Question

A commonly used free-radical initiator is AIBN (azobisiso-butyronitrile). What are the products of its decomposition in an inert solvent?

Short answer

The products of AIBN decomposition in an inert solvent are dinitrogen (N2) gas and two isobutyronitrile free radicals, which can be represented as: AIBN -> N2 + 2 (·CH2C(CH3)2CN). The inert solvent does not react with the free radicals generated.

Step-by-step solution

Identify the structure of AIBN

AIBN, or azobisisobutyronitrile, has the chemical formula: C8H12N4. Its structure consists of two isobutyronitrile groups connected by an azo group (-N=N-). Each isobutyronitrile group contains a -C(CH3)2-CN segment. The azo group is responsible for its properties as a free-radical initiator.

Decomposition of AIBN

When AIBN is heated or exposed to UV light, the azo group (-N=N-) undergoes cleavage or bond dissociation, generating two nitrogen atoms (N2) and two isobutyronitrile free radicals. The process can be represented as the following equation: AIBN -> N2 + 2 (·CH2C(CH3)2CN) In this reaction, the two nitrogen atoms combine to form dinitrogen gas (N2), which is a major byproduct. Meanwhile, the remaining two isobutyronitrile groups become free radicals. Free radicals are highly reactive, as they possess unpaired electrons.

Products formed in an inert solvent

Since the decomposition of AIBN takes place in an inert solvent, this means that the solvent will not react with the free radicals generated. Thus, the products of AIBN decomposition in an inert solvent will be dinitrogen (N2) gas and two isobutyronitrile free radicals. These free radicals may further react with other compounds in the reaction system if they are present, like in polymerization reactions. To summarize, the products of AIBN decomposition in an inert solvent are: 1. Dinitrogen (N2) gas 2. Two isobutyronitrile free radicals

Key concepts

Free-Radical Initiator

A free-radical initiator is a crucial component in many chemical reactions, especially in polymerization processes. It is a compound that can easily decompose to produce radicals. These radicals are species with unpaired electrons, which are highly reactive. When a free-radical initiator like AIBN is used, it begins the process of breaking chemical bonds. Once initiated, a chain reaction occurs, forming polymers or other significant molecular structures.
The role of a free-radical initiator is to kickstart the creation of radicals which then participate in further reactions. This characteristic makes initiators indispensable for various industrial and experimental chemical processes. Without initiators, many reactions would not proceed effectively at mild conditions, requiring harsh environments instead.

Azobisisobutyronitrile

Azobisisobutyronitrile, or AIBN, is one of the most common free-radical initiators. It is especially valued in the polymer chemistry field. AIBN is known for its chemical formula: C8H12N4. Its structure comprises two isobutyronitrile groups connected by an azo group (-N=N-).

• The -N=N- or azo group is the key to its reactivity. This bond is relatively weak and can cleave easily when energy is applied.
• When AIBN decomposes, it splits into two isobutyronitrile free radicals and nitrogen gas (N2).

This decomposition is helpful in generating radicals without the need for harsh conditions. AIBN's controlled decomposition makes it ideal for many synthetic applications.

Inert Solvent

An inert solvent is a solvent that does not undergo chemical reactions with either the solute or any reagents in the process. When AIBN decomposes, using an inert solvent is crucial to isolate the desired reactions.
Inert solvents, such as hexane or toluene, provide an unreactive environment that allows free radicals to form and engage in the intended reaction. If the solvent reacts with the free radicals, unwanted byproducts could be created.
Therefore, by using an inert solvent, chemists can ensure that the free radicals produced from AIBN decomposition primarily participate in the desired chemical pathways, such as polymerization.

Chemical Structure

Understanding the chemical structure of a compound like AIBN is critical in predicting its behavior and interactions. AIBN's chemical structure is composed of distinct elements:

• The central azo group (-N=N-) is the reactive site that allows for free radical formation.
• The two isobutyronitrile moieties impart stability to the radical majority upon decomposition.

The structural arrangement of AIBN facilitates its easy breakdown into free radicals and dinitrogen gas. Each component plays a specific role in the compound's overall reactivity. This knowledge of structure-function relationships is vital for designing experiments and anticipating reaction outcomes.

Dinitrogen Gas

During the decomposition of AIBN, one of the primary products is dinitrogen gas, or simply nitrogen gas (N2). This gas is odorless, colorless, and inert.
Formation of N2 in this context is beneficial as it removes excess energy from the system. The generation of nitrogen gas is an indicator of successful AIBN decomposition, as it accounts for the energy lost when the azo group is split.
One appealing aspect of N2 production in chemical reactions is its non-reactivity. Since it is inert, it does not interfere with the ongoing reactions once formed, thus allowing other radicals to engage without disruption.