CHEM 334 1nd Edition Lecture 14Outline of Last Lecture I. Carboxylic acidsOutline of Current Lecture II. Acyl Substitution ReactionsIII. Fischer EsterficationIV. DecarboxylationCurrent Lecture Carboxylic acid derivatives:Acyl substitution reactions:Acyl substitution essentially means carbonyl. These reaction all go through a common mechanism(nucleophilic addition, then elimination). O O- OR LG R nuc LG R nucYou need a good leaving group for this reaction to take place. Leaving group can be Cl-, H2O, HOR, or carboxylate.Fischer esterification: O H2SO4 O OH OH OFischer esterification reactions form an ester from a carboxylic acid. This is an equilibrium reaction, meaning that, to drive the reaction to product formation, we have to remove H2O. Adding excess alcohol also helps to drive the reaction.Mechanism: OH OH H O H–O+ O+–H OH OH H–O+ OH H OH OH HO H–O O:OH H–O OH O H2O O OThese notes represent a detailed interpretation of the professor’s lecture. GradeBuddy is best used as a supplement to your own notes, not as a substitute.OInternal version: The same reaction can be used to make an ester ring from a chain with two alcohols already attached. Cyclic esters such as this are called lactones. OOH OH H2SO4 ODiazo Methane:These reaction only make methyl estersO CH2N2 O OH OMechanism: O O OR O–H H2C-–N≡N R O- H3C–N≡N R O N2Reactions to do with carboxylic acid:Acid chloride formation:O SOCl2 O OH PCl5 ClDecarboxylation: Decarboxylation is the loss of CO2. Most carboxylic acids cannot do this, but there are a few special ones that can;A) Beta-ketoacids: Meaning that the carbonyl group is in the beta positon to the carboxylic acid O O Δ O OH +CO2Mechanism: O O Δ H O O–H :O–H O+–H OOH O -B) Malonic acid O O Δ O OH OH This reaction has the same mechanism as the reaction of beta-ketoacids. This reaction will also work the same way if one carboxylic acid is an ester instead; O O Δ OO OH O Reactivity of Acyl Compounds with nucleophiles;Acid Chloride > Anhydride > ester > amide > lactone > lactamAcid Chlorides (Chlorides are the most common, but you can also have acid bromides)O ClNomenclature: Change suffix of carboxylic acid (ic acid to yl chloride)O SOCl2 O OH Cl Propyl chlorideAnhydrides:These are two carbonyls bonded to an oxygen. These don’t have to be symmetrical and they can also be cyclic. O O O O O OOHAmides: Amides are amines attached to a carbonyl. These can be classified as primary, secondary, or tertiary, depending on the number of carbons attached to the nitrogen.O O O NH2 N NPrimary Secondary TertiaryCyclic amides are called
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