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Larry Emme Chemeketa Community College

Carboxylic Acids and Esters Chapter 24. Larry Emme Chemeketa Community College. Carboxylic Acids. A poem by Ogden Nash. The ant has made himself illustrious Through constant industry industrious So what? Would you be calm and placid

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Larry Emme Chemeketa Community College

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  1. Carboxylic Acids and Esters Chapter 24 Larry Emme Chemeketa Community College

  2. Carboxylic Acids

  3. A poem by Ogden Nash The ant has made himself illustrious Through constant industry industrious So what? Would you be calm and placid If you were full of formic acid?

  4. The functional group of the carboxylic acid is called a carboxyl group and is represented in the following ways:

  5. Nomenclature and Sources of Aliphatic Carboxylic Acids

  6. To establish the parent name, identify the longest carbon chain that includes the carboxyl group. • Drop the final –e from the corresponding hydrocarbon name. • Add the suffix –oic acid. IUPAC Rules for Naming Carboxylic Acids HCOOH, methanoicacid CH3COOH ethanoicacid CH3CH2COOH propanoicacid

  7. Naming Carboxylic Acids • Other groups bonded to the parent chain are numbered and named as we have done previously.

  8. Common Names for Acids • HCOOH Formic Formica (ant) • CH3COOH Acetic Acetum (sour) • CH3CH2COOH Propionic Pro (first) + Pion (fat) • CH3(CH2)2COOH Butyric Butyrum (butter) • CH3(CH2)3COOH Valeric Valere (strong) • CH3(CH2)4COOH Caproic Caper (goat)

  9. Common Names for Acids • CH3(CH2)6COOH Caprylic Caper (goat) • CH3(CH2)8COOH Capric Caper (goat) • CH3(CH2)10COOH Lauric Laurel • CH3(CH2)12COOH Myristic Muron (perfume) • CH3(CH2)14COOH Palmitic Palm Oil • CH3(CH2)16COOH Stearic Stear (solid fat)

  10. Nomenclature of Carboxylic Acids • Use of Greek letters:

  11. Physical Properties of Carboxylic Acids

  12. Physical Properties of Carboxylic Acids • Each aliphatic carboxylic acid molecule is polar and consists of a carboxylic acid group and a hydrocarbon group (-R). • Carbons 1-4 = water soluble • Carbons 5-8 = slightly water soluble • Carbons 8 and above = virtually insoluble in water

  13. Physical Properties of Carboxylic Acids • The comparatively high boiling points for carboxylic acids are due to intermolecular attractions resulting from hydrogen bonding.

  14. Physical Properties of Carboxylic Acids • Carboxylic acids are generally weak acids; that is, they are only slightly ionized in water.

  15. Classification of Carboxylic Acids

  16. Types of Carboxylic Acids There are five major types of carboxylic acids in addition to the saturated monocarboxylic acids like acetic acid (CH3COOH ). These acids are summarized and discussed in this section.

  17. Types of Carboxylic Acids 18

  18. Unsaturated Carboxylic Acids • An unsaturated acid contains one or more C=C. • Acrylic acid, CH2=CHCOOH, also called propenoic acid. • Even one C=C bond exerts an influence on the physical and chemical properties of the acid. Ex: stearic acid CH3(CH2)16COOH, mp = 70 ºC vs. oleic acid CH3(CH2)7CH=CH(CH2)7COOH, mp = 16 ºC

  19. Aromatic Carboxylic Acids • In an aromatic carboxylic acid, the carbon of the carboxyl group (-COOH) is bonded directly to a carbon in an aromatic ring.

  20. Dicarboxylic Acids Dicarboxylic acids have two carboxyl (COOH) groups. These acids undergo a decarboxylation reaction ( i.e.loss of CO2 ) to form a monocarboxylic acid or an anhydride as shown below.

  21. Citric acid is a hydroxytricarboxylic acid. It is 5-8% of lemon juice and widely distributed in plant and animal tissues. It is also an important acid in the citric acid cycle. Examples of other dicarboxylic acids are listed in Table 24.2.

  22. Hydroxy Acids • Hydroxy acids have the functional group of an alcohol and a carboxylic acid.

  23. Hydroxy Acids Malic acid and tartaric acid are two other common -hydroxy acids found in apples and grapes respectively.

  24. Amino Acids • Each amino acid molecule has a carboxyl group that acts as an acid and an amino group that acts as a base. • About 20 biologically important amino acids, each with a different group represented by R, are found in nature. The R group does not necessarily represent an alkyl group in amino acids.

  25. Preparation of Carboxylic Acids

  26. Preparation of Carboxylic Acids • oxidation of an aldehyde or primary alcohol • oxidation of alkyl groups attached to aromatic rings • hydrolysis of nitriles

  27. Oxidation of an Aldehyde or a Primary Alcohol

  28. Oxidation of Alkyl Groups Attached to an Aromatic Ring Alkyl benzenes are oxidized in basic solution to the carboxylate salt and then protonated with acid to form benzoic acid.

  29. Hydrolysis of Nitriles • RCN + 2 H2O  RCOOH + NH4+ H+

  30. Chemical Properties of Carboxylic Acids

  31. Chemical Properties of Carboxylic Acids • Acid-Base reactions • Substitution reactions • acid chlorides • acid anhydrides • esters • amides

  32. Acid-Base Reactions • Because of their ability to form hydrogen ions in solution, acids in general have the following properties: • Sour taste • Change blue litmus to red and affect other suitable indicators. • Form water solutions with pH values less than 7. • Undergo neutralization reactions with bases for form water and a salt.

  33. Acidity of Carboxylic Acids

  34. Substitution Reactions • acid chlorides • acid anhydrides • esters • amides

  35. Acid Chloride Formation Acid chlorides are prepared by reacting thionyl chloride (SOCl2) and a carboxylic acid.

  36. Reactivity of Acid Chlorides Acid chlorides are very reactive and will hydrolyze back to the carboxylic acid if exposed to moisture.

  37. Acid Anhydride Formation • An organic anhydride is formed by the elimination of water from two molecules of carboxylic acid.

  38. Ester Formation • An ester is formed by the reaction of an acid with an alcohol or a phenol; water is also produced in the reaction:

  39. Nomenclature of Esters

  40. Nomenclature of Esters • The alcohol part is named first, followed by the name of the acid modified to end in –ate.

  41. Occurrence and Physical Properties of Esters

  42. Properties of Esters • Simple esters derived from monocarboxylic acids and monohydroxy alcohols are colorless, generally nonpolar liquids or solids. • Low- and intermediate-molar-mass esters (both acids and alcohols up to about 10 carbons) are liquid with characteristic (usually fragrant or fruity) odors.

  43. Occurrence and Properties of Esters • High-molar-mass esters (formed from acids or alcohols of 16 or more carbons) are waxes and are obtained from various plants. • They are used in furniture wax and automobile wax preparations. • Carnauba wax contains esters of 24-and 28-carbon fatty acids and 32- and 34-carbon alcohols.

  44. Chemical Properties of Esters

  45. Hydrolysis • The most important reaction of esters is hydrolysis – the splitting of molecules through the addition of water. • A catalyst is often required. • An acid or base • In living systems, enzymes act as catalysts.

  46. Acid Hydrolysis • The hydrolysis of an ester involves the reaction with water to form a carboxylic acid and an alcohol.

  47. Alkaline Hydrolysis (Saponification) • Saponification is the hydrolysis of an ester by a strong base (NaOH or KOH) to produce an alcohol and a salt (or soap if the salt formed is from a high-molar-mass acid). • Notice that in saponification, the base is a reactant and not a catalyst.

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