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Chapter 20(part 1)

Organic Chemistry

Section 20.1

Carbon Bonding

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Carbon Chemistry

• Carbon is unusual

Bonds strongly to itself

Forms long chains or rings

• Biomolecule – molecule that functions in maintaining and reproducing life

• Organic compounds – vast majority of carbon compounds

Exceptions – oxides and carbonates

Section 20.1

Carbon Bonding


Carbon Chemistry

• When carbon has 4 atoms bound to it these atoms have a tetrahedral shape.

Section 20.1

Carbon Bonding


Double Bond

• Sharing of 2 pairs of electrons.

C C C

H H

H

H

H

H

Section 20.1

Carbon Bonding

C C C

H

H

H

H


Triple Bond

• Sharing of 3 pairs of electrons.

Section 20.2

Alkanes

• Hydrocarbons – compounds composed of carbon and hydrogen

Saturated – all carbon-carbon bonds are single bonds

Unsaturated – containing carbon-carbon multiple bonds


Section 20.2

Alkanes

• Alkanes are saturated hydrocarbons.


Section 20.2

Alkanes

Normal, Straight-chain, or Unbranched Hydrocarbons

• Contain strings or chains of carbon atoms

Can be represented by the structure


Section 20.2

Alkanes

Formulas of the First Ten Straight-Chain Alkanes


Section 20.3

Structural Formulas and Isomerism

Structural Isomerism

• Occurs when two molecules have the same atoms but different bonds.

Butane and all succeeding members of the alkanes exhibit structural isomerism.


Section 20.3

Structural Formulas and Isomerism

The Structural Isomers of C4H10


Section 20.4

Naming Alkanes

Rules for Naming Alkanes

1. Find the longest continuous chain of carbon atoms. This chain (called the parent chain) determines the base alkane name. . For alkanes beyond butane, add –ane to the Greek root for the number of carbons.

CH3–CH2–CH2–CH2–CH2–CH3 = hexane

Alkyl substituents: drop the –ane and add –yl.

C2H6 is ethane

–C2H5 is ethyl


Section 20.4

Naming Alkanes


2. Number the carbons in the parent chain, starting at the end closest to any branching (the first alkyl substituent). When a substituent occurs the same number of carbons from each end, use the next substituent (if any) to determine from which end to start numbering.

3. Using the appropriate name for each alkyl group, specify its position on the parent chain with a number.

CH3

|

CH3–CH2–CH–CH2–CH2–CH3

1 2 3 4 5 6

3-methylhexane


Section 20.4

Naming Alkanes


4. When a given type of alkyl group occurs more than once, attach the appropriate prefix (di– for two, tri– for three, and so on) to the alkyl name.

5. The alkyl groups are listed in alphabetical order, disregarding any prefix.

CH3 CH3

| |

CH3–CH2–CH–CH–CH2–CH3

1 2 3 4 5 6

3,4-dimethylhexane


Section 20.4

Naming Alkanes

The Most Common Alkyl Substituents and Their Names


Section 20.4

Naming Alkanes

Exercise

Name each of the following:

a)

2,2,4,5-tetramethylhexane

b)

3,6-diethyl-3-methyloctane


H3C C CH2 CH CH2 CH3

CH3

CH3 CH3

CH3

H3C C CH2 CH2 CH CH2

CH2

CH2

CH2CH3

CH3

CH3

CH3

Section 20.5

Petroleum

• Hydrocarbons are an energy resource.

• Petroleum – thick, dark liquid composed mostly of hydrocarbon compounds

• Natural gas – consists mostly of methane, usually associated with petroleum deposits


Section 20.6

Reactions of Alkanes

Combustion Reactions

• At a high temperature, alkanes react vigorously and exothermically with oxygen.

• Basis for use as fuels.


4 10 2 2 22C H ( ) + 13O ( ) 8CO ( ) + 10H O( )®g g g g

Section 20.6


Substitution Reactions

• Primarily where halogen atoms replace hydrogen atoms.


4 2 3

3 2 2 2

2 2 2 3

3 2 4

CH + Cl CH Cl + HCl

CH Cl + Cl CH Cl + HCl

CH Cl + Cl CHCl + HCl

CHCl + Cl CCl + HCl

¾¾®

¾¾®

¾¾®

¾¾®

hv

hv

hv

hv

Section 20.6


Dehydrogenation Reactions

• Hydrogen atoms are removed and the product is an unsaturated hydrocarbon.


chapter 20 - hsbr1.com€¦ · naming alkanes rules for naming alkanes 2. number the carbons in the...

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