InterviewSolution
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InterviewSolution
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A certain hydrocarbon (A) was found to contain 85.7% of C and 14.3% of H. This compound consumes 1 molar equivalent of hydrogen to give a saturated hydrocarbon (B). 1g of hydrocarbon (A) just decolourised 38.05g of a 5% solution (by weight) of Br_(2) in C Cl_(4). Compound (A), on oxidation with concentrated KMnO_(4), gave compound (C ) (molecular formula C_(4)H_(8)O) and acetic acid. Compound (C ) could easily be prepared by the action of acidic aqueous mercuric sulphate on 2-butyne. Determine the molecular formula of (A) and deduce the structures of (A), (B) and ( C) |
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Answer» Solution :Moles of `C: H` in (A) `=(85.7)/(12): (14.7)/(1)= 7.14: 14.3= 1:2` `therefore` empirical formula of (A) is `CH_(2)` and empirical formula weight is 14. As (A) consumes I molar equivalent of hydrogen to give a saturated hydrocarbon (B), (A) should have one double bond. Reaction of (A) with `Br_(2)` will also be an addition reaction in which 1 MOLE of (A) will combine with 1 mole of `Br_(2)`. THUS, Moles of (A)= moles of `Br_(2)` or `(1)/(M)= ((5 xx 38.05)//100)/(160) " " {{:("M = mol . wt of (A)"),(Br_(2)=160):}}` `therefore M=84` `therefore n=("molecular formula wt.")/("empirical formula wt")=(84)/(14)=6` `therefore` molecular formula of (A) is `C_(6)H_(12)` Now from the given reaction sequece, we have, `{:(C_(6)H_(12)underset(KMnO_(4))overset((O))rarrC_(4)H_(8)O+ CH_(3)COOH),("(A)I(C)" ),(""IIuarr H^(+)//HgSO_(1)),(""CH_(3).C -=C.CH_(3)),("2-butyne"):}` We CONCLUDE that `C_(6)H_(12)` (A) must be represented as `C_(4)H_(8)=CH.CH_(3)` (step I) and `C_(4)H_(8)O` (C ) must be a KETONE `CH_(3).overset(overset(C )(||))(C )CH_(2).CH_(3)` (step II) further, addition of `H_(2)` to compound (A) will produce `C_(6)H_(14)` (B) (an alkane). The structure of (A), (B) and (C ) MAY be represented as 
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