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Synthesies the following ethers, selec-ting the given methods. (I) Williamson's synthesis (II) Alkoxy mercuration-demercuration (III) Intermolecular dehydration Given reasons for the selection of the method. a.Divinyl ether b.Dicyclohoexyl ether c.Propyl sec-butyl ether d.1-Propoxy-2-methyl propane e.1-(3-Mrthyl butoxy)-3-methyl butane |
Answer» Solution :a.Write the structures of ether:  since it is an unstable compopund and tautomerise to `H_(3)C--CH=O`. Double BOND is introduced after the formation of ether by method (III).  Method (I) cannot be used because of unreactive vinyl halide  and vinyl oxide both are stabilised by reasonance.Method (II) cannot be used because of unreactive vinyl alcohol.b.Structure of ether :  Method (II) will give desired result with   Although it is symmetrical ether, but method (III) cannot be used because intromlecular dehydration of `2^(@)` ROH would give mainly cyclohexene.Method (I) cannot be used because `2^(@)` RX  does not favour the reaction. c.Structure of ether.  By method (II): i.  ii.  Path (ii) is not feasible because it would give different ether (isopropyl-sec-butyl ether) (F).  Path (i) would give the required ether:  d.Structure of the ether:  Method I is feasible:  Methods II and III are not feasible and method II would give different isomers.  Path (i):  Path (ii):  Method III is not feasible. It is a non-symmetrical ether, dehydration gives mixtures and both alkyl groups are `1^(@)` . `R--O--H + R'O---H OVERSET (Conc.H_(2)SO_(4)) underset (Low TEMP) rarr` `R--O--R' + R--O--R + R'--O--R`  e.Structure of ether:  Method III is feasible. It is a symmetrical ether and with `1^(@) (R---)` groups.  Method I is not feasible. Both RX and R'ONa wold be `1^(@)`. Better yield of ether is OBTAINED FORM `1^(@)` RX and `3^(@)` RONa.Method II is not feasible, it would give a different ether. |
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