1. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Isomerism University of Lincoln presentation

2. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Isomerism ISOMERS are compounds with the same molecular formula (but different arrangements of atoms)

3. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Types of Isomerism 1.Structural isomerism 2.Stereoisomerism Geometric (cis/trans) Optical

4. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 1. Structural isomerism

5. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Structural Isomerism C2H6OC2H6O These two compounds are structural isomers methoxymethane ethanol

6. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Structural Isomerism Structural isomers often have different chemical & physical properties o– m– p– –nitromethylbenzene

7. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Exercise Q What two compounds, with different functional groups, are isomers with the formula: C 3 H 6 O 2

8. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Answer A carboxylic acid An ester

9. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 2. Stereoisomerism a. Geometric isomerism

10. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Geometric Isomerism (cis/trans) If two compounds have the same formulae and the same structural framework, but differ in the spatial arrangement of different atoms or groups about a central atom

11. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Geometric Isomerism (cis/trans) or about a double bond,

12. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Geometric Isomerism (cis/trans) then the compounds are called GEOMETRIC ISOMERS –Cis– on the same side –Trans– on the opposite side

13. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Geometric Isomerism (cis/trans) [Pt(NH 3 ) 2 Cl 2 ] Cis–diamminedichloroplatinum(II) Trans–diamminedichloroplatinum(II)

14. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Geometric Isomerism (cis/trans) There is restricted rotation about a C=C double bond and the two isomers are not inter-convertible without first breaking the C=C bond Cis-but-2-ene Trans-but-2-ene

15. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Geometric isomerism helps you see! This reaction is the central feature of human vision 11-cis-retinal 11-trans-retinal 11 12 R R’ R’ 11 12 R CisTrans

16. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License 2. Stereoisomerism b. Optical isomerism

17. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Optical Isomerism Optical isomerism is caused by a lack of symmetry in a molecule’s structure so that the molecule and its mirror image are actually different –like a left hand and a right hand: They are non-superimposable

18. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License For example Nonsuperimposable mirror images Optical isomers are called ENANTIOMER S

19. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Enantiomers Labels L– and D– are given to two enantiomers to distinguish them from each other Only one optical isomer of DOPA called L-DOPA, is effective in the treatment of Parkinson’s disease

20. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Asymmetric Carbon A compound that is NOT SUPERIMPOSABLE on its mirror image is described as being CHIRAL Many chiral compounds contain an asymmetric carbon atom – a carbon atom with FOUR different groups attached

21. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License CHIRAL Carbon

22. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License For example – limonene LemonsOranges

23. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License For example – limonene LemonsOranges CHIRAL C

24. This work is licensed under a Creative Commons Attribution-Noncommercial-Share Alike 2.0 UK: England & Wales License Acknowledgements JISC HEA Centre for Educational Research and Development School of natural and applied sciences School of Journalism SirenFM http://tango.freedesktop.org