control. • Electrophilic aromatic substitution of benzene and substituted benzene derivatives; examples (including halogenation, sulfonation, nitration, Friedel-Crafts acylation and alkylation), mechanism, and substituent effects upon rate and regioselectivity. Carbanions • Structure, stability and methods of formation. Anion-driven rearrangements. Revision of acid-base equilibria and pKa, basicity and pKa(H). Chemistry of Enols and Enolates • Enolisation. • Enols and enolate ions as reactive intermediates – enolate formation by deprotonation, regioselectivity of deprotonation. Aldol addition and condensation, including intramolecular and crossed versions. Claisen and Dieckmann condensation, Knoevenagel. Enolate alkylation. • Silyl enol ethers – preparation and reactivity. Nucleophilic Addition to p-Systems • Conjugate addition of alcohols, thiols, amines, enolates, cyanide to alpha,beta-unsaturated carbonyl compounds. Discussion of factors affecting 1,2 vs 1,4-addition, including kinetic and thermodynamically controlled cyanide addition. • Nucleophilic aromatic substitution. Addition-elimination and benzyne mechanisms.
Learning and Teaching
Teaching and learning methods
Lectures, problem-solving Seminars with group working and tutor support
|Preparation for scheduled sessions||35|
|Total study time||75|
Resources & Reading list
Ogden. Introduction to Molecular Symmetry.
Housecroft and Sharpe. Inorganic Chemistry.
Brisdon. Inorganic Spectroscopic Methods.
M. Hesse, H. Meier, B. Zeeh (2008). Methods in Organic Chemistry.
D Williams, I. Flemming (2008). Spectroscopic Methods in Organic Chemistry.
|Examination (2 hours)||100%|
|Examination (2 hours)||100%|