Question

Synthesize pentane from 2,3 -dibromopentane using any inorganic reagents.

Short answer

To synthesize pentane from 2,3-dibromopentane, perform a dehalogenation reaction by applying zinc metal (Zn) as the inorganic reducing agent. The balanced chemical equation for this reaction is \(2 \, BrCH_2CHBrCH_2CH_2CH_3 + 2 \, Zn \rightarrow 2 \, CH_3CH_2CH_2CH_2CH_3 + 2 \, ZnBr_2\), where the final product is pentane (CH3CH2CH2CH2CH3), formed by the removal of the two bromine atoms from 2,3-dibromopentane.

Step-by-step solution

Write the given compound and the reagent

Write the structure of 2,3-dibromopentane, which is BrCH2CHBrCH2CH2CH3. Write the structure of the reducing agent, Zn.

Identify the reaction mechanism

The mechanism of this dehalogenation reaction involves transferring two electrons from zinc metal to the carbon-bromine bonds, which leads to the loss of bromine atoms and the formation of a single bond between the two carbons. This results in the formation of pentane.

Write the balanced chemical equation

Write the balanced chemical equation for the reaction of 2,3-dibromopentane with Zn: \(2 \, BrCH_2CHBrCH_2CH_2CH_3 + 2 \, Zn \rightarrow 2 \, CH_3CH_2CH_2CH_2CH_3 + 2 \, ZnBr_2\)

Describe the final product

The final product of this reaction is pentane (CH3CH2CH2CH2CH3) which is obtained by the removal of the two bromine atoms from 2,3-dibromopentane using zinc metal as an inorganic reagent.

Key concepts

Dehalogenation Reaction

Dehalogenation reactions are a subset of organic reactions where two halogen atoms are removed from an organic molecule. In the context of synthesizing pentane from 2,3-dibromopentane, dehalogenation specifically refers to the elimination of bromine atoms.

Dehalogenation can occur through various mechanisms, but a common method involves using a metal such as zinc, which acts as a reducing agent. The metal donates electrons to the carbon-halogen bonds, cleaving them and resulting in the formation of the corresponding alkane and a metal halide.

One significant aspect of dehalogenation reactions is their use in simplifying complex organic molecules. They are crucial in synthetic organic chemistry for the preparation of desired hydrocarbon structures from more complex starting materials.

2,3-Dibromopentane

2,3-Dibromopentane serves as the starting material in the synthesis of pentane in this exercise. Its structure consists of a five-carbon chain with bromine atoms attached to the second and third carbon atoms, as indicated by the name 'dibromopentane'.

The presence of two bromine atoms makes it an ideal candidate for dehalogenation, as zinc metal can effectively remove both atoms to yield the desired product, pentane. The molecular structure of 2,3-dibromopentane is important in understanding the reaction mechanism, as the position of the bromine atoms influences the outcome of the reaction.

Understanding the structure of compounds like 2,3-dibromopentane is critical when predicting the products of chemical reactions and planning synthetic routes in organic chemistry.

Reaction Mechanism

The reaction mechanism describes the step-by-step sequence of events at the molecular level that leads to a chemical reaction. In the case of dehalogenation of 2,3-dibromopentane to synthesize pentane, the mechanism involves electron transfer.

Zinc, the metal used in this reaction, is a reducing agent that provides electrons to the carbon-bromine bonds. This electron transfer weakens the bonds, ultimately breaking them and causing the bromine atoms to leave as zinc bromide (ZnBr2). The remaining carbon atoms where the bromine atoms were attached now form a single bond with each other, creating pentane.

This mechanism can be visualized as a step in which the electrons from zinc push out the bromine atoms, resulting in a simpler hydrocarbon without halogen substituents. Understanding this mechanism is essential for predicting the outcomes of reactions and manipulating conditions for the desired results.

Chemical Equation

The chemical equation provides a concise representation of a chemical reaction using symbols and formulas to convey the substances involved in the reaction and their stoichiometry. In the synthesis of pentane from 2,3-dibromopentane, the balanced chemical equation is:

\[2 \, BrCH_2CHBrCH_2CH_2CH_3 + 2 \, Zn \rightarrow 2 \, CH_3CH_2CH_2CH_2CH_3 + 2 \, ZnBr_2\]

This equation shows that two molecules of 2,3-dibromopentane react with two atoms of zinc to produce two molecules of pentane and two molecules of zinc bromide as a byproduct. The stoichiometry - the '2' before each compound - indicates the relative amounts of reactants and products involved. Chemical equations are fundamental to understanding chemical reactions, as they lay out the reactants, products, and quantities required for the reaction to proceed completely.