Organic Chemistry II
CHEM 271
Chapter One
Alcohols, Diols and Thiols
Nomenclature of Alcohols
Functional Class Nomenclature
of Alcohols( Common Names)
Name the alkyl group and add "alcohol" as a
separate word.
CH3CH2OH
Ethyl alcohol
CH3CHCH2CH2CH2CH3
CH3
CH3CCH2CH2CH3
OH
1,1-Dimethylbutyl
alcohol
OH
1-Methylpentyl alcohol
4
IUPAC Nomenclature of Alcohols
•Name as "alkanols." Replace –e ending of alkane
name by -ol.
•Number chain in direction that gives lowest number
to the carbon that bears the —OH group.
CH3CH2OH
Ethanol
CH3CHCH2CH2CH2CH3
OH
2-Hexanol
CH3
CH3CCH2CH2CH3
OH
2-Methyl-2-pentanol
Name these:
CH3
CH3
CH CH2OH
2-methyl-1-propanol
OH
CH3
CH CH2CH3
2-butanol
CH3
CH3
C
OH
OH
CH3
2-methyl-2-propanol
Br
CH3
3-bromo-3-methylcyclohexanol
=>
6
Unsaturated Alcohols
 Number the chain in thedirection that gives the
lowest number to the carbon that bears the OH
group
OH
CH2
CHCH2CHCH3
4-penten-2-ol (old)
pent-4-ene-2-ol
=>
7
Naming Priority
•
•
•
•
•
•
Acids
Esters
Aldehydes
Ketones
Alcohols
Amines
•
•
•
•
•
Alkenes
Alkynes
Alkanes
Ethers
Halides
=>
Chapter 10
8
Hydroxy Substituent
• When -OH is part of a higher priority class of
compound, it is named as hydroxy.
• Example:
OH
CH2CH2CH2COOH
4-hydroxybutanoic acid
=>
9
• Primary: carbon with –OH is bonded to one
other carbon.
-CH2OH
• Secondary: carbon with –OH is bonded to two
other carbons.
-CHOH
• Tertiary: carbon with –OH is bonded to three
other carbons.
-COH
=>
10
CH3
CH3
CH3
CH3
CH CH2OH
C
OH
CH3
OH
CH3
CH
CH2CH3
=>
12
Diols
• Two numbers are needed to locate the two
-OH groups.
• Use -diol as suffix instead of -ol.
OH
HO
1,6-hexanediol
=>
Chapter 10
13
Glycols
• 1, 2 diols (vicinal diols) are called glycols.
• Common names for glycols use the name of the
alkene from which they were made.
CH2CH2
CH2CH2CH3
OH OH
OH OH
1,2-ethanediol
1,2-propanediol
ethylene glycol
propylene glycol
=>
14
Glycrol
• 1, 2,3 Triols are called glycrol>
C H2 CHCH2
OH OHOH
Thiols
• Contains an –SH (sulfhydryl) group.
• Is named by selecting the longest carbon chain that
contain the -SH. We add -thiol to the name of the parent
alkane.
• Parent chain is numbered from the end nearest tothe -SH
group.
Methanethiol
Ethanethiol
CH3─S─H
CH3─CH2─S─H
Physical Properties of Alcohols
1. Alcohols are polar molecules (because of O-H and CO).
2. Have higher boiling point than Alkanes, Alkenes &
Alkynes due to Hydrogen bonding involves oxygen of
one molecule and hydrogen of another in alcohol
molecules.
3. As the molecular weight increase, boiling point
decrease.
4. As the molecular weight increase, solubility in water
decrease .
5. The solubility of alcohols in water is due to hydrogen
bonding between alcohol and water molecules.
6. They are weak acids (weaker than Phenol).
PHYSICAL PROPERTIES OF ALCOHOLS, cont.
• The –OH group can hydrogen bond between alcohol molecules
leading to relatively high boiling points.
• Hydrogen bonding in pure ethanol:
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:
Acidity of Alcohols
pKa range: 15.5-18.0 (water: 15.7)
Acidity decreases as alkyl group
increases.
Halogens increase the acidity.
Phenol is 100 million times more acidic
than cyclohexanol!
=>
Chapter 10
21
Preparation of Alcohols by Hydration of
Alkenes
Water molecule add to double bond in accordance with
Markovnikov’s rule
Preparation of Alcohols by Grignard
Reagents
By reaction of grignard reagents with aldehydes and
ketones to form Primary, Secondary and Tertialy
Alcohols.
H
CH 3CH2MgBr
Ether
+
C
O
H3O +
H
primary alcohol
CH 3
H3 C
CH 3CH 2MgBr
+
C
O
Ether
H3O +
H
CH 3CH 2CHOH
Secondry alcohol
CH 3
H3 C
CH 3CH 2MgBr
CH 3CH2CH2OH
Ether
+
C
H3 C
O
H3O +
CH 3CH 2COH
CH 3
Tertiary alcohol
Preparation of Alcohols by Reduction of
Aldehydes and Ketone
Preparation of Alcohols by reduction of
Carboxylic acids and Esters
Preparation of Alcohols from
Epoxides
Preparation of Diols
Diols formed by reduction of dialdehyde by
catalytic hydrogenation as the following
reaction.
Mechanism of Reaction
Preparation of Thiols
By the reaction of alkyl halide with
thiourea to give thiol compound
Reactions of Alcohols
1- Reaction with Hydrogen Halide
2- Reaction with Thionyl Chloride
3- Acid Catalyzed Dehydration
4- Conversion of Alcohols to Ethers
By Heating primary alcohols in the presence of
Sulfuric acid (Condensation reaction)
5- Esterification
6- Oxidation of Alcohols
Primary alcohol is oxidized under strong or mild
oxidizing agents to give acid or aldehyde
PCC : Pyridinium Chlorochromate
Reaction of Diols
Oxidative Cleavage of Vicinal Diols
Reactions of Thiols
Thiols are weak acids but more acidic
than alcohols.
2- Oxidation of Thiols