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CARBOXYLIC ACID
Carboxylic Acid
Carboxylic acids are organic acids characterized by the presence of at
least one carboxyl group.
The general formula of a carboxylic acid is R-COOH, where R is
some monovalent functional group.
Carboxylic acids are Brnsted-Lowry acids because they are proton
donors.
They are the most common type of organic acid. Among the simplest
examples are formic acid H-COOH, that occurs in ants, and aceticacid CH3-COOH, that gives vinegar its sour taste.
Acids with two or more carboxyl groups are
called dicarboxylic,tricarboxylic, etc.
Preparation
Properties
Uses
http://en.wikipedia.org/wiki/Organic_acidhttp://en.wikipedia.org/wiki/Valence_(chemistry)http://en.wikipedia.org/wiki/Functional_grouphttp://en.wikipedia.org/wiki/Br%C3%B8nsted-Lowry_acid-base_theoryhttp://en.wikipedia.org/wiki/Organic_acidhttp://en.wikipedia.org/wiki/Formic_acidhttp://en.wikipedia.org/wiki/Anthttp://en.wikipedia.org/wiki/Acetic_acidhttp://en.wikipedia.org/wiki/Acetic_acidhttp://en.wikipedia.org/wiki/Methylhttp://en.wikipedia.org/wiki/Methylhttp://en.wikipedia.org/wiki/Methylhttp://en.wikipedia.org/wiki/Vinegarhttp://en.wikipedia.org/wiki/Vinegarhttp://en.wikipedia.org/wiki/Methylhttp://en.wikipedia.org/wiki/Acetic_acidhttp://en.wikipedia.org/wiki/Acetic_acidhttp://en.wikipedia.org/wiki/Anthttp://en.wikipedia.org/wiki/Formic_acidhttp://en.wikipedia.org/wiki/Organic_acidhttp://en.wikipedia.org/wiki/Br%C3%B8nsted-Lowry_acid-base_theoryhttp://en.wikipedia.org/wiki/Functional_grouphttp://en.wikipedia.org/wiki/Valence_(chemistry)http://en.wikipedia.org/wiki/Organic_acid8/2/2019 GO 4 Preparation of Carboxylic Acid
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Carboxylicacid
compounds whichcontain a -COOH
group that is
attached either to ahydrogen atom orto an alkyl group.
Preparation
Oxidation ofalkenes
The oxidation ofprimary alcoholsand aldehydes
The oxidation ofalkyl benzenes
Hydrolysis of nitriles
The carbonation ofGrignard reagents
Properties
Solubility in Water
Boiling point
Melting point
Acidity
Odour
Uses
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Preparation of Carboxylic acid
Oxidation of alkenes
Alkenes are oxidized to acids by heating them with solutions of potassium
permanganate (KMnO4) or potassium dichromate (K2Cr2O7).
Oxidation of alkenes
The ozonolysis of alkenes produces aldehydes that can easily be further
oxidized to acids.
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The oxidation of primary alcohols and aldehydes
The oxidation of primary alcohols leads to the formation of alde-hydes that
undergo further oxidation to yield acids.
All strong oxidizing agents (potassium permanganate, potassium dichromate,
and chromium trioxide) can easily oxidize the aldehydes that are formed
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The oxidation of alkyl benzenes
Alkyl groups that contain benzylic hydrogenshydrogen(s) on a carbon to a
benzene ringundergo oxidation to acids with strong oxidizing agents.
In the above example, t-butylbenzene does not contain a benzylic hydrogen and
therefore doesn't undergo oxidation
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The carbonation of Grignard reagents
Grignard reagents react with carbon dioxide to yield acid salts, which, upon
acidification, produce carboxylic acids.
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Hydrolysis of nitriles
The hydrolysis of nitrilescontaining a cyano group,
leads to carboxylic acidformation. It can take place in
either acidic or basicsolutions.
Themechanis
follows thesteps:
The nitrogen atom of thenitrile group is protonated.
The carbocation generated inStep 1 attracts a water
molecule.
The oxonium ion loses aproton to the nitrogenatom, forming an enol.
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The enol tautomerizes to themore stable keto form.
The amide is protonated bythe acid, forming a
carbocation.
A water molecule isattracted to the
carbocation.
The oxoniumion loses a
proton.
The amine group isprotonated.
An electron pair onone of the oxygens
displaces theammonium groupfrom the molecule.
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Uses
Higher fattyacids
manufacture ofsoaps. Soaps aresodium potassiumsalts of higher fatty
acids such as stearicacid.
Organic acids
used in foods, colddrinks
used aspreservatives.
Organic acids
used for thepreparation of many
drugs such as aspirin,phenacetin etc.
Acetic acid
coagulant in themanufacture of
rubber.
manufacture ofvarious dye stuffs,
perfumes and rayon.
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Ester
Preparation
Properties
Uses
Esters are chemical compounds derived by reacting an oxoacid with
a hydroxyl compound such as an alcohol or phenol. Esters are usually
derived from an inorganic acid or organic acid in which at least one -OH
(hydroxyl) group is replaced by an -O- alkyl (alkoxy) group, and most
commonly from carboxylic acids and alcohols. That is, esters are formed
by condensing an acid with an alcohol.
Preparation
Properties
Uses
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Preparation
Carboxylic acids + alcohols ester + water
Heat
Catalyst (concentrated H2SO4)
The equation for the reaction between an acid RCOOH andan alcohol R'OH (where R and R' can be the same ordifferent) is:
Example: ethanoic acid + ethanol ethyl ethanoate + water
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Step in producing ester
Reflux
The reaction mixtureconsisting of the
alkanol, the alkanoicacid and a small
amount ofconcentrated sulfuric
acid is heated in avessel with a water-cooled condenser
(Liebig condenser) toprevent loss of volatile
material.
Separation
After heating, thereaction mixture is then
poured into aseparating funnel.
Calcium carbonate(CaCO3), or a similarneutralizing agent, is
added to the mixture toreact with any
unreacted acid presentin the mixture.
Purification
The organic layerseparated in theseparating funnel
above contains theester. This organiclayer is distilled to
obtain the pure ester. Asharp boiling point isan indication of thepurity of the ester.
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Properties
more volatilethan carboxylic acids
colourless and existin liquid state at room
temperature.
polar due to the presenceof carbonyl (=C=O)groupand act as hydrogen bondacceptors not as donors.
have low boiling and
melting points
highly soluble in organicsolvents and partly
soluble in water.
sweet odour
Properties
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Use of ester
To makea substance less
water solublemeaning
the carboxylic
acid is moresoluble then itsester.
To combine twosubstances
togetherEg. Procaine
with Penicillin so1 drug 2 effects
To createsurfactantsEg. Soap
used in flavouringand perfumes
Uses
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Amides
Amides are derived from carboxylic acids. A carboxylic acid contain the
COOH group and in an amide the OH part of that group is replaced
by anNH2group. Soamides contain the CONH2 group.
Three simplest amides are:
HCONH2 methanamide
CH3CONH2 ethanamide
CH3CH2CONH2 propanamide
Notice that, the name derived from the acid by replacing the oic acid
endin b amide
Preparation
Properties
Uses
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The carboxylic acid isfirst converted into anammonium salt which
then produces an amideon heating.
The ammonium salt isformed by adding solid
ammonium carbonate toan excess of the acid.
When the reaction iscomplete, the mixture is
heated and theammonium salt
dehydrates producingethanamide.
The excess ofethanoic acid isthere to preventdissociation ofthe ammonium
salt before itdehydrates.
Ammonium salts tendto split into ammonia
and the parent acid onheating, recombining
on cooling.
Thedissociation is
reversible:
The presence ofthe excess
ethanoic acidhelps to prevent
this fromhappening bymoving theposition of
equilibrium to theleft.
Preparation
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Propertiesof Amides
The meltingpoints of theamides are
high
The small amides aresoluble in water becausethey have the ability tohydrogen bond with the
water molecules.
weak bases
muchstronger bases than carboxylic acids, esters, aldehydes,
and ketones
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Uses of Amides
Amides
use as
color, in crayons, pencils and inks, paper industry , plastic and rubber industry,and water and sewage treatment.
Polyacrylamide
used in the treatment of drinking water and sewage. In paper industry polyacrylamide is used as a binder and for retention for fibres
It is also used to retain the color pigments on the paper. as a coating on many household appliances and car parts with thermosetting
acrylics.
Nylons arepolyamides
used to make tyre cords (the inner structure of a vehicle tyre which isunderneath the rubber)
to make ropes and nylon can be cast easily into solid shapes and used for cogsand bearings in machines.
Acrylamides
used in the cosmetic industry to prepare hair products, soaps, and pre-shavelotions.
printing inks, explosives, latex thickeners, adhesives and emulsion stabilizers.
Kevlar
a form of polyamide. Is a very strong material which is about five times asstrong as steel, weight for weight. It is used in composites for boat constructionin manufacture of bulletproof vests, and in lightweight mountaineering ropes anskis and racquets.
Acetaminophen anamide
used as asanalgesic (pain-killer) used as active ingredient in products such as Amadil, Datril, Cetadol, Naprinol,
Tylenol, and Panadol. Another amide analgesic is phenacetin, used in productssuch as Empirin and APC (aspirin, phenacetin, and caffeine) tablets.
Othercommercial
ly used
N,N-dimethyl-m-toluamide, used as insect repellant) lidocaine (Xylocaine) and dibucaine (Nupercaine), used as the local anesthetics the tranquilizer meprobromate (Equaine, Miltown), and Sevin and Mipcin used
as insecticides.