Carbon and Organic Compounds
The position of carbon in the periodic table.
Carbon’s Key Properties
• Has a mid-range electronegativity value so it
forms covalent bonds and shares electrons
• Can form a maximum of four bonds
• Can form chains, sheets, and rings
• Usually combined with H and often bonds
with O, S, N and P
Forms
HYDROCARBONS
Carbon Skeletons and Hydrogen Skins
Each C can form a maximum of four single bonds, OR two single and
one double bond, OR one single and triple bond.
The arrangement of C atoms determines the skeleton, so a straight
chain and a bent chain represent the same skeleton.
Groups joined by single bonds can rotate, so a branch pointing down
is the same as one pointing up.
The Other Carbon Bonds
• If carbon is not bound to anything else in an organic
compound, it will be attached to hydrogen.
C –C– C – C – C
|
C
Ways of depicting formulas and models of an alkane.
ring
Some five-carbon skeletons.
C
single bonds
C
C
double bond
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
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
C
C
C
C
C
C
C
C
C
C
C
C
Saturated and Unsaturated
• When the carbon in organic compounds forms
only single bonds we say that the compound is
saturated (can’t add anything more).
• If there are double or triple bonds, these can
be broken to add more atoms. In this case we
say that the compound is unsaturated.
Isomers
• When two compounds have the same
chemical formula but different structural
formulas they are called isomers.
• There are many kinds of isomers depending
on where the carbons are placed and how
bonds are arranged.
Isomers and Vision
• If you take beta carotene and split the
molecule, you get 2 Vitamin A molecules.
These are related to retinal.
• Retinal changes form when a photon of light
strikes it.
• http://www.elmhurst.edu/~chm/vchembook/
531vision.html
Depicting cycloalkanes.
H
H
C
H C
H
C H
H
H C
C H
H C
C H
H
H
cyclobutane
cyclopropane
H
H
Boiling points of the first 10 unbranched alkanes.
An analogy for optical isomers.
Some molecules with the alcohol functional group.
Some common aldehydes and ketones.
methanal
(formaldehyde)
used to make
resins in plywood,
dishware,
countertops;
biological
preservative
ethanal
(acetaldehyde)
narcotic product of
ethanol
metabolism; used
to make perfume,
flavors, plastics,
other chemicals
benzaldehyde
artificial almond
flavoring
2-butanone
2-propanone
(methyl ethyl
(acetone) solvent for
fat, rubber, plastic, ketone) important
solvent
varnish, lacquer;
chemical feedstock
Some molecules with the carboxylic acid functional group.
methanoic acid
(formic acid)
an irritating
component of ant
and bee stings
benzoic acid
calorimetric
standard; used in
preserving food,
dyeing fabric, curing
tobacco
butanoic acid
(butyric acid)
odor of rancid butter;
suspected component
of monkey sex
attractant
octadecanoic acid
(stearic acid)
found in animal fats;
used in making candles
and soap
Some lipid molecules with the ester functional group.
cetyl palmitate
the most common
lipid in whale
blubber
lecithin
phospholipid found in all cell membranes
tristearin
typical dietary fat used as an
energy store in animals
Polymers
• Long chain molecules made of small repeating
units
• Can be made by addition reactions (adding
molecules) or condensation (splitting
something out and joining the pieces.
• Building polymers….
Crosslinking
• Some polymers make bridges across chains
rather than just adding to chains. These are
“cross-linked” polymers.
• Some cross-links are covalent bonds and are
permanent. Some links are made with
intermolecular forces and can be broken more
easily (like the alginate worms).