The major product '$P$' formed in the given reaction is:

Which of the following is most reactive towards $S_N2$ reaction?

Arrange the following in order of their leaving group tendency:
$(I) Br^{-}$,$(II) CH_3COO^{-}$,$(III) CH_3CH_2O^{-}$,$(IV) PhO^{-}$

Explain the concept of retention of configuration in a chemical reaction with an example.

The mechanism of $S_{N}1$ reaction is given as:
$R-X$ $\rightarrow R^{\oplus} X^{\ominus}$ $\rightarrow R^{\oplus} | X^{\ominus}$ $\xrightarrow{Y^{\ominus}} R-Y + X^{\ominus}$
(Ion pair) (Solvent separated ion pair)
$A$ student writes general characteristics based on the given mechanism as:
$(a)$ The reaction is favoured by weak nucleophiles
$(b)$ $R^{\oplus}$ would be easily formed if the substituents are bulky
$(c)$ The reaction is accompanied by racemization
$(d)$ The reaction is favoured by non-polar solvents.
Which observations are correct?

Toluene $\xrightarrow[{heat}]{{NBS\,/\,CCl_4}} A$ $\xrightarrow{{CH_3ONa}} B,$
The final product $(B)$ formed in the reaction sequence is: