Chapter 19 (weeks 0-2 of Fall 2019)
CLASS LOGISTICS
This module consists of all of chapter 19, which was covered in week zero through a bit of the first lecture of week two (a bit over three lectures total). Remember to check out peer tutor office hours! Jonathan and I have a lot of experience teaching organic chemistry so I highly recommend that you come to our office hours.
Chapter 19 Table of Contents
1.) Nomenclature of Carboxylic Acids
2.) Properties of Carboxylic Acids (Acidity, basicity, solubility, boiling point)
3.) Synthesis of Carboxylic Acids (8 reactions)
4.) Reactions of Carboxylic Acids (6 reactions)
Check the reaction summaries tab for a detailed list of reactions. Chapter 19 covers half of midterm 1 (Thursday, 10/24).
Chapter 19 Table of Contents
1.) Nomenclature of Carboxylic Acids
2.) Properties of Carboxylic Acids (Acidity, basicity, solubility, boiling point)
3.) Synthesis of Carboxylic Acids (8 reactions)
4.) Reactions of Carboxylic Acids (6 reactions)
Check the reaction summaries tab for a detailed list of reactions. Chapter 19 covers half of midterm 1 (Thursday, 10/24).
Chapter 19: Carboxylic acids
Nomenclature of carboxylic acids
For nomenclature
Synthesis OF CARBOXYLIC ACIDS (8 reactions)
-Mostly review reactions from Che118A/B
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Additional reactions to synthesize carboxylic acid:
1.) Recall that reacting carbonyls with X2, base will cause polysubstitution of the alpha positions). The less substituted (methyl-position) will be substituted first, then act as a leaving group when OH- acts as a nucleophile) 2.) 3 Different reactions from aldehydes:
-Tollen's Reagent ( 1. AgNO3, NH4OH 2. H3O+) -Fehling's Reagent ( 1. Cu2+, OH- 2. H3O+) -Baeyer Villiger (any peroxycarboxylic acid like MCPBA) |
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reactivity of cARBOxylic acid derivatives
This chart is foundational to Che118C. Understand it well. It shows four carboxylic acid derivatives and their relative reactivity to carboxylic acid. Note that it is easy to form carboxylic acids from anhydrides and acyl chlorides because they are more reactive than carboxylic acids. It is easy to form more stable products from less stable reactants. However, forming carboxylic acids from esters and amides are more difficult and thus require heat.
Reactions of Carboxylic acids (6 reactions)
1.) synthesis of acyl chlorides
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We've seen these reagents in Che 118A! We use these when turning alcohols into alkyl halides
(SN 2 mechanism for primary/secondary alcohols; SN 1 mechanism for tertiary alcohols) Note: SOCl2 can be used with or without pyridine. Pyridine will increase the yield of our product and also protect us from poisonous HCl gas formation. Professor Nasiri went over mechanisms both with and without pyridine. |
The following is the mechanism without pyridine. With pyridine, the pyridine acts as a base to deprotonate the carboxylic alcohol. Then the negative oxygen will act as the nucleophile in the first step rather than the carbonyl.
2.) Synthesis of anhydrides
Professor Nasiri also uses a reaction of two identical carboxylic acids under high heat to form an anhydride
3.) SYNTHESIS OF esters
4.) SYNTHESIS OF amides
5.) Reduction of carboxylic acid by liAlh4
Reduction of carboxylic acids
NaBH4 is not strong enough to react with COOH (only reacts with acyl halides and anhydrides)
6.) Hell-voldhart zelinsky reaction
In comparison to PBr3, which turns a carboxylic acid into an acyl bromide, trace phosphorus and dibromides (which will combine to form PBr3) will result in addition of Bromine to the alpha position. This occurs because having trace PBr3 will cause PBr3 to react with three carboxylic acids (one for each Br) instead of one. This results in the formation of phosphoric acid, H3PO3, which catalyzes the next step of the mechanism, alpha bromination of the carboxylic acid (see mechanism in ch19 lecture notes for more details).
