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UNIT 4: Alcohols, Phenols and Ethers
12.1 Alcohols: Structure & Physical PropertiesAlcohol- organic compound that contains a
hydroxyl group (-OH) attached to an alkyl group.Has similar bond angle to water.-OH groups are very polar because the O and H
have different electronegativities.H bonds hold alcohol molecules together.Very high boiling points because of the H bonds.The smaller the molecule, the more soluble in
water (much more insoluble past 6 carbons)Solubility has to do with the alcohol being able to
form the intermolecular H bonds with water molecules.
As the nonpolar portion of the alcohol grows (carbon chain), solubility decreases.Think hydrophobic/hydrophilic (from biology)
12.2 Alcohols: NomenclatureUsing the IUPAC system1. Determine the name of the parent
compound (the longest carbon chain with the –OH group)
2. Replace the –e ending of the alkane parent name with –ol ending for alcohol.Ex. Ethane becomes ethanol, Propane becomes
propanol3. Number the parent chain to give the carbon
with the hydroxyl group the lowest number.Name & number all substituents & add them as
prefixes to the alcohol parent name.
Nomenclature Continued
Nomenclature ContinuedIUPAC- 1,2,3-propanetriolCommon- glycerol
12.3 Medically Important Alcohols1. Methanol (Methyl alcohol)- colorless, odorless, liquid, toxic- used as a solvent for other organic
compounds-used to make methanal (formaldehyde)-can be made by heating wood in the
absence of air-can be used as fuel
Medically Important Alcohols2. Ethanol (Ethyl alcohol)-colorless, odorless, liquid-drinkable alcohol OR can be used as a solvent for
other organic compounds-comes from fermentation of carbohydrates
(sugars/ starches)-type of beverage depends on the starting
material (scotch-grain, bourbon-corn, red wine- red/purple grapes)
C6H12O6 → 2CH3CH2OH + 2CO2
Glucose enzyme Ethanol (sugar) action
Medically Important AlcoholsBeverages can have diff. concentrations.
Beverages with high concentrations must be distilled.
Pure ethanol (100%) is for lab use only and is denatured (not drinkable).
Does not change chemical composition, mixed with other chemicals to make toxic.
Medically Important Alcohols3. 2-Propanol (isopropyl alcohol)-called “rubbing alcohol” because it was
once used to give patients baths who had high fevers
-used as disinfectant and astringent-colorless, slight odor, toxic4. 1, 2-Ethanediol (ethylene glycol)-antifreeze-when added to water, decreases freezing
point and increases boiling point-sweet taste, poisonous-colorless, so dye is added
Medically Important Alcohols5. 1,2,3-propantriol (glycerol)-viscous (thick, less fluid), sweet, non-toxic,
liquid-soluble in water-used in make-up, lubricants and
pharmaceuticals-comes from the hydrolysis of fats (the
addition of water causes the formation of soap)
12.4 Classification of AlcoholsBased on the number of alkyl groups
attached to the carbinol carbon (the carbon bonded to the –OH group)
Primary (1°)- single alkyl groupSecondary (2°)- 2 alkyl groupsTertiary (3°)- 3 alkyl groupsNo alkyl groups- Methyl alcohol
12.5 Reactions Involving AlcoholsPreparation of AlcoholsAlcohol is created by adding a water molecule
to the carbon-carbon double bond of an alkene (addition reaction)
-called hydration-requires small amount of acid as a catalyst-can also be created through the hydrogenation
of an aldehyde of ketone (adding H, therefore reducing the aldehyde or ketone)
-catalyst also needed
Preparation of Alcohols Other examples:
Reduction of an aldehyde by adding H2
o Propanal Hydrogen Propanol
Reduction of a ketone by adding H2
+ H2 →
Propanone Hydrogen 2-Propanol
Reactions Involving AlcoholsDehydration of Alcohols-loss of water when heated with acid
(sulfuric acid or phosphoric acid)-elimination reaction because losing atoms
or ions from structure (-OH and –H)-water and alkene produced-reverse of hydration
Dehydration of AlcoholsSometimes you can produce multiple products.
Recall major and minor products. The major product in an elimination reaction is the alkene with the greatest number of alkyl groups on the double bonded carbon. (Zaitsev’s Rule)
Oxidation ReactionsOxidation Reactions-gain of oxygen or loss of hydrogen-need oxidizing agent to complete reaction
(potassium permanganate or chromic acid)-in book, the symbol [O] is used over the
arrow to show that an oxidizing agent is being used
-creates an aldehyde or ketone
Oxidation Reactions
Oxidation ReactionsOxidation of methanol or a 1° alcohol produces
an aldehyde, 2° produces ketone, 3° cannot be oxidized
Side note on oxidation-Ethanol is oxidized in the liver to become
ethanol (acetaldehyde). If too much ethanol in the blood, then too much ethanol will be formed. This causes the effects of the “hangover.” Continued oxidation makes ethanoic acid (acetic acid) which is used as energy in the body. It is then oxidized to carbon dioxide and water.
12.6 Oxidation and Reduction in Living Systems
LEO the lion says GERLose electrons- oxidationGain electrons- reduction This occurs in inorganic compounds (Recall
from Chemistry)Ex. Ag° → Ag+ + 1e- oxidation Br + 1e- → Br- reduction
Oxidation and ReductionWith organic compounds it is hard to tell
whether Oxidation or Reduction has occurred because there may not be a change in charge.
Oxidation = gain of O or loss of HReduction = loss of O or gain of H
oxidizealkane + oxygen alcohol – hydrogen aldehyde +
oxygen carboxylic acid
reduce
12.7 PhenolsCompounds in which a hydroxyl group is
attached to a benzene ring.-polar like alcohols because of the –OH-simpler phenols are somewhat soluble in
water-found in flavorings, used as preservatives,
used in germicides-dilute solutions of phenol used as
antiseptics and disinfectants-concentrated phenols can cause severe
burns
12.8 Ethers-2 alkyl groups bonded to an oxygen
(center)-polar-no –OH group so they do not bond
together using H bonds-lower boiling points than alcohol of a
similar molar mass, but higher boiling points than that of alkanes of similar molar mass.
Nomenclature of EthersIUPAC-Name is based on alkoxy group (alkyl group
bonded to oxygen atom)- substituentEx. CH3 - O methoxy
CH3CH2 - O ethoxy
Ex. IUPAC- Ethoxyethane Common- Diethyl ether
Common SystemName both alkyl groups as prefixes in front of the
etherCan name alphabetically or by size
Ether Properties-Chemically inert-do not react under normal conditions-extremely volatile, highly flammablePrepared in synthesis of 2 alcohols which
removes water (dehydration)
H+
+ → + H2O
Heat
Methanol Methanol Dimethyl ether
Diethyl ether first general anesthetic