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