Chapter 10--Alkanes

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Chapter 10--Alkanes

• Dr. Ellen Wilson, RPh, PhD
• CHE1230

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Why Are There So Many Organic Compounds?
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Why are there so Many Carbon Compounds?

• Carbon forms stable, covalent bonds with
• other carbon atoms
• What does this mean?

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Types of bonding

• Covalent Bonding

• Ionic Bonding

Sharing of electrons
CH3CH2CH2CH2CH3
Organic chemistry bonding
Partial charges dipole moments
Discrete molecules
Dissolve but dont dissociate
Nonelectrolytes
Transfer of electrons
Na Cl- NaCl
Inorganic chemistry bonding
Full charges, ions
Lattice structures
Dissociate in water
Electrolytes
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Why Are There So Many Organic Compounds?

• Carbon forms stable, covalent bonds with other
• atoms such as H, O, N, S, and halogens

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What is a Functional Group?

• A specific group of atoms within a molecule that
  help
• define the properties and reactivity of the
  molecule
• Will have the same properties regardless of the
• molecule to which it is attached

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Common Functional Groups

• See inside back cover of text for these examples
  and more.

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Functional Groups Make A Big Difference
Butane Pentane Butanol
Gas Liquid Liquid
BP-0.5oC 36.1oC 117.73oC
Insoluble in water Insoluble in water Soluble
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Functional Groups Give Unique Properties

• Many biologically active molecules are esters,
  ethers, carboxylic acids, and amines

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Functional Groups Allow Us to Predict Properties
of Molecules

• All alcohols will have the same general
  properties
• All amines will have the same general properties
• All carboxylic acids will have the same general
  properties
• Even within a larger molecule, the functional
  group will have predictable properties even if
  they are not the properties of the entire molecule

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Why Are There So Many Organic Compounds?

• Carbon can form double and triple bonds
• with other carbon atoms or other atoms

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Why Are There So Many Organic Compounds?

• The number of ways that carbon and other atoms
• can combine is almost limitless

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Two compounds can have exactly the same molecular
formulas but have different properties based on
the arrangement of the atoms
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• Each of the statements given below is true but
• John Dalton may have had trouble explaining them
• with his atomic theory. Give explanations for
  each
• of the following statements
• ethyl alcohol and dimethyl ether have the same
  composition by mass52 carbon, 13 hydrogen, and
  35 oxygen. However, they have different melting
  points, boiling points, and solubility in water.

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Compounds that have the same molecular formula
but different structural formulas are called
structural isomers
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In lab, you have already discovered some of the
properties of hydrocarbonsWhat makes the
physical properties of hydrocarbons different
from the physical properties of inorganic
compounds?
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Bonding Makes the Difference

• Covalent Bonding

• Ionic Bonding

Sharing of electrons
CH3CH2CH2CH2CH3
Organic chemistry bonding
Partial charges dipole moments
Discrete molecules
Dissolve but dont dissociate
Nonelectrolytes
Transfer of electrons
Na Cl- NaCl
Inorganic chemistry bonding
Full charges, ions
Lattice structures
Dissociate in water
Electrolytes
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How Do Melting/Boiling Points Differ?

• Organic Compounds

• Inorganic Compounds

• Low MP and BP

• High MP and BP

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How Does Solubility Differ?

• Organic Compounds

• Inorganic Compounds

• Often insoluble in water
• Why?
• Why not?

• Soluble in water
• Why?

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How Do Reaction Rates Differ?

• Organic Compounds

• Inorganic Compounds

• Often slow to react

• Much easier to react

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Comparison

• METHANE

• NaCl

• Type of bonding?
• BP -164oC
• MP -182oC
• Slightly soluble in water
• Flammable
• Slow to react
• Can be S, L or G
• Nonelectrolyte

• Type of bonding?
• BP 1433oC
• MP 801oC
• 36g/100mL water
• Nonflammable
• Quick to react
• Exists at S at RT
• Electrolyte

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Overview of Hydrocarbons
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What are Alkanes?

• Saturated
• Base molecule contains only C and H
• No double or triple bonds

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The First Four Alkanes

• Methane, ethane, propane, butane
• CH4, C2H6, C3H8, C4H10

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A Molecular FormulaCH4, C2H6, C3H8,
C4H10gives the type and number of atoms in the
compound but tells nothing about the structure of
the compound
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A Structural Formula gives the actual
arrangement of the atoms in a molecule
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A Condensed Formula represents the arrangement of
the atoms without drawing all the bonds

• CH4
• CH3CH3
• CH3CH2CH3
• CH3CH2CH2CH3

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Structural and Condensed Formulas Are Especially
Useful When Dealing With Structural Isomers

• butane

• isobutane

• C4H10
• CH3CH2CH2CH3

• C4H10
• (CH3)3CH

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Remember, Remember, RememberCarbon forms 4
bondsHydrogen forms 1 bond
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Structural and Condensed Formulas Are Especially
Useful When Dealing With Isomers

• pentane

• isopentane

• C5H12
• CH3CH2CH2CH2CH3

• C5H12
• CH3CH(CH3)CH2CH3

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PRACTICE

• Write the structural formulas from the following
  condensed formulas
• CH3CH2C(CH3)3
• (CH3)3CC(CH3)3
• (CH3)3CBr

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PRACTICE

• Write the
• condensed formulas
• from the following
• structural formulas

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Nomenclature of Alkanes

• NAME the parent compound
• The first TEN straight chain alkanes are
• Methane
• Ethane
• Propane
• Butane
• Pentane
• Hexane
• Heptane
• Octane
• Nonane
• Decane

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Nomenclature of Alaknes

• NUMBER the parent compound
• Find the longest chain
• Start numbering so that any substituents get the
  lowest number possible

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Representative Substituents

• --CH3
• --CH2CH3
• --CH2CH2CH3
• --CH2CH2CH2CH3
• --CH2CH2CH2CH2CH3
• --F
• --Br
• --Cl
• --I

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Examples

• Name number the longest continuous carbon chain
• Name and number the substituent

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Examples

• Name number the longest continuous carbon chain
• Name and number the substituent

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Examples

• Name number the longest continuous carbon chain
• Name and number the substituent

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More Examples

• Name number the longest continuous carbon chain
• Name and number the substituent

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More Examples

• Name number the longest continuous carbon chain
• Name and number the substituent

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Reactions of Alkanes

• Combustion
• An alkane oxygen gives carbon dioxide plus
  water
• An important side reaction?

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Reactions of Alkanes

• Halogenationan alkane plus a halogen gives an
  alkyl halide (substituted alkane) plus a hydrogen
  halide (acid)
• CH4 Br2 ? CH3-Br HBr
• CH3CH3 Cl2 ? CH3CH2-Cl HCl

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Is your Cycloalkane a BOAT or a CHAIR?
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Is Your Hydrogen Axial or Equatorial?