Carbon and the Molecular
Diversity of Life
Chapter 4
Organic chemistry is the study of carbon
compounds
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Organic chemistry -- Branch of chemistry that
specializes in the study of carbon compounds;
includes most compounds important to life.
Great variety of structures and functions of
organic molecules are due to carbon’s ability of
carbon to bond with itself and many other
elements.
Pioneers of organic chemistry began to
synthesize organic compounds from inorganic
molecules.
Friedrich Wohler (1828) synthesized urea.
Stanley Miller (1953) demonstrated the
possibility that organic compounds could have
been produced under the chemical conditions of
primordial Earth.
Miller-Urey Apparatus
Carbon atoms are versatile building blocks
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The kinds and number of bonds carbon
will form are determined by its
tetravalent electron configuration. (4
valence e-)
Completes its outer energy shell by
sharing valence electrons in four
covalent bonds. (Not likely to form ionic
bonds.)
Carbon atom is a central point from
which the molecule branches off into
four directions; results in large, complex
molecules.
An organic molecule's 3-dimensional
shape will affect its function.
When carbon forms four single covalent
bonds, the four e- orbitals angle from the
carbon atom to form a tetrahedron.
Methane/Ethane/Ethene
Variation in carbon skeletons.
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Carbon chains may vary in:
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Length.
Shape (straight chain, branched, ring).
Number and location of double bonds.
Other elements covalently bonded to available
sites.
This variation in carbon skeletons
contributes to the complexity and diversity
of organic molecules.
Hydrocarbons -- Molecules containing only
carbon and hydrogen.
Major components of fossil fuels produced
from the organic remains of organisms
living millions of years ago, though they are
not prevalent in living organisms.
Hydrocarbon chains are hydrophobic
because the C-C and C-H bonds are
nonpolar.
Isomers
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Isomers -- Compounds
with the same molecular
formula but with
different structures and
different properties.
1. Structural isomers -Isomers that differ in the
covalent arrangement of
their atoms.
Number of possible
isomers increases as the
carbon skeleton size
increases.
May also differ in the
location of double bonds.
Isomers (cont)
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Geometric isomers -Same covalent
relationships, but
differ in spatial
arrangements.
Result from the fact
that atoms cannot
rotate freely around
double bonds.
Subtle differences
between isomers
affects their biological
activity (Vyvanse vs
Adderall)
Isomers (cont)
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Enantiomers -- Isomers
that are mirror images of
each other.
When four different
atoms or groups of
atoms are bonded to the
same carbon
(asymmetric carbon).
Two different spatial
arrangements of the four
groups are mirror
images.
Usually one form is
biologically active and its
mirror image is not.
L-isomer (levo/left)
D-isomer (dextro/right)
Thalidomide: Very different
enantiomers
Functional groups also contribute to the
molecular diversity of life
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Functional groups -- Small groups of atoms
bonded to the carbon skeleton of organic
molecules.
Functional groups:
• Have specific chemical and physical
properties.
• Are commonly the chemically reactive
regions of the molecule.
• Behave consistently from one organic
molecule to another.
• Depending upon their number and
arrangement, determine chemical properties
of organic molecules in which they occur.
Hydroxyl Group (R--OH)
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Functional group that
consists of a hydrogen
atom bonded to an
oxygen atom, which in
turn is bonded to
carbon.
Is a polar group (O-H
bond is polar
covalent).
Makes the molecule to
which it is attached
water soluble.
Hydrogen bonds form
between polar water
molecules and
hydroxyl group.
Organic compounds
with hydroxyl groups
are called alcohols.
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Functional group that
Carbonyl Group
consists of a carbon atom
(R--C=O)
double-bonded to oxygen.
Is a polar group (O can
hydrogen bond)
Molecules with this
functional group are
water soluble.
Is a functional group
found in sugars.
If carbonyl is at the end
off the carbon skeleton,
the compound is an
aldehyde.
If the carbonyl is NOT at
the end of the carbon
skeleton, the compound is
a ketone.
Carboxyl Group
(R—COOH)
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Functional group that
consists of a carbon atom
which is both doublebonded to an oxygen and
single-bonded to the
oxygen of a hydroxyl
group.
Is a polar group and
water soluble.
Since it donates protons,
this group has acidic
properties.
Compounds with this
functional group are
called carboxylic acids.
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Amino Group
(R--NH2)
Functional group that
consists of a nitrogen
atom bonded to two
hydrogens and to the
carbon skeleton.
Is a polar group and
soluble in water.
Acts as a weak base; the
nitrogen can accept a
proton.
Organic compounds with
this function group are
called amines.
Sulfhydryl Group
(R--SH)
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Functional group
which consists of an
atom of sulfur
bonded to an atom
of hydrogen.
Help stabilize the
structure of
proteins.
Organic compounds
with this functional
group are called
thiols.
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Phosphate Group
(R--PO4)
Functional group in
which the phosphate is
attached to carbon
skeleton by O.
Loss of two protons
leaves the phosphate
group with a negative
charge; has acid
properties.
Polar group and soluble
in water.
Organic phosphates are
important in cellular
energy storage and
transfer (ATP).