Question

In which cases, free radicals can be formed by hemolytic fission? C=O hv (a) \(\mathrm{CH}_{3} \mathrm{CCH}_{3}\) (b) \(\mathrm{R}-\ddot{\mathrm{N}}=\ddot{\mathrm{N}}-\mathrm{R}\) hv (c) O=CCc1ccccc1 (d) in all cases

Short answer

(d) in all cases

Step-by-step solution

Understanding Hemolytic Fission

Hemolytic fission occurs when a covalent bond breaks evenly so that each of the bonded atoms retains one electron, leading to the formation of radicals. This process can occur when sufficient energy, such as UV light (indicated by \( hv \)), is provided to break certain bonds.

Analyzing Option (a): Isomer of Propane

Option (a) represents a hydrocarbon, \(\mathrm{CH}_{3} \mathrm{CCH}_{3}\), which is a type of alkane. Alkanes can undergo hemolytic fission under the influence of UV light, although they are generally less reactive compared to other compounds like halogens or peroxides. UV light can break the C-H bonds, forming free radicals.

Analyzing Option (b): Diimide Compound

Option (b) represents a diimide compound \(\mathrm{R}-\ddot{\mathrm{N}}=\ddot{\mathrm{N}}-\mathrm{R}\). The presence of \( \ddot{\text{N}} = \ddot{\text{N}} \) bonds is crucial; these bonds can undergo hemolytic fission due to their higher reactivity, especially when exposed to UV light. The breaking of the N=N bond can result in the formation of nitrogen-centered radicals.

Analyzing Option (c): Benzyl Ketone Structure

Option (c) involves a benzyl ketone structure \( \text{O=CCc}_1\text{ccccc}_1 \), which can undergo hemolytic fission. UV light can break the C=O (carbonyl) bond, leading to the formation of an acyl radical and another radical species. This is a common occurrence in photochemical reactions.

Conclusion

Each of the compounds in options (a), (b), and (c) can potentially form radicals through hemolytic fission when exposed to sufficient energy like UV light. Therefore, the correct answer is (d) all cases, as each alternative can undergo hemolytic fission under the right conditions.

Key concepts

Free Radicals

Free radicals are quite fascinating in the world of chemistry. They are molecules or atoms containing an unpaired electron, making them highly reactive. The presence of this single electron is symbolized by a dot (\( \cdot \)) in chemical structures. Because they are so reactive, radicals often initiate chain reactions, where they react with other substances to form new radicals.
These species are formed by the cleavage of covalent bonds. This process, known as hemolytic fission, evenly splits the bond between two atoms, gifting each atom one electron from the pair. Since they're left with unpaired electrons, both resulting atoms become free radicals. Think of a free radical as a restless electron seeker, always on the hunt for a partner to stabilize itself.
The energy for this bond-breaking often comes from external sources such as heat or UV light, which provides the necessary power to overcome the bond's energy threshold.

Covalent Bond

A covalent bond is a fundamental concept in chemistry. It represents the sharing of electrons between two atoms. This bond forms when atoms want to achieve a stable electron configuration, often resembling the nearest noble gas. By sharing electrons, atoms fill their outer shells, settling into a lower energy, more stable state.
In a covalent bond:

• Electrons are shared evenly or unevenly, depending on the atoms' electronegativities.
• These bonds are strong, meaning they require significant energy to break, which often comes from external sources like UV light.
• When broken evenly in a process called hemolytic fission, radicals form, transforming these stable molecules into highly reactive species.

This bond-breaking is common when strong external forces or energy inputs disrupt the stable electron sharing, as seen with UV light in chemical scenarios.

UV Light

UV Light, short for ultraviolet light, is a type of electromagnetic radiation. It falls just beyond the visible light spectrum, which means we can’t see it, but it plays a critical role in many chemical processes.

In hemolytic fission, UV light provides the energy needed to break covalent bonds. Think of it as extra energy that "shakes up" the molecules, allowing bonds that are otherwise stable to crack open. This is particularly important in the context of free radical formation.

• The energy from UV light is often enough to break specific bonds, like the N=N or C=O bonds, especially those with double or higher bond character.
• Its high energy makes UV light ideal for inducing photochemical reactions, where light causes chemical changes.
• In environmental contexts, UV light can be both beneficial and harmful, as it fosters processes like the creation of Vitamin D in human skin, but also causes degradation of sensitive materials.

Understanding how UV light interacts with molecules, especially in the formation of radicals, is crucial for fields ranging from materials science to biology.