InterviewSolution
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InterviewSolution
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A mixture of two organic compound is added to cold water. After filtration, water-insoluble compound (A) burns with a smoky flame and it does not respond to Lassaigne's and Beilsteins test. When a small amount of this is added to NaHCO_(3) solution, a colourless gas is evolved with effervescene. when this comopound is heated with CH_(3)OH in acidic medium, it gives the characteristic smell of oil of wintergreen. compound (B), which is water soluble, burns with a non-smoky flame and its sodium extract is prepared with cane sugar. It gives the Prussian blue colour with freshly prepared solutions of FeSO_(4)+2-3 drops NaOH and with few drops of H_(2)SO_(4). when a small amount of this compound is heated in a dry test tube, a colourless gas is evolved that turns moist red litmus paper blue and a white residue is left. this white residue is dissolved in water and a drop of CuSO_(4) is added in the basic medium -a violet colour is obtained. identify the compounds (A) and (B) with the help of the reactions involved. |
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Answer» Solution :(i) Compound `(A)` is insoluble in water and burns with a smoky flame, hence it should be an aromatic compound. (ii) It has no specific element such as `N,S` and halogens and gives `CO_(2)` gas with `NaHCO_(3)` solution, hence it should contain `(-COOH)` group. (iii) It gives oil of wintegreen (methyl salicylate) with `CH_(3)OH` in acidic medium, hence it is salicylic acid.  (iv) Compound `(B)` is water soluble and burns with a non-smoky flame. hence it should be an aliphatic compound. (V) This compound has less carbon content because its sodium extract is prepared with sucrose and it gives PRUSSIAN blue colour with freshly prepared solution of `FeSO_(4)+2-3` drops of `NaOH` and a few drops of `H_(2)SO_(4)`, hence it is nitrogen-containing compound. `NaCN+FeSO_(4)toNa_(4)[FE(CN)_(6)]+Na_(2)SO_(4)` `FeSO_(4)overset([O])toFe_(2)(SO_(4))_(3)` `3Na_(4)[Fe(CN)_(6)]+3Fe_(2)(SO_(4))_(3)toFe_(4)[Fe(CN)_(6)]_(3)+6Na_(2)SO_(4)` (vi) On heating, it gives ammonia gas, which turns red litmus blue. hence, it contains `(-COONH_(2))` group. (vii) It ALSO gives the biuret test. `2NH_(2)CONH_(2)overset(triangle)toNH_(2)CONHCONH_(2)+NH_(3)uarr` `NH_(2)CONHCONH_(2)overset(Cu^(2+))to`violet colour Hence, this compound is urea `(NH_(2)CONH_(2))`. |
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