carboxylic acid & ester

8/17/2019 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

carboxylic acid & ester

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