Question

Dry distillation of calcium benzoate will give (a) acetophenone (b) benzophenone (c) benzaldehyde (d) 2-phenyl ethanol

Short answer

Answer: (c) Benzaldehyde

Step-by-step solution

1. Identify the reactant

Calcium benzoate is the reactant in this exercise. Its molecular formula is Ca(C6H5COO)2.

2. Write the dry distillation reaction for calcium benzoate

During dry distillation, calcium benzoate is heated in the absence of air, leading to the formation of a product. The general reaction is: Ca(C6H5COO)2 -> Product + Calcium Carbonate (CaCO3)

3. Identify the product formed

When calcium benzoate undergoes dry distillation, the benzoate group is lost, and the remaining part of the molecule rearranges to form the product. In this case, calcium benzoate will form benzaldehyde (C6H5CHO) along with calcium carbonate (CaCO3): Ca(C6H5COO)2 -> C6H5CHO + CaCO3 Comparing the formed product with the given options, we can see that the correct answer is (c) benzaldehyde.

Key concepts

Calcium Benzoate

Calcium benzoate is a compound used in this chemical process, primarily as a preservative in the food industry. Its molecular formula is \( \text{Ca(C}_6\text{H}_5\text{COO)}_2 \), which tells us that it consists of calcium ions and benzoate ions. These ions bond together to create a stable solid used in industrial applications.

In organic chemistry, calcium benzoate plays a crucial role due to its ability to form other organic compounds when heated. Understanding the structure is important because it gives insight into how it might react under certain conditions. Each benzoate ion contains a benzene ring attached to a carboxylate group, which is significant when we look at the potential products of its reactions.

Dry Distillation

Dry distillation is a process involving the heating of solid materials to break them down into simpler substances without the presence of a liquid or oxygen. This is different from regular distillation which typically uses liquids and involves boiling and condensing actions. In our example, calcium benzoate is subjected to dry distillation.

During this process, the compound decomposes while the heat causes changes in its chemical structure, leading to the formation of new products. In essence, dry distillation helps separate components of a compound based on how they respond to high thermal energy. It's a method commonly utilized in organic chemistry for creating desired products, particularly useful for turning complex molecules into simpler ones.

Benzaldehyde

Benzaldehyde, with the chemical formula \( \text{C}_6\text{H}_5\text{CHO} \), is a simple aromatic aldehyde. It's one of the key components that is derived from the dry distillation of calcium benzoate. Benzaldehyde is well known for its pleasant almond scent and is used in flavorings and perfumes.

In the context of this chemical reaction, understanding how benzaldehyde is formed is essential. The process involves breaking apart the calcium benzoate, leading to a reconfiguration of its atoms. The formal group of benzaldehyde is vital in many synthesis reactions in organic chemistry because it can act as a precursor to various complex molecules.

Reaction Mechanism

The reaction mechanism describes the sequential steps and transformations that occur during a chemical reaction. In the case of dry distillation of calcium benzoate, the mechanism involves breaking and forming chemical bonds.

Initially, the high temperatures cause the benzoate ions in calcium benzoate to decouple from the calcium ions. This is followed by a rearrangement of atoms within the benzoate ions which involves breaking the C-O bond and forming a new C-H bond, resulting in the creation of benzaldehyde and calcium carbonate as the by-product.

• This breaking and rearranging of bonds define the pathway by which the reaction proceeds, shedding light on the transformation from reactants to products.
• Understanding this process is critical for chemists as it helps in predicting the outcomes and by-products of similar reactions.