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.

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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