Problem 12 - A Complete Resource Book in Chemistry for JEE Main

Question

Diethyl ether is heated with one mole of HI, the products formed are (a) ethyl alcohol and ethyl iodide (b) ethyl iodide only (c) ethyl alcohol only (d) ethyl iodide and ethane

Step-by-Step Solution

Answer

(a) ethyl alcohol and ethyl iodide

Step 1: Understanding the Reaction

Diethyl ether reacts with hydroiodic acid (HI) in a reaction that leads to the cleavage of the ether (R-O-R') bond. Once the ether bond is cleaved, it forms two molecules capable of further reaction with HI.

Step 2: Analyzing the Cleavage Products

When the ether bond in diethyl ether is cleaved, it forms ethanol (C2H5OH) and ethyl iodide (C2H5I). Here, one of the ethyl groups bonds with an iodine ion and the other forms ethanol.

Step 3: Determining the Final Products

The HI will react with the ethanol formed (if excess HI is present) to form additional ethyl iodide and water, but given one mole of HI, the major initial products will still be ethyl alcohol and ethyl iodide as formed directly from ether cleavage.

Key Concepts

Diethyl Ether

Diethyl ether, often simply called "ether," is a volatile and highly flammable organic compound. Ether is characterized by the ether bond, represented chemically as R-O-R', where R and R' are alkyl groups. In the case of diethyl ether, both R and R' are ethyl groups ( C_2H_5). This compound is not only used in laboratory settings as a solvent due to its relatively low reactivity but also has historical significance as one of the first anesthetics used in surgeries. However, when subjected to certain reagents like hydroiodic acid (HI), diethyl ether can undergo cleavage, breaking the ether bond and forming new products.

Hydroiodic Acid

Hydroiodic acid, abbreviated as HI, is a strong acid and a source of the iodide ion (I^-). It is one of the strongest acids known and is highly corrosive. When HI is introduced to diethyl ether, it initiates a chemical reaction called ether cleavage. In this reaction, HI serves a dual role: acting as both an acid and a nucleophile. It donates a proton (H^+) and provides iodide ions (I^-) that attach to the carbon atom of the ether after cleavage. The reaction efficiently breaks the R-O-R' bond in diethyl ether, resulting in the formation of two different products.

Ethyl Iodide

Ethyl iodide, also known as iodoethane, is an organoiodine compound with the formula C_2H_5I. In the context of ether cleavage, ethyl iodide forms when one of the ethyl groups from diethyl ether bonds with an iodide ion (I^-). This occurs after the ether bond is broken by hydroiodic acid. Ethyl iodide is a useful compound in various chemical syntheses. It serves as an alkylating agent, meaning it can add an ethyl group (C_2H_5-) to other molecules in chemical reactions. Its formation in ether cleavage is a classic example of how relatively non-reactive ethers can be transformed into more reactive compounds.

Ethanol Formation

Ethanol, commonly known as alcohol, is a simple two-carbon alcohol with the formula C_2H_5OH. It is one of the cleaved products when diethyl ether reacts with hydroiodic acid. During this reaction, the O-H bond forms in one of the separated ethyl groups, producing ethanol. Ethanol has a wide range of uses, from being a fuel and industrial solvent to serving in beverages and as an antiseptic. In the reaction with HI, if more hydroiodic acid were available in excess, ethanol could undergo further reaction to form more ethyl iodide and water. However, with limited HI, ethanol remains as one of the primary products.