The compound formed when alcoholic solution of ethylene dibromide is heated with granulated zinc is (a) ethene (b) ethyne (c) ethane (d) bromoethane.

Ethylene dibromide, known scientifically as 1,2-dibromoethane, is a colorless, heavy liquid halogenated compound. It contains two bromine atoms attached to a two-carbon chain, hence the name 'dibromide'. Widely used in the past as a pesticide and a fumigant, it's now often encountered in organic chemistry, especially in reactions involving halogenated compounds.

When heated with a reductant like granulated zinc, ethylene dibromide undergoes a dehydrohalogenation reaction. The 'dehydro' part of the term refers to the removal of hydrogen, while 'halogenation' pertains to the removal of a halogen—in this case, bromine. As students study this reaction, it's important to recognize that the presence of the halogens in the structure makes this organic molecule highly reactive and a good candidate for further chemical transformations.

Granulated zinc is essentially zinc metal that has been processed into small granules. In organic chemistry, it operates as a powerful reducing agent owing to its ability to donate electrons to other substances during a chemical reaction. The surface area of granulated zinc is quite high due to its particulate form, accelerating reactions that require electron transfer.

In the dehydrohalogenation of ethylene dibromide, zinc effectively removes the bromine atoms by accepting their electrons (reduction), forming zinc bromide as a byproduct. The concept is crucial because it showcases how different forms of a metal can influence the rate and success of a chemical reaction; finer granules provide a greater area for the reaction to occur, resulting in faster and more complete reactions.

Organic chemistry is the branch of chemistry that deals with carbon-containing compounds and their reactions. It's a vast field that covers the structure, properties, composition, reactions, and synthesis of organic molecules. Understanding the behavior of different organic compounds and their reactivity patterns is fundamental to mastering organic chemistry.

A pivotal aspect of organic chemistry lies in the functional groups that define the chemical behavior of molecules. Halides, like those in ethylene dibromide, represent a major category of such functional groups. Reactions like dehydrohalogenation are key to transforming molecules and crafting new compounds with desirable properties. These reactions are among the core topics that students must grasp to build a robust foundation in organic chemistry.

Alkene synthesis is the process of creating alkenes, which are hydrocarbons containing at least one carbon-carbon double bond. Alkenes are significant in both natural processes and industrial applications due to their reactivity and as intermediates in the syntheses of more complex molecules. There are several methods to synthesize alkenes, and one of the common techniques is dehydrohalogenation—particularly useful for generating alkenes from alkyl halides like ethylene dibromide.

During dehydrohalogenation, an alkane with halogen substituents, upon treatment with a reagent such as granulated zinc, loses halogen atoms along with adjacent hydrogen atoms. This elimination results in the formation of a double bond—an alkene. This basic concept is central to organic chemistry and is a powerful tool for students to understand how simple reactions can lead to the creation of diverse molecules with varying properties and functions.