Question

Explain the following with an example.
A. Kolbe's reaction.
B. Reimer-Tiemann reaction.
C. Williamson ether synthesis.
D. Unsymmetrical ether.

Answer 1

Hint: All these reactions are the preparation method of one or the functional groups of hydrocarbons. Various types of hydrocarbons with different types of functional groups in them can be obtained from these reactions.

Complete step by step answer:
Let us understand these reactions one by one:
Kolbe's reaction: This reaction is used to produce hydroxy carboxylic acid. When phenol is treated with sodium hydroxide, sodium phenoxide is produced. When this sodium phenoxide is treated with carbon dioxide which is followed by the acidification, it undergoes electrophilic substitution reaction which forms ortho-hydroxybenzoic acid, also known as salicylic acid.
$ \underset { Sodium\quad Phenoxide }{ { C }_{ 6 }{ H }_{ 5 }{ O }^{ - }{ Na }^{ + } } \quad +\quad C{ O }_{ 2 }\quad \xrightarrow [ 400\quad K ]{ 4-7\quad atm } \quad o-HO-{ C }_{ 6 }{ H }_{ 4 }-CO{ O }^{ - }{ Na }^{ + }$
$ o-HO-{ C }_{ 6 }{ H }_{ 4 }-CO{ O }^{ - }{ Na }^{ + }\quad \xrightarrow [ dil\quad HCl ]{ NaOH } \quad \underset { Salicylic\quad acid }{ o-HO-{ C }_{ 6 }{ H }_{ 4 }-COOH }$
Reimer-Tiemann reaction: When phenol is treated with chloroform in the presence of sodium hydroxide at 340 K followed by dil. HCl, an aldehyde group is introduced at the ortho position of the benzene ring.
$ \underset { Phenol }{ { C }_{ 6 }{ H }_{ 5 }OH } \quad +\quad \underset { Chloroform }{ CH{ Cl }_{ 3 } } \quad \xrightarrow [ NaOH ]{ 340\quad K } \quad o-NaClO-{ C }_{ 6 }{ H }_{ 4 }-CHO$
$ o-NaClO-{ C }_{ 6 }{ H }_{ 4 }-CHO\quad \xrightarrow [ dil\quad HCl ] \quad \underset { Salicylaldehyde }{ o-HO-{ C }_{ 6 }{ H }_{ 4 }-CHO }$
Williamson ether synthesis: This reaction is used in the preparation of symmetrical and unsymmetrical ethers when sodium alkoxides react with alkyl halides . ${S}_{N}2$ reaction takes place in this reaction.
$ { C }_{ 2 }{ H }_{ 5 }ONa\quad +\quad { C }_{ 2 }{ H }_{ 5 }Cl\quad \longrightarrow \quad { C }_{ 2 }{ H }_{ 5 }-O-{ C }_{ 2 }{ H }_{ 5 }\quad +\quad NaCl$
Unsymmetrical ether: These are the ethers in which the two groups on the two sides of oxygen differ from each other. $ R-O-{ R }^{ | }$. For example, ethyl methyl ether.
$ C{ H }_{ 3 }-C{ H }_{ 2 }-O-C{ H }_{ 3 }$

Note: The naming of the unsymmetrical ether is done as follows: The alkyl or the aryl that is attached to the two sides of the oxygen atom has to be named in alphabetical order followed by the functional name 'ether'. For example, ${ C }_{ 6 }{ H }_{ 5 }-O-{ C }_{ 2 }{ H }_{ 5 }$, has to be named as methyl phenyl ether.