Chapter Seventeen Carboxylic Acids and Their Derivatives Fundamentals of General, Organic & Biological Chemistry 4th Edition Mohammed Hashmat Ali Southeast Missouri State University  2003 Prentice Hall, Inc.

Prentice Hall © 2003 Chapter One Carboxylic Acids and Their Derivatives: Properties and Names  Caboxylic acids have an –OH group bonded to a carbonyl group. In their derivatives, OH is substituted by other group. Such as,  Esters have a –OR group bonded to a carbonyl group.  Amides have an –NH 2 group bonded to a carbonyl group.

Prentice Hall © 2003 Chapter One 3  Carboxylic acid their derivatives all contain polar functional group, as a result they have higher boiling points than alkanes.  Carboxylic acid their derivatives all participate in carbonyl-group substitution reaction, in which the group bonded to the carbonyl group is replaced by another group.  The parts of molecules the alkyl group is bonded to the carbonyl group is known as an acyl group, RC=O.

Prentice Hall © 2003 Chapter One 4 Carboxylic Acids  Carboxylic acids donate proton to bases.  Carboxylic acids hydrogen bond with each other. As a result of hydrogen bonding, they have higher boiling points than similar alkanes.

Prentice Hall © 2003 Chapter One 5  Carboxylic acids have sharp and strong odor.  Up to four carbon containing Carboxylic acids are water soluble.  Carboxylic acids are named systematically (IUPAC) by replacing the –e at the end of the alkane name with –oic acid. If alkyl or other substituents are present, the chain is numbered beginning at the –COOH end.

Prentice Hall © 2003 Chapter One 6  Dicarboxylic acids, which contains two – COOH groups, are named by adding the ending –dioic acid to the alkane name.  Unsaturated acids are named systematically in the IUPAC system with the ending – enoic acid.  Acids with larger saturated alkyl groups are waxy, odorless solids.  Water solubility decreases as the size of the alkyl group increases.

Prentice Hall © 2003 Chapter One 7  Esters In carboxylic acid, OH group of is replaced with OR group to create an ester. Esters can not form hydrogen bonds with each other. Therefore, esters have lower boiling points than the carboxylic acids from which they are derived.

Prentice Hall © 2003 Chapter One 8  The simple esters are colorless, volatile liquid with pleasant smell.  Esters are neither acids nor bases in aqueous solution.  Esters name consists of two words. The name of the alkyl group in the ester group, - COOR, and the name of the parent carboxylic acid with the family name –oic replaced with –ate.

Prentice Hall © 2003 Chapter One 9 Amides  Amides may contain –NH 2 group or one or both of the hydrogen replaced with alkyl groups.  Unsubstituted amides, RCONH 2, can form three hydrogen bonds to other amide molecules and are thus have higher melting and boiling points than the acids from which they are derived.

Prentice Hall © 2003 Chapter One 10  Monosubstituted amides, RCONHR’, can form hydrogen bonds to other amide molecules.  Disubstituted amides, RCONR’ 2, can not form hydrogen bonds to other amide molecules, therefore, they have lower boiling points.

Prentice Hall © 2003 Chapter One 11  Unsubstituted amides, RCONH2, are named by replacing the –ic or –oic acid by –amide.  Substituted amides are named by first specifying the alkyl group and then identifying the the amide name. The alkyl substituents are preceded by the letter N to specify that the alkyl groups are attached to the nitrogen.

Prentice Hall © 2003 Chapter One Some Common Carboxylic Acids  Formic acid, HCOOH: Chemical that is present in the sting of ants.  Acetic acid, CH 3 COOH: dilute (5%) aqueous acetic acid is known as vinegar.  Butyric acid, CH 3 CH 2 CH 2 COOH: Chemical responsible for odor of rancid butter.  Caproic acid, CH 3 CH 2 CH 2 CH 2 CH 2 COOH: First isolated from the skin of goats-which has distict smell.  Citric acid: Present in citrous fruits and blood.

Prentice Hall © 2003 Chapter One Acidity of Carboxylic Acids  Carboxylic acids are weak acids.  Acid strengths of common carboxylic acids are about the same as that for acetic acid.  Carboxylic acids undergo neutralization reactions with bases and produce water and a carboxylic acid salt.  The sodium and potassium salts of carboxylic acids are ionic solids that are more soluble in water than the carboxylic acids themselves.

Prentice Hall © 2003 Chapter One Reactions of Carboxylic Acids: Esters and Amide Formation The reactions of alcohols and amines with carboxylic acids follow the same pattern – both replaces –OH group in acid with another group. Esterification: Esterification is carried out by warming a mixture of a carboxylic acid and an alcohol in the presence of a catalytic amount of a strong acid catalyst.

Prentice Hall © 2003 Chapter One 15 Amide Formation: Unsubstituted amides are formed by warming a mixture of a carboxylic acid and ammonia. Substituted amides are formed by warming a mixture of a carboxylic acid and a primary or secondary amine.

Prentice Hall © 2003 Chapter One Aspirin and Other Over-the- Counter Carboxylic Acid Derivatives Aspirin: A member of a group of drugs known as salicylates. Aspirin is an analgesic (relief pains), antipyretic (reduces fever), and anti-inflammatory (reduces inflammation). Salicylates are esters of salicyclic acid.

Prentice Hall © 2003 Chapter One 17 Acetaminophen: An amide that also contain a hydroxyl group. It is best known as Tylenol. An alternative to Aspirin for pain relief but it unlike aspirin it is not an anti-innflammatory agent.

Prentice Hall © 2003 Chapter One Hydrolysis of Esters and Amides Esters and amides undergo hydrolysis to give back the carboxylic acid and alcohol or amine. Ester hydrolysis: Ester hydrolysis reactions can be catalyzed by either an acid or a base.

Prentice Hall © 2003 Chapter One 19 Acid catalyzed ester hydrolysis is simply the reverse of esterification reaction. In this reaction, an ester is treated with water in the presence of a strong acid catalyst such as sulfuric acid. Base catalyzed ester hydrolysis with a base such as NaOH or KOH is known as saponofication. The product of saponification reaction is a carboxylate anion rather then a free carboxylic acid.

Prentice Hall © 2003 Chapter One 20 Amide hydrolysis: Amides are stable in water but undergo hydrolysis when heated in the presence of a base or an acid. The product of amide hydrolysis reaction in the presence of a base or an acid are shown below.

Prentice Hall © 2003 Chapter One Polyamides and Polyesters  Polymer molecules are composed of thousands of repeating unit, known as monomer.  Both polyamides and polyesters are polymer and they have many uses.  Polyamides are formed by reaction between diamines and diacids.  Nylons are polyamides.  Polyesters are formed by reaction between diacids and dialcohols.

Prentice Hall © 2003 Chapter One Phosphoric Acid Derivatives  Phosphoric acid is an inorganic acid with three ionizable hydrogen atoms allowing it to form three different anions.  Phosphoric acids react with alcohols to form phosphate esters.  Phosphoric acid produces mono, di, or triester by reacting with one, two, or three molecules of alcohols respectively.

Prentice Hall © 2003 Chapter One 23  Phosphate mono and diesters are acids because they still contain acidic hydrogen atoms. In biochemical reactions and equations, the phosphate groups are thus written in their ionic forms.  Two molecules of phosphoric acid lose water between them and form a phosphoric acid anhydride. The resulting phosphoric acid anhydride (also an acid) reacts with another molecule of phosphoric acid in a similar reaction to produce a triphosphoric acid.

Prentice Hall © 2003 Chapter One 24  Transfer of a phosphoryl group, -PO 3 2-, from one molecule to another is known as phosphorylation.  In biochemical reaction, phosphorylation reactions provide energy. Such as ATP, a triphosphate, converting to ADP, a diphosphate, releases energy that is used by other biochemical reactions body.

Prentice Hall © 2003 Chapter One 25 Chapter Summary  Most carboxylic acids are weak acids but esters and amides are neither acids nor bases.  Carboxylic acids, esters, and amides undergo carbonyl group substitution reactions.  Simple acids and esters are liquids; all amides except formamide are solids.  In esters, -OH group in acid is replaced by a - OR group of an alcohol.

Prentice Hall © 2003 Chapter One 26 Chapter Summary Contd.  In amides, -OH group in acid is replaced by a –NH 2 group of ammonia, or a NHR or –NR 2 groups of a primary or secondary amine.  Phosphoric acids are inorganic acids.  Phosphoric acid forms mono-, di-, or triesters.  Phosphorylation is the transfer of a phophoryl, -PO 3 2-, group from one molecule to another.  Phosphorylation reaction in living organisms is associated with release of energy.

Prentice Hall © 2003 Chapter One 27 End of Chapter 17