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Carboxylic Acid Derivatives: Nucleophilic Acyl Substitution. Chapter 19. Reading Assignment. DO: Sections 19.0 - 19.1, 19.4, 19.5, 19.7 - 19.15, 19.17 - 19.20, 19.22 - 19.24, 19.35 Problems READ WITHOUT LECTURE: Sections 19.16, 19.26 - 19.34 SKIP: Sections 19.2 - 19.3, 19.6, 19.21, 19.25.

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Carboxylic acid derivatives nucleophilic acyl substitution

Carboxylic Acid Derivatives:Nucleophilic Acyl Substitution

Chapter 19

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Reading assignment
Reading Assignment

  • DO:

    • Sections 19.0 - 19.1, 19.4, 19.5, 19.7 - 19.15, 19.17 - 19.20, 19.22 - 19.24, 19.35

    • Problems

  • READ WITHOUT LECTURE:

    • Sections 19.16, 19.26 - 19.34

  • SKIP:

    • Sections 19.2 - 19.3, 19.6, 19.21, 19.25

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Organic nomenclature assignment
Organic Nomenclature Assignment

  • Esters

  • Amides

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Problem assignment
Problem Assignment

  • In-Text:

    • 19-4 - 19-7, 19-9 - 19-27, 19-31 - 19-40

  • End-of-Chapter:

    • 1 - 3 (parts)

    • 4 - 21

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The acyl group
The Acyl Group

All carboxylic acid derivatives contain an acyl group. The substituent attached to the acyl group determines the class of carboxylic acid derivative.

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The esters
The Esters

Every ester consists of two components, the acyl part and the alkylpart.

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Naming the esters
Naming the Esters

  • Esters may be treated as if they were the product of the reaction of a carboxylic acid and an alcohol.

  • Thus their names derive from the names of the carboxylic acid and the alcohol.

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Nomenclature of the esters
Nomenclature of the Esters

  • IUPAC

    • Change carboxylic acid ending from “-oic acid” to “-oate”

    • Add name of alkyl group

    • Form:

      • Alkyl alkanoate

  • Common

    • Same as above: change “-ic acid” to “-ate” and add alkyl group name.

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Ethyl pentanoate

Ethyl valerate

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Methyl 2-methylpropanoate

Methyl a-methylpropionate

Methyl isobutyrate

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Isopropyl benzoate

Isopropyl benzenecarboxylate

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tert-Butyl phenylethanoate

tert-Butyl phenylacetate

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Methylcyclohexanecarboxylate

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Nomeclature of the amides
Nomeclature of the Amides

  • IUPAC

    • Change carboxylic acid ending from “-oic acid” to “-amide”.

    • Form:

      • Alkanamide

  • Common

    • Same as above: change “-ic acid” to “-amide”.

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Butanamide

Butyramide

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4-Methylbenzenecarboxamide

4-Methylbenzamide (acceptable IUPAC alternative name)

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A well-known characteristic of the esters is that they are the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

On the next image, you will see a partial list of esters and their characteristic flavors and fragrances.

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Esters as flavoring substances
Esters as Flavoring Substances the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

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Carboxylic acid derivatives
Carboxylic Acid Derivatives the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

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Functional group interconversions
Functional Group Interconversions the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

  • The next image outlines interconversions that can be made among the carboxylic acid derivatives.

  • The purpose of the image is to illustrate that all of the carboxylic acid derivatives are inter-related and that all can, in principle, be converted into one another.

  • Note the central location of the acid chlorides. All conversions from carboxylic acids to derivatives are best conducted through the corresponding acid chloride.

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Functional group interconversions1
Functional Group Interconversions the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

H2O

OH-

R’OH

H2O

H2O

SOCl2

R’OH

OH-

NH3

NR’2H

NH3

NR’2H

RCOOH

H2O

RCOOH

NH3

NR’2H

NH3

NR’2H

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Nucleophilic acyl substitution
Nucleophilic Acyl Substitution the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

  • All of the interconversions among carboxylic acids and their derivatives take place following one general mechanism

  • This mechanism is nucleophilic acyl substitution.

  • For each case, the only significant differences lies in the nature of the leaving group and the nucleophile.

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Nucleophilic acyl substitution1
Nucleophilic Acyl Substitution the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

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Energy profile for nucleophilic acyl substitution
Energy Profile for Nucleophilic Acyl Substitution the substances responsible for the characteristic flavors and fragrances of fruits and flowers.

Intermediate

Energy

Reactants

Products

Reaction Coordinate

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This intermediate can collapse either by loss of the the substances responsible for the characteristic flavors and fragrances of fruits and flowers. Y group (leads to a forward reaction) of by the loss of the Nu group (leads to a reverse reaction). Either pathway can take place, as this is a reversible process.

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Nucleophilic substitution acid catalyzed mechanism
Nucleophilic Substitution the substances responsible for the characteristic flavors and fragrances of fruits and flowers. (Acid-catalyzed Mechanism)

  • When the nucleophile is relatively weak (e.g., water, alcohols), an acid-catalyzed mechanism is preferred.

  • The role of the acid is to protonate the acyl oxygen, thus increasing the positive charge character on the acyl carbon (through resonance).

  • This makes the acyl carbon a better site for nucleophilic attack.

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Nucleophilic acyl substitution acid catalyzed
Nucleophilic Acyl Substitution the substances responsible for the characteristic flavors and fragrances of fruits and flowers. (Acid-Catalyzed)

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This intermediate can collapse either by loss of the the substances responsible for the characteristic flavors and fragrances of fruits and flowers. Y group (leads to a forward reaction) of by the loss of the Nu group (leads to a reverse reaction). Either pathway can take place, as this is a reversible process.

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The nucleophile ( the substances responsible for the characteristic flavors and fragrances of fruits and flowers. Nu) can be any of the following:

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