310_10 - Organic Lecture Series CH 310 N LECTURE 10...

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Organic Lecture Series 1 CH 310 N LECTURE 10 Textbook Assignment: Chapter 17 Carboxylic Acids Homework (for credit): Problem Set 3-Posted Today’s Topics: Esterification; Notice & Announcements: EXAM 1: Pick up papers in the Hall-after class Organic Lecture Series 2 Carboxylic Acids Carboxylic Acids Chapter 17
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Organic Lecture Series 3 • Esters can be prepared by treating a carboxylic acid with an alcohol in the presence of an acid catalyst, commonly H 2 SO 4 , ArSO 3 H*, or gaseous HCl Ethyl ethanoate (Ethyl acetate) Ethanol (Ethyl alcohol) Ethanoic acid (Acetic acid) + + H 2 SO 4 H 2 O OH O HO O O Fischer Fischer Esterification Esterification H 3 C S O O Toluene Sulfonic Acid TsOH * Organic Lecture Series 4 Fischer esterification is an equilibrium reaction: ± by careful control of experimental conditions, it is possible to prepare esters in high yield ± if the alcohol is inexpensive relative to the carboxylic acid, it can be used in excess to drive the equilibrium to the right ± alternatively, water can be removed by azeotropic distillation and a Dean-Stark trap Fischer Fischer Esterification Esterification
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Organic Lecture Series 5 a key intermediate in Fischer esterification is the tetrahedral carbonyl addition intermediate formed by addition of ROH to the C=O group CO C H 3 O H O R H H O RC O C H 3 O R HOCH 3 + HOH + H + H + TCAI Fischer Fischer Esterification Esterification Refer to mechanism worksheet Organic Lecture Series 6 • The functional group of an acid halide is a carbonyl group bonded to a halogen atom – among the acid halides, acid chlorides are by far the most common and the most widely used Functional group of an acid halide Acetyl chloride Benzoyl chloride -C-X CH 3 CCl OO C-Cl O Acid Chlorides Acid Chlorides
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Organic Lecture Series 7 –acid chlorides are most often prepared by treating a carboxylic acid with thionyl chloride OH O SOCl 2 Cl O SO 2 HCl + + + Butanoic acid Thionyl chloride Butanoyl chloride Acid Chlorides Acid Chlorides Organic Lecture Series 8 Decarboxylation Decarboxylation • Decarboxylation: Decarboxylation: loss of CO 2 from a carboxyl group – carboxylic acids, if heated to a very high temperature , undergo thermal decarboxylation – most carboxylic acids, however, are quite resistant to moderate heat and melt or even boil without decarboxylation R- C-O H O R- H CO 2 decarboxylation + heat
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Organic Lecture Series 9 The most important exceptions are carboxylic acids that have a carbonyl group beta to the carboxyl group i.e.- β keto-acids –this type of carboxylic acid undergoes decarboxylation on mild heating O H O O O CO 2 Acetone 3-Oxobutanoic acid (Acetoacetic acid) + warm β α
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This note was uploaded on 11/21/2011 for the course CH 51455 taught by Professor Colapret during the Spring '11 term at University of Texas at Austin.

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310_10 - Organic Lecture Series CH 310 N LECTURE 10...

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