CARBOXYLIC ACIDS

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CARBOXYLIC CARBOXYLIC ACID are acidic compoundshaving one or more carboxyl group COOH in their Molecules The namecarboxyl is derived by the combination of.
the term carbonyl and hydroxyl The carboxylic acid are classifiedas mono di or tri carboxylic acidsaccording to the number ofcarboxyl groups present in.
molecule The mono carboxylicacids may be represented asRCOOH where R represent NOMENCLATURE1 COMMON SYSTEM The aliphatic mono.
carboxylic acids are commonly called fattyacids branched chain acids having onebranch of methyl group farthest away fromthe carboxyl group are named by addingprefix iso to the name of corresponding.
straight line acid CH3 CH CH3 CH2COOHAROMATIC ACIDS ASIS KNOWN having the carboxylISOVALERIC group.
directly attached to the aromatic nucleus aregenerally referred to as derivatives of benzoicacid example methyl benzoic acids aregenerally called toluic acid 2 IUPAC SYSTEM the IUPAC names.
of carboxyl acids are obtained inaccordance with the general IUPAC rule thesuffix used for the carboxyl group being oicFor example CH3 CH CH3 CH2 COOH3 Methylbutanoic acid.
IUPAC names of some carboxylic acids ACIDIC CHARACTER OF CARBOXYLICEven though the carboxyl group is generallyrepresented by COOH actually it is a resonance hybrid of the following.
contributing structures In the resonance hybrid oxygen of the hydroxylgroup carries some positive charge As a result theelectron pair of the O H bond is largely displacedtowards oxygen Due to this displacement of.
electron pair the hydrogen of O H can be releasedas H ion ORBITAL STRUCTURE The resonance in carboxyl ion can also beunderstood in term of molecular orbital concept .
Carboxyl ion is in state of sp hybridisation Thishybrid orbital are directed towards the corners ofthe triangle and lie in the same plane at an angleof 120 with each other These three orbitals formthree sigma bonds one each with two oxygen.
atoms and the third with carbon atom GENERAL METHODS OF1 OXIDATION OF PRIMARY ALCOHOLS PREPARATIONcarboxyl acids are readily obtained by.
oxidation of primary alcohols The usualoxidising agents employed are acidifiedpotassium dichromate potassiumpermanganate or nitric acid RCH2OH RCOOH carboxylic acid .
2 OXIDATION OF ALKYLBENZENE on heatingalkylbenzene with oxidising agents suchas acidified potassium dichromate thealkyl side chain gets oxidised to carboxyl 3 HYDROLYSIS OF NITRILES .
Hydrolysis of a nitrile with an aqueousacid or alkali is an important method ofpreparing carboxylic acids Acidic hydrolysis of Alkaline hydrolysis of nitriles.
4 HYDROLYSIS OF ACID DERIVATIVES 5 CARBONATION OF GRIGNARDREAGENTS carboxylic acids mayprepared by reaction of Grignard withcarbon dioxide .
6 MALONIC ESTER SYNTHESIS malonate CH2 COOC2H5 2 generally refer to as melonicacid forms its sodium salt onreaction with sodium ethoxide .
7 HYDROLYSIS OF TRIHALOGENDERIVATIVESTrihalogen derivatives having allthe three halogen atoms attachedto the same carbon atom give.
carboxylic acids on hydrolysiswith an alkali 8 OXIDATION OF METHYLKETONES when treated withsodium hypohalite methyl.
ketones are oxidised tosodium to sodium salts ofR CH3 R OH X X9 ARNDT EISTERT HOMOLOGATION this is a convenient method of.
homologation of an acid i e conversion of a given acid into its nexthigher homologue The acid firstlyconvert to acid chloride by treatmentwith SOCL2 .
PHYSICAL1 PROPERTIESPHYSICAL STATE the loweraliphatic acids such as formicacid are color less liquids having.
irritating smell Acid forms arecolorless Oily liquids havingunpleasant2 SOLUBILITY smells acids arethe aliphatic.
not soluble in water but solubility fallsoff rapidly with increase in molecularweight and higher acids are insolublein water Simplest acids i e benzoicacid is only sparingly soluble in water .
3 BOILING POINT carboxylic acid forminter molecular hydrogen bonds andexist in form of associated molecules As carboxylic acids have high boilingpoints The boiling points are higher.
than those of alcohols of comparablemolecular weight 4 MELTING POINT DONOT FOLLOW A REGULARPATTERN WITH INC IN MOLECULAR SIZE ITOBSERVED FROM ACIDS CONTAINING UP TO 10.
CARBON ATOMS THE MELTING POINTS OF ACIDCONTAINING EVEN NO OF CARBON ATOMS AREHIGHER THAN THOSE OF IMMEDIATELY LOWER AS CHEMICAL PROPERTIESCLEAVAGE OF OH BOND.
1 ACIDITY all carboxylic acids ionise inaqueous solution and exist inequilibrium with carboxyl ate anion andthe hydronium ion RCOOH H2O RCOO H3O .
2 SALT FORMATION carboxylic acidare attacked by stronglyelectropositive metals such as Na Znand K to form salt and liberate2RCOOH 2Na RCOONa H2O.
3 FORMATION OF ESTER whenheated with alcohols in presenceof a strong mineral acid or a Lewisacid carboxylic acids form esters The reaction is reversible in.
nature and is known asesterification 4 FORMATION OF ACID CHLORIDE ontreatment with phosphorus pentachloride phosphorus trichloride or thionyl chloride .
hydroxyl group of carboxylic acids isreplaced by chlorine to form acid chlorides RCOOH PCl5 RCOCl POCl3 HCL3RCOOH PCl3 3RCOCl H3PO3RCOOH SOCl2 RCOCl SO2 SO2 HCl.
5 FORMATION OF AMIDES whentreated with ammonia acids formammonium salts which on heatinglose a molecule of water to form6 FORMATION OF ANHYDRIDES when.
RCOOH NH3 RCOONH4treated with acid chlorides in thepresence of pyridine carboxylic acidsform the corresponding anhydrides RCOOH RCOCl pyridine.
RCO 2O Pyridine HCl 7 REDUCTION carboxylic acids areresistant to catalytic hydrogenation However they can be reduced bylithium aluminium hydride to form.
primary alcohols the carbonyl grouppart of carboxyl group gettingreduced to CH2 RCOOH RCH2OHMECHANISM .
ELIMINATION OF CARBONYLDECARBOXYLATION SIMPLE CARBOXYLICACIDS GET DECARBOXYLATED TO FORMHYDROCARBONS WHEN THEIR SALTS ARERCOONa WITH SODA.
NaOH LIME RH Na2CO3MECHANISM 9 KOLBE S ELECTROLYSIS Alkali salts of carboxylic acids.
on electrolysis getdecarboxylated to formhydrocarbons DISTILLATION OF CALCIUMSALTS OF ACIDS when.
distilled in the absence of air calcium salts of acids yielddifferent products as given DECARBOXYLATION HALOGENATION HUNSDIECKER REACTION THE SILVER.
SALT OF A CARBOXYLIC ACID REACTS WITHBROMINE OR IODINE IN DRY CARBONTETRACHLORIDE TO FORM AN ALKYLBROMIDE OR IODIDE WITH THE LOSS OFCARBON DIOXIDE .
HALOGENATION OF ALKYL GROUPS in thepresence of small amounts of redphosphorus the hydrogen atoms of alkylgroup of aliphatic acids can be replaced bychlorine or bromine to form a halo acid .
ACIDITY CONSTANT OFCARBOXYLIC ACIDSIt has been already pointed out that inaqueous solution a carboxylic acid exists inequilibrium with carboxy late anion and the.
hydronium ion that is RCOOH H2O RCOO H3O Acc To law of mass action the equilibriumconstant can be expressed as Kc RCOO H3O .
RCOOH H2O Since water is taken in large excess and itsconcentration is constantKa RCOO H3O Ka is referred to as the acidity.
constant Since Ka is directlyproportional to H3O ions it would bepKa in casevalue theseofdaysweaktheacids.
acidicand highofan acid is value for stronginacidsalso represented terms of pKavalue which is the negative logarithm of theacidity constant That is .
pKa log KaExample pKa of acetic acid is equal to 4 75It may be noted that a strong acid has alarge pKa value but small pKa value while aweaker acid has smaller pKa value but large.
pKa value Most of the simple unsubstitutedcarboxylic acids are of moderate strengthhaving pKa values of about 3 5 EFFECT OF SUBSTITUENTS ONSince OF CARBOXYLIC.
carboxyl group consists of carbonyl and hydroxylACIDSgroups itis expected that acids show reactions due to both these groups However the reactions expected of these groups are modified as aresult of interaction between these groups due to close proximity .
Carboxylic acids are resonance hybrid of the following structures It is clear that the carbonyl part of the carboxyl group does nothave a double bond character but a reduced double bondcharacter Thus it does not give the reactions of the carbonylgroup The carbonyl carbon in carboxyl group is less electrophilic.
than the carbonyl carbon in aldehydes and ketones due toresonance Therefore many nucleophilic addition reactions ofaldehydes and ketones do not take place with carboxylic acids Thesame effect makes the hydroxyl group of carboxylic acids moreacidic than the hydroxyl group of alcohols and phenols justifying.
ALIPHATIC1 The stronger the electron withdrawing grouppresent in an acid the greater is the acidity Example flouroacetic acid is stronger thanchloroacetic acid because flourine is stronger.
electron withdrawing than chlorine 2 The large the no of electron withdrawinggroup present in acid the greater is the effecton the acidity 3 As a group having electron withdrawing.
inductive effect moves away from thecarboxylic group Its effect on the aciditybecomes less pronounced 4 The effect of electron releasing group It is AROMATIC.
BENZOIC ACID ACIDSIT IS AN SIMPLESTACID CONTAINING A CARBOXYL GROUPATTACHED TO AN UNSUBSTITUTEDBENZENE RING .
A B A B A BC O O H C O O H C O O HCO O H C O O H 2 PHENYLACETIC ACID simplearomatic acids containing the.
carboxyl group in the side chain Here resonance effect is notpossible due to interveningcarbon atom between the phenyland carboxyl groups Therefore.
phenyl group exerts weaklyelectron withdrawing inductiveeffect It is a strong acid thanacetic acid and higher aliphaticacids containing electron.
EFFECT OF SUBSTITUENTS ONACIDIC STRENGHTS OFAROMATIC ACIDS THE EFFECT OF SUBSTITUENTGROUP PRESENT ON THE.
BENZENE RING ON THE BENZENERINGIN THE ACIDIC STRENGTH OFAROMATIC CARBOXYLIC ACIDS DEPENDS UPON BOTH THEINDUCTIVE AND THE RESONANCE.
EFFECTS OPERATING GROUP ISPRESENT IN DIFFERENT POSITIONS A Group having electronwithdrawing inductive effect as wellas electron withdrawing resonance.
effect such as NO2 group Let us consider the effect of nitrogroup on benzene nitro groupexert an electron withdrawinginductive effectHO.
as well aswithdrawing resonance effect b EFFECT OF HALOGENS halogens have electronwithdrawing inductive effect and.
electron releasing resonanceeffect but the inductive effect isstronger than resonance effect c Group having electronwithdrawing inductive effect.
and electron releasingresonance effect butresonance effect is strongerthan inductive effect d Group having only electron.
releasing inductive effectsuch as CH3 and CH2CH3groups Such groups haveacid weakening effect whenpresent in Para and meta.
THANK YOUTrihalogen derivatives having all the three halogen atoms attached to the same carbon atom give carboxylic acids on hydrolysis with an alkali. 8. OXIDATION OF METHYL KETONES: when treated with sodium hypohalite, methyl ketones are oxidised to sodium to sodium salts of carboxylic acids. 9. ARNDT – EISTERT HOMOLOGATION: this is a convenient ...

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