14.1 Properties of alcohols

uses of methanol

high performance fuel, chemical feedstock

uses of ethanol

alcoholic drinks, solvent, feedstock

list the physical properties of alcohols compared to alkanes of the same carbon chain length

less volatile, higher melting points, greater water solubility

explain the effect of polarity on the physical properties of alcohols compared to their corresponding alkanes

1) alkanes have nonpolar bonds as the electronegativity of H and C are very similar

2) therefore alkane molecules are nonpolar

3)the IMF between nonpolar molecules include very weak London forces only

4) alcohols have a polar O-H bond because of the difference in electronegativity of the OH and H atoms

5) therefore alcohol molecules are polar

6) IMF include very weak London forces and the stronger H-bonds

explain the trend of volatility and boiling point of alcohols

1) in the liquid state the intermolecular H-bonds hold alcohol molecules together

2) these H-bonds must be broken to go from a liquid to a gas which requires more energy than overcoming the weaker London forces in alkanes

3) therefore alcohols have lower volatility than their corresponding alkanes

explain why alcohols are completely soluble in water

H-bonds form between the polar -OH group of the alcohol and the water molecules

state the trend of solubility of alcohols as hydrocarbon chain size increases

as hydrocarbon chain size increases, solubility decreases