chapter 17 carbonyl compounds i reactions of carboxylic acids and carboxylic acid derivatives

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Organic Chemistry 6 th Edition Paula Yurkanis Bruice. Chapter 17 Carbonyl Compounds I Reactions of Carboxylic Acids and Carboxylic Acid Derivatives. Class I Carbonyl Compounds. Class II Carbonyl Compounds. Nomenclature of Carboxylic Acids. - PowerPoint PPT Presentation

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Slide 1Organic Chemistry
6th Edition
always C-1
carbonyl is the a-carbon
The functional group of a carboxylic acid is called a
carboxyl group
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Amides
If a substituent is bonded to the nitrogen, the name of the
substituent is stated first:
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carboxylic acids, and amides:
because…
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Carboxylic Acid Derivatives
polarity of the carbonyl group:
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The tetrahedral intermediate is a transient species that eliminates the leaving group Y– or the nucleophile Z–:
This is a nucleophilic acyl substitution reaction
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Both reactant and product will be present if Y– and Z–
have similar leaving abilities:
(c) the Nu– and the leaving group have similar basicities
Reaction Coordinate Diagrams for
Nucleophilic Acyl Substitution Reactions
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susceptibility to nucleophilic attack:
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intermediate collapses:
A carboxylic acid derivative can be converted only into a
less reactive carboxylic acid derivative:
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A base is required to trap the HCl product
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Tertiary amines cannot form amides
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Reactions of Acid Anhydrides
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Mechanism for the conversion of an acid anhydride into an ester (and a carboxylic acid):
In the absence of an acid catalyst, the reaction is sluggish, but the reaction speeds up as acid products are formed
Addition facilitated by protonation
Elimination facilitated by protonation
phenolate ions are weaker bases than alkoxide ions:
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groups can be catalyzed by an acid
The carbonyl oxygen is first protonated,
Because…
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Alcohols that have low boiling points can be removed by
distillation as they are formed
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more rapidly than do others:
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Hydroxide ion increases the rate of formation as well as
the collapse of the tetrahedral intermediate:
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substitution:
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The nonpolar tails are buried in the hydrophobic interior.
The polar carboxylates are positioned at the aqueous exterior.
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or POCl3
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Ammonia anion is a very poor leaving group
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Formation of lactones:
to a benzene ring:
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The goal is to convert the OH group into a better leaving
group:
The acyl halide can be used to prepare other carboxylic
acid derivatives:
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The carbonyl carbon of a thioester is more susceptible to
nucleophilic attack than is the carbonyl carbon of an
oxygen ester
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The two pKa values of a dicarboxylic acid are different:
Why?
The neighboring COOH group withdraws electrons and lowers the first pKa.
Electrostatic interaction between like charges raises the second pKa.
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Dicarboxylic Acids
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Sucrose esterified with fatty acids
Tastes like a fat, but the sterically hindered esters cannot be digested
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Mechanism involves acetyl transfer to a serine oxygen
Cholinergic activity = SLUD
Nerve gases phosphorylate the active-site serine oxygen of acetylcholinesterase.
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Bioactivation of Acetate
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The acetylcholine is stored for the next nerve impulse
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Penicillin
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Bacteria can become resistant to penicillin by producing an enzyme that hydrolyzes the lactam ring:
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