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Organic Chemistry II Carboxylic Acid Derivatives. Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University. Chapter Objectives. Nomenclature Properties Preparation Reactions Spectroscopy. Carboxylic Derivatives. Functional Groups we will consider are:.

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organic chemistry ii carboxylic acid derivatives

Organic Chemistry IICarboxylic Acid Derivatives

Dr. Ralph C. Gatrone

Department of Chemistry and Physics

Virginia State University

chapter objectives
Chapter Objectives
  • Nomenclature
  • Properties
  • Preparation
  • Reactions
  • Spectroscopy
carboxylic derivatives
Carboxylic Derivatives
  • Functional Groups we will consider are:
carboxylic derivatives4
Carboxylic Derivatives
  • Chemistry is similar
  • Chemistry is dominated by one reaction
nomenclature acid halides rcox
NomenclatureAcid Halides RCOX
  • Derived from the carboxylic acid name by replacing the -ic acid ending with -yl or the -carboxylic acid ending with –carbonyl and specifying the halide
nomenclature acid anhydrides rco 2 cor
Nomenclature Acid Anhydrides, RCO2COR’
  • If symmetrical replace “acid” with “anhydride” based on the related carboxylic acid
  • For substituted monocarboxylic acids: use bis- ahead of the acid name
  • Unsymmetrical anhydrides— cite the two acids alphabetically
nomenclature esters rco 2 r
NomenclatureEsters, RCO2R
  • Name R’ and then, after a space, the carboxylic acid (RCOOH), with the “-ic acid” ending replaced by “-ate”
nomenclature amides rconh 2
Nomenclature Amides, RCONH2
  • With unsubstituted NH2 group. replace -oic acid or -ic acid with -amide, or by replacing the -carboxylic acid ending with –carboxamide
  • If the N is further substituted, identify the substituent groups (preceded by “N”) and then the parent amide
examples
Examples
  • Try these
examples10
Examples
  • Answers
properties
Properties
  • Amides have higher boiling point than other derivatives due to H-bonding
  • Esters have pleasant odors associated with fruits and flavors
  • Acid halides have pungent odors due to hydrolysis to HCl or HBr
stability
Stability
  • Amides more stable than
  • Esters, more stable than
  • Acid anhydrides, more stable than
  • Acid halides
  • Esters and amides are commonly found in natural materials.
  • Amides make up foundation of animals
  • Acid halides and anhydrides don’t exist in nature
relative reactivity of carboxylic acid derivatives
Relative Reactivity of Carboxylic Acid Derivatives
  • Nucleophiles react more readily with unhindered carbonyl groups
  • More electrophilic carbonyl groups are more reactive to addition (acyl halides are most reactive, amides are least)
  • The intermediate with the best leaving group decomposes fastest
reactions of carboxylic acids
Reactions of Carboxylic Acids
  • OH is poor leaving group
  • Must enhance reactivity
  • Specific reagents can produce acid chlorides, anhydrides, esters, amides
acids to acid chlorides
Acids to Acid Chlorides
  • Reaction with thionyl chloride, SOCl2
acids to acid anhydrides
Acids to Acid Anhydrides
  • Heat cyclic dicarboxylic acids that can form five- or six-membered rings
  • Acyclic anhydrides are not generally formed this way - they are usually made from acid chlorides and carboxylic acids
acids to esters
Acids to Esters
  • Carboxylate anion with a primary alkyl halide
fischer esterification
Fischer Esterification
  • Heating a carboxylic acid in an alcohol solvent containing a small amount of strong acid produces an ester from the alcohol and acid
esterification using diazomethane
Esterification using Diazomethane

Reaction only provides the methyl ester

Glassware must be polished (no ground glass joints)

acids to amides
Acids to Amides
  • Direct reaction cannot be done
  • Due to acid base reaction that occurs first
acids to amides23
Acids to Amides
  • Must make OH a better leaving group
  • Generally done in the laboratory via the acyl halide
  • Can also use dicyclohexylcarbodiimide to activate the OH
chemistry of acid halides
Chemistry of Acid Halides
  • Acid chlorides are prepared from carboxylic acids by reaction with SOCl2
  • Reaction of a carboxylic acid with PBr3 yields the acid bromide
reactions of acid halides
Reactions of Acid Halides
  • Nucleophilic acyl substitution
  • Halogen replaced by OH, by OR, or by NH2
  • Reduction yields a primary alcohol
  • Grignard reagent yields a tertiary alcohol
acid halides into acids hydrolysis
Acid Halides into Acids(Hydrolysis)
  • Acid chlorides react with water to yield carboxylic acids
  • HCl is generated during the hydrolysis: a base is added to remove the HCl
acid halides to anhydrides
Acid Halides to Anhydrides
  • Acid halides react with carboxylate anions
acid halides to esters
Acid Halides to Esters
  • Esters are produced in the reaction of acid chlorides react with alcohols in the presence of pyridine or NaOH
  • The reaction is better with less steric bulk
acid halides into amides
Acid Halides into Amides
  • Amides result from the reaction of acid chlorides
    • with NH3,
    • primary amines (RNH2)
    • secondary amines (R2NH)
  • The reaction with tertiary amines (R3N) gives an unstable species that cannot be isolated
  • HCl is neutralized by the amine or an added base
acid chlorides into alcohols
Acid Chlorides into Alcohols
  • LiAlH4 reduces acid chlorides to yield primary alcohols through the aldehyde (not isolated)
acid halides with organometallics
Acid Halides with Organometallics
  • Grignard reagents react with acid chlorides to yield tertiary alcohols in which two of the substituents are the same
acid chlorides to ketones
Acid Chlorides to Ketones
  • Reaction of an acid chloride with a lithium diorganocopper (Gilman) reagent, Li+ R2Cu
  • Reaction of an acid chloride with organocadmium reagent
chemistry of acid anhydrides
Chemistry of Acid Anhydrides
  • Prepared by carboxylate nucleophile with an acid chloride
reactions of acid anhydrides
Reactions of Acid Anhydrides
  • Similar to acid chlorides in reactivity
anhydrides to esters or amides
Anhydrides to Esters or Amides
  • Anhydrides form esters with alcohols
  • Anhydrides form amides with amines
anhydrides more selective than acid halides
Anhydrides: More Selective than Acid Halides
  • Anhydrides react with amines in presence of alcohols, Not so acid chlorides
chemistry of esters
Chemistry of Esters
  • Many esters are pleasant-smelling liquids: fragrant odors of fruits and flowers
  • Also present in fats and vegetable oils
preparation of esters
Preparation of Esters
  • Esters are usually prepared from carboxylic acids
reactions of esters
Reactions of Esters
  • Less reactive toward nucleophiles than are acid chlorides or anhydrides
  • Cyclic esters are called lactones and react similarly to acyclic esters
esters into carboxylic acids
Esters into Carboxylic Acids
  • An ester is hydrolyzed by aqueous base or aqueous acid to yield a carboxylic acid plus an alcohol
slide41
Soap
  • Ester (Fat) hydrolysis into carboxylate anion
esters to amides
Esters to Amides
  • Ammonia reacts with esters to form amides
  • Reaction is easier from the acid chloride
esters into alcohols reduction
Esters into Alcohols: Reduction
  • Reaction with LiAlH4 yields primary alcohols
reduction of esters
Reduction of Esters
  • LAH is reducing agent of choice
  • NaBH4 does not reduce esters
  • H2 does not reduce esters
  • BH3 – THF does not reduce esters
  • DIBAH reduces esters to the aldehyde
esters with grignard reagents
Esters with Grignard Reagents
  • Reacts with 2 equivalents of a Grignard reagent to yield a tertiary alcohol
chemistry of amides
Chemistry of Amides
  • Prepared by reaction of an acid chloride with ammonia, primary amines, or secondary amines
  • Amides are the least reactive of derivatives
reactions of amides
Reactions of Amides
  • Heating in either aqueous acid or aqueous base produces a carboxylic acid and the amine
amides into amines
Amides into Amines
  • Reduced by LiAlH4 to an amine rather than an alcohol
  • Converts C=O  CH2
reduction of amides
Reduction of Amides
  • Works with cyclic and acyclic
  • Good route to cyclic amines
amide to amine the hoffmann rearrangement
Amide to AmineThe Hoffmann Rearrangement
  • Preparation of amine with loss of a carbon
infrared spectroscopy
Infrared Spectroscopy
  • Acid chlorides: 1800cm-1
  • Acid anhydrides: 1820 and 1760cm-1
  • Esters: 1735cm-1
  • Amides: 1650 - 1690cm-1 depending on N substitution
nmr spectroscopy
NMR Spectroscopy
  • Carbon-13 NMR
  • Difficult to assign with certainty
nmr spectroscopy54
NMR Spectroscopy
  • Proton NMR
  • Protons adjacent to C=O resonate near 2d
  • Identity of the C=O cannot be determined