Organic Chemistry – Diagrams and Isomers

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Organic Chemistry Diagrams and Isomers

• Chemical Formula
• Structural Formula
• Isomers structural
• Isomers - geometrical

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Chemical Formula Revision

• Just a quick reminder
• Pb(NO3)2
• In organic chemistry, because we are dealing with
  non-metal compounds, we can also call them
  molecular formulae.

• Organic chemicals can be named in exactly the
  same ways but because the components can be
  rearranged in many different ways we need a bit
  more detail. For example C6H12O6 could be
  glucose or about 100 other chemicals depending on
  how it is arranged

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Structural Formula

• Structural formulae (many formula) show how the
  carbon atoms are arranged and what else they are
  attached to. There are two types of structural
  formulae
• Structural formula this is the normal way a
  structural formula is written. It shows every
  bond, represented as a line e.g.
• Condensed structural formula this version has
  the lines missing. It takes up less room, is
  easier to type, but it can get confusing if you
  have a complex organic molecule e.g. CH3CH2CHClCH3

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Isomers - Structural

• As mentioned earlier, two chemicals may have the
  same molecular formula but they may be two
  completely different chemicals. In the case we
  call them isomers.
• There are a number of different sorts of isomers.
  The first we will look at are structural isomers.
  
• Structural isomers have the same molecular
  formula but there atoms are arranged differently
  so that they have different structures.
• Lets take this chemical for example C6H14. We
  know it as hexane, but hexane can have many
  different structures

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Isomers Geometrical I

• Bonds can rotate freely meaning that an organic
  molecule, like an alkane, can bend an rotate
  forming many different types of shapes. But no
  matter what rotation the bonds undergo they are
  still the same molecule, with the same structure
• Double bonds cannot rotate freely. This mean that
  we can form molecules with the same chemical
  formulae that are almost identical
• Spot the differences (if any) in the four
  chemicals below

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Isomers Geometrical II

• In the previous example we had three chemicals
  that would have to be given the same name (1,2
  dichloro ethane). In fact two of those molecules
  were identical. But, there were two different
  types of 1,2 dichloro ethanes. One type had the
  chlorines on the same side, the other had them on
  opposite sides.
• This leads to how we name these geometrical
  isomers, once again with a prefix
• Different sides trans (like transport moves
  stuff to different ports)
• Same side cis (like .?)

trans 1,2 dichloro ethane
cis 1,2 dichloro ethane
trans 1,2 dichloro ethane
cis 1,2 dichloro ethane