NCERT

1 To identify the functional groups present in an organic compound. Organic compounds containing > C = C < and / or C C bonds are calledunsaturated compounds. These compounds undergo addition reaction withbromine water or the solution of bromine in carbon tetrachloride, chloroform orglacial acetic acid. Addition of bromine to an alkene results in the formation ofvicinal dibromide. The reddish orange colour of the solution of bromine in carbontetrachloride disappears on reaction with an alkene. The reaction is as follows :Alkenes decolourise the neutral/alkaline KMnO4 solution and vicinal glycolsare formed (Bayer s test). Reaction takes place as follows :Both the above reactions are used as tests for Test tubes:Two Test tube holder:One Potassium hydroxidesolution:1 2 mL Carbon tetrachloride/chloroform:2 mL Bromine water/solutionof bromine in CCl4 orchloroform:2 mL Potassium permanganatesolution:As per need Compound to be tested:As per need water testDissolve g or 5 drops of organic compound in 2 mL of carbontetrachloride in a test tube and add 2% solution of bromine incarbon tetrachloride or bromine water drop by drop withcontinuous shaking.

2 Decolourization of bromine solution indicatesthe presence of unsaturation in organic s testDissolve 25-30 mg of organic compound in 2 mL of water oracetone (free of alcohol) and add 1% potassium permanganatesolution containing equal volume of 1% sodium carbonatesolution. The discharge of the colour of more than one drop ofpotassium permanganate indicates the presence of unsaturationin the organic compound. Carrying out the reaction under alkalineconditions removes the possibility of confusion due to substitutionin aromatic :(i)Unsaturation in an organic compound is confirmed only whenboth of the above tests are positive.(ii)In place of CCl4 any other solvent such as CHCl3/dioxan andeven water can be used to dissolve the organic compound forcarrying out the reaction. (a)The tests should be performed at room temperature.(b)Handle bromine solution carefully. Do not inhale the vapours and also avoid itscontact with the Alcoholic compounds on reaction with ceric ammonium nitrategive a red colouration due to the formation of a complex.

3 (NH4)2 [Ce(NO3)6] + 3 ROH [Ce(NO3)4(ROH)3] + 2NH4NO3 Ceric ammonium Red complex nitrateDistinction between primary, secondary and tertiary alcoholscan be done on the basis of iodoform test and Lucas and secondary alcohols which contain CH3 CH(OH)Rgroup (iodoform reaction) give positive iodoform test. To carry outreaction, potassium iodide and sodium hypochlorite solution areadded to the compound in the presence of sodium hydroxidesolution. Probably sodium hypochlorite first oxidses potassiumiodide into potassium hypoiodite, which oxidises CH3 CH(OH)Rgroup to CH3 COR group and then iodinates it in the alkalinemedium of the reaction mixture by replacing the -hydrogenattached to the carbon atom adjacent to carbonyl group by is formed after cleavage of C C Potassium hypoioditehypoioditeNaOHCHCHOHCHCHOCICHO CHI + HCOONa Lucas TestLucas reagent contains zinc chloride and concentratedhydrochloric acid. This reagent reacts with primary, secondaryand tertiary alcohols at different rates.

4 Tertiary alcohols reactalmost instantaneously, secondary alcohols react in about 1-5minutes and primary alcohols react very slowly. The reaction maytake 10 minutes to several +HClNo reaction/Slow reaction 222 ZnCl2 RCHOH+HClRCHCl+HO 332 ZnCl2 RCOH+HClRCCl+HO Alcohols are soluble in Lucas reagent but the formed alkylhalides are not soluble. Therefore, formation of two layers in thereaction medium indicate the occurrence of the alcohols Layers do not separateSecondary alcohols Layers separate within 1-5 minutesTertiary alcohols Layers separate immediately24-04-2018 *Potassium iodide-iodine reagent is prepared by dissolving 20 g of potassiumiodide and 10 g of iodine in 100 mL of water. Ceric ammoniumnitrate solution:As per need Sodium hydroxide:As per need Iodine solution:As per need Lucas reagent:As per need Dioxan:As per need Test tube holder:One Test tubes:As per need ammonium nitrate testTake 1 mL solution of organic compound dissolved in a suitablesolvent.

5 Add a few drops of ceric ammonium nitrate of red colour shows the presence of alcoholic OH :The red colour disappears after keeping the reaction mixture forsometime. The colour also disappears if excess of cericammonium nitrate solution is added. Therefore, use of excessof ceric ammonium nitrate solution should be testFirst methodTake mL of the compound in a test tube, add 10 mL of 10%aqueous KI solution and 10 mL of freshly prepared NaOCl gently; yellow crystals of iodoform methodDissolve g or 4 to 5 drops of compound in 2 mL of water. If itdoes not dissolve, add dioxane drop by drop to get a homogeneoussolution. Add 2 mL of 5% sodium hydroxide solution followed bypotassium iodide-iodine reagent* dropwise with continuousshaking till a definite dark colour of iodine persists. Allow thereactants to remain at room temperature for 2-3 minutes. If noiodoform separates, warm the reaction mixture in a water bath at60 C. Add more drops of potassium iodide iodine reagent.

6 If colourof iodine disappears continue addition of reagent till the colour ofiodine persists even after two minutes of heating at 60 C. Removeexcess iodine by adding a few drops of sodium hydroxide solutionwith shaking. Dilute the mixture with equal volume of water andkeep it at room temperature for 10-15 minutes. A yellow precipitateof iodoform is obtained if test is C. Lucas testTake 1 mL of compound in a test tube. Add 10 mL of Lucas well and note the time for the separation of two distinct : Lucas test is applicable to only those alcohols which are solublein the reagent because the test is based on separation of alkylhalides as separate layer. The OH group attached directly to the ring carbon of an aromaticring is called phenolic OH group . Phenols are weakly acidic,therefore they are soluble in NaOH solution but at the same timethey are not sufficiently acidic to be soluble is sodiumhydrogencarbonate solution. Phenols give coloured complex withneutral ferric chloride solution.

7 For example, phenol gives acomplex of violet colour as follows :6C6H5OH + FeCl3 [Fe(C6H5O)6]3 + 3 HCl + 3H+ Violet complexResorcinol, o , m and p cresol give violet or blue colouration,catechol gives green colour which rapidly darkens. 1 and 2 Naphtholdo not give characteristics colours. Phenols condense with phthalicanhydride in the presence of concentrated H2SO4, Phenol condeses togive phenolphthalein which gives a dark pink colour with NaOHsolution. This is called phthalein dye Colouro Cresolredm Cresolbluish-purplep CresolNo colourCompoundCompoundColourCatecholUsua lly blue takeslonger time to appearResorcinolGreen fluorescentcolour of fluorescein Test tube holder:One Test tubes:As per need chloride testTake 2 mL of aqueous or alcoholic solution of the organiccompound in a test tube, add neutral ferric chloride solutiondropwise and note the colour change. Appearance of a blue, green,violet or red colour indicates the presence of phenolic OH dye testTake g of organic compound and g of phthalic anhydridein a clean dry test tube and add 1-2 drops of conc.

8 H2SO4. Heatthe test tube for about 1 minute in an oil bath. Cool and pour thereaction mixture carefully into a beaker containing 15 mL of dilutesodium hydroxide solution. Appearance of pink, blue, green, redetc. colours indicates the presence of phenolic OH group in thecompound. However, the colour disappears on addition of largeexcess of sodium hydroxide solution. Blue litmus paper Ferric chloride solution Conc. sulphuric acid Sodium hydroxide Phthalic anhydride Organic compoundcontaining phenolic OH groupAccordingtorequirementTable : Colours produced by some other phenolic compounds in phthalein dye testNote :(i)Neutral ferric chloride solution is prepared by adding dilute sodium hydroxide solution toferric chloride solution drop by drop till a small but permanent brown precipitate is filtered and the clear filtrate is used for the test.(ii)Some phenols like 2,4,6 trinitrophenol and 2,4 dinitrophenol, which contain electronwithdrawing groups are strong acids and dissolve even in sodium hydrogencarbonate 2, 4-Dinitrophenylhydrazine2, 4 Dinitrophenyl hydrazone of carbonyl compound (a)Always use freshly prepared, neutral and very dilute solution of ferric chloride.

9 (b)Phenol is toxic and corrosive in nature and should be handled with care. Both aldehydes and ketones contain carbonyl group (>C = O) andare commonly known as carbonyl compounds. Identification ofaldehydes and ketones is done by two important reactions ofcarbonyl group (i)addition reaction on double bond of >C = O group and(ii)oxidation of carbonyl reactions of derivatives of ammonia are important fromthe point of view of identification of carbonyl compounds. Additionis generally followed by elimination resulting in the formation ofunsaturated compound. (R = alkyl, aryl or C6H5NH etc.)These reactions are catalysed by an acid or a base and do notoccur under strongly acidic or basic conditions. Each reactionrequires an optimum pH for its occurrence. Therefore, maintenanceof pH is very important while carrying out these far as oxidation is concerned, aldehydes are easily oxidisedto carboxylic acids while ketones require relatively strongeroxidising agents.

10 Distinction can be made between these two typesof carbonyl compounds on the basis of difference in their tests are performed for the identification of aldehydicand ketonic groups:(i) On reaction with 2,4-dinitrophenylhydrazine (2,4-DNP), theyform the respective 2,4 dinitrophenyl These two carbonyl compounds (aldehydes and ketones) aredistinguished on the basis of tests using mild oxidising reagents,like Tollen s reagent and Fehling s reagent or Benedict s s reagent is an alkaline solution of silver cation complexedwith ammonia, and Fehling s and Benedict s reagents are alkalinesolutions containing cupric ions complexed with tartarate andcitrate ions respectively. Fehling s reagent is freshly prepared bymixing equal amounts of Fehling s solution A and Fehling ssolution B. Fehlings reagent deteriorates on keeping while Fehling ssolutions A and B are quite stable. Fehling s solution A is anaqueous copper sulphate solution while Fehling s solution B isan alkaline solution of sodium potassium tartarate (Rochelle s salt).