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What is organic chemistryAn 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

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.

Recall carbon’s properties!

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

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

Organic molecules have….

In organic molecules, • valence electrons are shared.• covalent bonds form between carbon atoms.

H H H H • • • •

H C C H H C C H

• • • • H H H H

ethane, CH3─CH3

What are alkanes?

Alkanes are written with structural formulas that are

• expanded to show each bond.• condensed to show each carbon atom and its

attached hydrogen atoms.

Expanded Condensed H

H C H CH4 , methane

H

Expanded vs condensed!

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

How to name alkanes?The 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

Methane 1 CH4

Ethane 2 CH3CH3

Propane 3 CH3CH2CH3

Butane 4 CH3CH2CH2CH3

Pentane 5 CH3CH2CH2CH2CH3

Hexane 6 CH3CH2CH2CH2CH2CH3

Heptane 7 CH3CH2CH2CH2CH2CH2CH3

Octane 8 CH3CH2CH2CH2CH2CH2CH2CH3

Nonane 9 CH3 CH2

CH2CH2CH2CH2CH2CH2CH3

Decane 10

CH3CH2CH2CH2CH2CH2CH2CH2CH2CH3

Learning Check

A. Write the condensed formula for: H H H H H

H C C C C C H H H H H HB. What is its molecular formula?C. What is its name?

A. CH3─CH2─CH2─CH2─CH3

B. C5H12

C. pentane

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Writing Structural Formulas

Carbon atoms in a chain• maintain tetrahedral shape.• are connected in a zig-zag pattern.• are drawn as 2-dimensional. • Ccan be written in several conformations.

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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.

What are cycloalkanes?

Cycloalkanes

• are cyclic alkanes.• have two hydrogen atoms fewer than the

open chain.• are named by using the prefix cyclo- before

the name of the alkane chain with the same number of carbon atoms.

Learning check

Name the following.

A. CH3─CH2─CH2─CH3

B.

C. CH3─CH2─CH2─CH2─CH2─CH2─CH2─CH3

D.

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Need to use substituent with alkanes

Isomers of Butane• have the same molecular formula.• have different atom arrangements.• of butane (C4H10) are a straight chain and a

branched chain. Alkyl groups are• alkanes that are missing one H. • substituents attached to carbon chains.• named with a –yl ending.• CH3 methyl

• CH3 CH2 ethyl

Alkanes with substituents

CH3

CH3 CH CH3

methylpropane

methyl groups

CH3 CH3

CH3 CH CH2 CH CH3 2,4-

dimethylpentane

Naming alkanes

Give the name of CH3 CH3

CH3─CH─CH─CH3

STEP 1 Name the longest continuous chain.

CH3 CH3

CH3─CH─CH─CH3

butane

Naming Alkanes

Give the name of CH3 CH3

CH3─CH─CH─CH3

STEP 2 Number chain. CH3 CH3

CH3─CH─CH─CH3

1 2 3 4STEP 3 Locate substituents and name.

2,3-dimethylbutane

Let’s practice again!

STEP 1 Longest chain is pentane.

STEP 2 Number chain from end nearest substituent.

Cl CH3

CH3─CH2─CH─CH─CH3

5 4 3 2 1

STEP 3 Locate substituents and name alphabetically.

3-chloro-2-methylpentane

Learning Check

Give the IUPAC name for each of the following:

A. CH3 CH3

| | CH3─CH─CH2 ─CH─CH3

B. Cl CH3 | |

CH3─CH2─CH─CH2─C─CH2─CH3

|

Cl

Learning Check

Draw the condensed structural formula for 2-bromo-1-chlorobutane.

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Naming Cycloalkanes with Substituents

The name of a substituent is placed in front of the

cycloalkane name.

methylcyclobutane CH3

chlorocyclopentane Cl

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Learning Check

Name each of the following.

1. CH3

CH2─ CH3

2.

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Some Properties of AlkanesAlkanes are• nonpolar.• insoluble in water.• less dense than water.• flammable in air. Alkanes with 1-4 carbon atoms are• methane, ethane, propane, and butane.• gases at room temperature.• used as heating fuels.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

Alkanes with 18 or more carbon atoms• have high molar masses.• are waxy solids at room

temperature.• used in waxy coatings of

fruits and vegetables.

Reactions of alkanes: Combustion

In combustion reactions,• alkanes react with oxygen. • CO2, H2O and energy are produced.

Alkane + O2 CO2 + H2O + heat

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Learning CheckWrite a balanced equation for thecomplete combustion of propane

Unbalanced equation

C3H8 + O2 CO2 + H2O

Balance C

C3H8 + O2 3CO2 + H2O

Balance H

C3H8 + O2 3CO2 + 4H2O

Balance O

C3H8 + 5O2 3CO2 + 4H2O

(Balanced)

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Other elements in organic compounds

In organic molecules,

carbon atoms bond • with four bonds.• mostly with H

and other C atoms.

• sometimes to O, N, S,

• sometimes to halogens F, Cl, and Br.

Functional groups are• a characteristic feature

of organic molecules that behave in a predictable way.

• composed of an atom or group of atoms.

• groups that replace a hydrogen atom in the corresponding alkane.

• a way to classify families of organic compounds.

What are functional groups?