Question

The major product (X) formed when ethane-1, 2-diol is heated with excess of hydrogen iodide is
A.2-iodoethanol
B.1,2-diiodoethane
C.Iodoethane
D.ethene

Answer 1

The chemical formula for ethane-1,2-diol is ${\left( {C{H_2}OH} \right)_2}$. Ethane-1,2-diol is also called Ethylene glycol, the simplest member of the glycol family of organic compounds.
We know that $HI$ is a source of ${H^ + }$then ethane-1,2-diol react with$HI$(excess) we get $C{H_2}I - C{H_2}I$ since $2I$ on adjacent carbon are unstable under heating. So, if we lose $2I$ we get the result.

Complete answer: Chemical reaction when ethane-1, 2-diol is heated with excess of hydrogen iodide is
${\left( {C{H_2}OH} \right)_2} + \mathop {2HI}\limits_{excess} \xrightarrow{\Delta }C{H_2} = C{H_2} + {I_2}$
In this reaction a major product is $C{H_2} = C{H_2}$.
Where ${C_2}{H_4}$or $C{H_2} = C{H_2}$ is a chemical formula for ethylene. Ethylene is the most produced compound in organic chemistry. Ethylene is also called Ethene. It is the simplest Alkene, is an organic compound containing a $C = C$ double bond.
Hence, the correct option is (D).

Note:
Note that Ethylene is an unsaturated hydrocarbon (also called olefin). Ethane-1,2-diol is also known as Ethylene glycol. It is an organic compound. It is mainly used for two purposes, as a raw material in the manufacture of polyester fibers and for antifreeze formulations. It is an odourless, colourless, sweet-tasting, viscous liquid. Also note that, a glycol is an alcohol with two hydroxyl groups on adjacent carbon atoms (a 1,2-diol). The common name ethylene glycol literally means “the glycol derived from ethylene.