Question

The pesticide DDT slowly changes to (a) p, p-dichlorodiphenyldichloroethene (b) p, p'-dichlorodiphenyldichloroethane (c) p, p'-dichlorodiphenylethene (d) \(\mathrm{CCl}_{3}-\mathrm{CHO}\) and chlorobenzene

Short answer

The answer is (a) p, p'-dichlorodiphenyldichloroethene.

Step-by-step solution

Understanding the Problem

The problem asks for the compound into which the pesticide DDT primarily degrades. DDT stands for dichlorodiphenyltrichloroethane, a chlorinated hydrocarbon pesticide. Understanding its degradation pathway can help us identify the correct answer from the options provided.

Degradation Pathway of DDT

DDT degrades primarily through a dehydrochlorination reaction. During this process, DDT loses molecules of hydrochloric acid (HCl) to form a more stable compound. The first and main degradation product of DDT is known as DDE, which is the common name for dichlorodiphenyldichloroethene, with the chemical formula (p, p'-DDE).

Identifying the Correct Answer

Given the degradation pathway of DDT, where it loses HCl to form DDE, we need to select the answer that matches this degradation product. Amongst the options, option (a) represents p, p'-dichlorodiphenyldichloroethene, which is the chemical structure for DDE.

Finalizing the Answer

Based on the understanding of DDT's degradation into DDE, the correct answer to the question is option (a) - p, p'-dichlorodiphenyldichloroethene. This aligns with the known chemical process that occurs as DDT breaks down.

Key concepts

dehydrochlorination reaction

Dehydrochlorination is a crucial chemical reaction that plays a significant role in the degradation of many organic compounds, including the pesticide DDT. In this process, a chlorine (Cl) atom and a hydrogen (H) atom are removed from a molecule, typically resulting in the formation of a double bond in its place. This also leads to the release of hydrochloric acid (HCl).

Understanding dehydrochlorination is important because it helps explain how larger, more complex molecules break down into simpler forms. This reaction is a significant step in environmental chemistry, especially when it comes to the degradation of persistent organic pollutants, such as DDT.

As DDT degrades, it primarily undergoes a dehydrochlorination reaction, losing HCl, which leads to the formation of a compound known as DDE. Recognizing this reaction assists in mapping out how stable, though environmentally persistent, compounds like DDT transform into less harmful substances over time.

dichlorodiphenyldichloroethene (DDE)

Dichlorodiphenyldichloroethene, commonly abbreviated as DDE, is the main degradation product of DDT. When DDT undergoes dehydrochlorination, it loses HCl and converts into this compound. Understanding DDE is essential, as it reflects both the structure and behavior of those chemicals left in the environment after DDT breaks down.

DDE retains much of the structure of its parent compound, DDT, yet it differs due to the loss of a hydrogen and a chlorine atom, which is illustrated in its chemical structure. This compound is known to be less reactive than DDT, but it is still a significant environmental concern due to its persistence and accumulation in living organisms.

Knowing about DDE's chemical properties helps scientists and environmentalists design better strategies to manage and remediate areas affected by historical usage of DDT. Since it is the primary metabolite formed, understanding DDE is key in ecological risk assessments related to pesticide pollution.

chemical structure identification

Chemical structure identification is a fundamental skill in chemistry that enables scientists to determine the nature of a compound through its structural formula. This process involves recognizing the arrangements of various atoms, predicting stability, reactivity, and understanding its potential transformations.

In the context of DDT and its degradation, identifying the correct structure of DDE involves understanding how dehydrochlorination modifies the structure of the original compound. This requires knowledge of atomic bonds, molecular geometry, and chemical transitions. Identifying DDE's chemical structure confirms that one of DDT's chlorine atoms has been replaced by a double bond, a typical outcome of dehydrochlorination.

Proficiently identifying chemical structures like DDE helps in distinguishing it from other potential degradation products, such as those listed in multiple-choice questions regarding pesticide degradation. Such accuracy helps in predicting environmental behaviors and human health implications.