Transcript Fiddlehead 2005 - The Marilyn Maxwell Latch Academic

Chapter 4 - Carbon
• All living organisms
– Made of chemicals, based mostly on the
element carbon
• Carbon is unparalleled in its ability to form
large, complex and diverse molecules
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Organic Chemistry
• Organic chemistry is the study of carbon
compounds
• Organic compounds
– Range from simple molecules to colossal ones
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Molecular Diversity of Carbon
• Carbon chains
– Form the skeletons of most organic
molecules
– Vary in length and shape
H H H
H C C C H
H H H
Propane
H
H C H
H
H
H H H H
(b) Branching
H C C C C H
H C C C H
H H H
H H H H
2-methylpropane
Butane
(commonly called isobutane)
H H H H
H H H H
(c) Double bonds H
H C C C C H
C C C C H
H
H
H H
1-Butene
2-Butene
H
H
H
H
C
H
H
C C H
C H
(d) Rings
H C
C
H
H C
C
H
H
C
C
C
H H
H C C H
H H
Ethane
(a) Length
Figure 4.5 A-D
Cyclohexane
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Benzene
Carbon’s Four Bonding Sites
Remember electron configuration determines the
kind and number of bonds an atom will form
• Carbon has __ valence electrons, it must form
__ bonds
• Carbon is covalently compatible with many
different elements
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Carbon’s Four Bonding Sites
• The electron configuration of carbon
– Gives it covalent compatibility with many
different elements
Hydrogen
Oxygen
Nitrogen
Carbon
(valence = 1)
(valence = 2)
(valence = 3)
(valence = 4)
H
O
N
C
Figure 4.4
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Hydrocarbons
• Hydrocarbons
– Are molecules consisting of only carbon and
hydrogen
– Are hydrophobic
– Undergo reactions that release relatively large
amounts of energy
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Hydrocarbons
• Hydrocarbons
– Are found in many of a cell’s organic
molecules
Fat droplets (stained red)
Figure 4.6 A, B
(a) A fat molecule
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100 µm
(b) Mammalian adipose cells
Isomers
• Isomers
– Are molecules with the same molecular
formula but different structures and properties
• Three types of isomers are
– Structural
– Geometric
– Enantiomers (mirror)
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Isomers
•Structural isomers
– Differ in the covalent arrangement of
atoms
– Location of double bond(s) may also differ
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Isomers
•Geometric isomers
– Differ in spatial arrangements
– Arrangements can be cis or tran
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Isomers
• Enantiomers
– Mirror images
L-Dopa
Figure 4.8
(effective against
Parkinson’s
disease)
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D-Dopa
(biologicall
y inactive)
So, given a chemical formula, how do you know
what a molecule should look like structurally?
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Functional Groups
• Functional groups
– Are the chemically reactive groups of atoms
within an organic molecule
– Behave consistently from one molecule to the
next
– The arrangement of the groups help give the
molecule its properties
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Functional Groups
• Six functional groups are important in the
chemistry of life
– Hydroxyl
– Carbonyl
– Carboxyl
– Amino
– Sulfhydryl
– Phosphate
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Functional Groups
• Some important functional groups of organic
compounds
FUNCTIONAL
GROUP
HYDROXYL
CARBONYL
CARBOXYL
O
OH
(may be written HO
C
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C
OH
)
STRUCTURE In a hydroxyl group (—OH),
a hydrogen atom is bonded
to an oxygen atom, which in
turn is bonded to the carbon
skeleton of the organic
molecule. (Do not confuse
this functional group with the
hydroxide ion, OH–.)
Figure 4.10
O
The carbonyl group
( CO) consists of a
carbon atom joined to
an oxygen atom by a
double bond.

When an oxygen atom is doublebonded to a carbon atom that is
also bonded to a hydroxyl group,
the entire assembly of atoms is
called a carboxyl group (—
COOH).
Functional Groups
• Some important functional groups of organic
compounds
NAME OF
COMPOUNDS
Alcohols (their specific
names usually end in -ol)
EXAMPLE
H
H
H
C
C
H
H
Ketones if the carbonyl group is Carboxylic acids, or organic
within a carbon skeleton
acids
Aldehydes if the carbonyl group
is at the end of the carbon
skeleton
H
OH
H
C
H
C
H
H
Ethanol, the alcohol
present in alcoholic
beverages
H
O
C
H
H
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H
C
OH
H
Acetone, the simplest ketone
Figure 4.10
C
O
H
H
C
C
H
H
O
C
Propanal, an aldehyde
H
Acetic acid, which gives vinegar
its sour tatste
Functional Groups
• Some important functional groups of organic
compounds
FUNCTIONAL  Is polar as a result of the
PROPERTIES electronegative oxygen atom
drawing electrons toward
itself.
 Attracts water molecules,
helping dissolve organic
 Has acidic properties because
it is a source of hydrogen ions.
The covalent bond between
oxygen and hydrogen is so polar
that hydrogen ions (H+) tend to
dissociate reversibly; for
example,
 A ketone and an
aldehyde may be
structural isomers with
different properties, as
is the case for acetone
and propanal.
compounds such as sugars
(see Figure 5.3).
H
H
C
H
Figure 4.10
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H
O
C
OH
H
C
H
O
+ H+
C
O
 In cells, found in the ionic
form, which is called a
carboxylate group.
Functional Groups
• Some important functional groups of organic
compounds
AMINO
SULFHYDRYL
H
O
SH
N
(may be written HS
H
The amino group (—NH2)
consists of a nitrogen atom
bonded to two hydrogen
atoms and to the carbon
skeleton.
PHOSPHATE
)
O P OH
OH
The sulfhydryl group
consists of a sulfur atom
bonded to an atom of
hydrogen; resembles a
hydroxyl group in shape.
Figure 4.10
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In a phosphate group, a
phosphorus atom is bonded to four
oxygen atoms; one oxygen is
bonded to the carbon skeleton; two
oxygens carry negative charges;
abbreviated P . The phosphate
group (—OPO32–) is an ionized
form of a phosphoric acid group (—
OPO3H2; note the two hydrogens).
Functional Groups
• Some important functional groups of organic
compounds
H
O
C
HO
C
H
H
N
H
H
Glycine
Figure 4.10
H
C
C
H
H
OH OH H
SH
H
C
C
C
H
H
H
O
O
P
O
O
Ethanethiol
Because it also has a carboxyl
group, glycine is both an amine
and a carboxylic acid;
compounds with both groups
are called amino acids.
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H
Glycerol phosphate
Functional Groups
• Some important functional groups of organic
compounds
 Acts as a base; can pick
up a proton from the
surrounding solution:
H
N
H
+N
H
(nonionized)
H
H
(ionized)
 Ionized, with a charge
Figure 4.10
of 1+, under cellular
conditions.
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 Two sulfhydryl groups can
 Makes the molecule of which
interact to help stabilize
protein structure (see
Figure 5.20).
it is a part an anion (negatively
charged ion).
Can transfer energy between
organic molecules.
The Chemical Elements of Life: A Review
• The versatility of carbon
– Makes possible the great diversity of organic
molecules
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