1. Carboxylic Acids, Esters, Amides
Unit 13

2. Carboxylic Acids
When a carbonyl carbon also bears a hydroxyl group, then these compounds are appreciably acidic, and are called carboxylic acids.
Carboxylic acids are classified according to the substituent bonded to the carboxyl carbon:
Aliphatic acids have an alkyl group bound to the carboxyl group
An aromatic acid has an aryl group bound to the carboxyl group
The simplest acid is formic acid

3. Introduction
The functional group of carboxylic acids consists of a C═O with —OH bonded to the same carbon.
Carboxyl group is usually written —COOH.
Aliphatic acids have an alkyl group bonded to —COOH.
Aromatic acids have an aryl group.
Fatty acids are long-chain aliphatic acids.

4. Common Names Many aliphatic acids have historical names.
Positions of substituents on the chain are labeled with Greek letters starting at the carbon attached to the carboxylic carbon.

5. Carboxylic Acids IUPAC Formulation:
The root name is based on the longest continuous chain of carbon atoms bearing the carboxyl group
The –e is replaced by –oic acid
The chain is numbered starting with the carboxyl carbon atom
The carboxyl group takes priority over any other functional groups previously discussed

6. Carboxylic Acids
Unsaturated acids are named using the name of the alkene with –e replaced with –oic acid
The chain is numbered starting with the carboxyl group; a number designates the location of the multiple bond
Aromatic acids of the form Ar-COOH are typically named as derivatives of benzoic acids, with ortho, meta and para indicating the location relative to the carboxyl group (non-IUPAC)

7. IUPAC Names

8. Unsaturated Acids
Remove the final -e from alkene name, add the ending -oic acid.
Stereochemistry is specified.

9. Aromatic Acids
Aromatic acids are named as derivatives of benzoic acid.
Ortho-, meta- and para- prefixes are used to specify the location of a second substituent.
Numbers are used to specify locations when more than 2 substituents are present.

10. Dicarboxylic Acids
Dicarbolylic Acids are named by adding the suffix dioic acid to the root name.
The root name comes from the longest carbon chain containing both carboxyl groups.
Numbering starts at the end closest to a substituent.
3-bromohexanedioic acid

11. Carboxylic Acid Derivatives
Carboxylic derivatives are described as compounds that can be converted to carboxylic acids via simple acidic or basis hydrolysis
The most important acid derivatives are esters, amides and nitriles, although acid halides and anhydrides are also derivatives (activated forms of a carboxylic acid)
Esters of carboxylic acids are derivatives where the hydroxyl group of replaced by an alkoxy group

12. Most anhydrides are named by dropping the word acid from the name of the carboxylic acid and then adding the word “anhydride”
Acid chloride as parent (suffix): ending with “–oyl chloride”
Ester as parent (suffix): ending with “–oate”
Amide as parent (suffix): ending with “amide”
Nitrile as parent (suffix): ending with “nitrile”

13. Examples

14. Examples

15. Carboxylic Esters
Nomenclature of carboxylic esters are derived from the names of the compounds that are used to create them.
The first word of the name comes from the alkyl group of the alcohol and the second part comes from the carboxylate group of the acid used.
A cyclic ester is called a lactone. IUPAC names of lactones are derived by adding the term lactone at the end of the name of the parent hydroxycarboxylic acid from which it came.

16. Carboxylic Amide
An amide is a composite of a carboxylic acid and an amine (or ammonia).
Heating the salt formed when an amine and carboxylic acid react together, drives off the water produced and an amide is formed.
Amides are much less basic than their parent amines since the lone pairs of electrons on Nitrogen are delocalized onto the carbonyl carbon.

17. Carboxylic Amide
To name a primary amide, identify the acid part and remove the –oic acid suffix and add –amide
To name a secondary or tertiary amide, the alkyl groups on nitrogen are treated as substituents, and are given the prefix N (since they are on the nitrogen)
Cyclic amides are known as Lactams.
Lactams are produced from amino acids, where the amino acid and the carboxylic acid groups react together to form an amide linkage.
They are named by adding the word lactam to the correct IUPAC name of the parent amino acid.

18. Boiling Points
Higher boiling points than similar alcohols, due to the formation of a hydrogen-bonded dimer.

19. Melting Points
Aliphatic acids with more than 8 carbons are solids at room temperature.
Double bonds (especially cis) lower the melting point. The following acids all have 18 carbons:
Stearic acid (saturated): 72C
Oleic acid (one cis double bond): 16C
Linoleic acid (two cis double bonds): -5C

20. Solubility
Water solubility decreases with the length of the carbon chain.
With up to 4 carbons, acid is miscible in water.
Very soluble in alcohols.
Also soluble in relatively nonpolar solvents like chloroform because the hydrogen bonds of the dimer are not disrupted by the nonpolar solvent.

21. Acidity of Carboxylic Acids
A carboxylic acid may dissociate in water to give a proton and a carboxylate ion.
The equilibrium constant Ka for this reaction is called the acid-dissociation constant.
The acid will be mostly dissociated if the pH of the solution is higher than the pKa of the acid.