Ch13 Carb. Acids

7/24/2019 Ch13 Carb. Acids

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WILLIAM H. BROWN

THOMAS POON

www.wiley.com/college/brown

C H A P T E R T H I R T E E N

Carboxylic Acids

Copyright2014 John Wiley & Sons, Inc. All rights reserved.


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Structure

The !"c#io"al $ro!% o a carboxylic acid is a

carboxyl $ro!%.

& The $e"eral or'!la o a" ali%ha#ic carboxylic

acid is RCOOH.

& Tha# o a" aro'a#ic carboxylic acid is ArCOOH.

2014 John Wiley & Sons, Inc. All rights reserved.


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Nomenclature

I(PAC "a'es) dro% #he -ero' #he %are"#

al*a"e a"d add #he s!ix -oicacid.& I #he co'%o!"d co"#ai"s a carbo"+carbo"

do!ble bo"d, cha"$e #he i"ix -an-#o -en-.



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Nomenclature

& icarboxylic acids) add -dioic acid#o #he "a'e o #he

%are"# al*a"e co"#ai"i"$ bo#h carboxyl $ro!%s.& There is "o "eed #o !se "!'bers #o loca#e #he carboxyl

$ro!%s/ #hey ca" o"ly be o" #he e"ds o #he chai".



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Nomenclature

& I #he carboxyl $ro!% is bo"ded #o a ri"$, "a'e

#he ri"$ co'%o!"d a"d add #he s!ix -carboxylicacid.



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Nomenclature

& Be"0oic acid is #he si'%les# aro'a#ic carboxylic

acid.& (se "!'bers #o sho1 #he loca#io" o

s!bs#i#!e"#s.



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Nomenclature

& Whe" co''o" "a'es are !sed, #he le##ers 23 23 23 23e#c.

are o#e" !sed #o loca#e s!bs#i#!e"#s.

&I" co''o" "o'e"cla#!re, *e#o i"dica#es #he %rese"ce oa *e#o"e, a"d CH4CO&is "a'ed a" ace#o $ro!%.



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Nomenclature

&Problem) I" o'e$a+4 a##y acids, #he las# carbo"

o #he las# do!ble bo"d o #he hydrocarbo" chai"e"ds #hree carbo"s ro' #he 'e#hyl #er'i"al o

#he chai". The las# carbo" o #he chai" is called

#he o'e$a carbo", he"ce #he desi$"a#io"

o'e$a+4. Eicosa%e"#ae"oic acid is a co''o"

%oly!"sa#!ra#ed a##y acid o!"d i" cold 1a#er

a##y ish a"d heal#h ood s!%%le'e"#s.

& Ho1 'a"y cis+#ra"s iso'ers are %ossible or #his

a##y acid5 2014 John Wiley & Sons, Inc. All rights reserved.


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Physical Properties

I" #he li6!id a"d solid s#a#es, carboxylic acids

are associa#ed by hydro$e" bo"di"$ i"#odi'eric s#r!c#!res.



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Physical Properties

Carboxylic acids ha-e si$"iica"#ly hi$her

boili"$ %oi"#s #ha" o#her #y%es o or$a"icco'%o!"ds o co'%arable 'olec!lar 1ei$h#.& They are %olar co'%o!"ds a"d or' -ery s#ro"$

i"#er'olec!lar hydro$e" bo"ds. Carboxylic acids are 'ore sol!ble i" 1a#er

#ha" are alcohols, e#hers, aldehydes, a"d

*e#o"es o co'%arable 'olec!lar 1ei$h#.& They or' hydro$e" bo"ds 1i#h 1a#er 'olec!les#hro!$h #heir C7O a"d OH $ro!%s.



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Physical Properties

& Wa#er sol!bili#y decreases as #he rela#i-e si0e o

#he hydro%hobic %or#io" o #he 'olec!lei"creases.



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Acidity

Carboxylic acids are 1ea* acids

& 8al!es o %9aor 'os# ali%ha#ic a"d aro'a#ic carboxylicacids all 1i#hi" #he ra"$e : #o ;.

& The $rea#er acidi#y o carboxylic acids rela#i-e #o

alcohols, bo#h o 1hich co"#ai" a" OH $ro!%, is d!e #o

reso"a"ce s#abili0a#io" o #he carboxyla#e a"io".2014 John Wiley & Sons, Inc. All rights reserved.


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Acidity

Elec#ro"+1i#hdra1i"$ s!bs#i#!e"#s "ear #he

carboxyl $ro!% i"crease acidi#y #hro!$h #heiri"d!c#i-e eec#.



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Acidity

& The acid+s#re"$#he"i"$ eec# o a halo$e"

s!bs#i#!e"# alls o ra%idly 1i#h i"creasi"$dis#a"ce ro' #he carboxyl $ro!%.



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Carboxylic acids, 1he#her sol!ble or i"sol!ble i"

1a#er, reac# 1i#h NaOH, 9OH, a"d o#her s#ro"$bases #o $i-e 1a#er+sol!ble sal#s.

They also or' 1a#er+sol!ble sal#s 1i#h a''o"ia

a"d a'i"es.

Reaction with Bases



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Reaction with Bases

Carboxylic acids reac# 1i#h sodi!'

bicarbo"a#e a"d sodi!' carbo"a#e #o or'1a#er+sol!ble sal#s a"d carbo"ic acid.& Carbo"ic acid, i" #!r", brea*s do1" #o carbo"

dioxide a"d 1a#er.



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Reaction with Bases


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Reduction

The carboxyl $ro!% is -ery resis#a"# #o red!c#io".

& I# is "o# aec#ed by ca#aly#ic hydro$e"a#io" !"derco"di#io"s #ha# easily red!ce aldehydes a"d *e#o"es #o

alcohols, a"d red!ce al*e"es a"d al*y"es #o al*a"es.

& Carboxyl $ro!%s are "o# red!ced by NaBH:.

Li#hi!' al!'i"!' hydride red!ces a carboxyl $ro!%#o a => alcohol.& Red!c#io" is carried o!# i" die#hyl e#her, TH


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Selective Reduction

Ca#aly#ic hydro$e"a#io" does "o# red!ce a COOH

$ro!%.& 1e ca" !se H?@M #o red!ce a" al*e"e i" #he %rese"ce o a

COOH $ro!%.

& 1e ca" !se NaBH:#o red!ce a" aldehyde or *e#o"e i" #he

%rese"ce o a COOH $ro!%.



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Fischer Esterification

Es#ers ca" be %re%ared by #rea#i"$ a carboxylic acid 1i#h

a" alcohol i" #he %rese"ce o a" acid ca#alys#, co''o"lyH?SO:or $aseo!s HCl.


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Fischer Esterification

&A *ey i"#er'edia#e i"


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Acid hlorides

The !"c#io"al $ro!% o a" acid halide is a

carbo"yl $ro!% bo"ded #o a halo$e" a#o'.&A'o"$ #he acid halides, acid chlorides are by ar

#he 'os# co''o" a"d #he 'os# 1idely !sed.



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Acid hlorides

Acid chlorides are 'os# o#e" %re%ared by

#rea#i"$ a carboxylic acid 1i#h #hio"ylchloride.



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!ecarboxylation

!ecarboxylation)loss o CO?ro' a carboxyl $ro!%.

& Mos# carboxylic acids, i hea#ed #o a -ery hi$h #e'%era#!re, !"der$o#her'al decarboxyla#io".

& Mos#, ho1e-er, are 6!i#e resis#a"# #o decarboxyla#io".

& Exce%#io"s are carboxylic acids #ha# ha-e a carbo"yl $ro!% be#a #o

#he carboxyl $ro!%.& +*e#oacids !"der$o decarboxyla#io" o" 'ild hea#i"$.



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!ecarboxylation

& Ther'al decarboxyla#io" o a +*e#oacid

i"-ol-es rearra"$e'e"# o six elec#ro"s i" acyclic six+'e'bered #ra"si#io" s#a#e.



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!ecarboxylation

& Ther'al decarboxyla#io" o 'alo"ic acids also

i"-ol-es rearra"$e'e"# o six elec#ro"s i" acyclic six+'e'bered #ra"si#io" s#a#e.



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!ecarboxylation

&Problem) ra1 #he %rod!c# o decarboxyla#io".

&Problem) ra1 #he +*e#oacid #ha# !"der$oesdecarboxyla#io" #o $i-e #his *e#o"e.



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arboxylic Acids

End Chapter13 2014 J h Wil & S I All i ht d

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Ch13 Carb. Acids