Chemistry 2100 Chapter 14
Dec 27, 2015
Common Nomenclature
• alkyl "alcohol"
• dialkyl "ether"
IUPAC Nomenclature
• "e" "ol"
• locator numbers
Alcohols
Alcohol: A compound that contains an -OH (hydroxyl) group bonded to a tetrahedral carbon.– Methanol, CH3OH, is the simplest alcohol.
Nomenclature1. Select the longest carbon chain that contains the
-OH group as the parent alkane and number it from the end that gives the -OH the lower number.
2. Change the ending of the parent alkane from -e to -ol and use a number to show the location of the -OH group; for cyclic alcohols, the carbon bearing the -OH group is carbon-1.
3. Name and number substituents and list them in alphabetical order.
Nomenclature– In the IUPAC system, a compound containing two
hydroxyl groups is named as a diol, one containing three hydroxyl groups as a triol, and so forth.
– IUPAC names for diols, triols, and so on retain the final "-e" in the name of the parent alkane.
– We commonly refer to compounds containing two hydroxyl groups on adjacent carbons as glycols.CH3CHCH2
HO OHCH2CH2OH OH
CH2CHCH2
OH OHOH1,2-Ethanediol
(Ethylene glycol)1,2-Propanediol
(Propylene glycol)1,2,3-Propanetriol
(Glycerol, Glycerin)
CH3OH 65° CH3CH2CH2OH 97°
CH3CH3 -88° CH3CH2CH2CH3 0°
CH3Cl -24° CH3CH2CH2Cl 46°
PhOH 182° CH3CH2CH2CH2OH 118°
PhCH3 110° (CH3)2CHCH2OH 108°
PhCl 132° (CH3)3COH 83°
boiling points (°C)
solubility (g / 100 mL H2O)
∞
∞
8.3
2.4
0.6
0.05
7.8
10.0
∞
3.6
CH3CH2OH
CH3CH2CH2OH
CH3CH2CH2CH2OH
CH3CH2CH2CH2CH2OH
CH3CH2CH2CH2CH2CH2OH
CH3CH2CH2CH2CH2CH2CH2CH2OH
CH3CH2OCH2CH3
(CH3)2CHCH2OH
(CH3)3COH
C6H11OH
Acidity of Alcohols
Alcohols have about the same pKa values as water.
• Aqueous solutions of alcohols have the same pH as that of pure water.– Alcohols and phenols both contain an OH group.– Phenols are weak acids and react with NaOH and
other strong bases to form water-soluble salts.
– Alcohols are weaker acids than phenols and do not react in this manner.
n
11
zymase
sucrose ethanol
2O
2O
C12H22O11 + H 4 C2H5OH + 4 CO
Preparing AlcoholsFermentation
Alkene Hydration +
H2SO 4
H OH
H2OCC C C
OHH
H
H H
H H
H H
H
DehydrationCH3CH2OH
H2SO4 CH2=CH2 H2O+Ethanol Ethylene
180°C
OHH2SO4 H2O140°C
Cyclohexanol Cyclohexene
+
CH3CCH3
OH
CH3H2SO4 CH3C=CH2
CH3
H2O50°C
2-Methyl-2-propanol (tert -Butyl alcohol)
2-Methylpropene (Isobutylene)
+
Physical Properties
Ethers are polar molecules in which oxygen bears a partial negative charge and each carbon bonded to it bears a partial positive charge.
Physical Properties
However, only weak forces of attraction exist between ether molecules in the pure liquid.– Consequently, boiling points of ethers are
close to those of hydrocarbons of similar molecular weight.
– Ethers have lower boiling points than alcohols of the same molecular formula.
Reactions of Ethers
Ethers resemble hydrocarbons in their resistance to chemical reaction.– They do not react with oxidizing agents such as
potassium dichromate.– They do not react with reducing agents such as H2
in the presence of a transition metal catalyst or with hydride reducing agents such as NaBH4.
– They are not affected by most acids or bases at moderate temperatures.
Because of their general inertness and good solvent properties, ethers, such as diethyl ether and THF, are excellent solvents in which to carry out organic reactions.
(diethyl) etherbp 36°C
7.8 g/100 mL
1-butanol bp 118°C
8.3 g/100 mL
pentanebp 36°C
H C C O C C H
H
H
H
H
H
H
H
H
H C C C C C H
H
H
H
H
H
H
H
H
H
H
H C C C C O H
H
H
H
H
H
H
H
H
isoflurane
F C
F
O
F
C C
Cl
H
F
F
F
halothane enflurane
F C C
F
F
Br
Cl
H
F C
H
O
F
C C
F
F
Cl
F
H
Anesthetics
ThiolsThiol: A compound containing an -SH (sulfhydryl group).– The most outstanding property of low-
molecular-weight thiols is their stench.– They are responsible for smells such as
those from rotten eggs and sewage.– The scent of skunks is due primarily to
these two thiols.
Physical PropertiesBecause of the small difference in electronegativity between sulfur and hydrogen (2.5 - 2.1 = 0.4), an S-H bond is nonpolar covalent. – Thiols show little association by hydrogen
bonding.– Thiols have lower boiling points and are
less soluble in water and other polar solvents than alcohols of similar molecular weight.
hydrogen
bond
CH2 OH
CH2O
H
NH
H C
OH
O
hydrogenbond
salt bridge NH3
+ -helix
-helix-pleated sheet -pleated sheet
C-O
O
hydrogen
bond
CH2 OH
CH2O
H
NH
H C
OH
O
hydrogenbond
salt bridge NH3
+ CH2
HO
hydrophilicinteractionto water
CH2
C
NH2
O
CH2
HO
-helix
-helix-pleated sheet -pleated sheet
C-O
O
CH2
CH2
hydrophobicinteraction
hydrogenbond
CH2 OH
CH2O
H
NH
H C
OH
O
hydrogenbond
salt bridge NH3
+ CH2
HO
hydrophilicinteractionto water
CH2
C
NH2
O
CH2
HO
-helix
-helix-pleated sheet -pleated sheet
C-O
O
CH
CH3 CH3 CH3
CH2 CH2
hydrophobicinteraction
hydrogenbond
CH2 OH
CH2O
H
NH
H C
OH
O
hydrogenbond
salt bridge NH3
+ CH2
HO
hydrophilicinteractionto water
CH2
C
NH2
O
CH2
HO
-helix
-helix-pleated sheet -pleated sheet
C-O
O