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प्रश्न
Explain the following with an example.
Williamson ether synthesis
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उत्तर
It is an important laboratory method for the preparation of symmetrical and unsymmetrical ethers. In this method, an alkyl halide is allowed to react with sodium alkoxide.
\[\ce{R - X + R' - \overset{\overline{\bullet\bullet}}{\underset{\bullet\bullet}{O}}N\overset{+}{a} -> R - \overset{\bullet\bullet}{\underset{\bullet\bullet}{O}} - R' + NaX}\]
Ethers containing substituted alkyl groups (secondary or tertiary) may also be prepared by this method. The reaction involves SN2 attack of an alkoxide ion on primary alkyl halide.
Better results are obtained if the alkyl halide is primary. In case of secondary and tertiary alkyl halides, elimination competes over substitution. If a tertiary alkyl halide is used, an alkene is the only reaction product and no ether is formed. For example, the reaction of CH3ONa with (CH3)3C–Br gives exclusively 2-methylpropene.
\[\begin{array}{cc}
\ce{CH3}\phantom{.................................................}\\
|\phantom{....................................................}\\
\ce{CH3 - C - Br + N\overset{+}{a} \overset{\overline{\bullet\bullet}}{\underset{\bullet\bullet}{O}} - CH3 -> CH3 - C = CH2 + NaBr + CH3OH}\\
\phantom{}|\phantom{.................................}|\phantom{...................}\\
\phantom{}\ce{CH3}\phantom{..........................}\ce{\underset{2-Methylpropene}{CH3}}\phantom{............}
\end{array}\]
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संबंधित प्रश्न
Explain the mechanism of the following reaction:
Which of the following is an appropriate set of reactants for the preparation of 1-methoxy-4-nitrobenzene and why?
 |
 |
| (i) | (ii) |
Write the name of the reagent and the equation for the preparation of the following ether by Williamson’s synthesis:
1-Propoxypropane
Write the name of the reagent and equation for the preparation of the following ethers by Williamson’s synthesis:
1-Methoxyethane
Preparation of ethers by acid dehydration of secondary or tertiary alcohols is not a suitable method. Give reason.
Account for the following :
t-butyl chloride on heating with sodium methoxide gives 2-methylpropene instead of t-butyl methyl ether.
The major product [B] in the following reactions is:
\[\begin{array}{cc}\ce{CH3}\phantom{..................................}\\|\phantom{.....................................}\\\ce{CH3 - CH2 - CH - CH2 - OCH2 - CH3 ->[HI][Heat] [A] alcohol ->[H2SO4][\Delta] [B]}\end{array}\]
Which of the following reactions are feasible?
Write the name of the reaction, structure and IUPAC name of the product formed when:
\[\ce{CH3CH2CH(CH3)CH(CH3) ONa}\] reacts with \[\ce{C2H5Br}\]
What is metamerism? Give the structure and IUPAC name of metamers of 2-methoxy propane.
Write the name of the reagent and equation for the preparation of the following ether by Williamson’s synthesis:
2-Methoxy-2-methylpropane
Short Answer Question.
Identify the product (s) is / are formed when 1 – methoxy propane is heated with excess HI. Name the mechanism involved in the reaction
Write the names of reagents and equations for the preparation of the following ether by Williamson’s synthesis:
2-Methoxy-2-methylpropane
Write the name of reagent and equation for the preparation of the following ethers by Williamson’s synthesis:
2-Methoxy-2-methylpropane
Short Answer Question.
Identify the product (s) is/are formed when 1 – methoxy propane is heated with excess HI. Name the mechanism involved in the reaction.
Write the name of reagent and equation for the preparation of the following ethers by Williamson’s synthesis:
2-Methoxy-2-methylpropane
Write the name of reagent and equation for the preparation of the following ether by Williamson’s synthesis:
2-Methoxy-2-methylpropane
Write the name of reagent and equation for the preparation of the following ether by Williamson’s synthesis:
2-Methoxy-2-methylpropane
