Which of the following is incorrect?

The correct answer is option 2.

Let us look at each of these reaction

1. Dehydration of alcohol:

When alcohol reacts with protic acids, it tends to lose a molecule of water in order to form alkenes. These reactions are generally known as dehydration of alcohols. It is a basic example of an elimination reaction. The rates differ for the primary, secondary, and tertiary alcohols. The carbonation is very much stable in the case of tertiary alcohols; hence, the rate of dehydration is highest for tertiary alcohols as compared to secondary and primary alcohols. So, the given reaction is correct.

2. Reaction of tertiary alcohol with copper:

Tertiary alcohol reacts with copper metal at high temperature as 573 K, they undergo dehydration. SO the provided reaction is incorrect. The correct reaction will be :

3. Reaction of secondary alcohol with phosphoric acid:

Secondary alcohols reacts with 85% \(H_3PO_4\) at high temperature to give an alkene and water. So, he given reaction is correct.

4. Dehydrogenation of alcohol using copper:

When the vapours of a primary or a secondary alcohol are passed over heated copper at 573K, dehydrogenation takes place and an aldehyde or a ketone is formed. In case of tertiary alcohols, it goes dehydration. So, he given reaction is correct.