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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 - PowerPoint PPT Presentation
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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
Phenols
Ethers -O- CH3-O-CH3
OHOH
Practice Problem 1
Classify each as an alcohol (1), phenol (2), or an ether (3):
A. _____ CH3CH2-O-CH3 C. _____ CH3CH2OH
B. _____
OH
CH3
Solution 1
Classify each as an alcohol (1), phenol (2), or an ether (3):
A. ____ CH3CH2-O-CH3 C. ____ CH3CH2OH
B. _ __
OH
CH3
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
R O
H
O
H
H
O
R
H
O
HH
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.
• 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
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.
H3C CH2
OHA. OR
H3C
H2C
CH2
H2C
OH
B.OH
OH
OR OH
C. OROH
Solution 2
• Circle the more soluble alcohol in each pair.
H3C CH2
OHA. OR
H3C
H2C
CH2
H2C
OH
B.OH
OH
OR OH
C. OROH
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 (methyl alcohol)
CH3CH3 ethane
CH3CH2OH ethanol (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
OHB.
HomeworkPages 379-380 13.11-13.14
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. 360-361) 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.
C
H
HH
OH
H3C C
H
OH
H
H3C C
CH3
OH
H H3C C
CH3
CH3
OH
Methanol 1° alcohol 2° alcohol 3° alcohol
ethanol 2-propanol 2-methyl-2-propanol
Practice Problem 4
Classify each of the following alcohols as primary, secondary, tertiary, or aromatic.
1. 1-butanol
2. 3-pentanol
3. 1-methylcyclopentanol
4. 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
RR
R R
+
H
O H
H+ HR
R
R OH
R
Alkene Water Alcohol Markovnikov’s rule applies!!Markovnikov’s rule applies!!
Hydration Examples
• Ethene
• 1-butene
Preparation of Alcohols
• Hydrogenation of aldehydes and ketones
O
R1 R2
+H
HH
R2R1
OH
Catalyst
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
• Ethanol
• 2-butanol
RCH2CH2OHH +
RCH=CH2 + H2O
CH3CH2OHH +
C C C CH
H
H H
H H
OH
H
H
HH +
H e a t
Heat
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 ketone
O
R-C-R
EXAMPLE:
2-propanol
Oxidation of Tertiary Alcohols
• General equation:– Tertiary alcohol NO REACTION!!!
YOU TRY THESE!C C C CH
H
H H
H H
OH
H
H
H[O ]
OH
[O ]
OH
[O ]
CH3CH2OH[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
OH
(CH3)2HC Thymol (mint)
CH3
OH
(CH3)2HCCarvacrol (savory)
Common Phenols and their Uses
OH
(CH3)3C
CH3
C(CH3)3
Butylated hydroxytoluene, BHT(Food preservative)
OH
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:
CH3-O-CH3
• Both “R” groups have one carbon
• “R” groups can be different:
CH3CH2CH2-O-CH3
• 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
– prop- + -oxy
= methoxy
= ethoxy
= propoxy
Naming ethers – IUPAC Way
1. Find the root name of the smaller “R” group Ex: meth-, eth-, prop-
2. Add –oxy
Ex: methoxy, ethoxy, propoxy
3. Add the full name of the larger “R” group
EXAMPLE:
Omethoxypropane
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 O
O
Diethyl Ether Ethyl methyl ether
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
Molecular Formula:
C3H8OMolecular Weight:
60.09g/molBoiling Point:
7.9°C
Alcohol
CH3CH2CH2-OH
Molecular Formula:
C3H8OMolecular Weight:
60.09g/molBoiling Point:
97.2°C
Preparing ethers
• Ethers are formed from alcohols
R-OH + R’-OH R-O-R’ +H2O
– R and R’ can be the same or different
– Called a dehydration reaction
H+
Predict the products
CH3OH + CH3CH2OH H+
CH3CH2CH2OH + CH3CHCH3H+
OH
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
H2C
CH3H
H
SH
Trans-2-butene-1-thiol
Naming Thiols
• Use the same rules as for alcohols except that the full name of the alkane is retained.
• Add the suffix –thiol.
CH3CH2SH
CH3CHCH2CH2
CH3
SH
HSCH2CH2SH
ethanethiol
3-methyl-1-butanethiol
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