Why esterification is carried in presence of little acid?

What is esterification reaction?

Why acylation of amine is carried out inpresence of pyridine?

What happens when: Nitro benzene reacts with scrap iron in press-ence of little HCI.

What happens when: 1-methyl cyclo hexanol is dehydrated in presence of acid catalyst.

How is the presence of SO_2 detected?

An organic compound (A) on treatment with acetic acid in presence of sulphuric acid pro-duces as ester(B). (A) on mild oxidation gives (C). (C) with 50% KOH followed by acidifica-tion with dill HCI generates (A) and (D). (D) with PCI_5 followed by reaction with ammonia give (E). (E) on dehydration produces HCN-acid. Identify A to E.

What happens when: benzene is treated with propene in presence of phosphoric acid.

How is respiration carried out in annelids?