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The University of Southampton

CHEM2001 Organic Reaction Mechanisms

Module Overview

Aims and Objectives

Learning Outcomes

Learning Outcomes

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.
  • Perform multi-step syntheses under normal or inert conditions using standard or microwave heating, or cooling baths using cardice;
  • Monitor reactions by TLC;
  • Separate by-products and to purify products by various methods (liquid-liquid extraction, inclusive of pH-manipulations during extractive work-up, column chromatography, recrystallisation, trituration)
  • Safely handle flammable, corrosive, harmful, toxic and pyrophoric substances;
  • Evaluate green credentials of reactions;
  • Analyse the outcome of reactions via melting point, spectroscopic methods (1H-, 13C-NMR and DEPT experiments), IR (ATR) and mass spectrometry (ES and EI ionisation);
  • Maintain a laboratory notebook and to write a formal report using appropriate text and chemistry artwork software;
  • Present results formally and informally, individually or as a group;
  • Suggest mechanisms for the reactions performed and to draw these using curly arrows.
  • Generate full COSHH assessments;
  • Design experiments to probe mechanisms, particularly using stereochemistry or isotopic labelling.
  • Recognise neighboring group participation and rearrangement reactions.
  • Use analytical 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.


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 π-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 in multiple substitution reactions. Chemistry of Enols and Enolates • Enolisation: revision of general aspects of carbonyl chemistry, including acid-base equilibria and pKa. • Enols and enolate ions as reactive intermediates – structure, stability and methods of formation, regioselectivity of deprotonation (kinetic vs thermodynamic control), general aspects of enolate ion reactivity. • Using enolates as reactive substrates. Enolate alkylation. Aldol addition and condensation, including intramolecular and crossed versions. Claisen and Dieckmann condensation, Mannich. • Silyl enol ethers – preparation and reactivity including substrate selectivity through control of reaction conditions. • Dicarbonyl compounds: synthesis, reactivity and use as substrates in enolate chemistry; decarboxylation and Knoevenagel condensation. Nucleophilic Addition to π-Systems • Conjugate addition of carbanions (Grignard), alcohols, thiols, amines, enolates, cyanide to alpha,beta-unsaturated carbonyl compounds. Discussion of factors affecting 1,2 vs 1,4-addition • Nucleophilic aromatic substitution. Addition-elimination and benzyne mechanisms. Practical Completion of three practical experiments and associated reports covering a range of topics and skills in organic chemistry including the application of a variety of fundamental techniques and methodologies (including spectroscopy) to the synthesis and analysis of molecules and materials; the ability to analyse experimental data to provide an explanation for the observed experimental outcomes; understanding the importance of experimental safety and time management. There is also a workshop on NMR assignment to reinforce 1st year work.

Learning and Teaching

Teaching and learning methods

Lectures, Seminars, tutorials, lab practical classes Practical hours includes pre-laboratory e-learning. Preparation for scheduled sessions hours includes other independent study.

Practical classes and workshops29
Preparation for scheduled sessions57
Completion of assessment task24
Total study time150

Resources & Reading list

M. Hesse, H. Meier, B. Zeeh (2008). Spectroscopic Methods in Organic Chemistry. 

J Clayden, N Greeves, S Warren (2012). Organic Chemistry. 

D Williams, I. Flemming (2008). Spectroscopic Methods in Organic Chemistry. 


Assessment Strategy

All absences from practical sessions must be validated and unexcused absences will result in failure of the module. Repeat year externally: allowed if practical attendance criteria has been met. The practical marks are retained, the theory assessment is exam only. Repeat year internally: note that practical may be reassessed by resubmission of reports or repeated.


MethodPercentage contribution
Assessed Tutorials 10%
Final Assessment   (2 hours) 65%
Lab proficiency 
Practical write-ups 25%


MethodPercentage contribution
Final Assessment   (2 hours) 100%
Lab proficiency 

Repeat Information

Repeat type: Internal & External

Linked modules

Pre-requisites: CHEM1031 AND CHEM1032

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