Question

R-H can be converted into R-Cl by using (A) \(\mathrm{Cl}_{2} / \mathrm{h} v\) (B) \(\mathrm{SO}_{2} \mathrm{Cl}_{2} / \Delta\) (C) \(\mathrm{HCl}\) (D) \(\mathrm{t}-\mathrm{BuOCl}, \Delta\)

Short answer

The correct reagent and condition for converting R-H to R-Cl is (A) \(\mathrm{Cl}_{2} / \mathrm{h} v\), as it involves free radical halogenation.

Step-by-step solution

Option (A)

In this option, we have Cl2/hv which represents the use of chlorine gas (Cl2) and light (hv). This process is known as free radical halogenation, which typically targets the hydrogen atoms attached to the most accessible carbon in R-H and replaces it with a chlorine atom. Therefore, Option (A) Cl2/hv is a suitable method to convert R-H to R-Cl. #Step 2: Option (B) assessment#

Option (B)

Option (B) uses a mixture of SO2 and Cl2 under heating conditions (Δ). This reaction is mainly used for the chlorination of aromatic compounds, not for converting alkyl halides, R-H, into R-Cl. Therefore, option (B) SO2Cl2 / Δ is not the correct choice for converting R-H to R-Cl. #Step 3: Option (C) assessment#

Option (C)

Option (C) uses HCl, which is hydrochloric acid. This reagent is not suitable for converting alkyl halides (R-H) into R-Cl since it is not a strong enough chlorinating agent. Hence, option (C) HCl is not the correct choice for converting R-H to R-Cl. #Step 4: Option (D) assessment#

Option (D)

Option (D) involves the use of t-BuOCl and heating (Δ). Tert-butoxychloride (t-BuOCl) is not used for halogenation reactions – it is generally used for the synthesis of ethers via the Williamson Ether synthesis. Therefore, option (D) t-BuOCl, Δ is not the correct choice for converting R-H to R-Cl. #Step 5: Final Answer#

Choose the correct option

Based on our assessment, we found that option (A) Cl2/hv is the appropriate reagent and condition for converting R-H to R-Cl. Therefore, the correct answer is (A) Cl2/hv.

Key concepts

Organic Chemistry

Organic Chemistry is the study focused on the structure, properties, composition, reactions, and synthesis of carbon-containing compounds. These compounds also commonly contain other elements such as hydrogen, oxygen, nitrogen, sulfur, and halogens. Organic chemistry is central to many facets of science and is a fundamental subject for students pursuing chemistry-related fields.

The main goal of organic chemistry is to understand how molecules behave and react under different conditions. This understanding allows scientists to create new molecules with a wide range of applications, such as in pharmaceuticals, plastics, fuels, and agrochemicals.

• Carbon's versatility allows it to form long chains and rings due to its tetravalency.
• Compounds are studied in terms of their functional groups, which dictate their chemical behavior.
• Reactions in organic chemistry include addition, substitution, elimination, and rearrangement reactions.

Mastering organic chemistry concepts is essential for tackling more complex chemical reactions like Free Radical Halogenation.

Chlorination Reaction

The chlorination reaction is a type of free radical halogenation where chlorine (Cl extsubscript{2}) is added to a molecule, typically replacing a hydrogen atom. This process requires the presence of visible light or ultraviolet light (denoted as hv) to initiate the reaction.

The reaction proceeds through a free radical mechanism consisting of three stages: initiation, propagation, and termination.

• Initiation: Chlorine molecules are broken into two chlorine radicals by light.
• Propagation: Chlorine radicals collide with an alkane, abstracting a hydrogen atom to form hydrochloric acid (HCl) and leaving a carbon radical, which can further react.
• Termination: Radical species react with one another to form stable molecules, ending the reaction chain.

Chlorination can produce a mix of products if multiple hydrogen atoms are present. Therefore, achieving high specificity requires thoughtful control over reaction conditions and possibly selecting other related techniques or reagents.

Alkyl Halides Conversion

Alkyl halides are organic compounds where one or more halogen atoms are bonded to an alkane. The conversion of alkanes to alkyl halides is a key process in organic synthesis, particularly through halogenation reactions such as chlorination.

This conversion takes a non-polar alkane and introduces a polar component via the halogen atom, altering the chemical properties significantly, including reactivity and solubility.

• Alkyl halides are crucial as synthetic intermediates and can be transformed further into a variety of functional groups.
• The carbon-halogen bond is susceptible to different reaction pathways like nucleophilic substitution or elimination, offering broad utility for further chemical transformations.
• Free radical halogenation with Cl extsubscript{2}/hv is an efficient process for converting less reactive hydrocarbons into more reactive alkyl halides.

Understanding the conversion mechanisms helps in planning synthetic pathways for complex molecules.

JEE Main and Advanced Chemistry

JEE Main and Advanced are highly competitive exams in India for students seeking admission to premier engineering institutes like the IITs. Organic Chemistry is a significant portion of the JEE Chemistry syllabus, where reactions and mechanisms, including free radical halogenation, are commonly tested.

To excel in JEE Chemistry, students should deeply understand various chemical reactions and their mechanisms, alongside practising problem-solving skills.

• Focus on understanding core concepts, as they form the foundation for more advanced topics.
• Regular practice with past exam questions can help familiarize with the format and types of questions asked.
• Building a strong grasp of reaction intermediates, such as free radicals, aids in solving complex reaction mechanism questions.

Preparing for JEE requires a strategic approach—balancing theory, practical application, and problem practices to build a solid foundation and excel in the exams.