Chem 150 Unit 7 - Organic Molecules II Carboxylic Acids, Phenols & Amines In this unit and the next we look at the chemical and physical properties of.
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Chem 150Chem 150Unit 7 - Organic Molecules IIUnit 7 - Organic Molecules II
Carboxylic Acids, Phenols & AminesCarboxylic Acids, Phenols & Amines
In this unit and the next we look at the In this unit and the next we look at the chemical and physical properties of a chemical and physical properties of a
variety of organic families, all of which variety of organic families, all of which play important roles in biochemistry. play important roles in biochemistry. These include the These include the carboxylic acidscarboxylic acids, ,
phenolsphenols, , aminesamines and and amidesamides. We also look . We also look at a new type of stereoisomer that at a new type of stereoisomer that figures predominantly in biological figures predominantly in biological
chemistry; the chemistry; the optical isomeroptical isomer..
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IntroductionIntroduction
TThe organic groups covered in this Unit all have important he organic groups covered in this Unit all have important biological rolesbiological roles• Carboxylic acids Carboxylic acids • Fatty acidsFatty acids• Amino acids and proteinsAmino acids and proteins
• PhenolsPhenols• Colors and flavoringsColors and flavorings• Amino acids and proteinsAmino acids and proteins• Signal moleculesSignal molecules
• AminesAmines• Amino acids and proteinsAmino acids and proteins• Signal moleculesSignal molecules• DrugsDrugs
• AmidesAmides• Amino acids and proteinsAmino acids and proteins
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Carboxylic AcidsCarboxylic Acids
Naming carboxylic acidsNaming carboxylic acids• The IUPAC ending is The IUPAC ending is -oic acid-oic acid..
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QuestionQuestion
Give the IUPAC names for the following carboxylic acids:Give the IUPAC names for the following carboxylic acids:
A)A)
B)B)
CH3 CH2 CH2 CH2 C
O
OH
HO C
O
CH2 CH CH2 CH
CH3
CH3
CH3
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Carboxylic AcidsCarboxylic Acids
• Carboxylic acid have high melting pointsCarboxylic acid have high melting points• Small carboxylic acids are quite soluble in waterSmall carboxylic acids are quite soluble in water
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Carboxylic AcidsCarboxylic Acids
Small (volatile) carboxylic acids have noticeable odors.Small (volatile) carboxylic acids have noticeable odors.• Ethanoic acid (acetic acid) vinegarEthanoic acid (acetic acid) vinegar
• Butanoic acid (butyric acid) vomit, dirty socksButanoic acid (butyric acid) vomit, dirty socks
• Hexanoic acid (caproic acid) goats, ripe cheeseHexanoic acid (caproic acid) goats, ripe cheese
CH3 C
O
OH
CH3 CH2 CH2 C
O
OH
CH3 CH2 CH2 CH2 CH2 C
O
OH
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PhenolsPhenols
Simplest phenol is Simplest phenol is phenolphenol..• A hydroxyl group attached to a benzene ring.A hydroxyl group attached to a benzene ring.
OH
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PhenolsPhenols
All phenols contain hydroxyl groups attached to aromatic All phenols contain hydroxyl groups attached to aromatic rings.rings.
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PhenolsPhenols
All phenols contain hydroxyl groups attached to aromatic All phenols contain hydroxyl groups attached to aromatic rings.rings.
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These have These have 2 hydroxyl 2 hydroxyl
groups groups attached to a attached to a benzene ringbenzene ring
These have These have 2 hydroxyl 2 hydroxyl
groups groups attached to a attached to a benzene ringbenzene ring
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Carboxylic Acids & Phenols as Weak AcidsCarboxylic Acids & Phenols as Weak Acids
Both carboxylic acids and phenols are weak acidsBoth carboxylic acids and phenols are weak acids
CH3 C
O
OH + H2O CH3 C
O
O + H3O+
acid acidbasebase
OH + H2O O + H3O+
acid acidbasebase
pKpKaa ≈ 5 ≈ 5pKpKaa ≈ 5 ≈ 5
pKpKaa ≈ 10 ≈ 10pKpKaa ≈ 10 ≈ 10
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Questions (Clickers)Questions (Clickers)
Which is the stronger acid?Which is the stronger acid?
A)A) Acetic acidAcetic acid
B)B) PhenolPhenol
CH3 C
O
OH + H2O CH3 C
O
O + H3O+
acid acidbasebase
OH + H2O O + H3O+
acid acidbasebase
pKpKaa ≈ 5 ≈ 5pKpKaa ≈ 5 ≈ 5
pKpKaa ≈ 10 ≈ 10pKpKaa ≈ 10 ≈ 10
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Carboxylic Acids & Phenols as Weak AcidsCarboxylic Acids & Phenols as Weak Acids
The acidity of hydroxyl groups depend on what they are The acidity of hydroxyl groups depend on what they are connected to:connected to:
OC
O
O H H C O H
acidic weakly acidic non-acidic
carboxylicacids
phenols alcohols
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Question (Clickers)Question (Clickers)
At At pHpH 7, which will be the predominant species? 7, which will be the predominant species?
A)A) Carboxylic acidCarboxylic acid
B)B) Carboxylate ionCarboxylate ion
CH3 C
O
OH + H2O CH3 C
O
O + H3O+
acid acidbasebase
pKpKaa ≈ 5 ≈ 5pKpKaa ≈ 5 ≈ 5
carboxylic acidcarboxylic acidcarboxylic acidcarboxylic acid carboxylate ioncarboxylate ioncarboxylate ioncarboxylate ion
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Question (Clickers)Question (Clickers)
At At pHpH 7, which will be the predominant species? 7, which will be the predominant species?
A)A) PhenolPhenol
B)B) Phenoxide ionPhenoxide ion
phenolphenolphenolphenol phenoxide ionphenoxide ionphenoxide ionphenoxide ion
OH + H2O O + H3O+
acid acidbasebase
pKpKaa ≈ 10 ≈ 10pKpKaa ≈ 10 ≈ 10
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Carboxylic Acids & Phenols as Weak AcidsCarboxylic Acids & Phenols as Weak Acids
• At At pHpH 7, the carboxylate ion of carboxylic acids predominate 7, the carboxylate ion of carboxylic acids predominate
• At At pHpH 7, the phenol of phenol predominate 7, the phenol of phenol predominate
CH3 C
O
OH + H2O CH3 C
O
O + H3O+
acid acidbasebase
OH + H2O O + H3O+
acid acidbasebase
pKpKaa ≈ 5 ≈ 5pKpKaa ≈ 5 ≈ 5
pKpKaa ≈ 10 ≈ 10pKpKaa ≈ 10 ≈ 10
pHpH = 7 = 7pHpH = 7 = 7
pHpH = 7 = 7pHpH = 7 = 7
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Carboxylic Acids & Phenols as Weak AcidsCarboxylic Acids & Phenols as Weak Acids
Strong bases can be used to convert carboxylic acids and Strong bases can be used to convert carboxylic acids and phenols to their corresponding carboxylate and phenoxide phenols to their corresponding carboxylate and phenoxide ionsions
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Carboxylic Acids & Phenols as Weak AcidsCarboxylic Acids & Phenols as Weak Acids
Fatty acids are carboxylate ions at Fatty acids are carboxylate ions at pHpH 7 7
• Fatty acids with less that 12 carbons are soluble in waterFatty acids with less that 12 carbons are soluble in water• Fatty acids with greater than 12 carbons are Fatty acids with greater than 12 carbons are amphipathicamphipathic, ,
and form micelles when mixed with water.and form micelles when mixed with water.
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Carboxylic Acids & Phenols as Weak AcidsCarboxylic Acids & Phenols as Weak Acids
IUPAC names for carboxylate ions:IUPAC names for carboxylate ions:• Remove the “-Remove the “-ic acidic acid” from the corresponding conjugate ” from the corresponding conjugate
acids name and replace it with “-acids name and replace it with “-ate ionate ion”.”.
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Carboxylic Acids & Phenols as Weak AcidsCarboxylic Acids & Phenols as Weak Acids
Examples:Examples:
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Carboxylic Acids & Phenols, Other ReactionsCarboxylic Acids & Phenols, Other Reactions
We have already seen how We have already seen how carboxylic acidscarboxylic acids and and carboxylate ionscarboxylate ions can be made from from the hydrolysis of can be made from from the hydrolysis of estersesters..• Base-catalyzed hydrolysis of esters:Base-catalyzed hydrolysis of esters:
• Acid-catalyzed hydrolysis of esters:Acid-catalyzed hydrolysis of esters:
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Carboxylic Acids & Phenols, Other ReactionsCarboxylic Acids & Phenols, Other Reactions
The acid-catalyzed hydrolysis of esters is reversible and can The acid-catalyzed hydrolysis of esters is reversible and can be used to make esters from carboxylic acids and alcohols:be used to make esters from carboxylic acids and alcohols:• Synthesis of Synthesis of estersesters from from carboxylic acidscarboxylic acids and and alcoholsalcohols::
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Carboxylic Acids & Phenols, Other ReactionsCarboxylic Acids & Phenols, Other Reactions
A biologically important reaction involving carboxylic acids is A biologically important reaction involving carboxylic acids is the the decarboxylationdecarboxylation of of αα-keto-keto and and ββ-keto acids-keto acids::
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Carboxylic Acids & Phenols, Other ReactionsCarboxylic Acids & Phenols, Other Reactions
The decarboxylation of The decarboxylation of ββ-keto acids produces -keto acids produces ketonesketones
The decarboxylation of The decarboxylation of αα-keto acids produces -keto acids produces aldehydesaldehydes
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Carboxylic Acids & Phenols, Other ReactionsCarboxylic Acids & Phenols, Other Reactions
The The oxidationoxidation of of hydroquinones is also hydroquinones is also an important biological an important biological reaction.reaction.
• A chemical oxidation A chemical oxidation of hydroquinones of hydroquinones can be carried out can be carried out the oxidizing agent the oxidizing agent KK22CrCr22OO7 7 ((potassium potassium dichromatedichromate))
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Carboxylic Acids & Phenols, Other ReactionsCarboxylic Acids & Phenols, Other Reactions
Example:Example:• Coenzyme Q and the Electron Transport ChainCoenzyme Q and the Electron Transport Chain
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Carboxylic Acids & Phenols, Other ReactionsCarboxylic Acids & Phenols, Other Reactions
Example:Example:• Coenzyme Q and the Electron Transport ChainCoenzyme Q and the Electron Transport Chain
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AminesAmines
Amines are a nitrogen with one or more carbons attached:Amines are a nitrogen with one or more carbons attached:
• Amines are classified based on the number of carbons that Amines are classified based on the number of carbons that are attached to the nitrogen.are attached to the nitrogen.• Primary amine (1°): 1 carbonsPrimary amine (1°): 1 carbons• Secondary amine (2°): 2 carbonsSecondary amine (2°): 2 carbons• Tertiary amine (3°): 3 carbonsTertiary amine (3°): 3 carbons
N
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AminesAmines
It is possible for a fourth carbon to attach to the nitrogenIt is possible for a fourth carbon to attach to the nitrogen• The nitrogen will take on a positive charge to become an The nitrogen will take on a positive charge to become an
ion.ion.
• Quaternary (4°) ammonium ions: 4 carbon atomsQuaternary (4°) ammonium ions: 4 carbon atoms
N
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AminesAmines
The IUPAC names for 1°, 2°, and 3° amines.The IUPAC names for 1°, 2°, and 3° amines.• Create the parent name by picking the longest chain of Create the parent name by picking the longest chain of
carbons that is attached to the nitrogen.carbons that is attached to the nitrogen.• Replace the “-Replace the “-ee” in the parent with the ending “-” in the parent with the ending “-amineamine”.”.• Number the longest chain from the end that gets you to the Number the longest chain from the end that gets you to the
the carbon to which the nitrogen is attached in the fewest the carbon to which the nitrogen is attached in the fewest number of carbons.number of carbons.
• Use a numbered prefix to indicate which the carbon in the Use a numbered prefix to indicate which the carbon in the longest chain the nitrogen is bonded to.longest chain the nitrogen is bonded to.
• If other substituents are attached to the nitrogen, list them If other substituents are attached to the nitrogen, list them and use the prefix “and use the prefix “N-N-” to indicate that they are attached to ” to indicate that they are attached to the nitrogen. the nitrogen.
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QuestionsQuestions
Give the IUPAC names for the following amines:Give the IUPAC names for the following amines:
A)A) CH3 CH2 CH NH2
CH3
CH3 CH2 CH
CH3
N CH2 CH3
CH2 CH2 CH3
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QuestionsQuestions
Give the IUPAC names for the following amines:Give the IUPAC names for the following amines:
A)A) CH3 CH2 CH NH2
CH3
CH3 CH2 CH
CH3
N CH2 CH3
CH2 CH2 CH3
2-butanamine2-butanamine2-butanamine2-butanamine
2-butanamine2-butanamine2-butanamine2-butanamine
N-ethyl-N-ethyl-N-ethyl-N-ethyl-
N-propylN-propylN-propylN-propyl
N-ethyl-N-propyl-2-butanamineN-ethyl-N-propyl-2-butanamineN-ethyl-N-propyl-2-butanamineN-ethyl-N-propyl-2-butanamine
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AminesAmines
For For heterocyclic aminesheterocyclic amines the nitrogen is part of a ring. the nitrogen is part of a ring.• The ring can be either aromatic or not.The ring can be either aromatic or not.• The nucleic acid nucleotide bases are good examples of The nucleic acid nucleotide bases are good examples of
hetoercyclic amineshetoercyclic amines
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AminesAmines
Hydrogen BondingHydrogen Bonding• 1° and 2° amines can serve as both a hydrogen bond 1° and 2° amines can serve as both a hydrogen bond
donor and acceptor.donor and acceptor.• 3° amines can server as a hydrogen bond acceptors, but 3° amines can server as a hydrogen bond acceptors, but
not donors.not donors.
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AminesAmines
Hydrogen BondingHydrogen Bonding• 4° ammonium ion cannot form hydrogen bonds, but 4° ammonium ion cannot form hydrogen bonds, but
because they are charged, form ionic bonds:because they are charged, form ionic bonds:
CH3 N CH3
CH3
CH3
Cl-
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The ability to hydrogen bond give amines moderately high The ability to hydrogen bond give amines moderately high boiling points and high solubilities in water.boiling points and high solubilities in water.
AminesAmines
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Another notable property of amines is their odor.Another notable property of amines is their odor.• Like carboxylic acids, they can also produce foul odor.Like carboxylic acids, they can also produce foul odor.• The produce a “fishy” smell.The produce a “fishy” smell.
• Examples of amines, whose names imply their odoriferous Examples of amines, whose names imply their odoriferous properties, includeproperties, include
AminesAmines
H2NNH2
putrescine
H2N NH2
cadaverine
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Amines as Weak BasesAmines as Weak Bases
In Unit 6, while discussing the definitions of acids and bases, In Unit 6, while discussing the definitions of acids and bases, we saw that ammonia, NHwe saw that ammonia, NH33, is operationally a base, is operationally a base• That is, when added to water ammonia causes the That is, when added to water ammonia causes the pHpH to to
rise above rise above pHpH 7. 7.
• Ammonia was the example we used to demonstrate the need for the Ammonia was the example we used to demonstrate the need for the Brønsted-Lowry definitionBrønsted-Lowry definition of acids and bases. of acids and bases.
NH3 (aq) + H2O (l) NH4+ (aq) + OH- (aq)
See the Unit 6 Elaboration -See the Unit 6 Elaboration -Definitions of Acids and Bases - Part III:Brønsted-Lowry Definition
See the Unit 6 Elaboration -See the Unit 6 Elaboration -Definitions of Acids and Bases - Part III:Brønsted-Lowry Definition
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Amines as Weak BasesAmines as Weak Bases
Like ammonia, 1°, 2° and 3°, act as Brønsted-Lowry bases.Like ammonia, 1°, 2° and 3°, act as Brønsted-Lowry bases.
+ H2O (l) + OH- (aq)N H (aq)
H
CH3 N H (aq)
H
CH3
H
methanamine(base)
methylammonium ion(acid)
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Amines as Weak BasesAmines as Weak Bases
The conjugate acids are called ammonium ionsThe conjugate acids are called ammonium ions• When placed in water, these ammonium ions will behave When placed in water, these ammonium ions will behave
like acids.like acids.
+ H3O+ (aq)+ H2O (l) N H (aq)
H
CH3N H (aq)
H
CH3
H
methanamine(base)
methylammonium ion(acid)
pKa ≈ 10
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Amines as Weak BasesAmines as Weak Bases
Because it is charged, the conjugate acid is even more Because it is charged, the conjugate acid is even more soluble that the amine.soluble that the amine.• Many drugs are amines and are sold the ammonium salts, Many drugs are amines and are sold the ammonium salts,
which are more readily absorbed, due to their increased which are more readily absorbed, due to their increased solubility.solubility.
• Ephedrine is used as a decongestant.Ephedrine is used as a decongestant.
CH
OH
CH
CH3
N
H
CH3
CH
OH
CH
CH3
N
H
CH32
+ HCl
+ H2SO4
CH
OH
CH
CH3
N
H
CH3
H
Cl-
CH
OH
CH
CH3
N
H
CH3
H
SO42-
2
ephedrine ephedrine HCl
ephedrine ephedrine sulfate
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Amines as Weak BasesAmines as Weak Bases
EphedrineEphedrine is an example of an is an example of an alkaloidalkaloid..• Alkaloids are alkaline molecules that are derived from Alkaloids are alkaline molecules that are derived from
plants.plants.• ““alkaline” and another name for basic.alkaline” and another name for basic.
• Ephedrine is isolated from the Chinese Ephedrine is isolated from the Chinese ma huang ma huang plantplant(Ephedra sinica)hyperlink(Ephedra sinica)hyperlink
CH
OH
CH
CH3
N
H
CH3
ephedrine
CH2 CH
CH3
N
H
CH3
methamphetamine
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AmidesAmides
• When a carboxylic acid reacts with an amine it also When a carboxylic acid reacts with an amine it also produces and ammonium saltproduces and ammonium salt
• If the ammonium salt is then heated, an If the ammonium salt is then heated, an amideamide is is produced.produced.
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AmidesAmides
Amides are important in Amides are important in biochemistry.biochemistry.• For example, amino For example, amino
acids are connected acids are connected together to form together to form proteins using amide proteins using amide groups.groups.
amino acidamino acidamino acidamino acid
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AmidesAmides
Amides can be hydrolyzed back to carboxylic acids and Amides can be hydrolyzed back to carboxylic acids and amines by heating them in the presence of an acidamines by heating them in the presence of an acid
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StereoisomersStereoisomers
So far we have encountered two different types of isomers.So far we have encountered two different types of isomers.• Constitutional IsomersConstitutional Isomers• StereoisomersStereoisomers• cis/transcis/trans isomers isomers with alkenes and cycloalkanes, that arise from with alkenes and cycloalkanes, that arise from
restricted rotation about bonds.restricted rotation about bonds.
There is one more type of stereoisomer, which is important in There is one more type of stereoisomer, which is important in biochemistry.biochemistry.• optical isomersoptical isomers
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StereoisomersStereoisomers
Optical isomers arise when a carbon atom has four different Optical isomers arise when a carbon atom has four different things attached to it.things attached to it.• These carbons are called These carbons are called chiral carbonschiral carbons..• The a molecule containing a chiral carbon is non The a molecule containing a chiral carbon is non
superimposable on its mirror image.superimposable on its mirror image.• The molecule and its mirror image are referred to as The molecule and its mirror image are referred to as enantiomersenantiomers
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StereoisomersStereoisomers
When developing drugs that are chiral, it is important to look When developing drugs that are chiral, it is important to look at the effects of both the enantiomers.at the effects of both the enantiomers.
RR-thalidomide-thalidomideRR-thalidomide-thalidomide SS-thalidomide-thalidomideSS-thalidomide-thalidomide
is effective in is effective in treating morning treating morning
sickness in sickness in pregnant womenpregnant women
is effective in is effective in treating morning treating morning
sickness in sickness in pregnant womenpregnant women
is a is a teratogen, , causing birth causing birth
defectsdefects
is a is a teratogen, , causing birth causing birth
defectsdefects
N
O
O
NH
O
O
H
N
O
O
NH
O
O
H
RR and and S S are another way of distinguishing enantiomers; are another way of distinguishing enantiomers; RR is is the the rectus rectus (right) isomer, while (right) isomer, while SS is the is the sinistersinister (evil) isomer! (evil) isomer!RR and and S S are another way of distinguishing enantiomers; are another way of distinguishing enantiomers; RR is is the the rectus rectus (right) isomer, while (right) isomer, while SS is the is the sinistersinister (evil) isomer! (evil) isomer!
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StereoisomersStereoisomers
When chiral molecules contain more than one chiral carbon, When chiral molecules contain more than one chiral carbon, it is possible for two molecules to be stereoisomers without it is possible for two molecules to be stereoisomers without being mirror images.being mirror images.• Such molecules are referred to as Such molecules are referred to as diastereomersdiastereomers..
C
OH
CH
CH3
N
HCH3
ephedrine pseudoephedrine
H
C
H
CH
CH3
N
HCH3OH
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StereoisomersStereoisomers
Each chiral carbon that a chiral molecule contains doubles Each chiral carbon that a chiral molecule contains doubles the number of stereoisomers for that molecule.the number of stereoisomers for that molecule.• Ephedrine has two chiral carbons, it therefore has 2 x 2 = 4 Ephedrine has two chiral carbons, it therefore has 2 x 2 = 4
stereoisomers.stereoisomers.• pseudoephedrine is one of 4 stereoisomers.pseudoephedrine is one of 4 stereoisomers.
C
OH
CH
CH3
N
HCH3
ephedrine pseudoephedrine
H
C
H
CH
CH3
N
HCH3OH
5858
Question (Clicker)Question (Clicker)
How many stereoisomers does the sugar glucose have?How many stereoisomers does the sugar glucose have?
A)A) 22
B)B) 44
C)C) 88
D)D) 1616
E)E) 3232
O
C
H
C
C
C
C
C OH
H
H
HO
H OH
H
OH
OH
H
H
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