Esters can be prepared by: 1. Reaction of acid chlorides with alcohols 2. Reaction of carboxylic acids with alcohols in presence of conc. H2SO4 3. Reaction of acid anhydrides with alcohols

To determine which reactions can prepare esters, we will evaluate each statement:

1. Reaction of acid chlorides with alcohols: This is a common method for ester synthesis. Acid chlorides are highly reactive and readily react with alcohols to form esters and hydrogen chloride.

   $$\text{RCOCl} + \text{R'OH} \longrightarrow \text{RCOOR'} + \text{HCl}$$

   This statement is true.

2. Reaction of carboxylic acids with alcohols in presence of conc. $\text{H}_2\text{SO}_4$: This is known as Fischer esterification. Carboxylic acids react with alcohols in the presence of an acid catalyst (like concentrated sulfuric acid) to form esters and water. The sulfuric acid also acts as a dehydrating agent, shifting the equilibrium towards ester formation.

   $$\text{RCOOH} + \text{R'OH} \xrightarrow{\text{conc. H}_2\text{SO}_4} \text{RCOOR'} + \text{H}_2\text{O}$$

   This statement is true.

3. Reaction of acid anhydrides with alcohols: Acid anhydrides are also effective acylating agents. They react with alcohols to form an ester and a carboxylic acid.

   $$(\text{RCO})_2\text{O} + \text{R'OH} \longrightarrow \text{RCOOR'} + \text{RCOOH}$$

   This statement is true.

All three listed reactions are valid methods for the preparation of esters.