Unit 6Chapter 10

Introduction to Organic Chemistry

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Organic Chemistry

Why is it important?

>90% of compounds are organic

What is an organic compound • is a compound made from carbon atoms.• has one or more C atoms. • has many H atoms.• may also contain O, S, N, and halogens.

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Organic Compounds

Typical organic compounds

• have covalent bonds.

• have low melting points.

• have low boiling points.

• are flammable.

• are soluble in nonpolar solvents.

• are not soluble in water.oil (organic) and water (inorganic)

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Organic vs. Inorganic

• Propane, C3H8, is an organic compound used as a fuel.

• NaCl, salt, is an inorganic compound composed of Na+ and Cl- ions.

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Comparing Organic and Inorganic Compounds

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Learning Check

Identify each characteristic as most typical of compounds

that are 1) inorganic 2) organic.

A. has a high melting point

B. is not soluble in water

C. has a formula CH3─CH2─CH3

D. has a formula MgCl2

E. burns easily in air

F. has covalent bonds

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1

2

2

2

2 (some 1)

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In organic compounds • carbon has 4 valence electrons and hydrogen has 1.

•

• C • H • •

• to achieve an octet, C forms four bonds. H H

H C H H C H

H H CH4 , methane

Writing Formulas for Alkanes

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Tetrahedral Structure of Carbon

A carbon atom with four single, covalent bonds, has a tetrahedral shape.

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Organic Molecules

In organic molecules,

• valence electrons are shared.

• covalent bonds form between carbon atoms.

• C-C bonds are very strong, can form long chains.

H H H H • • • •

H C C H H C C H

• • • • H H H H

ethane, CH3─CH3

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Tetrahedral Structure of Carbon

In molecules with two or more carbon atoms, each carbon atom with four single bonds has a tetrahedral shape.

(Rotation,

Maximum space)

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Alkanes

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

•Compounds containing only C and H•All bonds are single bonds (2 electrons are shared)

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Structural Formulas

Alkanes are written with structural formulas that are

• expanded to show each bond (Lewis Structure).

• condensed to show each carbon atom and hydrogen atoms attached to that carbon.

Expanded (Lewis) Condensed

H

H C H CH4 , methane

H

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Expanded and Condensed Structures

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Structural Formulas

Condensed formulas are written for expanded structural formula by showing each carbon and the attached hydrogen atoms.

Expanded Condensed

H H H H │ │ │ │H─C ─C ─C ─C ─ H CH3─CH2─CH2─CH3

│ │ │ │ H H H H

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Names of AlkanesThe names of alkanes

• are determined by the IUPAC (International Union of Pure and Applied Chemistry) system.

• end in –ane.

• with 1-4 carbons in a chain use prefixes as follows.

Name # Carbons Structural Formula

Methane1 CH4

Ethane 2 CH3CH3

Propane 3 CH3CH2CH3

Butane 4 CH3CH2CH2CH3

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Names of AlkanesAlkanes with 5-10 carbon atoms in a chain use Greek prefixes.

Name # Carbons Structural Formula

Pentane 5 CH3CH2CH2CH2CH3

Hexane 6 CH3CH2CH2CH2CH2CH3

Heptane 7 CH3CH2CH2CH2CH2CH2CH3

Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3

Nonane 9 CH3 CH2 CH2CH2CH2CH2CH2CH2CH3

Decane 10 CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Know the 1st eight alkanes (name and structure)

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Learning Check

A. Write the condensed formula for:

H H H H H

H C C C C C H

H H H H H

B. What is its molecular formula?

(Gives total # of each atom, does not indicate how they are arranged)

C. What is its name?

CH3─CH2─CH2─CH2─CH3

C5H12

pentane

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Some Structures for Butane

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Hexane has Six Carbon Atoms

Hexane • is an alkane with six carbon atoms in a continuous

chain.• has a “zig-zag” look because each carbon atom is at

the center of a tetrahedron.• is represented by a ball-and-stick model as shown

below.

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Cycloalkanes

Cycloalkanes

• are cyclic alkanes.

• have two hydrogen atoms fewer than the open chain. (remember each carbon has 4 bonds)

• are named by using the prefix cyclo- before the name of the alkane chain with the same number of carbon atoms.

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Cycloalkanes

The structural formulas of cycloalkanes are usually

represented by geometric figures,

Cyclopropane CH2

CH2 CH2

CyclobutaneCH2 CH2

CH2 CH2

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More Cycloalkanes

Cyclopentane CH2

CH2 CH2

CH2 CH2

Cyclohexane

CH2

CH2 CH2

CH2 CH2

CH2

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Properties of Alkanes

Copyright © 2005 by Pearson Education, Inc.Publishing as Benjamin Cummings

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Some Properties of Alkanes

Alkanes are

• nonpolar.

• insoluble in water.

• less dense than water.

• flammable in air.

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Some Properties of Alkanes

Alkanes with 1-4 carbon atoms are

• methane, ethane, propane, and butane.

• gases at room temperature.

• used as heating fuels.

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Some Properties of Alkanes

Alkanes with 5-8 carbon atoms are• liquids at room temperature.• pentane, hexane, heptane, and octane.• very volatile.• used to make gasoline.

Alkanes with 9-17 carbon atoms • are liquids at room temperature• have higher boiling points.• are found in kerosene, diesel, and jet fuels.

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Some Properties of AlkanesAlkanes with 18 or more carbon atoms• have high molar masses.• are waxy solids at room temperature.• used in waxy coatings of fruits and

vegetables.

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Combustion

In combustion reactions,

• alkanes react with oxygen.

• CO2, H2O and energy are produced.

Alkane + O2 CO2 + H2O + heat

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Learning Check

Write a balanced equation for the

complete combustion of propane.

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Solution

Unbalanced equation

C3H8 + O2 CO2 + H2O

First: Balance C

C3H8 + O2 3CO2 + H2O

Then: Balance H

C3H8 + O2 3CO2 + 4H2O

Last: Balance O

C3H8 + 5O2 3CO2 + 4H2O (Balanced)

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