Chem 150 Unit 7 - Organic Molecules II Carboxylic Acids, Phenols & Amines

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Chem 150Unit 7 - Organic Molecules IICarboxylic
Acids, Phenols Amines

• In this unit and the next we look at the chemical
  and physical properties of a variety of organic
  families, all of which play important roles in
  biochemistry. These include the carboxylic acids,
  phenols, amines and amides. We also look at a new
  type of stereoisomer that figures predominantly
  in biological chemistry the optical isomer.

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Introduction

• The organic groups covered in this Unit all have
  important biological roles
• Carboxylic acids
• Fatty acids
• Amino acids and proteins
• Phenols
• Colors and flavorings
• Amino acids and proteins
• Signal molecules
• Amines
• Amino acids and proteins
• Signal molecules
• Drugs
• Amides
• Amino acids and proteins

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Carboxylic Acids

• Naming carboxylic acids
• The IUPAC ending is -oic acid.

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Question

• Give the IUPAC names for the following carboxylic
  acids

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Carboxylic Acids

• Carboxylic acid have high melting points
• Small carboxylic acids are quite soluble in water

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Carboxylic Acids

• Small (volatile) carboxylic acids have noticeable
  odors.
• Ethanoic acid (acetic acid) vinegar
• Butanoic acid (butyric acid) vomit, dirty socks
• Hexanoic acid (caproic acid) goats, ripe cheese

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Phenols

• Simplest phenol is phenol.
• A hydroxyl group attached to a benzene ring.

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Phenols

• All phenols contain hydroxyl groups attached to
  aromatic rings.

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Phenols

• All phenols contain hydroxyl groups attached to
  aromatic rings.

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These have 2 hydroxyl groups attached to a
benzene ring
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Carboxylic Acids Phenols as Weak Acids

• Both carboxylic acids and phenols are weak acids

pKa 5
pKa 10
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Carboxylic Acids Phenols as Weak Acids

• The acidity of hydroxyl groups depend on what
  they are connected to

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Carboxylic Acids Phenols as Weak Acids

• At pH 7, the carboxylate ion of carboxylic acids
  predominate
• At pH 7, the phenol of phenol predominate

pH 7
pKa 5
pH 7
pKa 10
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Carboxylic Acids Phenols as Weak Acids

• Strong bases can be used to convert carboxylic
  acids and phenols to their corresponding
  carboxylate and phenoxide ions

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Carboxylic Acids Phenols as Weak Acids

• Fatty acids are carboxylate ions at pH 7
• Fatty acids with less that 12 carbons are soluble
  in water
• Fatty acids with greater than 12 carbons are
  amphipathic, and form micelles when mixed with
  water.

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Carboxylic Acids Phenols as Weak Acids

• IUPAC names for carboxylate ions
• Remove the -ic acid from the corresponding
  conjugate acids name and replace it with -ate
  ion.

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Carboxylic Acids Phenols as Weak Acids

• Examples

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Carboxylic Acids Phenols, Other Reactions

• We have already seen how carboxylic acids and
  carboxylate ions can be made from from the
  hydrolysis of esters.
• Base-catalyzed hydrolysis of esters
• Acid-catalyzed hydrolysis of esters

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Carboxylic Acids Phenols, Other Reactions

• The acid-catalyzed hydrolysis of esters is
  reversible and can be used to make esters from
  carboxylic acids and alcohols
• Synthesis of esters from carboxylic acids and
  alcohols

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Carboxylic Acids Phenols, Other Reactions

• A biologically important reaction involving
  carboxylic acids is the decarboxylation of a-keto
  and ß-keto acids

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Carboxylic Acids Phenols, Other Reactions

• The decarboxylation of ß-keto acids produces
  ketones
• The decarboxylation of a-keto acids produces
  aldehydes

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Carboxylic Acids Phenols, Other Reactions

• The oxidation of hydroquinones is also an
  important biological reaction.
• A chemical oxidation of hydroquinones can be
  carried out the oxidizing agent K2Cr2O7
  (potassium dichromate)

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Carboxylic Acids Phenols, Other Reactions

• Example
• Coenzyme Q and the Electron Transport Chain

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Carboxylic Acids Phenols, Other Reactions

• Example
• Coenzyme Q and the Electron Transport Chain

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Amines

• Amines are a nitrogen with one or more carbons
  attached
• Amines are classified based on the number of
  carbons that are attached to the nitrogen.
• Primary amine (1) 1 carbons
• Secondary amine (2) 2 carbons
• Tertiary amine (3) 3 carbons

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Amines

• It is possible for a fourth carbon to attach to
  the nitrogen
• The nitrogen will take on a positive charge to
  become an ion.
• Quaternary (4) ammonium ions 4 carbon atoms

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Amines
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Amines

• The IUPAC names for 1, 2, and 3 amines.
• Create the parent name by picking the longest
  chain of carbons that is attached to the
  nitrogen.
• Replace the -e in the parent with the ending
  -amine.
• Number the longest chain from the end that gets
  you to the the carbon to which the nitrogen is
  attached in the fewest number of carbons.
• Use a numbered prefix to indicate which the
  carbon in the longest chain the nitrogen is
  bonded to.
• If other substituents are attached to the
  nitrogen, list them and use the prefix N- to
  indicate that they are attached to the nitrogen.

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Questions

• Give the IUPAC names for the following amines

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Questions

• Give the IUPAC names for the following amines

2-butanamine
2-butanamine
N-ethyl-
N-propyl
N-ethyl-N-propyl-2-butanamine
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Amines

• For heterocyclic amines the nitrogen is part of a
  ring.
• The ring can be either aromatic or not.
• The nucleic acid nucleotide bases are good
  examples of hetoercyclic amines

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Amines

• Hydrogen Bonding
• 1 and 2 amines can serve as both a hydrogen
  bond donor and acceptor.
• 3 amines can server as a hydrogen bond
  acceptors, but not donors.

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Amines

• Hydrogen Bonding
• 4 ammonium ion cannot form hydrogen bonds, but
  because they are charged, form ionic bonds

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Amines

• The ability to hydrogen bond give amines
  moderately high boiling points and high
  solubilities in water.

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Amines

• Another notable property of amines is their odor.
• Like carboxylic acids, they can also produce foul
  odor.
• The produce a fishy smell.
• Examples of amines, whose names imply their
  odoriferous properties, include

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Amines as Weak Bases

• In Unit 6, while discussing the definitions of
  acids and bases, we saw that ammonia, NH3, is
  operationally a base
• That is, when added to water ammonia causes the
  pH to rise above pH 7.
• Ammonia was the example we used to demonstrate
  the need for the Brønsted-Lowry definition of
  acids and bases.

See the Unit 6 Elaboration -Definitions of Acids
and Bases - Part IIIBrønsted-Lowry Definition
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Amines as Weak Bases

• Like ammonia, 1, 2 and 3, act as
  Brønsted-Lowry bases.

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Amines as Weak Bases

• The conjugate acids are called ammonium ions
• When placed in water, these ammonium ions will
  behave like acids.

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Amines as Weak Bases

• Because it is charged, the conjugate acid is even
  more soluble that the amine.
• Many drugs are amines and are sold the ammonium
  salts, which are more readily absorbed, due to
  their increased solubility.
• Ephedrine is used as a decongestant.

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Amines as Weak Bases

• Ephedrine is an example of an alkaloid.
• Alkaloids are alkaline molecules that are derived
  from plants.
• alkaline and another name for basic.
• Ephedrine is isolated from the Chinese ma huang
  plant(Ephedra sinica)hyperlink

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Amides

• When a carboxylic acid reacts with an amine it
  also produces and ammonium salt
• If the ammonium salt is then heated, an amide is
  produced.

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Amides

• Amides are important in biochemistry.
• For example, amino acids are connected together
  to form proteins using amide groups.

amino acid
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Amides

• Amides can be hydrolyzed back to carboxylic acids
  and amines by heating them in the presence of an
  acid

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Stereoisomers

• So far we have encountered two different types of
  isomers.
• Constitutional Isomers
• Stereoisomers
• cis/trans isomers with alkenes and cycloalkanes,
  that arise from restricted rotation about bonds.
• There is one more type of stereoisomer, which is
  important in biochemistry.
• optical isomers

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Stereoisomers

• Optical isomers arise when a carbon atom has four
  different things attached to it.
• These carbons are called chiral carbons.
• The a molecule containing a chiral carbon is non
  superimposable on its mirror image.
• The molecule and its mirror image are referred to
  as enantiomers

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Stereoisomers
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Stereoisomers
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Stereoisomers
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Stereoisomers
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Stereoisomers
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Stereoisomers

• When developing drugs that are chiral, it is
  important to look at the effects of both the
  enantiomers.

R-thalidomide
S-thalidomide
is effective in treating morning sickness in
pregnant women
is a teratogen, causing birth defects
R and S are another way of distinguishing
enantiomers R is the rectus (right) isomer,
while S is the sinister (evil) isomer!
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Stereoisomers

• When chiral molecules contain more than one
  chiral carbon, it is possible for two molecules
  to be stereoisomers without being mirror images.
• Such molecules are referred to as diastereomers.

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Stereoisomers

• Each chiral carbon that a chiral molecule
  contains doubles the number of stereoisomers for
  that molecule.
• Ephedrine has two chiral carbons, it therefore
  has 2 x 2 4 stereoisomers.
• pseudoephedrine is one of 4 stereoisomers.

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The End