Download L2 - Alcohols and Phenols

Alcohols
Alcohols
and
Phenols
• Organic compound containing one or
more hydroxyl groups, (-OH). General
formula R-OH.
Space-filling models for the three
simplest unbranched-chain alcohols:
methyl alcohol, ethyl alcohol, and propyl
alcohol.
Naming Alcohols
Step 1: Name the longest chain to which the –
OH group is attached. Use the alkane name of
the chain, drop the –e ending, and replace it with
–ol.
Step 2: Number the longest chain to give the
lowest number to the carbon with the –OH.
Step 3: Locate the –OH position.
Example:
Ethanol
OH
|
CH3—CH2—CH2—CH—CH2—CH3
6
5
4
3
2
1
propanol
Methanol
3-hexanol
Naming Alcohols, cont.
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.
Name the Following:
OH
1.
OH
2.
3.
Example:
4.
CH3 OH CH3
|
|
|
CH3—CH2—CH2—CH—CH—CH3
6
5
4
3
2
1
HO
OH
2,4-dimethyl-3-hexanol
1
Naming Alcohols, cont.
Name the Following:
Step 6: Compounds containing more than
one hydroxyl groups are called glycols and are
named by adding di, tri, etc… before the –ol
suffix of the parent chain name.
OH
1.
OH
HO OH
2.
OH
Example:
3.
OH CH3 OH CH3
|
|
|
|
CH3—CH2—CH2—CH—CH—CH3
1
2
3|
4
5
6
OH
4.
HO
OH
HO
3,5-dimethyl-2,3,4-hexantriol
Naming Alcohols, cont.
Alkyl Nomenclature: Short chained alcohols
are commonly named as alkyl substituents on
a hydroxyl parent chain.
•To name alcohols according to alkyl
nomenclature, treat the –OH group as the
parent chain and name the alkyl substituent
followed by the word alcohol.
OH
Example:
CH3-CH2-OH
ethyl alcohol
OH
Name the Following (giving both IUPAC
and alkyl nomenclature when possible):
1.
2.
OH
OH
OH
3.
OH
4.
OH
OH
5.
OH
iso-propyl alcohol
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:
Why are there no quaternary alcohols?
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Solubility
Physical Properties of Alcohols, cont.
•Solubilities
in water of
selected
primary (1o)
alcohols.
Larger alkanes have greater hydrophobic
regions and are less soluble or insoluble in
water.
Water interacts only with the hydrophilic
–OH group of 1-heptanol:
•Notice as
chain length
increases,
solubility
decreases
Physical Properties of Alcohols, cont.
Space-filling
molecular models
showing the nonpolar
(green) and polar (pink)
parts of methanol
and 1-octanol.
The –OH group can hydrogen bond between
alcohol molecules leading to relatively high
boiling points.
Hydrogen bonding in pure ethanol:
Boiling Points
•Boiling points of
selected primary
(1o) alcohols
compared to
alkanes and
ethers of similar
molecular
weights
•Notice B.P.’s
increase with
increasing M.W.
Important Alcohols:
Methanol
Methanol (Wood alcohol) CH3OH.
Production:
Useful as a solvent and industrial
starting material.
Highly toxic, causes blindness and/or
death.
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Important Alcohols, cont.
Ethanol
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).
found in alcoholic beverages. Moderately toxic.
Important Alcohols, cont.
2-propanol (isopropyl
isopropyl alcohol)
alcohol
is the main component of rubbing
alcohol.
OH
Important Alcohols, cont.
Antifreezes/deicers
ethylene glycol).
1,2-ethanediol (ethylene
glycol
1,2,3-propanetriol (glycerol
glycerol)
glycerol is used
as a food moistening agent (nontoxic)
and for its soothing qualities (soaps).
CH3 – CH -- CH2
OH
OH
OH
Alcohols vs. Phenols
Alcohol – has an –OH group attached to
an aliphatic carbon. General formula ROH.
Phenol – has an –OH group on a
benzene ring.
Naming Phenols as the Parent Chain
Step 1: Identify all substituents and number
from the hydroxyl group (1) to give all
substituents the lowest possible designation
Step 2: name all substituents in alphabetical
order
* ortho-, meta-, and para-,
designations may be used for phenols with
only one additional substituent.
Example:
OH
3-methyl phenol
Or
m-methyl phenol
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Naming Phenols as a Substituent
Step 1: Identify the parent chain, numbering
according to rules for alkanes, -enes, or
alcohols.
Step 2: list all substituents in alphebetical
order with positions, including phenols.
*use ortho-, meta-, and paradesignations to describe the position of the
hydroxyl in respect to the bond to the parent
chain.
2,3-dimethyl-5-mphenol heptane
Example:
OH
Name the Following:
1.
2.
OH
OH
OH
OH
3.
4.
Cl
OH
OH
OH
5.
OH
Uses of Phenols:
In a dilute solution, phenol is a
disinfectant.
Phenol derivatives used as disinfectants
o-phenylphenol
2-benzyl-4-chlorophenol
Phenol derivatives used as antioxidants
in food as preservatives
BHA (butylated hydroxy anisole)
BHT (butylated hydroxy toluene)
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