What are Phenols?
In this segment, we will understand phenols’ preparation process using haloarenes, benzene, cumene, and sulphonic acid. As the world of organic chemistry moves on, you must have come across the term ‘phenol’ multiple times by now, so before we dive deep into what goes into the preparation of phenols, let’s quickly understand phenols and the study that revolves around carrying out various methods and reactions.
Types of Preparation of Phenols
Now coming to the preparation and synthesis of phenol, there are multiple ways of obtaining the desired result. In the past, coal tar was one of the primary ingredients used in the synthesis of phenols. But, nowadays, advanced division of benzene-led preparations has taken over, most of which are explained below:
Preparation using haloarenes
Let’s take chlorobenzene as an example of haloarene in this case. The infusion of sodium hydroxide with chlorobenzene at 320 atm and 623K produces sodium phenoxide, which is further used and put through the process of acidification to obtain phenol at the end.
Preparation using benzene sulphonic acid
Benzene is infused in a reaction with oleum that results in the production of benzene sulphonic acid. At a very high temperature, benzene sulphonic acid is used with sodium hydroxide to ensure sodium phenoxide formation. And as we know, acidification of sodium hydroxide results in phenol.
Preparation using diazonium salts
Diazonium salts are obtained when nitrous acid (NaNO2 + HCI) ranging from 273 – 278K is treated in the presence of an aromatic primary amine. The diazonium salts produced are very much reactive as per their organic nature.
Preparations using cumene
Benzene, along with propylene, is put through Friedel-Crafts alkylation, which creates cumene – an organic compound. After cumene is oxidised, the resultant form is cumene hydroperoxide. After obtaining cumene hydroperoxide, it is treated with dilute acids, which results in phenol formation. Given multiple compounds are being produced, an extra step of purification is added in this preparation to obtain phenols.
Preparation of Phenols in Class 12
The chapter Alcohol, Phenols, and Ethers holds a weightage of 6 marks in total for Class 12. It includes the topic of preparation of phenols, which is considered the base of the chapter; this topic alone holds a weightage of 2-3 marks.Illustrated Examples
Following are the three illustrated examples of the different classifications of preparation of phenols:
Primary alcohol
Secondary Alcohol
FAQs regarding Uses of Phenols
Q. What kind of substance reacts with cumene to produce phenol?
A. Oxygen
Q. Why are phenols less soluble in water?
A. Phenols in their entirety are made from a non-polar group, so such a group’s capacity to form bonds with hydrogen at a molecular level with water is very limited.
Q. What’s the reason behind phenols being acidic in nature?
A. Any substance, when put in contact with water, produces a hydrogen ion, which is termed an acid. And phenol loses a hydrogen ion to form hydrogen peroxide – which makes it acidic.
Q. What’s another name for phenols?
A. Phenols are also known as carbolic acids.
Q. What’s the common driving factor for the advanced synthesis of phenols?
A. The introduction of benzene-led preparation brought in a change in the synthesis of phenols.
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