Account for the following:

(a) Haloalkanes react with AgCN to form isocyanide as main product.

(b) Allyl chloride shows high reactivity towards $\mathrm{S}_{\mathrm{N}} 1$ reaction.

(c) Haloarenes are extremely less reactive towards nucleophilic substitution reactions.

The rate constant of a reaction quadruples when the temperature changes from 300 K to 320 K . Calculate the activation energy for this reaction. $\left[\log 2=0.30, \log 4=0.60,2.303 \mathrm{R}=19.15 \mathrm{~J} \mathrm{~K}^{-1} \mathrm{~mol}^{-1}\right]$

A compound ' X ' with molecular formula $\mathrm{C}_3 \mathrm{H}_9 \mathrm{~N}$ reacts with $\mathrm{C}_6 \mathrm{H}_5 \mathrm{SO}_2 \mathrm{Cl}$ to give a solid, insoluble in alkali. Identify ' X ' and give the IUPAC name of the product. Write the reaction involved.

The oxidation number of the central atom in a complex is defined as the charge it would carry if all the ligands are removed along with the electron pairs that are shared with the central atom. Similarly the charge on the complex is the sum of the charges of the constituent parts i.e. the sum of the charges on the central metal ion and its surrounding ligands. Based on this, the complex is called neutral if the sum of the charges of the constituents is equal to zero. However, for an anion or cationic complex, the sum of the charges of the constituents is equal to the charge on the coordination sphere.

Based on the above information, answer the following questions:

(a) Define ambidentate ligand with an example.

(b) What type of isomerism is shown by

$$\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{Cl}\right] \mathrm{SO}_4 \text { and }\left[\mathrm{Co}\left(\mathrm{NH}_3\right)_5 \mathrm{SO}_4\right] \mathrm{Cl} \text { ? }$$

(c) Define chelate effect. How it affects the stability of complex?

OR

(c) Find the coordination number and oxidation state of chromium in $\mathrm{Na}_3\left[\mathrm{Cr}\left(\mathrm{C}_2 \mathrm{O}_4\right)_3\right]$.