Transcript Chapter 12 and 13 Notes

Alcohols, Thiols, and Ethers
Alcohols
 Contain the –OH group as in R-OH.
 Nomenclature of alcohols:
1. Find the longest chain of C’s, which also includes the
–OH group. Change the –e at the end of the usual base
name to –ol.
2. Number the chain so that the –OH group has the
lowest number ALWAYS!!!
3. Name any other substituents using these numbers.
 Cyclic alcohols are named as cycloalkanols.
 Benzene ring with an OH is called Phenol.
Classification of Alcohols
 Alcohols are classified as primary (1o), secondary (2o),
or tertiary (3o) based on how many C’s are bonded to
the C with the –OH group.
 LEP #1
H
H
H3C
C
H
Primary – has one
alkyl group
OH
H3C
C
CH3
– has
two alkyl groups
CH3
OH
H3C
C
CH3
Tertiary – has
three alkyl groups
OH
Thiols
 Contain the –SH group.
 Are known as compound with strong odors.
 CH3CH2 – SH = Ethane thiol, added to natural gas.
 CH3CH2CH2 – SH = Propane thiol, onions.
H
H
C
H
C
SH
C
H2
Ethers
 Contain an O atom between two alkyl groups.
 Oxygen atom does have lone pairs and make them
slightly polar.
 Some ethers with halogens were commonly used as
anesthetic agents.
O
H
C
H
C
H
H
H
H
Properties of Alcohols, Ethers
 Alcohols have Hydrogen Bonding type forces with the –OH
group.
 This significantly increases their boiling points and
solubility in water.
 Ethers are only slightly polar and have lower boiling points
and limited solubility.
Compound
Molar mass
Boiling pt.
H2O
CH3CH2CH3
44 g/mol
-42oC
insoluble
CH3OCH3
46 g/mol
-23oC
71g / 100mL
CH3CH2OH
46 g/mol
78oC
miscible
Properties
 Solubility of smaller alcohols like methanol and
ethanol are said to be miscible.
 As the number of C’s increases to three and four, they
have a solubility limit.
 By the time we get to six C’s, it is insoluble.
CH3-CH2-CH2-CH2-CH2-CH2 Non-polar carbon chain dominates
OH
Properties
 Environmental Issue – MTBE
 Methyl-t-butyl ether or MTBE – once added to
gasoline as an “oxygenate.”
 Problem: it is slightly soluble in water and is not
biodegradable.
CH3
H3C
O
C
CH3
CH3
Properties
 Phenol is slightly soluble in water due to the fact that it
is a weak acid.
Reactions of Alcohols
 Depends on the classification (1o, 2o, or 3o) for some




reactions.
Oxidation = removal of 2 H atoms OR the addition of
an O atom.
Reduction = removal of an O atom OR the addition of
2 H atoms.
I will show the oxidation processes for each type of
alcohol. Reduction reverses the process.
[O] = oxidizing agent (KMnO4, K2CrO4)
Reactions of Alcohols
 Primary
 Ex) CH3CH2OH
 Secondary
 Ex) CH3CHCH3

OH
 Tertiary
 Ex) (CH3)3-C-OH
Reactions of Thiols
 Oxidation of two thiols
produces something called a
disulfide.
 One amino acid contains this
and determines whether you
have straight or curly hair.
 2 CH3CH2-SH 
Aldehydes and Ketones
 Carbonyl group, C=O, is polar
with a partial negative charge
residing on the O atom.
 In an aldehyde, the carbonyl
group has one or more H atoms
bonded to the C atom.
 In a ketone, the carbonyl group
has two alkyl groups.
C=O
d+
d-
Aldehydes
 Naming these replaces the –e in the
base name with -al.
 Carbon #1 MUST be the carbonyl
carbon.
 Any other substituents are
numbered according to this
numbering.
Ketones
 Naming these replaces the –e
ending to –one.
 Will need a number for position
of carbonyl if five or more C’s are
present.
 Can also have cycloketones – then
carbonyl group is C #1.
Properties
 The boiling points of aldehydes and ketones are higher
than those of alkanes and ethers of similar mass.
 This is due to the polar carbonyl group.
 However, their boiling points are less than those of the
alcohols, because the alcohols have Hydrogen Bonding
forces.
Name
Butane
Ethyl methyl ether Propanal
Propanone
1-Propanol
Molar Mass
58 g/mol
60 g/mol
58 g/mol
58 g/mol
60 g/mol
BP
0oC
8oC
49oC
56oC
97oC
Properties
 Aldehydes and Ketones with four or less Carbons are
very soluble in water.
 Solubility is less than that for similar number of C’s
with alcohol group.
 Larger ones are not soluble.
 Oxidation of aldehydes and ketones is like that for the
alcohol series.
Chirality
 Some molecules have the exact same formula and
connections, but differ in their spatial arrangements.
 These are called stereoisomers and result from a chiral
carbon.
Chirality
 Decide whether the following objects would be chiral
or achiral.
Chirality
 When a C atom has four different groups bonded to it,
it said to be chiral.
 The mirror image is of this molecule is NOT the same.
 Test = Not Superimposable.
CH3
H
C
Cl
OH
Chirality
 Which molecules have chiral carbons?
CH2CH3
H
C
CH3
HO
F
CH2CH3
O
C
C
CH3
CH3
CH3
CH3
OH
CH3
CH3
H3C
CH2CH3
Carboxylic Acids, Esters, Amines, and Amides
Carboxylic Acids
 Contains both the carbonyl group and the hydroxyl
groups (-COOH).
 Collectively, these two are called the carboxylic group.
 The H atom on the hydroxyl group is acidic.
O
H
C
H
H
C
OH
Carboxylic Acids
 Naming:
 Identify longest chain with the
carboxylic group.
 Carboxylic group carbon is C#1.
 Any other substituents are numbered
based on this carbon.
 Aromatic carboxylic acid is called
benzoic acid.
O
C
OH
Properties
 -OH group forms Hydrogen Bonds
 Carbonyl group is also very polar.
 Have higher boiling points than
alcohols.
 1-propanol (bp = 97oC) or ethanoic
acid (bp = 118oC) both have molar
mass of 60. g/mol.
 Acids form a dimer.
Properties
 One to four carbon chain acids are very soluble in




water.
For five or more carbon acids, they are only slightly
soluble in water.
Carboxylic acids are weak acids.
The H atom on the –OH group can be donated to a a
base.
RCOOH + H2O  RCOO- + H3O+
Properties
 A strong base can be used to neutralize a carboxylic
acid to yield water and a salt.
 RCOOH + NaOH  RCOO-Na+ + H2O
 Some of the “salts” are used as preservatives in food
products.
 Ex) Sodium propionate and sodium benzoate
Reactions
 A carboxylic acid will react with an alcohol to form an
ester.
O
O
H+
CH3 C-OH + HO-CH3
H2O + CH3 C – O – CH3
Esters
 Are the fragrances of fruits, flavorings, and perfumes.
Ester
 A fat or oil is a tri-ester of glycerol and three fatty acids
(long chain carboxylic acids).
 This is the our vegetable oil in the biodiesel project.
 In the presence of a strong base (NaOH), the ester will
dissociate into the carboxylic acid salt and the alcohol.
 The carboxylic acid can then be converted to a single
ester with methanol.
Amines
 Amines are derivatives of ammonia (NH3)
 Each H atom of ammonia can be replaced by an alkyl
group.
 Amines are classified as 1o, 2o, and 3o based on how
many H atoms are replaced.
Trimethyl amine
Properties
 Amines with at least one H atom bonded to N will
have hydrogen Bonding forces.
 Those with HB will have higher boiling points, but less
than the alcohols.
 Propanol, 97oC; Propyl amine, 48oC, and
Trimethylamine, 3oC
 Amines are weak bases and will react with water like
NH3.
 Amine salt = reacting an amine with a strong acid.
Alkaloids
 Amines are commonly found in plants and may have
biological effects.
caffeine
Amides
 The reaction of a carboxylic acid and an amine
produces an amide – similar to ester reaction.
O
H
O H
heat
CH3CH2 C–OH + H-N-CH3
H2O + CH3CH2-C-N-CH3
 If you have a di-carboxylic acid plus a di-alcohol OR di-
amine, then you can make a condensation type
polymer.
 Ex) Terephthalic acid + Ethylene Glycol
 Ex) Hexamethyldiamine + Hexanedioic Acid