Question

Ethyl alcohol on heating with conc. ${{H}_{2}}S{{O}_{4}}$ gives
(A) $C{{H}_{3}}COO{{C}_{2}}{{H}_{5}}$
(B) ${{C}_{2}}{{H}_{6}}$
(C) ${{C}_{2}}{{H}_{4}}$
(D) ${{C}_{2}}{{H}_{2}}$

Answer 1

Hint: Dehydration occurs as a result of the reaction between ethanol and concentrated ${{H}_{2}}S{{O}_{4}}$. Dehydration is the process of removing water molecules to create alkenes. Sulphuric acid is a dehydrating agent. It is an elimination reaction.

Complete Step by Step Answer:
Alcohol dehydrates when an acid is present because the acid provides a proton that will attract oxygen from the alcohol to it, which will then combine to form an oxonium ion. The water molecule then gets released, forming a carbocation. Finally, the proton is released from the carbocation and, thus, an alkene is formed.

Hence, ethyl alcohol on heating with conc. ${{H}_{2}}S{{O}_{4}}$ gives ethene (${{C}_{2}}{{H}_{4}}$).
Correct Option: (C) ${{C}_{2}}{{H}_{4}}$.

Additional Information: The alcohol present in alcoholic beverages is ethyl alcohol. It is a combustible, colourless, mildly poisonous chemical molecule. Drugs, plastics, lacquers, polishes, plasticizers, and cosmetics are all made with ethyl alcohol. It is used in medicine as an antidote for ethylene glycol or methanol overdose. Ethene can be used to form polythene by the polymerization reaction. It can also be used to ripen the fruits artificially.

Note: The other reagent that can be used for the dehydration of alcohols is phosphoric acid (${{H}_{3}}P{{O}_{4}}$). The mechanism of dehydration of alcohol proceeds through the formation of carbocation. As we know, the tertiary carbocation is more stable than the primary carbocation. So, the tertiary alcohols can react very quickly under mild conditions and give alkenes, whereas primary alcohols require high temperatures to be converted into alkenes.