Carboxylic Acid & Ester
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Transcript of Carboxylic Acid & Ester
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Carboxylic acid
Chapter 10
http://rds.yahoo.com/_ylt=A0S020sfzsRMkDoA92GjzbkF/SIG=13uk32nm7/EXP=1288052639/**http%3A//upload.wikimedia.org/wikipedia/commons/thumb/b/b5/Carboxylic-acid.svg/748px-Carboxylic-acid.svg.png
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Nomenclature ofCarboxylic Acids
The longest chain must contain thecarboxyl group.
The carboxyl group is at the terminal,therefore the carbon of the carboxyl groupis not numbered.One COOH – carboxyl group is at one end
Two COOH – carboxyl groups are at bothends
Name the compound as alkane, drop ‘e’in alkane and add ‘oic acid’ eg!
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#$bromo$%$methylpentanoic acid
CH CH2
CH C OHCH3
3Br CH O
&f, two COOH groups, the compound will be
named as alkanedioic acid
CH2 CH2CH2 C OH
O
COH
O
pentanedioic acid
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CH2 CH2CH2 C OH
O
CHOH
CH3
CH CHCH2 CH CH3COH
O CH3
Name the followings !
1.
2.
3.
COOH
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4. COOH
5.
COOH
CH3
Br
6.
COOH
COOHCl
7.
COOH
CH3
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Odour
lower aliphatic carboxylic acid-pungent
eg : ethanoic acid (vinegar)
unpleasant odours as chain gets larger
eg : butanoic (perspiration)
pentanoic acid (rancid acid) hexanoic acid (voit)
!aste
"our
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Boiling Point
The boiling point of carboxylic acid is higher than an alcohol,
a ketone or an aldehyde (with Mr that almost the same)
because:
i. it exists as stable diers that form hydrogenbond.
ii. molecules in dimers are arranged closely pac#ed,
therefore the hydrogen bonds are relatively strong.
iii. high energy is needed to overcome the
intermolecular forces ,
∴ boiling point
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C
O
O
$
H
C
O
O
$
H
Hydrogen bond
Hydrogen bond
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olubility'olubility in water
Carboxylic acids are soluble in water due tothe formation of hydrogen bond between thewater molecules and carboxylic acid
molecules.
C
O
O
$
H
O H
HC
O
O
$
H
O
H
H
Hydrogen (onds
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)romatic carboxylic acids are slightly
soluble in water due to the hugearomatic ring.
*icarboxylic acids are relati+ely moresoluble since more hydrogen bondsare formed.
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Preparation of Carboxylic acid
Oxidation
Hydrolysis o% &itrile Copound
Carbonation o% 'rignard $eagent
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!eactions of Carboxylic Acid
$eaction with &aOH (&*+!$,.",!.O&)
C$
O
OH
/ &aOH C$
O
O-
&a/
/ H2O
COOH
/ &aOH
COO
/ H2O
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2 $eaction with *lectropositive 0etal
! "#
"
$ ! "
"
M $ #%M
3 $eaction with &aHCO3 (sodiu bicarbonate)
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$ C OH
O$ C Cl
O
$ C Cl
O
/ "O2 / HCl
/ 1OCl3 / HCl
"OCl2
1Cl
)cyl chloride can be prepared from the reaction of
carboxylic acids with thionyl chloride, 'OCl -phosphorous pentachloride, Cl/ - phosphorous
trichloride, Cl%
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*steri%ication
Carboxylic acids react with alcoholsin the presence of mineral acidcatalyst to produce esters"
/ HO$4C OH$
O
C O$ $5
O
0 / H2OH/
carboxylic acid alcohol ester
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6 ,cid ,nhydride 7oration
)cid anhydrides can be prepared fromcarboxylic acids by the loss of water throughheating.
$ C OH
O
$COH
O
/heat $ C O C $
O O
/ H2Oacid anhydride
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8 ,cid ,nhydride 7oration
1eaction of carboxylic acids with an ammonia oramine gi+e amide.
&H3
$&H2
$2&H
$ C &H$
O
$ C &$2
O
/ H2O
/ H2O
/ H2O
1o amide
2 o amide(1o amine)
(2 o amine)(3o amide)
$ C &H2
O
$ C OH
O
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9 $eduction
Carboxylic acid are reduced to primaryalcohols by reaction with lithiumaluminium hydride, 2i)lH# or Ni.
C O$ $5
O
&i H2
9;
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#sters
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#sters are named by $rst naming the group that came
from the alcohol"
%his &ord is follo&ed by a space and then the nameof the acid is changed by
dropping the 'oic acid ending of the parent acid and
adding 'oate"
#thyl ethanoate
#sters ha(e same molecular formula as carboxylicacids but are neutral compounds
Nomenclature of#ster
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)ra& the structure of these esters *
3. methyl ethanoate
. ethyl ethanoate
%. phenyl ethanoate
#. methyl ben4oate
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PhysicalProperties
The boiling points of esters are lower than carboxylic aci
Compounds 5xample (oiling point
5ster 6ethylmethanoate
%3./ 7C
Carboxylic acid 5thanoic acid 338.9 7C
Carboxylic acids has higher boiling point than ester.
Carboxylic acids able to form strong hydrogen bondbetween molecules.
5sters ha+e weaker +an der :aals forces betweenmolecules.
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+ydrolysis of #sters
#ster hydrolysis
odium salt , alcohol Acid , alcohol
Alkalinehydrolysis
Acid+ydrolysis
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)cid Hydrolysis of 5sters
)lkaline Hydrolysis of 5sters
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+ydrogenation of oils
Oils and fats are naturally occurring esters of long
chain fatty acids and glycerol.
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!he carboxylic acid coponents are called %atty acids
7atty acids are divided into saturated (stearic acid) and unsaturated
(oleic acid)
Oils can be converted to %ats by hydrogenation reaction
0argarines are ade by hydrogenation o% vegetable oils
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"oaps and detergents
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"oaps
"oaps are saponi%ication al#aline hydrolysis o% ester ("oap can be obtained through the reaction o% al#aline hydrolysis o% ester)
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*xaple o% soaps
sodiu stearate &aC8H3COO
sodiu palitate &aC8H3COO
!
"
"&
nonpolar polar
"oap is an eulsi%ying agent because the ionic end is
water soluble and the hydrocarbon end is %at soluble
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Cleaning action of soap
3. 2ong non$polar hydrocarbon chain dissol+es i
. )gitation will cause the grease drops to be lift
%. 5mulsi
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=etergents
most laundry detergents contain tripolyphosp % phosphoric acids =oin to make tripolyphosph
H1
3O
; / &aOH &a
1
3O
; / H
2O
roblem with phosphates in waste water willo+er$fertili4e
natural waters. This causes massi+e growth of blue$green
algae whichdepletes the water of more oxygen