GO 4 Preparation of Carboxylic Acid

8/2/2019 GO 4 Preparation of Carboxylic Acid

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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_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.

GO 4 Preparation of Carboxylic Acid

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