AP Biology I
Pennsbury High School
Water & Carbon Unit Part 1
2009-10 School Year
Introduction to Organic Chemistry
What are the factors that contribute to carbon’s unique ability among the
elements to produce such a staggering variety of chemical compounds?
Organic compounds are compounds of carbon. The organic molecules of living things
may contain C, O, H, N, S, and P among other atoms. Even though the molecules of all
living things are made up of these same six elements, the atoms of organic molecules can
be arranged so many different ways that the uniqueness of each organism is ensured.
Carbon’s versatility allows a limited assortment of atomic building blocks, taken in
roughly the same proportions, to be used to build an inexhaustible variety of organic
molecules.
1. Carbon atoms are tetravalent. That is, they form four bonds. “Intersection point”
Valences of atoms provide a set of simple rules that govern how atoms combine to
make molecules.
2. Stability of C-C bonds and the ability to form long stable chains. Organic molecules
can vary in the length of the carbon chain that makes up the molecule. (See list of
word roots for naming alkanes, alkenes, and alkynes of different lengths.)
3. Carbon chains do not have to be straight, they can be branched. Structural isomers.
4. In addition to forming single bonds between carbon atoms, atoms of carbon can also
form double and triple bonds with other carbon atoms.
5. When a carbon-carbon double bond exists within a carbon chain, there are two
isomers formed resulting from possible variation in the arrangement of chemical
groups around the double bond. Geometric isomers (cis-trans isomers).
AP Biology I
Pennsbury High School
Water & Carbon Unit Part 1
2009-10 School Year
6. The position of a carbon-carbon double or triple bond within a chain can vary
resulting in structural isomers.
7. When a carbon compound has an asymmetric (chiral) carbon, there will be
enantiomers (optical isomers). Enantiomers are distinguished as R (rectus) or S
(sinister) isomers. The R and S isomers of a given compound have different
biological activities. Enantiomers are mirror images of each other.
8. Different organic compounds can be made by adding different functional groups to
the carbon skeletons. Functional groups important in biological molecules include:
(hydroxyl, [-OH]; carboxyl, [-COOH]; carbonyl, [-CHO]; amino, [-NH2]; sulfhydryl,
[-SH]; phosphate, [-PO43-]; and ester [-R-COO].
9. In large organic compounds, different compounds are formed when functional groups
are located on different carbons on the carbon skeleton. Structural isomers.
10. Carbon skeletons can also exist in ring forms, where one end of the chain of carbons
is attached to the other end forming a cyclic compound. E.g., cyclohexane. In
addition, there is also an important group of chemical compounds based on a ring
compound known as benzene. These are aromatic compounds.
AP Biology I
Pennsbury High School
Water & Carbon Unit Part 1
2009-10 School Year
Some concept maps that illustrate the relationships between concepts.
Organic Compounds
Can be classified as
Aliphatic Compounds
Aromatic Compounds
May be
Straight-Chain
Cyclic
Includes
Alkanes
Alkenes
Alkynes
Isomers
Can Be
Structural Isomers
Stereoisomers
(Connectivity Differences)
(Configuration Differences)
Include
Branched
Chains
Include
Position of
Func. Group
Position of
Double/Triple
Bond
Enantiomers
Diastereomers
(mirror image)
(non-mirror image)
AP Biology I
Pennsbury High School
Water & Carbon Unit Part 1
2009-10 School Year
Word Roots for Naming Carbon Chains
Root
meth-
Number
of
Carbons
Example of an Alkene
methane
N/A
ethane
ethene
propane
propene
butane
1-butene
pentane
2-pentene
hexane
2-hexene
heptane
1-heptene
1
eth-
2
prop-
3
but-
4
pent-
5
hex-
6
hept-
Example of an Alkane
7
AP Biology I
Pennsbury High School
Water & Carbon Unit Part 1
2009-10 School Year
Word Roots for Naming Carbon Chains (cont.)
Root
Number
of
Carbons
oct-
8
non-
9
dec-
10
Example of an Alkane
Example of an Alkene
octane
4-octene
nonane
2-nonene
decane
1-decene