Carbon Compounds'

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Lecture 23

• Carbon Compounds.

Chapter 12.1 ? 12.9

• Carbon Bonds
• Structural Formulas
• Unsaturated Hydrocarbons
• Functional Groups

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Carbon
Carbon forms far more compounds than any other
element. Carbon compounds are the basis of
life. Part of chemistry describing carbon
compounds is called organic chemistry.
Carbon is element 6. The main isotope is
126C. The inner electronic shell is closed, the
outer one is half?full (contains 4 electrons out
of 8 permitted).
The outer electrons are attracted to the nucleus
by the effective charge of 4. The attractive
force is sufficient to keep all 4 outer e?, but
is not enough to accept another 4 to fill the
shell.
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Forming Carbon Compounds
Carbon forms covalent bonds, sharing 4 pairs of
electrons. A carbon atom can form bonds with
other carbon atoms too.
Diamond, a crystalline form of carbon, is the
hardest mineral.
Carbon compounds are mostly nonelectrolytes. Their
reaction rates are usually slow. Carbon easily
connects with hydrogen and oxygen. Due to the
presence of oxygen, many carbon compounds are
unstable at high temperatures.
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Alkanes
The simplest organic compounds contain only C and
H. They are called alkanes. They include methane
(CH4), ethane (C2H6), propane (C3H8), and butane
(C4H10), widely used fuels.
Alkane molecules have single covalent bonds
between their carbon atoms. Natural gas and
petroleum consists mainly of alkanes. Natural gas
includes the lowest alkanes, while petroleum
includes higher alkanes.
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Petroleum

• Petroleum (crude oil) can be separated into
  different alkanes according their boiling points.
• Fractional distillation is the process in which
  crude oil is heated and its vapors are condensed
  at progressively higher temperatures.

Gasoline is the most valuable product of crude
oil. However, its content in most petroleums is
low. To increase its concentration, its is
cracked.
C16H34 ? C8H18 C8H16 ? cracking reaction
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Petroleum
The second procedure of enriching crude oil in
gasoline is polymerization.
C3H8 C4H8? C7H16 ? polymerization reaction
Octane rating of gasoline is a measure of the
tendency to prevent engine knocking. The simplest
alkanes have the lowest rating, while more
complicated, branched-chain, hydrocarbons the
highest.
Alkane molecules are nonpolar and insoluble in
water. This leads the formation of thin layers of
oil from spills on the water surface.
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Structural Formulas
A structural formula shows the covalent bonds
between the atoms in a molecule.
Structural formulas show how the carbon atoms are
linked together. A carbon atom always forms four
bonds.
For the simplest hydrocarbons there is only one
way to connect the atoms together. More
complicated ones can be arranged
differently. Compounds with the same molecular
formulas, but different structural ones, are
called isomers.
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Unsaturated Hydrocarbons
Carbon atoms can be connected by double and even
triple bonds.
H ? C ? C ? H ? acetylene
Compounds with multiple bonds are much more
reactive than the alkanes. They can add other
atoms to their molecules and are called
unsaturated.
Compounds with single carbon bonds are called
saturated.
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Benzene
Benzene, C6H6, is a clear liquid which is not
mixed with water and has a strong odor. It is
widely used as a solvent and in making more
complex organic compounds.
The six C atoms are arranged in a flat hexagonal
ring. Six electrons are shared by the entire ring
(delocalized).
Compounds that contain a ring of six C atoms are
called aromatic. Those without ring structures
are called aliphatic.
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Hydrocarbon Groups

• Compounds that contain other elements besides C
  and H are regarded as derivatives of hydrocarbons.

The groups of C and H that appear in hydrocarbon
derivatives are named from the hydrocarbons. Examp
les methyl group (CH3), ethyl group
(C2H5). CH3Cl ? methyl chloride.
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Functional Groups. Alcohols.
The chemical behavior of many organic compounds
is largely determined by the presence of certain
atom groups, called functional groups.
Alcohols contain OH groups, which make them
slightly polar and soluble in water. The ethanol
(C2H5OH) can be produced by fermentation.
C6H12O6 ? 2C2H5OH 2CO2
Mendeleevs Doctoral Thesis On the Combinations
of Water with Alcohol. 40 is the best
concentration of alcohol.
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Functional Groups. Aldehydes and Ketones.
Aldehydes and ketones contain the carbonyl
group. The group is in the end of aldehyde
molecules and inside ketone molecules, between
two other C atoms.
The double bond between C and O is highly polar,
and aldehydes and ketones are soluble in
water. Oxidation of ethanol in the liver produces
acetaldehyde. The most familiar ketone is called
acetone.
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Functional Groups. Organic Acids.
Organic acids contain the carboxyl group
(?COOH). Since the H atom is loosely attached to
the molecule, it can be taken out to produce an
H ion.
Most organic acids are weak. Examples formic
acid (insect bites), acetic acid (vinegar),
citric acid (citrus fruits), acetylsalicylic acid
(aspirin).
Esters is a result of the reaction of alcohols
(organic hydroxides) with organic acids. Esters
are analogous to inorganic salts, but not
electrolytes.
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Summary
Carbon produces the largest amount of compounds,
including the base for living organisms. Carbon
forms covalent bonds which can be either single
or multiple. Organic molecules are best
represented by structural formulas.