1 chapter 11 introduction to organic chemistry: alkanes 11.4 properties of alkanes copyright © 2007...
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Chapter 11 Introduction to Organic Chemistry: Alkanes
11.4
Properties of Alkanes
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
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Some Properties of Alkanes
The properties of alkanes include
being Nonpolar. Insoluble in water. Less dense than water Flammable in air.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
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Alkanes with 1-4 Carbon Atoms
Alkanes with 1-4 carbon atoms are Methane, ethane, propane, and
butane. Gases at room temperature. Used as heating fuels.
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Alkanes with 5-17 Carbon Atoms
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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Alkanes with 18 or more Carbon Atoms
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.
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Boiling Points of Alkanes
Are lowest of organic compounds.
Increase with larger molecules due to increased dispersion forces.
Decrease for branched alkanes.
Increase for cycloalkanes.
TABLE 11.6
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Sample Question – Boiling Point
For the following pairs of hydrocarbon, which one has
the higher boiling point? Why?
1. butane or octane
2. hexane or 2,3-dimethylbutane
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Solution
For the following pairs of hydrocarbon, which one has
the higher boiling point? Why?
1. butane or octane octane has more carbon atoms
2. hexane or 2,3-dimethylbutane
hexane is not branched
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Crude Oil
The hydrocarbons incrude oil are Separated by
boiling points. Heated to higher
temperatures to produce gases that can be removed and cooled.
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Classification of Carbon Atoms
The classification of carbon atoms indicates the
number of carbon atoms attached. A primary carbon (1°) bonds to one carbon atom. A secondary carbon (2°) bonds to two carbon atoms. A tertiary carbon (3°) bonds to three carbon atoms.
CH3
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CH3 —CH2—CH2—CH3 CH3—CH—CH3
primary secondary tertiary
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Combustion of Alkanes
Alkanes
Undergo combustion by reacting with oxygen to produce carbon dioxide, water, and energy.
Are typically not very reactive due to strong C-C single bonds.
alkane + O2 CO2 + H2O + energy
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Balancing a Combustion Reaction
Propane is used to provide heat for
cooking or warming a room. Write a
balanced equation for the complete
combustion of propane.
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Halogenation of Alkanes (Substitution)
When alkanes react with halogens,
The reaction is called substitution, one or more H atoms are replaced with a halogen usually Cl or Br.
Light or heat is required.
A mixture of halogenated products result, but we write the
equation with the monosubstituted product.
Example: ethane and chloride
light
CH3—CH3 + Cl2 CH3—CH2 —Cl
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Example of Bromination
Give the structures and names of the possible monosubstituted products for the reaction of propane with bromine in the presence of light.
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Solution
Give the structures and names of the possible monosubstituted products for the reaction of propane with bromine in the presence of light.
CH3—CH2—CH2— Br
1-bromopropane; propyl bromide
Br
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CH3—CH—CH3
2-bromopropane; isopropyl bromide
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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 an H in the corresponding
alkane. A way to classify families of organic compounds.
Functional Groups
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Alkenes and Alkynes
Alkenes contain a double bond between adjacent carbon atoms.
Alkynes contain a triple bond.
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Alcohols and Ethers
An alcohol contains the hydroxyl (-OH) functional group.
In an ether, an oxygen atom is bonded to two carbon atoms
–C–O–C– .
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Aldehydes and Ketones
An aldehyde contains a carbonyl group (C=O), which is a carbon atom with a double bond to an oxygen atom, attached to at least one hydrogen.
In a ketone, the carbon of the carbonyl group is attached to two other carbon atoms.
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Carboxylic Acids and Esters
Carboxylic acids contain the carboxyl group, which is a carbonyl group attached to a hydroxyl group. O
— C—OH An ester contains the
carboxyl group between carbon atoms.
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Amines and Amides
In amines, the functional group is a nitrogen atom.
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—N —
In amides, the hydroxyl group of a carboxylic acid is replaced by a nitrogen group.
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Functional Groups in Everyday Items
Methyl amine (fish)
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings