Organic Chemistry
The Chemistry of Carbon
Why call it Organic?
• Fewer than 200 years ago, it was thought that
only living organisms could synthesize carbon
compounds.
• So, they called carbon compounds “organic”
How can carbon form 4 bonds?
• Carbon is in the 4th group on the periodic table.
• This means carbon has 4 valence electrons.
• Carbon will want to bond with 4 other atoms to
achieve the octet rule.
Hydrocarbons
• Hydrocarbons – any molecule that
contains only hydrogen and carbon
• Simple Hydrocarbons
Methane
and
Ethane
Fats are Hydrocarbons
Group 1: Alkanes
• Alkanes are hydrocarbons made of single
bonds only.
• Draw Methane
• Draw Ethane
• Draw Propane
• Draw Butane
Branched Alkanes – Each branch is
called a SUBSTITUENT.
Naming Branched
Alkanes
• Find the longest chain of carbons.
• (8 – Octane)
Naming Branched
Alkanes
• Number the longest chain starting with the end
that will give substituents the smallest
numbers.
Naming Branched
Alkanes
• To name these substituents, start with the
number. Add a dash. Add the type of
substituent (drop the –ane ending and add the
–yl ending)
• 4-methyl, 4-ethyl, 5-propyl
Naming Branched
Alkanes
• Add prefixes to indicate that the same
substituent appeared more than once.
• If there were two methyl groups on carbon 4,
we would put 4,4 dimethyl
Naming Branched
Alkanes
• List substituents in alphabetical order (ignore
prefixes di, tri, tetra)
• Combine all parts and use proper punctuation.
Write the entire name without any spaces. Use
commas to separate numbers and hyphens to
separate numbers and words.
4-ethyl-4-methyl-5-propyloctance
You Try!
4-ethyl-2-methylhexane
Group 2: Alkenes
• Alkenes are hydrocarbons that contain
one or more double bonds.
• The rules for naming is mostly the same,
except for…
– We drop the ending –ane and use –ene.
– We use numbers to indicate the position of
the double bond.
1-butene
3,3-dimethyl-1-butene
2-butene
4-methyl-2-pentene
Group 3: Alkynes
• Alkynes are hydrocarbons that contain one
or more triple bonds.
• The same rules apply with alkenes and
alkynes. The only difference is that you
drop the –ene ending and add –yne.
Isomers
• Isomers - compounds that have the same
molecular formula, but have different
structures.
• Example:
– C4H10
Stereoisomers
• Stereoisomers are molecules in which the
atoms are joined in the same order, but
the positions of the atoms in space are
different.
Cis-Trans Isomers
• Molecules with double bonds prevent rotating
with respect to each other.
• Because of this lack of rotation, the groups on
either side of the double bond can have
different orientations.
Cis-Trans Isomers
• Cis Configuration
– Similar groups are on the same side of the
double bond.
Cis-Trans Isomers
• Trans Configuration
– Similar groups are on opposite sides of the
double bond.
Cis-Trans Significance
• Cis-Trans configurations have different
physical and chemical properties.
Enantiomers
• Enantiomers – Optical Isomers
– Enantiomers have identical physical
properties, but behave differently when they
react.
– Enantiomers have asymmetric carbons.
Why are some enantiomers more
effective as medicines?
• Substrates and enzymes must fit correctly
(like puzzle pieces) for the enzyme to
function correctly. Certain enantiomers
work better than their mirror image.
Cyclic Hydrocarbons
• Clycloalkane
– Contains
only single
bonds
Aromatic Hydrocarbons
• An aromatic compound contains a
benzene ring.