Despite the limitations of radical chlorination of alkanes,...

Name: Problem 27, Chapter 6: Organic chemistry with biological applications
Uploaded: 2022-04-08T20:24:58-08:00
Duration: 1 min 13 s
Channel: Crystal Wang
Description: Despite the limitations of radical chlorination of alkanes, the reaction is still useful for synthesizing certain halogenated compounds. For which of the following compounds does radical chlorination give a single monochloro product?

Despite the limitations of radical chlorination of alkanes, the reaction is still useful for synthesizing certain halogenated compounds. For which of the following compounds does radical chlorination give a single monochloro product?

Key Concepts

Monochlorination

Monochlorination is the process of substituting one hydrogen atom in an alkane with a chlorine atom, resulting in a single chlorinated product. This concept is fundamental when designing synthetic routes that require a unique product, and it becomes especially relevant in symmetric molecules where only one possible monochloro derivative is formed.

Molecular Symmetry

Molecular symmetry refers to the uniform arrangement of atoms in a molecule such that all substituents (e.g., hydrogen atoms) are in equivalent positions. In the context of radical chlorination, if a molecule has a high degree of symmetry, every hydrogen atom is chemically equivalent, ensuring that chlorination at any site yields the same product. This concept is crucial for understanding why select compounds give a single monochloro product.

Radical Chain Mechanism

The radical chain mechanism involves three key steps—inception (initiation), propagation, and termination. In radical chlorination, a chlorine radical is generated (initiation), which then abstracts a hydrogen atom from the alkane (propagation) and forms a new radical that reacts with Cl2 to give the chlorinated product. Understanding this mechanism is essential because it underlies the formation of multiple products in less symmetric molecules.

Selectivity in Radical Halogenation

Selectivity refers to the preference for a reaction to occur at a particular position in a molecule. In radical chlorination, selectivity is generally low compared to bromination due to the high reactivity of chlorine radicals. This low selectivity means that most hydrogen atoms, regardless of their location (primary, secondary, tertiary), can be abstracted unless the molecule’s symmetry forces all sites to be equivalent.

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