9.1 carbon compounds carbon compounds form the structures of a whale’s cells and control reactions...

9.1 Carbon Compounds

Carbon compounds form the structures of a whale’s cells and control reactions that take place in those cells. The instructions for these processes are stored in organic compounds.


An organic compound contains carbon and hydrogen, often combined with a few other elements such as oxygen and nitrogen.

There are millions of organic compounds—more than 90 percent of all known compounds.


Carbon has four valence electrons. A carbon atom can form

• four single covalent bonds, • a double bond and two single bonds, or• a triple bond and a single bond.

Most of the bonds in organic compounds are carbon-to-carbon bonds or carbon-to-hydrogen bonds.


What are three forms of carbon?

Diamond, graphite, and fullerenes are forms of carbon.

Forms of Carbon


Diamond

Diamond is an example of a network solid, in which all the atoms are linked by covalent bonds.

• Covalent bonds connect each carbon atom to four other carbon atoms.

• The three-dimensional structure is rigid, compact, and strong.

• Diamond is harder than other substances because cutting a diamond requires breaking many covalent bonds.

Forms of Carbon


Graphite

Graphite is extremely soft and slippery. • Carbon atoms are arranged in widely spaced layers. • Within each layer, carbon atoms form strong covalent

bonds with three other carbon atoms.• Between layers the bonds are weak, so layers slide

easily past one another.

Forms of Carbon


Fullerenes

Fullerenes are large hollow spheres or cages of carbon.

On the surface of a 60-carbon fullerene (C60), the

atoms form alternating hexagons and pentagons. The C60 molecule is called buckminsterfullerene.

Forms of Carbon


A In diamond, carbon atoms are arranged in a rigid, three-dimensional network.

B In graphite, the atoms are arranged in layers.

C In fullerenes, carbon atoms are arranged in hollow spheres.

Forms of Carbon

Diamond Graphite

Buckminsterfullerene


What factors determine the properties of a hydrocarbon?

A hydrocarbon is an organic compound that contains only the elements hydrogen and carbon.

Factors that determine the properties of a hydrocarbon are the number of carbon atoms and how the atoms are arranged.

Saturated Hydrocarbons


In a saturated hydrocarbon, all of the bonds are single bonds.

A saturated hydrocarbon contains the maximum possible number of hydrogen atoms for each carbon atom.

Saturated hydrocarbons are also called alkanes. Their names end in –ane.



A hydrocarbon molecule can contain one carbon atom, as in methane, or more than 30 carbon atoms, as in asphalt.

The carbon atoms can be arranged in a straight chain, a branched chain, or a ring.



Microorganisms in the stomachs of a cow produce more than 500 liters of methane (CH4) per day.



Straight Chains• A molecular formula shows the type and number

of atoms in a molecule of the compound. • A structural formula shows how those atoms are

arranged. • The boiling point of a straight-chain alkane

depends on the number of carbon atoms. Methane and propane are gases at room temperature. Pentane and octane are liquids.



Branched Chains

Butane and isobutane both have a molecular formula of C4H10, but their structural formulas are

different.



Compounds with the same molecular formula but different structural formulas are isomers.

• In isobutane, there is a branch at the point where a carbon atom bonds to three other carbon atoms.

• Differences in structure affect some properties of isomers. Butane boils at –0.5°C, but isobutane boils at –11.7°C.



Rings

Carbon atoms in cyclobutane are linked in a four-carbon ring.



In a cycloalkane, each carbon atom forms bonds with two other carbon atoms and two hydrogen atoms.

• So cyclobutane (C4H8) molecules have two fewer

hydrogen atoms than butane (C4H10) molecules.

• Most ring alkanes, or cyclic hydrocarbons, have rings with five or six carbons.



What are the three types of unsaturated hydrocarbons?

A hydrocarbon that contains one or more double or triple bonds is an unsaturated hydrocarbon.

There are three types of unsaturated hydrocarbons—alkenes, alkynes, and aromatic hydrocarbons.

Unsaturated Hydrocarbons


Alkenes

There is a double bond between the two carbon atoms in ethene. Hydrocarbons that have one or more carbon-carbon double bonds are alkenes. The names of alkenes end in –ene.



Many fruit-bearing plants produce ethene (C2H4), which controls the rate at which fruits, such as this tomato, ripen.



Alkynes

Ethyne (C2H2) is an alkyne. Alkynes are straight-

or branched-chain hydrocarbons that have one or more triple bonds. Alkyne names end in –yne.



Alkynes are the most reactive hydrocarbon compounds. Ethyne (C2H2), also known as acetylene, is used in torches that cut metal or weld them together.



Aromatic Hydrocarbons

Benzene (C6H6) is an unsaturated hydrocarbon with a ring structure.



Although the formula for Benzene shows alternating single and double bonds, the six bonds in the ring are identical. All six carbon atoms share six of the valence electrons.

Hydrocarbons that contain similar ring structures are known as aromatic hydrocarbons. The name was chosen because many of these compounds have strong aromas, or odors.



What are the three main fossil fuels?

Three types of fossil fuels are coal, natural gas, and petroleum.

Fossil fuels are mixtures of hydrocarbons that formed from the remains of plants or animals.

Fossil Fuels


Coal• Giant tree ferns and other plants were buried in

swamps.• After millions of years of pressure, the plant

remains produced a mixture of hydrocarbons. • Most of the hydrocarbons in coal are aromatic

hydrocarbons with high molar masses. • Coal produces more soot than other fossil fuels.

Fossil Fuels


The ferns shown are similar to ferns that lived millions of years ago. Imprints of ferns in coal are evidence that coal formed when plant remains were compressed.

Fossil Fuels


Natural Gas• Natural gas formed from the remains of marine

organisms. • The main component of natural gas is methane.

Natural gas also contains ethane, propane, and isomers of butane.

• Natural gas is used for heating and cooking.• Deposits of natural gas are found along with

coal and petroleum.

Fossil Fuels


Petroleum• Petroleum also formed from marine organisms.• Petroleum is pumped from deep beneath Earth’s

surface. • Petroleum is a complex liquid mixture of

hydrocarbons, mainly long-branched alkanes and alkenes.

Fossil Fuels


Petroleum is separated into mixtures called fractions.

Fossil Fuels

Distillation Tower

Heating Burner



Fossil Fuels

Distillation Tower

Crude oil

Heating Burner



Fossil Fuels

Distillation Tower

Crude oil vapors

Crude oil

Heating Burner


What are the two primary products of the combustion of fossil fuels?

The primary products of the complete combustion of fossil fuels are carbon dioxide and water.

C3H8 + 5O2 3CO2 + 4H2O (complete combustion)

Combustion of Fossil Fuels


Incomplete Combustion

If there is not enough oxygen available for complete combustion of all the fuel, carbon monoxide is produced.

Carbon monoxide is a colorless, odorless gas that is poisonous. It keeps hemoglobin from carrying oxygen to cells.

2C3H8 + 7O2 6CO + 8H2O (incomplete combustion)



Acid Rain

Sulfur dioxide and nitrogen oxides released into the atmosphere by the combustion of fossil fuels forms sulfuric acid and nitric acid.

These acids damage stone structures, metal, and concrete.



Assessment Questions

1. Graphite is soft and slippery because its carbon atoms a. are arranged in layers with weak attractions between

layers.

b. have a large, interlocking network.

c. contain individual atoms with very weak bonds to other carbon atoms.

d. share a weak bond with hydrogen atoms.



1. Graphite is soft and slippery because its carbon atoms a. are arranged in layers with weak attractions between

layers.

b. have a large, interlocking network.

c. contain individual atoms with very weak bonds to other carbon atoms.

d. share a weak bond with hydrogen atoms.

ANS: A



2. In general, the boiling point of a hydrocarbon increases asa. the number of hydrogen bonds between molecules

increases.b. the number of carbon atoms in the chain increases.c. the branching of the carbon chain increases.d. the number of oxygen atoms in the molecule increases.



2. In general, the boiling point of a hydrocarbon increases asa. the number of hydrogen bonds between molecules

increases.b. the number of carbon atoms in the chain increases.c. the branching of the carbon chain increases.d. the number of oxygen atoms in the molecule increases.

ANS: B



3. An unsaturated hydrocarbon always contains a. double bonds between carbon atoms.

b. double or triple bonds.

c. at least one ring in its structure.

d. at least one atom that is neither carbon nor hydrogen.



3. An unsaturated hydrocarbon always contains a. double bonds between carbon atoms.

b. double or triple bonds.

c. at least one ring in its structure.

d. at least one atom that is neither carbon nor hydrogen.

ANS: B



4. A hydrocarbon in which two of the carbon atoms are joined by a triple covalent bond is ana. alkane.

b. alkene.

c. alkyne.

d. aromatic hydrocarbon.



4. A hydrocarbon in which two of the carbon atoms are joined by a triple covalent bond is ana. alkane.

b. alkene.

c. alkyne.

d. aromatic hydrocarbon.

ANS: C



5. Most of the hydrocarbon compounds in coal are a. short-chain alkanes.

b. long-chain unsaturated hydrocarbons.

c. cycloalkanes.

d. aromatic hydrocarbons.



5. Most of the hydrocarbon compounds in coal are a. short-chain alkanes.

b. long-chain unsaturated hydrocarbons.

c. cycloalkanes.

d. aromatic hydrocarbons.

ANS: D



6. Which of these compounds is formed during the combustion of fossil fuels and then reacts with water in the air to form acid rain? a. carbon dioxide

b. sulfur dioxide

c. iron (II) oxide

d. ozone



6. Which of these compounds is formed during the combustion of fossil fuels and then reacts with water in the air to form acid rain? a. carbon dioxide

b. sulfur dioxide

c. iron (II) oxide

d. ozone

ANS: B



1. Carbon forms the backbone structure of millions of different organic compounds because each carbon atom forms four covalent bonds with other atoms.

TrueFalse



1. Carbon forms the backbone structure of millions of different organic compounds because each carbon atom forms four covalent bonds with other atoms.

TrueFalse

ANS: T



2. The compound that is an indicator of incomplete combustion of hydrocarbons is carbon dioxide.

TrueFalse



2. The compound that is an indicator of incomplete combustion of hydrocarbons is carbon dioxide.

TrueFalse

ANS: F, carbon monoxide

9.1 carbon compounds carbon compounds form the structures of a whale’s cells and control reactions...

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