Download Structure and Shape - Chapter 12 Valence Shell Electron Pair

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Structure and Shape - Chapter 12
Valence Shell Electron Pair Repulsion (VSEPR) Theory
In a real structure, the electron pairs will repel each other, distributing themselves in
positions around the central atom so that they are as far away from each other as
possible.
This minimizes the potential energy of the molecule, something molecules like.
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Molecular Geometry
Bond Angle - the angle between two bonds formed by the same central atom.
Table 12. 2 - summarize
Examples: CO 2, H2O, NH3, H3O+, CO32-, NO3-
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Geometry of Multiple Bonds
The second and third electron pairs in double and triple bonds don’
don’t affect molecular
geometry:
Examples: BeF2, CO2, HCN
BF 3, HCOH
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Polarity of Molecules
A polar molecule is one in which there is an uneven or unbalanced distribution
of charge, resulting in + and - poles.
We must know something about the bond angles and geometry before we can decide
on polarity.
Examples: CO 2, H2O
NH 3, BF3, BF2H
HCOH
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Organic Chemistry
Organic chemistry - the chemistry of carbon compounds.
Hydrocarbons - compounds made up only of carbon and hydrogen.
Alkanes - one type of hydrocarbon molecule which consist of carbon atoms
attached to each other, forming chains.
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Hydrocarbons
Methane - CH 4
Ethane - C 2H6 (molecular formula) or CH 3CH3 (line formula)
Propane - C 3H8 or CH3CH2CH3
Butane - C4H10 or CH3CH2CH2CH3 or CH3(CH2)2CH3
Pentane - C5H12 or CH3(CH2)3CH3
General Formula: CnH2n+2
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Hydrocarbons
isomers - molecules with the same molecular formula but different arrangements of
atoms.
Examples: pentane, 2-methylbutane
2- methylbutane,, 2,2-dimethylpropane
2,2-dimethylpropane
Each isomer is different, having its own physical and chemical properties.
- e.g. boiling points and melting points
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Functional Groups
Functional groups - groups of atoms that have chemical properties that depend
on the molecular framework to which they are attached.
Functional groups are important to organic chemistry because they affect how a
molecule reacts.
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Other Structures of Organic Compounds - Functional Groups
1) Alcohols
- alkanes in which a hydrogen atom is replaced by a hydroxyl (OH)
OH) group.
- Example: ethanol, CH 3CH2OH.
2) Ethers
- compounds that have two hydrocarbon groups bonded to an oxygen atom.
- Example: diethyl ether, CH 3CH2OCH2CH3
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Other Structures of Organic Compounds - Functional Groups
3) Carboxylic Acids
- contain a carboxyl (COOH)
COOH) group.
- Example: acetic acid (vinegar), CH 3COOH
4) Esters
- are similar to carboxylic acids, except that the hydrogen atom on the COOH
group has been replaced by a group containing carbon.
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Show aspirin structure.
Show structures of codeine, morphine, and heroin.
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Questions:
You should be able to do the target check questions and examples throughout the
chapter, as well as the end - of - chapter questions that begin on pg. 341. The blue numbered questions have answers provided at the end of the chapter.
Other questions: #1 - 26, 30, 31, 33, 37