Question:

Consider the above reaction and identify the missing reagent/chemical.

Updated On: Nov 13, 2025

DIBAL-H
B₂H₆
Red Phosphorus
CaO

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The Correct Option is D

Solution and Explanation

To solve this problem, we need to identify the missing reagent in the given chemical reaction. The reaction involves \(\text{CH}_3\text{CH}_2\text{COO}^- \text{Na}^+\) leading to \(\text{CH}_3\text{CH}_3\), which is a decarboxylation process.

Let’s analyze the reaction:

The reaction involves the removal of a carboxyl group (\(-\text{COO}^-\text{Na}^+\)) and the formation of an alkane (\(\text{CH}_3\text{CH}_3\)).
The transformation from a carboxylate salt to an alkane typically requires a decarboxylation process.
Calcium oxide (CaO) is commonly used in the soda lime method for decarboxylation reactions where a carboxylate salt is heated with solid sodium hydroxide and calcium oxide, resulting in the formation of an alkane.

Now, let’s evaluate the options:

DIBAL-H: This is a reducing agent, commonly used for reducing esters to aldehydes and not suitable here.
B₂H₆: This is used for hydroboration reactions and doesn't fit in the decarboxylation context.
Red Phosphorus: Red phosphorus is used in reactions like the preparation of phosphine or reduction reactions with iodine, which is not applicable here.
CaO: Correct choice as it is used in decarboxylation of carboxylic acids to alkanes.

Therefore, the missing reagent in the reaction is CaO, which facilitates the conversion through the decarboxylation process.

Conclusion: The correct answer is CaO.

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Concepts Used:

Alkanes

In organic chemistry, an alkane, or paraffin (a historical trivial name that also has other meanings), is an acyclic saturated hydrocarbon. In other words, an alkane consists of hydrogen and carbon atoms arranged in a tree structure in which all the carbon-carbon bonds are single. Alkanes have the general chemical formula CnH2n+2. The alkanes range in complexity from the simplest case of methane (CH4), where n = 1 (sometimes called the parent molecule), to arbitrarily large and complex molecules, like pentacontane (C50H102) or 6-ethyl-2-methyl-5-(1-methylethyl) octane, an isomer of tetradecane (C14H30).

Alkane as saturated hydrocarbons:

Alkanes are a series of compounds that contain carbon and hydrogen atoms with single covalent bonds. These are known as saturated hydrocarbons. This group of compounds consists of carbon and hydrogen atoms with single covalent bonds. Also comprises a homologous series having a molecular formula of CnH2n+2.
Alkanes are the simplest family of hydrocarbons. They contain only carbon and hydrogen. Each carbon atom forms four bonds and each hydrogen atom forms one bond. Chemists use line-angle formulas because they are easier and faster to draw than condensed structural formulas. Structural formulas for alkanes can be written in yet another condensed form.

Properties of Alkanes:

1. The Solubility of Alkanes

Due to very little difference of electronegativity between carbon and hydrogen and covalent nature of C-C bond or C-H bond, alkanes are generally non-polar molecules.As we generally observe, polar molecules are soluble in polar solvents whereas non-polar molecules are soluble in non-polar solvents. Hence, alkanes are hydrophobic in nature that is, alkanes are insoluble in water.

2. The Boiling Point of Alkanes

As the intermolecular Van Der Waals forces increase with the increase of the molecular size or the surface area of the molecule we observe:The straight-chain alkanes are observed to have a higher boiling point in comparison to their structural isomers.

3. The Melting Point of Alkanes

The melting point of alkanes follow the same trend as their boiling point that is, it increases with increase in molecular weight.