Title 3.PRACTICAL ORGANIC CHEMISTRY_Final ( 129 - 146 ).pdf ✅

129 Nishith Multimedia India (Pvt.) Ltd PRACTICAL ORGANIC CHEMISTRY JEE ADVANCED VOL - V SYNOPSIS (A) FUNCTIONAL GROUPANALYSIS 1. Unsaturation : Alkenes & alkynes: (a) Bayers test : Cold dil alk. KMnO4 decolourisation test Purple colour  Colourless + MnO2 (Brown ppt) (b) Br2 water decolourisation test Violet colourless of Br2  Colourless 2. Terminal alkynes: Confirmed by ppt of Acetylide ion with NaNH2 or AgNO3 or Cu2Cl2NH4OH 3. Alkyl halides: (a) If they are capable of carbocation formation then they will give ppt with AgNO3 . (b) Beilstein’s test : A green colour is imported to the flame if small amount of organic compound is taken on copper wire. 4. Alcohol: (a) Cerric ammonium nitrate  Give red colour (b) Boil with acetic acid & conc. H2 SO4  fruity smell (c)2-alkanol & ethanol also give Iodoform test  Yellow ppt. of CH3 I on reaction with I 2 + OH  5. Aldehyde & Ketones: 2,4- Dinitrophenyl hydrazine (or) Braddy’s reagent give yellow, orange or red color with ald. & Ketones (2,4-DNP) 6. Aldehydes: (a) Tollen’s test  Silver mirror (b) Fehling’s test {except benzaldehyde} Red colour (c) Benedicts test  Red colour (d) Schiff’s dye colour regeneration test  Pink colour 7. Ketones: (a) Methyl Ketones give haloform test (b) -hydroxy Ketones give Tollen’s & Fehling test’s too. 8. Carboxylic acids: (a) Brisk effervescence with aq. NaHCO3 solution. (b) HCOOH alone gives silver mirror test with Tollen’s reagent. (c) Blue litmus  red (d) Give fruity smell on reaction with alcohols. 9. Phenols: (a) Violet colouration with neural FeCl3 (b) Liebermann test (c) White ppt with Br2 water (d) Brisk effervescence with aq. NaHCO3 is observed in case of Nitrophenols. PRACTICAL ORGANIC CHEMISTRY
PRACTICAL ORGANIC CHEMISTRY JEE ADVANCED VOL - V 130 Nishith Multimedia India (Pvt.) Ltd 10. Primary amines: (a) Carbylamine reaction  Isonitriles have very distinctive foul odours (b) Hoffmann mustard oil reaction Oily liquid with mustard like smell. 11. Aromatic 1° amine  diazo test 12. Amide boil with NaOH  NH3 13. Nitrobenzene  Mullikqn Baker test  Treat it with ZnNH4Cl then boil with Tollen’s re agent  Sil- ver mirror will appear 14. Proteins: (a) Biuret test : Also used for urea  Alkaline solution of protein treated with a drop of aq CuSO4 when bluish violet colour is obtained (b) Ninhydrin test : Protein treated with a puridine solution of ninhydrin give colour ranging from deep blue to violet pink. DIFFERENTATION TEST D1. 1°, 2° & 3° alcohols: (a) Luca’s test : Lucas reagent is conc. HCl + ZnCl2 (b) Victor Meyer’s test (RBC test) (i) 1° Alcohol  Blood red colour (ii) 2° Alcohol  Blue (iii) 3° Alcohol  Colourless D2. 1°, 2° & 3° amines: (a) Hinsberg’s reagent (i) 1° Amine yield a clear solution from which upon acidification an insoluble material separated. (ii) 2° Amine yield an insoluble compound which is unaffected by acid (iii) 3° Amine yield insoluble compound (b) Reaction with HNO2 QUALITATIVE ANALYSIS OF ORGANIC COMPOUNDS The elements present inorganic compounds aer carbon and hydrogen. In addition to these, they may also contain oxygen, nitrogen, sulphur,halogens and phosphorus. 1. Detection of Carbon and Hydrogen Carbon and hydrogen are detected by heating the compound iwth copper (II) oxide. Carbon present in the compound is oxidised to carbon dioxide (tested with lime-water, which develops turbidity) and hydro- gen to water (tested with anhydrous copper suphate, which turns blue). C + 2CuO  2Cu + CO2 2H + CuO  Cu + H2O CO2 + Ca(OH)2  CaCO3  + H2O 5H2O + CuSO4  CuSO4 . 5H2O White Blue 2. Detection of Other Elements Nitrogen, sulphur, halogens and phosphorus present in an organic comopund are detected by “Lassaigne’s test” . The elements present in the compound are converted from covalent form into the ionic form by fusing the compound with sodium metal. Following reactions take place:
131 Nishith Multimedia India (Pvt.) Ltd PRACTICAL ORGANIC CHEMISTRY JEE ADVANCED VOL - V Na + + N  NaCN 2Na + S  Na2 S Na + X  NaX (X = Cl, Br or I) C, N, S and X come from organic comopund. Cyanide, sulphide and halide of sodium so formed on sodium fusion are extracted from the fused mass by boiling it with distilled water. This extract is known as sodium fusion extract. (A) Test of Nitrogen The sodium fusion extract is boiled with iron(II) sulphate and then acidified with concentrated sulphuric acid. The formation of Prussian blue colour confirms the presence of nitrogne. Sodium cyanide first reacts with iron(II) sulphate and forms sodium hexacyanoferate(II). On heating with concentrated sulphuric acid some iron(II) ions are oxidised to iron(III) ions which react with sodium hexacyanoferrate(II) to produce iron(III) hexacyanoferrate(II) (ferriferrocyanide) which is Prussian blue in colour. 6CN– + Fe2+  [Fe(CN)6 ] 4– 3[Fe(CN)6 ] 4– + 4Fe3+ xH2O Fe4 [Fe(CN)6 ] 3 . xH2O Prussian blue (B) Test for Sulphur (a) The soldium fusion extract is acidified with acetic acid and lead acetate is added to it. A black precipi- tate of lead sulphide indicates the presence of sulphur. S 2– + Pb2+  PbS Black (b) On treating sodium fusion extract with sodium nitroprusside, appearance of a violet colour further indicates the presence of sulphur. S2– + [Fe(CN)5NO]2–  [Fe(CN)5NOS]4– Violet In case, nitrogen and sulphur both are present in an organic compuond, sodium thiocyanate is formed. It gives blood red colour and no Prussian blue since there are no free cyanide ions. Na + C + N + S  NaSCN Fe3+ + SCN–  [Fe(SCN)]2+ Blood red If sodium fusion is carried out with excess of sodium, the thiocyanate decomposes to yield cyanide and sulphide. These ions give their usual tests. NaSCN + 2Na  NaCN + Na2 S (C) Test of Halogens The sodium fustion extract is acidified with nitric acid and then treated with silver nitrate. A white precipi- tate, soluble in ammonium hydroxide shows the presence of chlorine, a yellowish precipitate, sparingly soluble in ammonium hydroxide shows the presence of bromine and a yellow precipitate, insolube in ammonium hydroxide shows the presence of iodine. X– + Ag+  AgX X represents a halogen – Cl, Br or I. If nitrogen or sulphur is also present in the compound, the sodium fusion extract is first boiled with concen- trated nitric acid to decompose cyanide or sulphide of sodium formed during Lassaigne’s test. These ions would otherwise interfere with silver nitrate test for halogens.
PRACTICAL ORGANIC CHEMISTRY JEE ADVANCED VOL - V 132 Nishith Multimedia India (Pvt.) Ltd (D) Test for Phosphorus The compound is heated with an oxidising agent (sodium peroxide). The phosphorus present in the com- pound is oxidised to phophate. The solution is boiled with nitric acid and then treated with ammonium molybdate. A yellow colouration or precipitate indicates the presence of phophorus. Na3 PO4 + 3HNO3  H3 PO4 + 3NaNO3 H3 PO4 + 12(NH4 ) 2MoO4 + 21HNO3  (NH4 ) 3 PO4 . 12MoO3 + 21NH4NO3 + 12H2O Ammonium molybdate Ammonium phophomolybdate LEVEL-V SINGLE ANSWER QUESTIONS 1. An organic compound weighing 0.2 grams, on combustion gave 0.108g of H2O.The percentage by weight of hydrogen in the compound is, A) 20 B) 6 C) 3.33 D) 40 2. Identify the correct statement from the following with regard to Lassaigne’s Test, A) violet coloration during the detection of sulphur is due to the formation of ferric ferrocyanide B) Blue coloration during the detection of nitrogen is due to the formation of ferric thiocyanate C) If both nitrogen and sulphur are present, the formed NaCNS decomposes into Na2 S and NaCN,in case when excess sodium is used. D) Red blood coloration is due to the formation of Na4 [Fe(CN)5NOS] 3. The Prussian blue colour obtained during the test of nitrogen by Lassaigne’s test is due to A)       4 6 3 Fe Fe CN B)       3 6 Na Fe CN C)   3 Fe CN D)       4 5 Na Fe CN NOS 4. Which of the following compound doesn’t give Lassaigne’s test for nitrogen ? A) H2N C NH2 O B) NH NH2 C) H2N NH2 D) H2N CH2 COOH 5. Consider the following pairs of organic compounds (i) C O CH3 , CH2 C O H (ii) H C O OH, H3C C O OH (iii) H C H O , H3C C O CH3 (iv) , C O H3C CH2 C O CH3 C O H3C CH2 C O H Tests that can make distinction between each and every pair is / are (A)Victor-Meyer’stest (B)Tollen’s test (C) Iodoform test (D)Mulliken’s test