The order of reactivity of the following halides towards $S_{N}1$ reaction is:
$(1) \ (CH_3)_3CBr$
$(2) \ (C_6H_5)_2CHBr$
$(3) \ (C_6H_5)_2C(CH_3)Br$
$(4) \ (CH_3)_2CHBr$
$(5) \ C_2H_5Br$

Match the reactions in List-$I$ with the features of their products in List-$II$ and choose the correct option.
| List-$I$ | List-$II$ |
| :--- | :--- |
| $(P)$ $(-)-1$-Bromo-$2$-ethylpentane $\xrightarrow{aq. NaOH, S_N2}$ | $(1)$ Inversion of configuration |
| $(Q)$ $(-)-2$-Bromopentane $\xrightarrow{aq. NaOH, S_N2}$ | $(2)$ Retention of configuration |
| $(R)$ $(-)-3$-Bromo-$3$-methylhexane $\xrightarrow{aq. NaOH, S_N1}$ | $(3)$ Mixture of enantiomers |
| $(S)$ $(3S, 5S)-5$-bromo-$3$-methylheptane $\xrightarrow{aq. NaOH, S_N1}$ | $(4)$ Mixture of structural isomers |
| | $(5)$ Mixture of diastereomers |

The compound which forms acetaldehyde when heated with dilute $NaOH$ is

Which one of the following is the best catalyst for the reaction shown below?
$CH_3(CH_2)_8CH_2Br \xrightarrow[benzene]{KCN} CH_3(CH_2)_8CH_2CN$

What is the major product formed when $3$-phenylpropene reacts with $HBr$?

The relative reactivity of the following halides toward $S_{N}2$ reaction follows the order:
$(P)$ $CH_2=CH-Cl$
$(Q)$ $CH_3-CH_2-Cl$
$(R)$ $CH_3-O-CH_2-CH_2-Cl$
$(S)$ $C_6H_5-CH_2-Cl$