Introduction to Organic and
Biochemistry
(CHE 124)
Reading Assignment
General, Organic, and Biological Chemistry: An Integrated Approach
3rd. Ed. Ramond
Chapter 8
Carboxylic Acids, Phenols, and Amines
Gasses, Solutions, Colloids, and Suspensions
Work Problems
8. 3,4,5,6,8,12,14,32,42,90
Functional Groups
• Carboxylic Acids
– Found in fatty acids and amino acids
• Phenols
• Esters
• Amines
– Found in amino acids
Characteristic of Carboxylic Acids
• High b.p.
– Form H-bonds with water and other carboxylic acids. See
p. 260.
– See Table 8.1 p. 260.
• Water soluble
– Water solubility ↓ as # of carbons ↑
• Odor
– Carboxylic acids with 3 – 10 carbons STINK
• E.g. Butyric acid
– Carboxylic acid with 10 + carbons have a low vapor
pressure, therefore, little or no odor.
• Weak Acid (discussed in a few slides)
– Acid is a compound that losses (donates) a proton.
Naming Carboxylic Acids
• 1. Select longest chain (parent compound)
containing the carboxylic acid and name as alkane
– Number carbon containing acid group as #1.
• 2. Drop e from name of alkane and add
• 3. Name / number side chains.
–oic acid.
# of
C
IUPAC
NAME
COMMON
NAME
B.P.
(C °)
1
Methanoic Acid
Formic Acid
100
2
Ethanoic Acid
Acetic Acid
118
3
4
Propanoic Acid
Butyric Acid
-
141
161
Characteristics of Phenols
• High b.p. for size
– H-bonding
• Water soluble
– Due to H-bonding with water
• Weak Acid
Naming Phenols
• Substituted Phenols
– 1. Number carbon containing hydroxyl group as
#1.
– 2. Number side chains so they have the lowest
possible number.
• Disubstituted phenols
– Ortho
– Meta
– Para
o
m
p
1,2 di-substituted benzenes
1,3 di-substituted benzenes
1,4 di-substituted benzenes
– Show the following examples
• 4-ethylphenol
(p-ethylphenol)
• 2-chlorophenol
(o chlorophenol)
• 2,4-dinitrophenol (Trisubstituted)
Carboxylic acids and Phenols are
Weak acids
• Acid – compound that losses (donates) a
proton.
– Draw acid (-oic acid) and carboxylate (-ate
ion) forms of acetic acid (ethanoic acid) and
phenol.
Acid Equilibrium Constant
or Acid Dissociation Constant (Ka)
• CH3COOH + H20 ↔ CH3COO- + H3O+
Acetic acid + water ↔
acetate + hydronium ion
• Ka = products = [CH3COO-] [H3O] = 1.8 x 105
reactants
[CH3COOH]
pKa = -log Ka
**remember do not include water, pure liquids or solids in this
equation. Only include species whose concentration can
change.
Acid Dissociation Constant (Ka) Cont’
• Most carboxylic acids have pKa values around 5. This means
at a pH of 7, the predominant species in solution is the
carboxylate ion.
• This is important for the solubility of fatty acids. At physiologic
pH, fatty acids are amphipathic.
• Amphipathic – has both hydrophobic and hydrophilic
properties.
– Hydrophobic – water fearing
– Hydrophilic – water loving
Reactions of Carboxylic Acids
• 1. Decarboxylation Rxn. – lose of carbon
dioxide from a carboxylic acid.
– This occurs to carboxylic acids with alpha (α) or
beta (β) keto group (carbon double bonded to an
oxygen). These compounds are called α or β
keto acids.
• Draw α or β keto acids.
– Alpha is carbon attached to carbon with carboxylic acid
– Beta carbon is next carbon.
– Example
• Decarboxylation of pyruvate to acetaldehyde by
pyruvate decarboxylase (first step in fermentation).
Produces carbon dioxide.
Reactions of Carboxylic Acids (Cont)
H 3 0+
• 2. Carboxylic acid + alcohol →
Ester
– Example
• Benzoic acid + methanol → methyl benzoate + water
– Benzene with carboxylic acid
Esters
• Naming Esters
– 1. Name the alcohol group.
– 2. Name carboxylic acid, change -oic acid to ate.
– 3. Combine the two names e.g. Methyl benzoate.
• Characteristics of Esters
– Lower b.p. than similar sized carboxylic acids.
• Does not readily H-bond
– Odor
• Sometimes pleasant, think perfumes.
Reactions of Carboxylic Acids (Cont)
• 3. Oxidation of Phenols
– Hydroquinone (p-hydroxyl groups) oxidized to
benzoquinone (p-ketone groups). The hydroxyl
groups are oxidized to ketone groups by the
oxidizing agent, potassium dichromate (K2Cr2O7)
Amines
• Amines are classified by the number of
carbons attached to the N.
– 1°
– 2°
– 3°
– 4°
primary amine
secondary amine
tertiary amine
quaternary ions
» (+ charge on N)
1 carbon
2 carbons
3 carbons
4 carbons
Naming Amines
• 1. Name longest C chain containing amine as
alkane. Drop the -e and add amine.
• 2. 2° or 3° amines require naming the shorter
chains. Put “N” in front of these substituents.
• 3. If 4° add “ammonium ion” instead of amine.
– Ethanamine
• 4. Cyclic amines
– Pyridine, pyrimidine, purine
– See figure 8.13 p. 273
Characteristics of Amines
• 1° and 2° amines
– form H-bonds with water.
– Higher b.p. than similar sized 3° amines
• Due to H-bonds
– Low MW amines are water soluble
– Unpleasant odor “dead fish odor”
• putrescine
• cadaverine
• 3° amines
– do NOT form H-bonds.
Amines are weak bases
• Base – compound that accepts H30+ or
produces OH-.
– pKa values 9 – 11
Reactions of Amines
• Strong acids react with amines to produce
ammonium salt.
– Ammonium salts are more water soluble than the amine
they are derived from.
• Amines react with carboxylic acids to form Amides.
(draw)
– Formed by reaction of carboxylic acid with ammonia or 1°
or 2°amine, the product is a caroxylate ion and the
conjugate acid of ammoniua or an amine. Heating this
produces an amide.
• See fig. 8.16 p. p 277.
– Amide bonds connect amino acids to form proteins.
Naming Amides
• 1. Name the carboxylic acid with parent
compound containing the amide. Change
ending form –oic acid to amide.
• If an amine is present use N then name the
group.