Week # 3 Lecture # 7 and 8 - Alcohols, Phenols, and Thiols
Concepts: Classes of alcohols - (primary, secondary, tertiary), hydrogen bonding,
polarity of all functional groups, solubility.
Reaction Summary:
4. Hydration: Alkene + water -
7. Dehydration : Alcohol +heat 
8. Oxidation - pri. Alcohol: Pri. Alcohol + (O) 
9. Oxidation - sec. Alcohol: Sec. Alcohol + (O) 
10. Oxidation - aldehyde: Aldehyde + (O) 
11. Ether Synthesis: Alcohol + alcohol 
Types or Classes of Alcohols:
The alcohols may be classified according to the number of carbons
attached to the carbon with the -OH group.
OH
H2
C
HO
H2
C
C
H2
A
H3C
CH3
CH
C
H2
OH
CH3
CH3
HO
B
H3C
CH
C
H2
CH3
C
Ques. 1: Write the IUPAC name of the alcohols above.
Primary alcohol: The -OH carbon has only one other carbon attached.
Example (A) above.
Secondary alcohol: The -OH carbon has two other carbons attached.
Example (B) above.
Tertiary alcohol: The -OH carbon has three other carbons attached.
Example (D) above
Ques. 2: What type of alcohol is (C) above?
Ques. 3: Classify the following alcohols and give the IUPAC names:
C
CH3
CH3
D
H2
C
H3C
C
HO
H3C
H2
C
HO
C
H2
CH3
B
CH3
CH3
H3 C
CH3
HO
CH
A
C
CH
CH3
CH
H3C
CH3
H3C
C
CH3
OH
D
OH
CH
E
CH3
Polarity of Organic Compounds:
http://www.elmhurst.edu/~chm/vchembook/213organicfcgp.html
The greater the electronegativity difference between atoms in a bond, the more polar
the bond. Partial negative charges are found on the most electronegative atoms, the
others are partially positive. In general, the presence of an oxygen is more polar than a
nitrogen because oxygen is more electronegative than nitrogen.
The combination of carbons and hydrogens as in hydrocarbons or in the hydrocarbon
portion of a molecule with a functional group is always NON-POLAR.
Polarity and Boiling Point:
The polarity of the molecules determines the forces of attraction between the molecules
in the liquid state. Polar molecules are attracted by the opposite charge effect (the
positive end of one molecule is attracted to the negative end of another molecule.
Molecules have different degrees of polarity as determined by the functional group
present.
Principle: The greater the forces of attraction, the higher the boiling point; or the
greater the polarity, the higher the boiling point.
Ques. 4: Polarity of Functional Groups (relatively constant number of C, H's)
salt
amide
acids
Aldehyde amine
ester
ether
ketone
Formula C4H7O2-M+ C3H7NO C3H6O2
C3H6O
C4H11 C4H8O2 C3H18O
N
Structure
Func gp
Name
Rank
1
2
3
4
5
An abbreviated polarity list to know well is:
6
7
alkane
C4H10
8
Amide > Acid > Alcohol > Amine > Ether > Alkane
HYDROGEN BONDING
Introduction: The hydrogen bond is really a special case of dipole forces. A hydrogen bond is
the attractive force between the hydrogen attached to an electronegative atom of one molecule
and an electronegative atom of a different molecule. Usually the electronegative atom is oxygen,
nitrogen, or fluorine, which has a partial negative charge. The hydrogen then has the partial
positive charge.
To recognize the possibility of hydrogen bonding, examine the Lewis structure of the molecule.
The electronegative atom must have one or more unshared electron pairs as in the case of oxygen
and nitrogen, and has a negative partial charge. The hydrogen, which has a partial positive
charge tries to find another atom of oxygen or nitrogen with excess electrons to share and is
attracted to the partial negative charge. This forms the basis for the hydrogen bond.
Hydrogen Bond Definition: The hydrogen on one molecule attached to O or N that is
attracted to an O or N of a different molecule.
In the graphic on the left, the hydrogen is partially positive and attracted to the partially negative
charge on the oxygen. Because oxygen has two lone pairs, two different hydrogen bonds can be
made to each oxygen. This is a very specific bond as indicated. Some combinations which are
not hydrogen bonds include: hydrogen to another hydrogen or hydrogen to a carbon.
Ques. 5: Draw an example of three water molecules engaged in hydrogen bonding.
Ques. 6: Write the structure of methanol and then draw three molecules of methanol
engaged in hydrogen bonding.
Ques. 7: Draw the figure for hydrogen bonding between two or three ethanol
molecules.
Ques. 8: An ether molecule is also a derivative of a water molecule. Both hydrogens
have been replaced by carbons.
a) Write the structure for dimethyl ether and diethyl ether.
b) Is hydrogen bonding between ether molecules possible?
Solubility - "Likes dissolve Likes" - Application of Polarity
Solubility is a measure of the ability of two substances to dissolve in each other. The
relative solubility of one compound in another depends largely on the type and
strength of intermolecular bonds between the molecules in the pure compounds. If the
bonding strength between molecules of substance A is roughly equal to the
intermolecular forces of substance B, substances A and B will probably be soluble in
each other.
For example, methyl alcohol dissolves in water because the hydrogen bonds between
water molecules and those between alcohol molecules are of roughly equal strength.
The hydrogen bonds between similar molecules can be broken and replaced by
hydrogen bonds between alcohol and water molecules. Alcohol molecules can "slip"
into the network of hydrogen bonds in water. Both molecules have polar O-H bonds.
The attraction of opposite partial charges allows the mixing of water and alcohol
molecules - such compounds are said to be hydrophilic-"water loving.
Ques. 9: Draw several water and methanol molecules hydrogen bonded together
On the other hand, hydrocarbons and water are not soluble in each other.
Hydrocarbon alkanes do not have any hydrogen bonds nor any polar attractions. Thus
the only appreciable attractions are between water molecules, so they effectively
"squeeze out" the hydrocarbon molecules. At the same time the hydrocarbon molecules
tend to prefer "their own company" and effectively keep out water molecules. These
compounds are said to be hydrophobic-"water hating". Hydrocarbons have non-polar
carbon-carbon and carbon-hydrogen bonds. The behavior of alkane or hydrocarbon
parts in all molecules imparts a non-polar character to the molecule.
Solubility principle:
The above relationships are usually summed up by the common generalization: "Likes
dissolve Likes". This means that a polar solvent will dissolve polar compounds but will
not dissolve non-polar compounds.
The generalization "likes dissolve likes" must be applied carefully. For example, all
alcohols are polar yet not all alcohols are soluble in water. The structure of the alcohols
must be carefully examined. The -OH part is polar and imparts water solubility. On
the other hand, the hydrocarbon part is non-polar and imparts water insolubility.
The relative dominance of one part over the other determines the overall behavior of
the molecule. If the hydrocarbon part is dominant, this results in a non-polar molecular
behavior. If the -OH polar part dominates, the molecule is essentially polar and water
soluble.
Ques. 10: Explain in detail the reasons for the solubility data
in the table below. Write structures for each alcohol.
Solubility Of Alcohols In Water
Alcohol Structure
a. Ethanol
b. 1-propanol
c. 1-butanol
d. 1-pentanol
e. 1-hexanol
Solubility at 20oC
g. ROH/100g. H2O
completely soluble
completely soluble
8.0
2.7
0.6
QUES. 11: Which compound is more soluble in hexane?
1- heptanol or 1-pentanol; Explain.
Ques. 12: Which compound is more soluble in water?
Pentanoic acid or 2-pentanol. Explain
Ques. 13: Which compound is more soluble in gasoline (octane)?
Diethyl ether or 2-butanol. Explain.
Ques. 14: Write the structures for :
Methanethiol (smell of chedder cheese); 1-propanethiol (smell of onions)
Ques. 15: Write the structures for:
Phenol, 3-hydroxyphenol (resourcinol - antiseptic), 2-phenylphenol (Lysol)
4. Hydration(HOH
Ques. 16: Addition Reaction
Alkene + water  alcohol
*Markovnikov's Rule
Propene + HOH 
2-propanol
Ques. 17: Subtraction Reactions - Dehydration and Oxidation
Reaction Name
Word Equation
Example
7. Dehydration
Alcohol +heat
2-propanol  propene +
 allkene + water
HOH
8. Oxidation - pri. alcohol
Pri. Alcohol + (O)
 aldehyde + water
9. Oxidation - sec. alcohol Sec. Alcohol + (O)
 ketone + water
10. Oxidation - aldehyde
Aldehyde + (O)  Acid
1-propanol + (O) 
propanal
2-propanol + (O) 
2-propanone
Propanal + (O) 
propanoic acid
Ques. 18: Combination Reactions
(generally remove a water molecule to combine two molecules)
Reaction Name
Word Equation
Example
11. Ether Synthesis
Alcohol + alcohol
Ethanol + ethanol 
 ether + water
diethyl ether + HOH
Ques. 19: Dehydration: Name the reactants.
a.
CH3
H3C
CH
OH
H2 C
H2SO 4
heat
CH2
b
CH 3
H2C
HO
c.
CH
H2C
CH 3
CH 2
H2SO4
heat
CH3
H2C
H2SO4
CH
H3C
OH
H2 C
heat
CH2
d.
H2C
CH2
H2C
OH
C
H2SO 4
heat
C
H2 H2C
CH3
Ques. 20: Oxidations - Name the Reactants
a
CH3
CH
H3C
CH
CH3
+ (O)
OH
b.
CH3
H3C
CH
OH
H2C
+ (O)
CH2
c.
CH3
H2C
H3C
CH
H2C
+ (O)
OH
d.
OH
+ (O)
CH
H3C
CH3
e.
H2
C
HO
C
H2
+ (O)
CH3
f.
H2
C
H3C
21.
H2
C
+
SH
H 3C
+ (O)
SH
Write the structures for the products and give the names of both.
H2
C
A.
H3C
OH
+
HO
CH3
B.
H3C
CH3
OH
+
HO
CH
CH3
C.
H2
C
HO
D.
C
H2
+
C
H2
CH3
CH3
CH3
HO
H2
C
HO
CH
CH3
+
HO
CH
CH3
CH3