Boiling Points
=>
Solubility in Water
Solubility decreases as the size
of the alkyl group increases.
=>
Methanol
•
•
•
•
“Wood alcohol”
Industrial production from synthesis gas
Common industrial solvent
Fuel at Indianapolis 500
– Fire can be extinguished with water
– High octane rating
– Low emissions
– But, lower energy content
Invisible flame
=> –
Ethanol
•
•
•
•
•
•
•
Fermentation of sugar and starches in grains
12-15% alcohol, then yeast cells die.
Distillation produces “hard” liquors
Azeotrope: 95% ethanol, constant boiling
Denatured alcohol used as solvent
Gasahol: 10% ethanol in gasoline
Toxic dose: 200 mL ethanol, 100 mL methanol
=>
2-Propanol
• “Rubbing alcohol”
• Catalytic hydration of propene
CH2 CH CH2 + H2O
100-300 atm, 300°C
catalyst
CH3 CH CH3
OH
=>
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!
=>
Table of Ka Values
CH3
OH
=>
Formation of Alkoxide
Ions
React methanol and ethanol with sodium
metal (redox reaction).
CH3CH2OH +
Na
CH3CH2O
Na
+ 1/2 H2
React less acidic alcohols with more
reactive potassium.
(CH3)3C OH +
K
(CH3)3CO
K
+ 1/2 H2
=>
Formation of Phenoxide
Ion
Phenol reacts with hydroxide ions to form
phenoxide ions - no redox is necessary.
O
O H
+
pKa = 10
OH
+
HOH
pKa = 15.7
=>
Synthesis (Review)
• Nucleophilic substitution of OH- on alkyl
halide
• Hydration of alkenes
– water in acid solution (not very effective)
– oxymercuration - demercuration
– hydroboration - oxidation
=>
Glycols (Review)
• Syn hydroxylation of alkenes
– osmium tetroxide, hydrogen peroxide
– cold, dilute, basic potassium permanganate
• Anti hydroxylation of alkenes
– peroxyacids, hydrolysis
=>
Organometallic Reagents
• Carbon is bonded to a metal (Mg or Li).
• Carbon is nucleophilic (partially
negative).
• It will attack a partially positive carbon.
–C-X
–C=O
• A new carbon-carbon bond forms.
=>
Grignard Reagents
•
•
•
•
Formula R-Mg-X (reacts like R:- +MgX)
Stabilized by anhydrous ether
Iodides most reactive
May be formed from any halide
– primary
– secondary
– tertiary
– vinyl
aryl
=> –
Some Grignard Reagents
Br
+
ether
Mg
Cl
CH3CHCH2CH3
+
Mg
CH3C CH2
Br
+
Mg
ether
ether
MgBr
MgCl
CH3CHCH2CH3
CH3C CH2
MgBr
=>
Organolithium Reagents
• Formula R-Li (reacts like R: +Li)
• Can be produced from alkyl, vinyl, or aryl
halides, just like Grignard reagents.
• Ether not necessary, wide variety of
solvents can be used.
=>
Reaction with Carbonyl
• R:- attacks the partially positive carbon in the
carbonyl.
• The intermediate is an alkoxide ion.
• Addition of water or dilute acid protonates the
alkoxide to produce an alcohol.
R
C O
R C O
R C OH
HOH
=>
OH
Synthesis of 1° Alcohols
Grignard + formaldehyde yields a primary
alcohol with one additional carbon.
CH3
H3C C CH2
C
H
H
CH3
H
H
MgBr
C O
CH3
CH CH2
H
CH2
H
MgBr
H
CH3
CH3
C O
CH CH2
H
CH2
HOH
C O H
H
=>