(i)

In the first reaction, propanone reacts with NaBH₄ and reduces to a secondary alcohol. In the second reaction, alcohol reacts with conc. H₂SO₄  and an alkene are obtained as a product. The reaction is an example of an elimination reaction. The reaction is as follows:

(ii)
In the first step, benzoic acid reacts with SOCl₂ and a nucleophilic substitution reaction occurs. In the second reaction, acyl chloride reacts H₂, Pd-BaSO₄ and benzaldehyde is obtained as a product. The reaction is known as the Rosenmund reaction. 

The reaction is as follows:

(iii)
In the first reaction, ethanol reacts with PCC(pyridinium chlorochromate) and an ethanal is obtained as a product. In the second reaction, ethanal undergoes an aldol reaction with dil.NaOH and the beta-hydroxy aldehyde is obtained as a product.

The reaction is as follows:

(iv)
In the first reaction, benzene reacts with acetyl chloride in the presence of anhydrous AlCl₃ , and acetophenone is obtained as a product. In the second reaction, acetophenone undergoes a nitration reaction.

A COCH₃ group is an electron-withdrawing group hence, they are meta-directing groups. 

The reactions are as follows:

(v)
In the first reaction, benzaldehyde undergoes an oxidation reaction with a mild oxidizing agent like nitric acid, potassium permanganate, potassium dichromate, etc. , and benzoic acid is obtained as a product.

In the second reaction, benzoic acid reacts with SOCl₂ , and benzoyl chloride is obtained as a product.

In the next step, benzoyl chloride reacts with benzene in the presence of anhydrous. AlCl₃ and a benzophenone is obtained as a product. 

The reactions are as follows:

(vi)
In this reaction, bromobenzene first reacts with Mg in the presence of dry ether, and the Grignard reagent is formed as a product. The Grignard reagent reacts with ethanal in the second step followed by water and secondary alcohol is obtained as a product. 

The reactions are as follows:

(vii)
In the first reaction, when benzaldehyde reacts with ethanal in the presence of a base followed by heat. Then, an aldol condensation reaction occurs, and α,β-Unsaturated aldehydes are obtained as a product. In the next step, the reduction of the double bond takes place by using Ni/H₂ (catalytic hydrogenation), and the desired product is obtained as
3-phenylpropan-1-ol. 

The reactions are as follows:

(viii)

In the first reaction, benzaldehyde reacts with NaCN in the acidic medium then cyanohydrin is obtained as a product. 

In the next step, cyanohydrin reacts with water in the acidic medium and α-hydroxyphenyl acetic acid is obtained as a product. 

The reactions are as follows:

(ix)
In the first step, benzoic acid reacts with nitric acid and sulphuric acid solution, and nitration occurs in the meta position. 

Then in the next step reduction of the COOH group takes place by using LiAlH₄ and m- Nitrobenzyl alcohol is obtained as a product. 

The reactions are as follows: