Ochem

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Review for exam II

Exam for Wednesday (part A)
General descriptions of organic molecules
Saturated versus unsaturated molecules
How to identify each and what properties each holds
Given a molecular formula- draw all isomers possible
Soluble or insoluble?
Enantiomers, diastereomers, not isomers, cis/trans, etc
Identify chiral centers
Identify the compounds as being an acid, base or neither
Hydrogen bonding, dipole-dipole interactions
Rank several compounds by boiling point, melting point or solubility

Boiling points increase as intermolecular attractive forces increase. For the alkanes, which are non-polar hydrocarbons, the intermolecular forces are induced dipole forces. In the case of the alcohols, the intermolecular forces include induced dipole forces, dipole forces, and hydrogen bonding.

Induced dipole forces increase with increasing molecular weight, so the boiling points of the straight chain alkanes increase as the number of carbon atoms in the chain increases. Therefore pentane, CH3CH2CH2CH2CH3, has a higher boiling point than butane, CH3CH2CH2CH3.

For the same reason, the boiling points of the straight chain alcohols also increase as the number of carbon atoms in the chain increases. Therefore butanol, CH3CH2CH2CH2OH, has a higher boiling point than propanol, CH3CH2CH2OH.

Because of hydrogen bonding, the boiling point of an alcohol is higher than that of the alkane with the closest molecular weight, which is the one with one more carbon atom. Therefore, CH3CH2CH2CH2OH has a higher boiling point than CH3CH2CH2CH2CH3.

Solubility Substances dissolve best when solute-solvent interactions are similar to solute-solute interactions. As a result of this, like things tend to dissolve like things: non-polar solutes dissolve best in non-polar solvents, and polar or ionic solutes dissolve best in polar solvents.

Since water is a polar solvent that is capable of hydrogen bonding, it will be a better solvent for polar solutes,...
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