Transcript Organic Chemistry

Full structure
H
HH H C
H H C H
H
C
C
H C
C H
H
C
O
H
C
C
C
H H
H
H
H H
H H
H H
H
H C
C
C
C
H H H
H
C
C
C
H H C
H
H
H
H
C
C
C
C
H
H
H C H
H
H C
H
C H C
H H
C H
H
How do we simplify this?
• we need a set of rules that is consistent
• rules should be based on simple (even
obvious) criteria
• rules need to make it easier to see the
important parts of the molecule
There are three kinds of atoms
• Carbon — C
• Hydrogen — H
• Heteroatoms — everything else in the
periodic table
Basis for structure-simplifying
rules
• Every organic compound has carbon
– let’s omit the symbol for carbon
• means that the reader will need to know that we
don’t explicitly show carbon atoms any more
H
H H H H H H
H
H C
C
C
C
H
H H C
H
C
C
H HC
H
H H H
H C
C
C
C
HHH C
H
H
H
H C
H
H HC H
H C
C H C C H
H C
C H C H
H H
H
C
C
C H
O H C
C H
H H
H
H H
H
HHH
H H
is simplified to
H
H
H
H
H H H
H
H
H
H
O H
H H
H
H
H H
H H
H
H
H H H
H H
H
H
H
H
H H H
H
H
H
H
Next…
• Hydrogen is almost always present in an organic
compound
• Carbon-hydrogen bonds are usually unreactive, so
they seldom participate in any reactions
– let’s omit the hydrogen atoms bonded to carbon
• the reader will now need to know that any hydrogen atom
bonded to carbon will not show up in the structural formula as
drawn.
H H
H
HHH
H H
H
H
H H
H H H
H
H
H
H
O H
H H
H
H
H H
H H
H
H
H
H
H H H
H H
H
H
H
H
H H H
H
H
is simplified to
H
O
Going the other way: Rules for
interpreting organic structures
• Carbon is always present in every organic
molecule
– assume carbon is at each end of every bond
unless another atom is explicitly specified.
• means that there is a carbon atom at the end of every
line
H
O
C
becomes
C
H
O
C
C
C
C
C
C
C
C
C
C
C
C
C C
C C
C
C
C
C
C
C
C
C
C
Rules for interpreting organic
structures (continued)
• Carbon is always tetravalent — it always has four
covalent bonds
• Hydrogen atoms bonded to carbon atoms are
usually omitted from the structure
– any carbons with less than four explicitly specified
bonds carry hydrogen atoms
– there must be enough hydrogen atoms to make up all
four bonds to carbon for every carbon atom in the
molecule
C
C
H
O
C
C
C
C
C
C
C
C
C
C
C
C
C
C C
C C
C
C
C
C
C
C
C
C
becomes
H
HH H C
H H C H
H
C
C
H C
C H
H
C
O
H
C
C
C
H H
H
H
H H
H H
H H
H
H C
C
C
C
H H H
H
C
C
C
H H C
H
H
H H
C
C
C
C
H
H
H
H C
H
H C
H
C H C
H H
C H
H
What is more visible in this
representation?
• The substructures of the molecule
– 4 rings
– a tail hanging off one end
H
O
• the chemically reactive parts of the molecule
– the —O—H group
– the carbon-carbon double bond
What advantages do we gain?
• we get a better idea of the actual shape of
the molecule
• we get a better focus on the important parts
of the molecule
• the drawing is much less busy and simpler
to interpret — we can see the functional
groups easily
Functional Groups
• Most of an organic compound does not react
• Carbon-carbon and carbon-hydrogen single bonds almost
never react
• Carbon-carbon multiple bonds react with many reagents
• Heteroatoms represent sites of reactivity in an organic
molecule.
• The reactive part of a molecule is called the
FUNCTIONAL GROUP
– multiple bonds are functional groups
– heteroatoms are functional groups
– C-C and C-H single bonds are not functional groups
So what does this molecule really
look like?
Three different kinds of
representation of the “real”
cholesterol molecule
Make-up of simple organic
compounds
• The compound
consists of two parts
R OH
alcohols
– the functional group
• site of reactivity
• “where the action is”
R C N
nitriles
O
R
C
R C C R
alkynes
O
H
aldehydes
R
C
O
R
R
ketones
C
OR
esters
– “Vegas Strip”
– the “rest of the
molecule”
• designated by “R”
R
R
C
C
R
R
R
R
alkenes
aromatic rings
N
R
amines