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Organic Chemistry II Carboxylic Acid Derivatives

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

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  1. Organic Chemistry IICarboxylic Acid Derivatives Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University

  2. Chapter Objectives • Nomenclature • Properties • Preparation • Reactions • Spectroscopy

  3. Carboxylic Derivatives • Functional Groups we will consider are:

  4. Carboxylic Derivatives • Chemistry is similar • Chemistry is dominated by one reaction

  5. 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

  6. 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

  7. NomenclatureEsters, RCO2R • Name R’ and then, after a space, the carboxylic acid (RCOOH), with the “-ic acid” ending replaced by “-ate”

  8. 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

  9. Examples • Try these

  10. Examples • Answers

  11. 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

  12. 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

  13. Stability

  14. 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

  15. General Reactions of Carboxylic Acid Derivatives

  16. Reactions of Carboxylic Acids • OH is poor leaving group • Must enhance reactivity • Specific reagents can produce acid chlorides, anhydrides, esters, amides

  17. Acids to Acid Chlorides • Reaction with thionyl chloride, SOCl2

  18. 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

  19. Acids to Esters • Carboxylate anion with a primary alkyl halide

  20. 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

  21. Esterification using Diazomethane Reaction only provides the methyl ester Glassware must be polished (no ground glass joints)

  22. Acids to Amides • Direct reaction cannot be done • Due to acid base reaction that occurs first

  23. 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

  24. 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

  25. 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

  26. 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

  27. Acid Halides to Anhydrides • Acid halides react with carboxylate anions

  28. 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

  29. 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

  30. Acid Chlorides into Alcohols • LiAlH4 reduces acid chlorides to yield primary alcohols through the aldehyde (not isolated)

  31. Acid Halides with Organometallics • Grignard reagents react with acid chlorides to yield tertiary alcohols in which two of the substituents are the same

  32. 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

  33. Chemistry of Acid Anhydrides • Prepared by carboxylate nucleophile with an acid chloride

  34. Reactions of Acid Anhydrides • Similar to acid chlorides in reactivity

  35. Anhydrides to Esters or Amides • Anhydrides form esters with alcohols • Anhydrides form amides with amines

  36. Anhydrides: More Selective than Acid Halides • Anhydrides react with amines in presence of alcohols, Not so acid chlorides

  37. Chemistry of Esters • Many esters are pleasant-smelling liquids: fragrant odors of fruits and flowers • Also present in fats and vegetable oils

  38. Preparation of Esters • Esters are usually prepared from carboxylic acids

  39. Reactions of Esters • Less reactive toward nucleophiles than are acid chlorides or anhydrides • Cyclic esters are called lactones and react similarly to acyclic esters

  40. Esters into Carboxylic Acids • An ester is hydrolyzed by aqueous base or aqueous acid to yield a carboxylic acid plus an alcohol

  41. Soap • Ester (Fat) hydrolysis into carboxylate anion

  42. Esters to Amides • Ammonia reacts with esters to form amides • Reaction is easier from the acid chloride

  43. Esters into Alcohols: Reduction • Reaction with LiAlH4 yields primary alcohols

  44. 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

  45. Esters with Grignard Reagents • Reacts with 2 equivalents of a Grignard reagent to yield a tertiary alcohol

  46. Chemistry of Amides • Prepared by reaction of an acid chloride with ammonia, primary amines, or secondary amines • Amides are the least reactive of derivatives

  47. Reactions of Amides • Heating in either aqueous acid or aqueous base produces a carboxylic acid and the amine

  48. Amides into Amines • Reduced by LiAlH4 to an amine rather than an alcohol • Converts C=O  CH2

  49. Reduction of Amides • Works with cyclic and acyclic • Good route to cyclic amines

  50. Amides to Nitriles

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