Suggest a reagent for the conversion of ethanol to ethanal.

When a Grignard reagent reacts with $(B)$,product $(D)$ is obtained. Reactant $(A)$ of the above reaction is:
$(A)$ $\xrightarrow{PBr_3} (C)$ $\xrightarrow{Mg, \text{ether}} \text{Grignard reagent}$
$(A) \xrightarrow{Na_2Cr_2O_7, H_2SO_4} (B)$
$\text{Grignard reagent} + (B) \to (D) \xrightarrow{H_3O^\oplus} (3,4-\text{dimethylhexan-3-ol})$

Which compounds among the following give a positive iodoform test?

$A$ compound with formula $C_4H_{10}O$ on oxidation gives $C_4H_8O$,which forms an oxime and gives a positive iodoform test. The original compound on reaction with concentrated $H_2SO_4$ gives $C_4H_8$. What is the structure of the compound?

Give the structures of the products you would expect when each of the following alcohols reacts with $(a)$ $HCl - ZnCl_{2}$,$(b)$ $HBr$,and $(c)$ $SOCl_{2}$: $(i)$ $Butan-1-ol$,$(ii)$ $2-Methylbutan-2-ol$.

Consider the above reaction and identify the product $P :$