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7.4 CHIRALITY: handedness in Molecules

7.4 CHIRALITY: handedness in Molecules. Many molecules exist in “right-handed” and “left-handed forms. Mirror Images. A MIRROR IMAGE IS A REFLECTION. Your left hand is a “mirror image” of your right hand. Some mirror images are ‘superimposable’. Some mirror images are

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7.4 CHIRALITY: handedness in Molecules

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  1. 7.4 CHIRALITY: handedness in Molecules Many molecules exist in “right-handed” and “left-handed forms

  2. Mirror Images

  3. A MIRROR IMAGE IS A REFLECTION

  4. Your left hand is a “mirror image” of your right hand

  5. Some mirror images are ‘superimposable’

  6. Some mirror images are not superimposable (‘nonsuperimposable’) Nonsuperimposable mirror images have ‘right –handed’ and ‘left-handed’ forms… stereoisomers.

  7. Molecules have mirror images too.

  8. Chirality Pronounced ‘kye-rality’ like reality

  9. IN A MOLECULE… A carbon that is tetrahedral (sp3) and has four different groups attached is called... a “chiral center”

  10. H F Cl Br Another name is …. stereocenter

  11. C l F H B r A molecule with one stereocenter is ‘chiral’.

  12. C l C l F F H H B r B r C l B r H F It’s mirror images are not superimposable mirror rotate this molecule is chiral note that the fluorine and bromine are interchanged in the mirror image non-superimposable mirror images do interchanges in class

  13. Practice with models • Make a molecule with a stereocenter • Make it’s mirror image • Try to superimpose them Are they the same or different molecules? • Interchange two of the atoms. • Now try to superimpose them. Are they the same or different molecules?

  14. PLANES OF SYMMETRY

  15. A SYMMETRIC OBJECT HAS A PLANE OF SYMMETRY - ALSO CALLED A MIRROR PLANE plane of symmetry mirror plane

  16. IF AN OBJECT HAS A PLANE OF SYMMETRY, ITS MIRROR IMAGE WILL BE IDENTICAL

  17. IDENTICAL MIRROR IMAGES WILL SUPERIMPOSE (MATCH EXACTLY WHEN PLACED ON TOP OF EACH OTHER) IF AN OBJECT HAS AN IDENTICAL MIRROR IMAGE IT’S………. ‘ACHIRAL’

  18. CHIRAL An object without symmetry is no symmetry The mirror image of a chiral object is different and will not superimpose on the original object.

  19. WHICH OBJECTS ARE SYMMETRIC ? WHICH OBJECTS ARE ACHIRAL ? (mirror image is identical) sym (outside) achiral sym achiral sym sym achiral achiral

  20. ACHIRAL The plane of the paper is a plane of symmetry F F C l C l B r B r C l C l TWO IDENTICAL GROUPS RENDERS A TETRAHEDRAL CARBON ACHIRAL

  21. C l C l B r C l B r C l TWO VIEWS OF THE PLANE OF SYMMETRY plane of symmetry F F side view edge view

  22. Cl Br ACHIRAL A CARBON ATOM WITH THREE SIMILAR GROUPS IS ALSO ACHIRAL …..

  23. C l C l C l C l B r C l B r C l plane of symmetry side view edge view

  24. The whole secret of the study of nature lies in learning how to use ones eye. George Sand, author

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