Question

What is the action of the following reagents on ethanol?
a.) Lucas reagent
b.) Phosphorus pentachloride
c.) Red phosphorus and bromine
d.) Acidified potassium dichromate.

Answer 1

Hint: Ethanol is also called ethyl alcohol. The functional group in the ethanol is alcohol. There are different reagents or chemicals are there to find the alcohol functional group. The molecular formula of ethyl alcohol is \[{{C}_{2}}{{H}_{5}}OH\].

Complete step by step solution:
In the question it is given that the action of Lucas reagent, Phosphorus pentachloride, Red phosphorus and bromine, and Acidified potassium dichromate on ethanol.
A. Lucas reagent: An aqueous solution of strong hydrochloric acid (\[HCl\]) and zinc chloride (\[ZnC{{l}_{2}}\]) is called Lucas reagent.
\[C{{H}_{3}}CH{}_{2}OH+HCl\xrightarrow{ZnC{{l}_{2}}}C{{H}_{3}}CH{}_{2}Cl+{{H}_{2}}O\]
Ethanol reacts with Lucas reagent and forms ethyl chloride and water.

B. Phosphorus pentachloride: The molecular formula of Phosphorus pentachloride is \[PC{{l}_{5}}\].
\[C{{H}_{3}}CH{}_{2}OH+PC{{l}_{5}}\xrightarrow{{}}C{{H}_{3}}CH{}_{2}Cl+HCl+POC{{l}_{3}}\]
Ethanol reacts with Phosphorus pentachloride and forms ethyl chloride, hydrochloric acid and phosphorous oxychloride.

C. Red phosphorus and bromine: Red phosphorus and bromine react together and form phosphorus tribromide.
\[\begin{align}
  & 2P+3B{{r}_{2}}\to 2PB{{r}_{3}} \\
 & 3C{{H}_{3}}CH{}_{2}OH+PB{{r}_{3}}\xrightarrow{{}}3C{{H}_{3}}CH{}_{2}Br+{{H}_{3}}P{{O}_{3}} \\
\end{align}\]
Ethanol reacts with phosphorus tribromide and forms ethyl bromide and phosphorus acid.

D. Acidified potassium dichromate. The molecular formula of potassium dichromate is \[{{K}_{2}}C{{r}_{2}}{{O}_{7}}\].
\[C{{H}_{3}}CH{}_{2}OH+{{K}_{2}}C{{r}_{2}}{{O}_{7}}\xrightarrow{dil.{{H}_{2}}S{{O}_{4}}}C{{H}_{3}}CHO\xrightarrow{O}C{{H}_{3}}COOH\]
Ethanol reacts with acidified potassium dichromate and forms acetaldehyde and further it undergoes oxidation and forms acetic acid.

Note: All the given reagents are useful to find the functional group of alcohols with various results. With Lucas reagent and Phosphorous pentachloride ethyl alcohol gives ethyl chloride. With Red phosphorus and bromine, ethanol gives ethyl bromide. Acidified potassium dichromate ethyl alcohol gives acetaldehyde and acetic acid.