Transcript Alcohols, Phenols, Thiols, and Ethers

Alcohols, Phenols,
Thiols, and Ethers
Chapter 13
Introduction
• Alcohol – organic compound that contains
a hydroxyl (-OH) group attached to an
alkyl group
• Phenol – organic compound that contains
a hydroxyl (-OH) group attached to an aryl
group
• Ether – organic compound that has two
alkyl or aryl groups attached to the oxygen
atom; can be thought of as a substituted
alcohol.
Examples
Alcohols -OH hydroxyl
CH3-OH
CH3CH2-OH
OH
OH
Phenols
Ethers
-O-
CH3-O-CH3
Practice Problem 1
Classify each as an alcohol (1), phenol (2), or
an ether (3):
A. _____ CH3CH2-O-CH3
OH
B. _____
CH3
C. _____ CH3CH2OH
Solution 1
Classify each as an alcohol (1), phenol (2), or
an ether (3):
A. ____ CH3CH2-O-CH3
OH
B. _ __
CH3
C. ____ CH3CH2OH
Structure and Properties
• R-O-H portion of alcohol is similar to the
structure of water.
– The oxygen and two atoms bonded to it lie in
the same plane.
– The bond angle is 104°
• Hydroxyl groups are very polar because of
significantly different electronegativities.
– Hydrogen bonding can form between alcohol
molecules.
Hydrogen Bonding

O


R
H
H
O
O
R
 H

H
O
H

H
Results of Hydrogen Bonding
• Alcohols boil at much higher temperatures
than hydrocarbons of similar molecular
weight.
• Alcohols with fewer than five carbons are
very soluble in water.
• Alcohols with five to eight carbons are
moderately soluble in water.
• As the nonpolar (R) portion of the alcohol
gets larger, the water solubility decreases.
Solubility of Alcohols
• Very large alcohols are not soluble in
water.
• Hydrophobic – “water fearing”; used to
describe nonpolar region of molecule
• Hydrophilic – “water loving”; used to
describe polar region of molecule
CH3CH2CH2CH2CH2CH2CH2CH2CH2OH
Hydrophobic
Hydrophilic
Solubility of Alcohols
• An increase in the number of hydroxyl
groups will increase the influence of the
polar hydroxyl group.
– Diols and triols are more water soluble
than alcohols with only a single hydroxyl
group.
Practice Problem 2
• Circle the more soluble alcohol in each pair.
H2
C
OH
A.
H3C
H2
C
OR
C
H2
H3C
C
H2
OH
OH
B.
C.
OH
OR
OR
OH
OH
Solution 2
• Circle the more soluble alcohol in each pair.
H2
C
OH
A.
H3C
H2
C
OR
C
H2
H3C
C
H2
OH
OH
B.
C.
OH
OR
OR
OH
OH
Nomenclature of Alcohols
• A carbon compound that contain -OH
(hydroxyl) group
• In IUPAC name, the -e in alkane name is
replaced with -ol.
CH4
methane
CH3OH
methanol
CH3CH3
ethane
CH3CH2OH
ethanol
(methyl alcohol)
(ethyl alcohol)
More Names of Alcohols
• IUPAC names for longer chains number the
chain from the end nearest the -OH group.
CH3CH2CH2OH
OH
CH3CHCH3
CH3
OH
CH3CHCH2CH2CHCH3
Alcohols that contain more than
one hydroxyl group
• Alcohols containing two hydroxyl groups
are named –diols.
• Alcohols containing three hydroxyl groups
are named –triols.
• A number giving the position of each of the
hydroxyl groups is needed in these cases.
Practice Problem 3
Name the following alcohols:
A.
OH
CH3CHCHCH2CH3
CH3
OH
B.
Solution 3
Name the following alcohols:
A.
OH
CH3CHCHCH2CH3
CH3
OH
B.
Homework
Pages 379-380 13.1113.14
Page 360 13.1 – 13.2
Due Tomorrow!!!!
Section 13.3
• It is your responsibility to read
over section 13.3 – Medically
Important Alcohols (pgs. 360361) and take notes on the
material covered!
• It will be on the weekly quiz
and the test!
Classification of Alcohols
• Alcohols can be classified as primary (1°),
secondary (2°), or tertiary (3°) depending on the
number of alkyl groups attached to the carbon
bearing
the –OH
group.
H
H
CH3
H
C
H
OH
Methanol
H3 C
C
H
1° alcohol
ethanol
OH
H3 C
C
OH
2° alcohol
2-propanol
CH3
H
H3 C
C
CH3
OH
3° alcohol
2-methyl-2-propanol
Practice Problem 4
Classify each of the following alcohols
as primary, secondary, tertiary, or
aromatic.
1.
2.
3.
4.
1-butanol
3-pentanol
1-methylcyclopentanol
2-methyl-2-pentanol
Solution 4
1. 1-butanol
2. 3-pentanol
3. 1-methylcyclopentanol
4. 2-methyl-2-pentanol
Homework
• Pages 380-381: 13.15,
13.16, 13.18, 13.19, 13.20,
13.21, 13.22, 13.27, and
13.28
Due Tomorrow!
Preparation of Alcohols
• REVIEW: Hydration – an addition reaction in
which a water molecule is added to an alkene;
requires acid as catalyst
R
R
R
H
+
R
R
H
R
OH
H
R
Alkene

O
H+
R
Water
Markovnikov’s rule applies!!
Alcohol
Hydration Examples
• Ethene
• 1-butene
Preparation of Alcohols
• Hydrogenation of aldehydes and ketones
OH
O
H
+
R1
R2
Catalyst
R1
R2
H
H
In an aldehyde, R1 and R2 may be either alkyl groups or H.
In a ketone, R1 and R2 are both alkyl groups.
We will discuss this in more detail in section 14.4.
Hydrogenation Examples
• Ethanal
• 2-propanone
Preparation of Alcohols
YOU TRY THESE!
+
Dehydration of Alcohols
• Alcohols undergo dehydration (lose water)
when heating with concentrated sulfuric or
phosphoric acid.
• Dehydration is an example of an
elimination reaction.
• Elimination reaction – a reaction in which a
molecule loses atoms or ions from its
structure.
• Dehydration is opposite of hydration!
Dehydration of Alcohols
• General Reaction
H+
RCH2CH2OH
RCH=CH2 + H2O
Heat
• Ethanol
H+
CH3CH2OH
Heat
• 2-butanol
H
H
H
OH H
C
C
C
C
H
H
H
H
H+
H
Heat
Dehydration of Alcohols
• Zaitsev’s rule – in an elimination reaction,
the alkene with the greatest number of
alkyl groups on the double bonded carbon
(more highly substituted alkene) is the
major product of the reaction
• Another example:
Oxidation Reactions
• Oxidation – loss of electrons; add O and/or
lose H
• Reduction – gain of electrons; add H
and/or lose O
• Common oxidizing agents:
– Basic potassium permanganate (KMnO4/OH-)
– Chromic Acid (H2CrO4)
• [O] Any general oxidizing agent
Oxidation of Primary Alcohols
• General equation:
– Primary alcohol
aldehyde
RCH2CH=O
EXAMPLE:
1-propanol
Oxidation of Secondary
Alcohols
• General equation:
– Secondary alcohol
EXAMPLE:
2-propanol
ketone
O
R-C-R
Oxidation of Tertiary Alcohols
• General equation:
– Tertiary alcohol
NO REACTION!!!
YOU TRY THESE!
H
H
H
OH H
C
C
C
C
H
H
H
H
[O]
H
[O]
OH
[O]
HO
CH 3CH 2OH
[O]
Phenols
• Phenols – compounds in which the
hydroxyl group is attached to a benzene
ring
• They are polar compounds because of the
polar hydroxyl group.
• Smaller phenols are somewhat soluble in
water.
• They are found in fragrances and
flavorings and are also used as
preservatives and germicides.
Common Phenols and their
Uses
(CH3)2HC
CH3
Thymol (mint)
OH
(CH3)2HC
CH3
OH
Carvacrol (savory)
Common Phenols and their
Uses
C(CH3)3
CH3
OH
(CH3)3C
OH
Butylated hydroxytoluene,
BHT(Food preservative)
Phenol
(Carbolic acid when dissolved in water)
Antiseptic and disinfectant used by
Joseph Lister to bathe wounds and sterlize
instruments
Ethers
Ethers
• What are they?
• How are they used?
• What do you know about them?
Structure of Ethers
• Similar structure to alcohols
Alcohols: R-OH
–OH is “hydroxy” group
Ethers: R-OR
–OR is “alkoxy” group
Alkoxy group
• “R” groups can be
the same:
• “R” groups can be
different:
CH3-O-CH3
CH3CH2CH2-O-CH3
• Both “R” groups
have one carbon
• One “R” group has
three carbons while
the other has one
Alkoxy group
• The root names are used with –oxy to
name that portion of the ether:
– meth- + -oxy
– eth- + -oxy = methoxy
= ethoxy
– prop- + -oxy
= propoxy
Naming ethers – IUPAC Way
1. Find the root name of the smaller “R” group
Ex: meth-, eth-, prop2. Add –oxy
Ex: methoxy, ethoxy, propoxy
3. Add the full name of the larger “R” group
EXAMPLE:
O
methoxypropane
Name that ether
O
O
O
Draw the structure of:
1. methoxypropane
2. methoxyoctane
3. propoxypropane
4. ethoxypentane
Naming Ethers – Common
Name
• Name by placing the names of the two alkyl
groups attached to the ether oxygen as words
in front of the word “ether.” Typically this is
done in alphabetical order.
O
Diethyl Ether
O
Ethyl methyl ether
O
Butyl propyl ether
Properties of ethers
• The C-O bond in ethers is polar, making
the molecule polar
• Ethers have very low boiling points
• Ethers are relatively inert, but flammable
in air
Let’s compare…
Ether
CH3 –O-CH2CH3
Alcohol
CH3CH2CH2-OH
Molecular Formula:
C3H8O
Molecular Weight:
60.09g/mol
Boiling Point:
7.9°C
Molecular Formula:
C3H8O
Molecular Weight:
60.09g/mol
Boiling Point:
97.2°C
Preparing ethers
• Ethers are formed from alcohols
R-OH + R’-OH 
R-O-R’ +H2O

H+
– R and R’ can be the same or
different
– Called a dehydration reaction
Predict the products
CH3OH + CH3CH2OH
H+
CH3CH2CH2OH + CH3CHCH3
OH
H+
Common uses
• Ethers as anesthetics:
– Penthrane
– Enthrane
• Ethers as additives in gasoline
– MTBE – methyl tert-butyl ether
Thiols
• Compounds that contain the sulfhydryl
group (-SH)
• Similar to alcohols in structure, but the
sulfur atom replaces the oxygen atom
• Have nauseating aromas – defense spray
of North American striped skunk
H
Trans-2-butene-1-thiol
H2C
SH
CH3
H
Naming Thiols
• Use the same rules as for alcohols except
that the full name of the alkane is retained.
• Add the suffix –thiol.
CH3CH2SH
ethanethiol
CH3
CH3CHCH2CH2
3-methyl-1-butanethiol
SH
HSCH2CH2SH
1,2-ethanedithiol
Uses of Thiols
• Thiols are involved in protein structure and
conformation.
• Cysteine is an amino acid that contains a
sulfhydryl group.
• BAL (British Anti-Lewisite) is used as an
antidote for mercury poisoning.
• Coenzyme A serves as a carrier of acetyl
groups in biochemical reactions.
Homework
•Pg. 381-382: 13.43,
13.44, 13.45, 13.48,
13.49, 13.51, 13.52,
13.53, 13.59, 13.60