Question

An organic compound "X" - on treatment with PDC in \[C{H_2}C{l_2}\] gives compound ''Y". Compound -, Y reacts with \[{l_2}\] an alkali to form a yellow precipitate. The compound "X" is
(A) acetone
(B) ethanal
(C) ethanol
(D) acetic acid.

Answer 1

Hint: Reagent can be a substance or mixture of compounds which are used in chemical analysis or reactions. When a reagent is added to a system it causes chemical reactions. For a particular reaction, a particular reagent gets consumed in the process of the chemical reaction.

Complete step by step answer:
We know that reaction with PDC in \[C{H_2}C{l_2}\] oxidation occurs. So, it is an oxidizing reagent. This reagent is used to oxidize alcohol into aldehyde or ketone. In the presence of \[{l_2}\] an alkali, an iodoform reaction takes place.
According to the options, in the case of ethanol on treatment with PDC in \[C{H_2}C{l_2}\] gives ethanal which is compound Y. compound Y reacts with \[{l_2}\] an alkali to form a yellow precipitate.
The overall reaction is,
  $C{H_3}C{H_2}OH\xrightarrow{{PDC\,iN\,C{H_2}C{l_2}}}C{H_3}CHO\xrightarrow{{\dfrac{{{l_2}}}{{NaOH}}}}CH{I_3} + HCOOH$

So, the correct option is C.

Additional information:
PCC is a yellow-orange colored salt used as a reagent primarily for the oxidation of alcohols to form carbonyls like aldehyde or ketones. This reagent is quite selective towards the oxidation of particularly alcohol to carbonyls, as some reagents are less selective.
PCC is a Pyridinium chlorochromate. From this, we know that there is a pyridine molecule in it having the chemical formula \[{C_5}{H_5}N\]. But as the structure will have other ions as well, pyridine will act as a pyridinium ion having chemical formula \[{C_5}{H_5}{N^ + }H\].
Next, we can see from the PCC chemical name that a chlorochromate ion having chemical formula \[[Cr{O_3}C{l^ - }]\] is also present. So, on combining these two structures, we get the desirable structure of PCC. Chromate ion is surrounded by the chlorine atom and three oxygen atoms but out of three, the valency of one oxygen atom is not complete.

Note: One might get confused between the charges seen in the structures in options. Pyridinium \[({C_5}{H_5}{N^ + }H)\] and anilinium \[({C_6}{H_5}NH_3^ + )\] ions have similar structures but are two different compounds related to benzene.