Question

Which compound can show position isomerism? (A) Butene (B) Allene (C) Propene (D) Isobutene

Short answer

The compound that can show position isomerism is (A) Butene.

Step-by-step solution

Analyse each compound

: Let's analyze each compound and see if they have the potential for position isomerism. (A) Butene (\(C_4H_8\)) is an alkene with a double bond between two carbon atoms. There are two possible position isomers for butene: 1-butene and 2-butene. (B) Allene (\(C_3H_4\)) is an alkene with two double bonds. In this compound, the central carbon atom is attached to two other carbon atoms by double bonds. As there is only one way to arrange this, allene cannot show position isomerism. (C) Propene (\(C_3H_6\)) is an alkene with one double bond between carbon atoms. With only three carbon atoms, there's only one possible position for the double bond (between the first and second carbon), so propene cannot show position isomerism. (D) Isobutene (\(C_4H_8\)) is an alkene with one double bond and a branched structure. There is only one way to arrange the double bond and the branching, so isobutene cannot show position isomerism.

Identify the compound with position isomerism

: Now, we can see that only (A) Butene has different possible positions for the functional group (double bond), and hence it can show position isomerism. So, the answer is (A) Butene.

Key concepts

Position Isomerism

Position isomerism is a type of structural isomerism observed in organic compounds, particularly where there is a variation in the position of the functional group on the parent chain. In simpler terms, it occurs when the basic carbon skeleton of a molecule remains the same but the position of a particular group or substituent changes.

For example, in alkenes, a functional group of interest is the double bond. When the location of this double bond changes along the chain, each variant is called a position isomer. Position isomerism is significant because even though isomers have the same molecular formula, their chemical and physical properties can differ greatly due to the positioning of the functional groups.

Butene

Butene, also known as butylene, is a molecule with the molecular formula \(C_4H_8\) and is a member of the alkene family. Alkenes are hydrocarbons that contain at least one carbon-to-carbon double bond, and the position of this double bond can vary.

There are different isomers of butene, such as 1-butene and 2-butene. In 1-butene, the double bond is located at the end of the molecule, between the first and second carbon atoms. In 2-butene, the double bond shifts one position along the chain, between the second and third carbon atoms. Each isomer exhibits unique properties, and recognizing their structural differences is crucial for understanding their reactivity and functionality in various chemical reactions.

Alkenes

Alkenes are a class of hydrocarbons characterized by the presence of at least one carbon-to-carbon double bond, denoted as \(C=C\). This double bond is the functional group of alkenes, and it is responsible for their unique chemical properties. Alkenes have the general formula \(C_nH_{2n}\), indicating that they have two fewer hydrogen atoms than the corresponding alkanes.

The most essential aspect of alkenes, apart from being unsaturated hydrocarbons, is their ability to undergo addition reactions due to the double bond. These reactions include hydrogenation, halogenation, and others, making alkenes highly reactive and useful in the chemical industry for producing a wide range of products, including plastics, detergents, and pharmaceuticals.