Carboxylic Acids and Reduction/Oxidation Carboxylic

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Carboxylic Acids and Reduction/Oxidation Carboxylic

Carboxylic Acids and Reduction/Oxidation • Addition of H (or “H-”) Reduction 2 • Loss of O2 or O carboxylic aldehyde alcohol alkane acid (or ketone) • Loss of H 2 Oxidation • Addition of O2 or O + Neither oxidation nor reduction: Addition or loss of H , H2O, or HX Carboxylic acids are the most oxidized functional group of carbon. Carboxylic Acids via Oxidation Chromate oxidation of primary alcohols: unavoidably Na2Cr2O7 H2SO4 aldehyde carboxylic alcohol acid Oxidation of aldehydes with Tollens’ reagent: 1. Ag2O, NH3 2. H O+ 3 Selective for aldehydes; will not oxidize alcohols. aldehyde carboxylic acid Carboxylic Acids via Oxidation Oxidative cleavage of alkynes: 1. O3 2. H2O internal alkyne Oxidation of benzylic carbons: KMnO4 Purifying Carboxylic Acids by Acid-Base Extraction Acidic and basic organic molecules can be separated from other substances by manipulating their protonation state and solubility. Let’s say we run a reaction. Na2Cr2O7 + unreacted H2SO4 + Na+ 3+ We want this… + Cr(H2O)6 + organic + HSO - …but not these. side products 4 How do we isolate our desired product from the other materials, without using distillation or chromatography? Acid-Base Extraction Step 1: Remove inorganics from organics via differential solubility. a separatory (sept) funnel - Na+ HSO4 Cr(H O) 3+ H2O 2 6 CHCl3 + organic side densities: products (H2O) = 1 g/mL (CHCl3) = 1.48 g/mL A large density difference ensures the two liquids separate completely and quickly. (Much faster than, say, oil and water.) Step 2: Add basic water to deprotonate carboxylic acid, and transfer it to the aqueous phase. - Na+ HSO4 3+ discard Cr(H2O)6 H2O layer + organic + organic side side products products add discard NaOH/ H2O CHCl3 layer + organic side products Step 3: Re-acidify carboxylate to return it to organic solution. Remove solvent in vacuo to yield pure acid. add HCl/ H2O, fresh CHCl3 discard H2O layer remove solvent in rotary evaporator Chemistry student, removing solvent in a “rotovap” Nucleophilic Addition to Carbonyls Heteroatom electron donors add reversibly to C=O groups. Equilibrium driven + to the left by entropy. Also true for Cl , HS , NH3 nucleophiles. Hydrogen anions (“hydride”) and carbon anions add irreversibly to C=O groups. + Reaction driven to the right by instability of - - charge on H , RCH2 . +.

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Aldehydes and Ketones
12 Aldehydes and Ketones Ethanol from alcoholic beverages is first metabolized to acetaldehyde before being broken down further in the body. The reactivity of the carbonyl group of acetaldehyde allows it to bind to proteins in the body, the products of which lead to tissue damage and organ disease. Inset: A model of acetaldehyde. (Novastock/ Stock Connection/Glow Images) KEY QUESTIONS 12.1 What Are Aldehydes and Ketones? 12.8 What Is Keto–Enol Tautomerism? 12.2 How Are Aldehydes and Ketones Named? 12.9 How Are Aldehydes and Ketones Oxidized? 12.3 What Are the Physical Properties of Aldehydes 12.10 How Are Aldehydes and Ketones Reduced? and Ketones? 12.4 What Is the Most Common Reaction Theme of HOW TO Aldehydes and Ketones? 12.1 How to Predict the Product of a Grignard Reaction 12.5 What Are Grignard Reagents, and How Do They 12.2 How to Determine the Reactants Used to React with Aldehydes and Ketones? Synthesize a Hemiacetal or Acetal 12.6 What Are Hemiacetals and Acetals? 12.7 How Do Aldehydes and Ketones React with CHEMICAL CONNECTIONS Ammonia and Amines? 12A A Green Synthesis of Adipic Acid IN THIS AND several of the following chapters, we study the physical and chemical properties of compounds containing the carbonyl group, C O. Because this group is the functional group of aldehydes, ketones, and carboxylic acids and their derivatives, it is one of the most important functional groups in organic chemistry and in the chemistry of biological systems. The chemical properties of the carbonyl group are straightforward, and an understanding of its characteristic reaction themes leads very quickly to an understanding of a wide variety of organic reactions.
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Nucleophilic Aromatic Substitution
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In this handout, all of our functional groups are presented as condensed line formulas, 2D and 3D formulas and with nomenclature prefixes and suffixes (if present). Organic names are built on a foundation of alkanes, alkenes and alkynes. Those examples are presented first and you need to know those rules. The strategies can be found in Chapter 4 of our textbook (alkanes: pages 93-98, cycloalkanes 102-104, alkenes: pages 104-110, alkynes: pages 112-113 and combinations of all of them 113-115). After introducing examples of alkanes, alkenes, alkynes and combinations of them, the functional groups are presented in order of priority. A few nomenclature examples are provided for each of the functional groups. Examples of the various functional groups are presented on pages 115-135 in the textbook. Two overview pages are on pages 136-137. Some functional groups have a suffix name when they are the highest priority functional group and a prefix name when they are not the highest priority group, and these are added to the skeletal names with identifying numbers and stereochemistry terms (E and Z for alkenes, R and S for chiral centers and cis and trans for rings). Several low priority functional groups only have a prefix name. A few additional special patterns are shown on pages 98-102. The only way to learn this topic is practice (over and over). The best practice approach is to actually write out the names (on an extra piece of paper or on a white board, and then do it again). The same functional groups are used throughout the entire course.
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