Download Chapter 13 Alcohols, Phenols, and Ethers

Spencer L. Seager
Michael R. Slabaugh
www.cengage.com/chemistry/seager
Chapter 13
Alcohols, Phenols, and Ethers
Jennifer P. Harris
ALCOHOLS, PHENOLS, & ETHERS
• A hydroxy group is the –OH functional group.
• An alcohol has an –OH group attached to an aliphatic
carbon. General formula: R-OH
• A phenol has an –OH group on a benzene ring.
• An ether has the functional group:
• General formula: R-O-R’
ALCOHOL EXAMPLES
NAMING ALCOHOLS
• Step 1: Name the longest chain to which the –OH group is
attached. Use the hydrocarbon name of the chain, drop the
final –e, and replace it with –ol.
• Step 2: Number the longest chain to give the lowest number to
the carbon with the attached –OH.
• Step 3: Locate the –OH position.
• Example:
OH
|
CH3—CH2—CH2—CH—CH2—CH3
6
5
4
3
2
1
3-hexanol
NAMING ALCOHOLS (continued)
• Step 4: Locate and name any other groups attached to the
longest chain.
• Step 5: Combine the name and location of other groups, the
location of the –OH, and the longest chain into the final
name.
CH3 OH CH3
• Example:
|
|
|
CH3—CH2—CH—CH—CH—CH3
6
5
4
3
2
1
2,4-dimethyl-3-hexanol
• Note: Alcohols containing two –OH groups are diols,
three –OH groups are triols. The IUPAC names for these
compounds have endings of –diol and –triol rather than
–ol.
NAMING PHENOLS
• Substituted phenols are usually named as derivatives of the
parent compound phenol.
• Examples:
CLASSIFICATION OF ALCOHOLS
PHYSICAL PROPERTIES OF ALCOHOLS
• The –OH group is polar and capable of hydrogen bonding.
• This makes low molecular weight alcohols highly soluble in
water.
• Hydrogen bonding in a water-methanol solution:
PHYSICAL PROPERTIES OF ALCOHOLS
(continued)
• Larger alkanes have greater hydrophobic regions and are
less soluble or insoluble in water.
• Water interacts only with the –OH group of 1-heptanol:
PHYSICAL PROPERTIES OF ALCOHOLS
(continued)
PHYSICAL PROPERTIES OF ALCOHOLS
(continued)
• The –OH group can hydrogen bond between alcohol
molecules leading to relatively high boiling points.
• Hydrogen bonding in pure ethanol:
PHYSICAL PROPERTIES OF ALCOHOLS
(continued)
ALCOHOL REACTIONS
• The removal of water (dehydration) from an alcohol at
180°C is an elimination reaction that produces an alkene.
ALCOHOL DEHYDRATION
TO ALKENE EXAMPLES
DEHYDRATION OF AN ALCOHOL
• Protonation of alcohol
• Formation of carbocation and water
• Formation of double bond and regeneration of catalyst
ALCOHOL REACTIONS (continued)
• Under slightly different conditions (140°C), a dehydration
reaction can occur between two alcohol molecules to
produce an ether.
ALCOHOL DEHYDRATION
TO ETHER EXAMPLE
ALCOHOL REACTIONS (continued)
• Oxidation – the removal of hydrogen atoms
• Alcohol oxidations with an oxidizing (O) agent, such as
K2Cr2O7 and KMnO4:
• Primary alcohols → aldehyde → carboxylic acid
• Secondary alcohols → ketone
• Tertiary alcohols → no reaction
ALCOHOL REACTIONS (continued)
• Primary alcohol oxidation
• Secondary alcohol oxidation
ALCOHOL REACTIONS (continued)
• Tertiary alcohol oxidation
ALCOHOL OXIDATION EXAMPLES
(2) After mixing, the ethanol is oxidized, and
(1) The tube on the left contains orange
K2Cr2O7 and is next to the colorless ethanol. chromium is reduced, forming a grayish green
precipitate.
ALCOHOL REACTIONS (continued)
MULTISTEP REACTIONS
IMPORTANT ALCOHOLS
• Methanol (wood alcohol): CH3OH
• Production:
• Useful as a solvent and industrial starting material
• Highly toxic, if taken internally causes blindness and/or death
IMPORTANT ALCOHOLS (continued)
• Ethanol (ethyl alcohol, grain alcohol): CH3CH2OH
• Produced commercially from ethylene and through biological
(yeast) fermentation of carbohydrates
• Useful as a solvent, industrial starting material, fuel
(gasohol), and found in alcoholic beverages
• Moderately toxic
ETHANOL PRODUCTION METHODS
• Hydration of ethylene:
• Yeast fermentation of carbohydrates:
IMPORTANT ALCOHOLS (continued)
• 2-Propanol (isopropyl alcohol) is the main component of
rubbing alcohol.
• 1,2,3-Propanetriol (glycerol) is used as a food moistening
agent (nontoxic) and for its soothing qualities (soaps).
IMPORTANT ALCOHOLS (continued)
• Antifreezes
1,2-ethanediol (ethylene glycol)
• 1,2-propanediol (propylene glycol)
EXAMPLES OF ALCOHOLS
PHENOLS
• Phenol behaves as a weak acid in water.
• Phenol can react with bases to form salt.
USES OF PHENOLS
• In a dilute solution, phenol is used as a disinfectant.
• Phenol derivatives used as disinfectants:
USES OF PHENOLS (continued)
• Phenol derivatives used as antioxidants in food:
NAMING ETHERS
• IUPAC name: Name the smaller of the two R groups as an
alkoxy group attached to the parent chain by replacing the
–yl ending of the R group with –oxy.
• Common name: Name the groups attached to the oxygen
alphabetically and add the word ether.
common: sec-butyl ethyl ether
CYCLIC ETHERS
• Heterocyclic rings contain atoms other than carbon in the
ring.
PROPERTIES OF ETHERS
• Much less polar than alcohols
• More soluble in water than alkanes,
but less soluble than alcohols
• Low boiling and melting points because of the inability to
hydrogen bond between molecules
• Inert and do not react with most reagents (like alkanes)
• Highly flammable (like alkanes)
PROPERTIES OF ETHERS (continued)
• Hydrogen bonding of dimethyl ether: (a) with water and
(b) no hydrogen bonding in the pure state.
THIOLS: THE –SH (SULFHYDRYL) GROUP
• Most distinguishing characteristic is their strong and offensive
odor
• ethanethiol – added to natural gas
• 1-propanethiol – odor in garlic and onions
• trans-2-butene-1-thiol – odor associated with skunks
THIOL REACTIONS
• Oxidation forms disulfide (-S-S-) linkages, which are
important structural features of some proteins:
• Specific example:
THIOL REACTIONS (continued)
• Oxidation reactions can be reversed with a reducing agent
(H):
THIOL REACTIONS (continued)
• Reacts with heavy metals (Pb2+, Hg2+) to form insoluble
compounds, with adverse biological results:
POLYFUNCTIONAL COMPOUNDS
• Polyfunctional compounds are compounds with two or
more functional groups.
• Functional groups determine chemical properties of
compounds.
• Example:
POLYFUNCTIONAL COMPOUNDS (continued)