Lecture 11-12 Carboxylic acids and Their Derivatives
Lecture 11-12 Carboxylic acids and Their Derivatives CHEM 225
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This 4 page Class Notes was uploaded by MelLem on Sunday February 28, 2016. The Class Notes belongs to CHEM 225 at Simmons College taught by Professor gurney in Spring 2016. Since its upload, it has received 30 views. For similar materials see Organic chemistry 2 in Chemistry at Simmons College.
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Date Created: 02/28/16
CHEM 225 Organic Chemistry II UNIT III – Carboxylic Acids and Carboxylic Acid Derivatives Lectures 11-12 Chapter 21 – carboxylic acids and their derivatives 21.1 – Introduction to carboxylic acids - Carboxylic Acids – compounds with a R-COOH moiety. These compounds are abundant in nature and are responsible for some familiar odors. o CH3COOH – acetic Acid – responsible for the smell of vinegar Found in a wide range of pharmaceutical products that are used to treat a variety of conditions. o For example – acetylsalicylic acid is found in aspirin. Vinyl acetate is a derivative of acetic acid, therefore said to be a carboxylic acid derivative 21.2 – Nomenclature of Carboxylic Acids -Monocarboxylic Acids Contain only one carboxylic acid moiety. Named with the suffic -–ic acid. The parent is the longest chain that includes the carbon atom of the carboxylic acid moiety. When a carboxylic acid moiety is connected to a ring, the compound will be named as an alkane carboxylic acid. Common carboxylic acids to memorize Formic acid Acetic Acid Propionic acid Butyric acid Benzoic acid -Diacids Compounds containing 2 carboxylic acid moieties Named with the suffix –dioic acid 21.3 – Structure and Properties of –COOH -Structure Carbon atom of the carboxylic acid moiety is sp2 hybridized and exhibits trigonal planar geometry. Bond angles are ~120 degrees Carboxylic acids can form 2 hydrogen bonding interactions allowing molecules to associate with each other in pairs. The hydrogen bonding interactions explain why carboxylic acids have high boiling points. -Acidity of Carboxylic Acids Carboxylic acids exhibit mildly acidic protons. Treatment of a carboxylic acid with a strong base yields a carboxylate salt. Carboxylate salts are ionic, therefore more soluble in water than their corresponding carboxylic acids. Carboxylate ions are named by replacing the suffix –ic acid with the suffix -ate. When dissolved in H2O an equilibrium is established in which both the carboxylic acid and the carboxylate ion are both present. In most cases, the equilibrium favors the carboxylic acid 21.4 Preparation of Carboxylic Acids Review of carboxylic acid preparation (Table 21.1 in Klein) 1. Oxidative Cleavage of Alkynes a. Reagents 1) O3 2) H2O b. Cleaves the triple bond and forms 2 carboxylic acids 2. Oxidation of Primary Alcohols a. Reagents Na2Cr2O7 / H2SO4, H2O b. Other strong oxidizing agents can be used as well c. Oxidizes from Oxidation level of  to  3. Oxidation of Alkyl benzenes a. Reagents Na2Cr2O7 / H2SO4, H2O b. Any alkyl group on an aromatic ring WILL be completely oxidized ti give benzoic acid (benzylic position much have atleast 1 H proton) Hydrolysis of Nitriles When treated with aqueous acid, a nitrile (a compound with a cyano group) can be converted to a carboxylic acic. This process of called Hydrolysis It is a 2 step RXN for converting an alkyl halide into a carboxylic acid. Carboxylation of Grignard Reagents Carboxylic acids can also be prepared by treating a Grignard reagent with CO2. 21.5 – Reactions of Carboxylic Acids Carboxylic acids are reduced to alcohols upon treatment with LAH (Lithium Aluminum hydride) They can also be reduced with Borane (BH3) Borane reacts selectively with the carboxylic acid moiety in the presence of another carbonyl group. BH3 * TFH Primary alcohol. 21.7 Introduction to carboxylic acid derivatives Classes of carboxylic acid derivatives 1. Reduction – those that change the oxidation state of the compound 2. No [o] level change – those that do not change the oxidation state of the compound. Replacement of the OH groups with a different group (Z – which is a heteroatom) does not involve a change in the oxidation state if Z is a heteroatom (Cl, O, N, F, ect. Anything but C and H) Compounds of this type are carboxylic acid derivatives Types of Carboxylic Acid derivatives 1. Acid Halides 2. Acid Anhydride 3. Ester 4. Amide 5. Nitrile ( 1 is the most reactive, 5 being least reactive) Carboxylic acid derivatives in Nature Acid halides and anhydrides DO NOT occur (commonly) naturally in nature due to their high reactivity. In contrast, Esters, are more stable and are abundant in nature. Amides are abundant in living organisms (proteins are comprised of repeating amide linkages) Naming Acid Halides Acid halides are named as derivatives of carboxylic acids by replacing the suffix –ic acid with the suffix –yl halide. When an acid halide moiety is connected to a ring, the suffic “carboxylic acid” is replaced with “carbonyl Halide” Naming Anhydrides Anhydrides are named as derivatives of carboxylic acids by replacing the suffix –acid with –anhydride Unsymmetrical anhydrides are prepared from 2 different carboxylic acids o They are named by indicating both acid alphabetically followed by the suffix anhydride Naming Esters Esters are named as derivatives of carboxylic acids by replacing the suffix –oic acid with the suffix –ate. What is attached to the C-O- is named first (the R group attached to O).
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