Alcohol Phenol And Ethers

11.22

There are many ways to this conversion. Two of them are given below:-

(a) In the above conversion, the chlorobenzene is treated with a base such as NaOH, KOH etc. (strong base). The base abstracts the hydrogen from the C-2 position (it can also abstract the hydrogen from the C-6 position, as both are equally acidic) leaving the negative charge at that position.

In the next step Cl^- leaves, leaving behind the positive charge at that carbon. Both the negative charge and positive charge forms a bond resulting Benzyne as the intermediate.

After the formation of the Benzyne intermediate OH^- of the base attacks at the C-1 position and further, the H⁺ attacks to stabilize the negative charge thus resulting in the phenol.

The reaction can start from benzene also. Chlorination of benzene gives Chlorobenzene. When it is further treated with NaOH and H₂O at 350°C it results in the formation of sodium phenoxide which on further treatment H⁺ gives Phenol as the final product.

11.18

The hydroboration-oxidation reaction is a two-step reaction that converts an alkene into a neutral alcohol by the net addition of water across the double bond. The hydrogen and hydroxyl group are added in a syn addition leading to the cis configuration. Hydroboration- oxidation is an anti-Markovnikov reaction, with the hydroxyl group attaching to the less substituted carbon. In first step Addition of Hydroborate group is done and in next step, it is oxidized by hydrogen peroxide.

For example: - When propene undergoes hydroboration-oxidation reaction, then it produces propan-1-ol as product. In this reaction diborane i.e., (BH₃)₂ reacts with propene, which in result generates trialkyl borane as an addition product. Then trialkyl borane is oxidised, by using hydrogen peroxide in the presence of aqueous sodium hydroxide to form alcohol, as final product.

11.15

The structures of all isomeric alcohols of C₅H₁₂O are given below:

Naming is done by the conventional method. The -OH group is attached on the first carbon.

(b) 3-Methylbutan-1-ol

Butane is the longest chain and methyl is the substituent group.

(c) 3-Methylbutan-1-ol

the longest chain is butane and conventional naming method is used.

(d) 2,2-Dimethylpropan-1-ol

Isomer is made by transforming the principal carbon into tertiary type. The longest chain is butane and named accordingly.

(e) Pentan-2-ol

the longest chain is pentane and the numbering is chosen from the minimum position.

Butane is the longest chain, further numbering is done by choosing a minimum position for the

-OH group followed by other substituents.

(g) Pentan-3-ol

Conventional method of naming is used.

(h) 2-Methylbutan-2-ol

Butane is the longest chain and substituents are named accordingly by looking into minimum position.

(f) 3-Methylbutan-2-ol

Butane is the longest chain, further numbering is done by choosing a minimum position for the

-OH group followed by other substituents.

(g) Pentan-3-ol

Conventional method of naming is used.

(h) 2-Methylbutan-2-ol

Butane is the longest chain and substituents are named accordingly by looking into minimum position.

11.14

Butane is the longest chain.

Propane is principle chain and substituents are numbered accordingly.

Hexane is the longest chain. There are three -OH substituents and 2 methyl groups.

-OH of phenol is numbered a 1.

Propane is the principle chain and the alkoxy group is ethyl group.

the longest chain is pentane and substituents are numbered accordingly.

In such cases, cyclo groups are named first, followed by conventional naming methods.

The cyclo group is named first, followed by conventional naming methods.

Cyclo group is named first. Pentane having a double bond is named then with the suffix -OL added to the end.

The longest chain is butane when looked for minimum numbering case.