1. Chapter 8 Properties of Alcohols
Nomenclature
Functional Groups
RCH2—OH = Hydroxy functional group
Alcohol = organic molecule having a hydroxy group
Replace one H of water with R: H—O—H  R—O—H
Ether = replace both H’s of water with R: R—O—R
Naming Alcohols
Modify the alkane name by dropping –e and adding –ol
CH3OH = methanol
CH3CH2CH2CH2OH = butanol
R-OH = alkanol
Branched Alcohols
Name based on longest
chain containing -OH

2. Number each carbon starting from the closest to –OH
Cyclic Alcohols = cycloalkanols
When referring to –OH as a substituent it is called hydroxy
Simple alcohols often have common names
CH3OH = methyl alcohol
CH3CH2OH = ethyl alcohol
(CH3)2CHOH = isopropyl alcohol
(CH3)3COH = tert-butyl alcohol

3. Structural and Physical Properties of Alcohols
Structure
Alcohol structures are similar to water: sp3 O atom with 2 lone pairs
Steric effects of the R groups slightly alter bond angles
Electronegativity of O shortens and strenthens the O—H bond compared to C—H
DHo(OH) = 104 kcal/mol
DHo(CH) = 98 kcal/mol
Electronegativity of O causes large molecular dipole moment for alcohols

4. Hydrogen Bonding
Hydrogen bond = weak, partial bond between a heteroatom bound H and another heteroatom (N, O, X, S, etc…)
DHo(OH…..H) = 5 kcal/mol
The sum of the multiple H-bonds in water or alcohols increases the boiling points of these liquids relative to alkanes or haloalkanes
Methane = -162o Chloromethane = -24.2o Methanol = 65o
Polar
No H-Bonds
Polar
H-Bonds
Nonpolar
No H-Bonds

5. Acid-Base Behavior of Alcohols
Solubility
Alcohols have high water solubility (Like dissolves Like)
Polarities of water and alcohols are similar
Hydroxy group is Hydrophilic (water loving)
Alkyl group is Hydrophobic (water fearing)
Alkanes have no solubility in water (hydrophobic)
Organic molecules with polar functional groups (-OH, -NH2, -CO2H) have much higher water solubilities
The longer the alkyl group, the less water soluble the alcohol (more soluble in hydrocarbons—like dissolves like)
MeOH and EtOH are very similar to water as solvents: many salts will dissolve in them, because they are polar enough to separate the charges
Acid-Base Behavior of Alcohols
Alcohols are Amphoteric = can be acids or bases
Acidity of Alcohols
R—OH H2O R—O H3O+ Ka
alkoxide

6. R
pKa
H2O
15.7
t-BuOH 18
MeOH
15.5
HCl
-2.2
EtOH
15.9
RCO2H
4.7
i-PrOH
17.1
CH4 50
Alcohols are relatively weak acids
Electronegativity of R—O- allows
it to stabilize (-) charge, but not
very well
Requires a strong base to fully deprotonate an alcohol
EtOH(pKa = 15.9) OH-  EtO H2O (pKa = 15.7)
MeOH(pKa = 15.5) NH2-  MeO NH3 (pKa = 35)
Acidity: MeOH > 2-Propanol > t-Butyl Alcohol (1o > 2o > 3o)
Steric disruption of solvation
of deprotonated product
50%
50%
99.999%
~ 0%

7. Inductive Effects = transmission of charge through s-bonds
Electronegative substituents increase an alcohol’s acidity
Electronegative groups remove electron density from R—O-, which stabilizes the anion. It is easier to deprotonate = more acidic.
Basicity of Alcohols
Lone pairs of electrons will accept H+ from strong acids
ROH HA  ROH A-
Conditions for Acid/Base behavior of Alcohols
ROH ROH RO-
weak
base
Strong
Conjugate
Acid pKa = -2
Mild base
Strong Base
Strong acid
Mild acid

8. Synthesis of Alcohols by Nucleophilic Substitution
For Industrial Alcohol Synthesis, see your book
Lab Scale Reactions
SN1 Reaction of Tertiary RX ROH
SN2 Reaction of Primary, Secondary RX ROH
Often harder to make the RX than the ROH (get RX from ROH)
E1/E2 products complicate these reactions
Use acetate (weak base) to prevent Elimination reactions
H2O
OH-
acetate
ester
Ester Hydrolysis
Acetic acid