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How would you provethe strutcureof glucoe? (OR) Elucidate the strcture of glucose . |
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Answer» Solution :(i) Elemental analysis and molecular weightdetermination shown thatthe molecularformulaof GLUCOSEIS `C_(6) H_(12)O_(6)`. (ii) On reductionwithConc.HI and red P at 373K, glucose gives a mixtureof h - hexaneand 2 -iodohexaneindicatingthat thesixcarbon atomsare BONDED linearly . Glucose  (iii)Glucosereacts withhydroxylamin to fromoximeandwith HCNto fromcyanohydrin. These reactions indicate thepresence ofcarboyl groupin glucose .  (iv) Glucose getsoxidised to gluconic acidwithbromine waterwith bromine water suggests that thecarbonylgroup is an aldehyde GROUP and itoccupiesone endof the carbonchain.When glucose is oxidised byconc. `HNO_(3)`glucaricacidis formedand itsuggest that theotherend id occupied bya primary alcoholi.  (v) Glucoseis oxidised to gluconicacid withammonicalsilvernitrate (Tolle.s reagent ) andalkaline coppersulphate(Fehling.s solution) . Thesereactions furtherconfirmthe presence of an aldehydegroup.  (vi) Glucose from penta acetat withacetic anhydridesuggestingthe presenceof fivealcohol groups.  (vii) Glucose is a stablecompound anddoesnot undergodehydration easily . It indicates that not more thanone hydroxylgroupis bonded to singlecarbon atom . Thusthe fivehydroxylgroups areattached to fivedifferent carbonatomsand the sixth carbonis analdehydegroup. (vii) Glucoseisstablecompoundand doesnot undergodehydration easily. Thusthe fivehydroxylgroups areattachedto fivedifferentcarbon atoms and thesixthcarbon is analdehyde group. (viii) The EXACT specialarragementof -OH groups was given byEmil Fischer as follows :  (ix)D (+ ) glucose has Dconfigurationnad it is dextrorotatory . |
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