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प्रश्न
Explain the following with an example.
Williamson ether synthesis
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
Write the equations involved in the following reactions : Williamson synthesis
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:
Ethoxybenzene
Write the name of the reagent and equation for the preparation of the following ethers by Williamson’s synthesis:
1-Methoxyethane
Account for the following :
t-butyl chloride on heating with sodium methoxide gives 2-methylpropene instead of t-butyl methyl ether.
Williamson's synthesis of preparing dimethyl ether is a/an ____________.
Which of the following cannot be made by using Williamson Synthesis:
Preparation of alcohols from alkenes involves the electrophilic attack on alkene carbon atom. Explain its mechanism.
Identify the following named reaction
\[\ce{C2H5Br ->[NaOCH3] C2H5OCH3}\]
Write the equations for the following reaction:
Tert butyl chloride is treated with sodium ethoxide.
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 reagent and equation for the preparation of the following ethers by Williamson’s synthesis:
2-Methoxy-2-methylpropane
Write the name of the reagent and equation for the preparation of the following ether by Williamson’s synthesis:
2-Methoxy-2-methylpropane
Identify the product(s) is/are formed when 1-methoxy propane is heated with excess HI. Name the mechanism involved in the reaction.
What will be the product (X and A)for the following reaction
\[\ce{acetylchloride->[i)CH3MgBr][ii)H3O+]X ->[acidk2crp3]A}\]
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
Identify the product (s) is/are formed when 1-methoxy propane is heated with excess HI. Name the mechanism involved in the reaction.
