10.22 Explain why (i) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride? (ii) Alkyl halides, though polar, are immiscible with water? (iii) Grignard reagents should be prepared under anhydrous conditions?

Let us explain each question from Haloalkane and Haloarenes chapter one by one. Students who are currently in school and plan to take the CBSE board exam for class 12th soon, need to prepare all these questions. Let us get started.

(i) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.

Sp² hybrid carbon (s-character=33.33%) in chlorobenzene is more electronegative than a sp³-hybrid carbon (s-character=25%) in cyclohexylchloride, due to greater s-character. Thus, Carbon atom of chlorobenzene has less tendency to release electrons to Cl than carbon atom of cyclohexylchloride.

Chlorine atom in chlorobenzene is atta

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Let us explain each question from Haloalkane and Haloarenes chapter one by one. Students who are currently in school and plan to take the CBSE board exam for class 12th soon, need to prepare all these questions. Let us get started.

(i) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.

Sp² hybrid carbon (s-character=33.33%) in chlorobenzene is more electronegative than a sp³-hybrid carbon (s-character=25%) in cyclohexylchloride, due to greater s-character. Thus, Carbon atom of chlorobenzene has less tendency to release electrons to Cl than carbon atom of cyclohexylchloride.

Chlorine atom in chlorobenzene is attached to the benzene ring. Here, the carbon-chlorine bond is polar. However, electron delocalization is possible in the benzene ring. Due to the electron delocalization, the overall dipole moment reduced since the polarity is distributed over the entire ring structure.

On the other hand, the chlorine atom in cyclohexyl chloride is attached to a saturated carbon atom in the cyclohexane ring. Because of this, there is no electron delocalization in the saturated structure. Hence, the dipole moment is more localized and stronger as compared to chlorobenzene.

 (ii) Alkyl halides, though polar, are immiscible with water.

Alkyl halides are polar because of the difference in electronegativity between carbon and halogen atoms. Here, there is not enough polarity to make them soluble in water.

The alkyl part of molecule is non-polar as well as hydrophobic in nature. This portion is large enough to dominate the solubility characteristics of the molecule. The entire molecule becomes insoluble in water due to this.

Water molecules create extensive hydrogen bonds with each other. However, Alkyl halides cannot form hydrogen bonds with water, which reduces their solubility in water. Haloalkane and Haloarene NCERT excercise discusses this question in further detail.

(iii) Grignard reagents should be prepared under anhydrous conditions.

Grignard reagents are very reactive organometallic compounds and they react readily with water to produce hydrocarbons. This destroys the Grignard reagent and makes it ineffective for its original purpose.

The reaction with water not only destroy Grignard reagent but also it produces by products that can complicate the synthetic pathway.

Preparing Grignard reagents under anhydrous conditions makes sure that they remain stable and effective for use in further reactions. Moisture-free conditions are important for the formation and utilization of reagents.

R-Mg-X + H-OH → R-H + Mg (OH)X

Do note that questions based on such equations from organic chemistry are also be asked in the CUET exam which makes it important for students to remember it.

Thus, Grignard reagents must be prepared under anhydrous conditions.

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<p>Let us explain each question from Haloalkane and Haloarenes chapter one by one. Students who are currently in school and plan to take the CBSE board exam for class 12th soon, need to prepare all these questions. Let us get started.</p><p><strong>(i) The dipole moment of chlorobenzene is lower than that of cyclohexyl chloride.</strong></p><p>Sp² hybrid carbon (s-character=33.33%) in chlorobenzene is more electronegative than a sp³-hybrid carbon (s-character=25%) in cyclohexylchloride, due to greater s-character. Thus, Carbon atom of chlorobenzene has less tendency to release electrons to Cl than carbon atom of cyclohexylchloride.</p><p>Chlorine atom in chlorobenzene is attached to the benzene ring. Here, the carbon-chlorine bond is polar. <strong>However, electron delocalization is possible in the benzene ring.</strong> Due to the electron delocalization, the overall dipole moment reduced since the polarity is distributed over the entire ring structure.</p><p>On the other hand, the chlorine atom in cyclohexyl chloride is attached to a saturated carbon atom in the cyclohexane ring. Because of this, <strong>there is no electron delocalization in the saturated structure.</strong> Hence, the dipole moment is more localized and stronger as compared to chlorobenzene.</p><div><div><picture><source srcset="https://images.shiksha.com/mediadata/images/articles/1690440127phpJLMv9w_480x360.jpeg" media=" (max-width: 500px)"><img src="https://images.shiksha.com/mediadata/images/articles/1690440127phpJLMv9w.jpeg" alt="" width="" height=""></picture></div></div><p><strong>&nbsp;(ii) Alkyl halides, though polar, are immiscible with water.</strong></p><p>Alkyl halides are polar because of the difference in electronegativity between carbon and halogen atoms. Here, there is not enough polarity to make them soluble in water.</p><p>The alkyl part of molecule is non-polar as well as hydrophobic in nature. This portion is large enough to dominate the solubility characteristics of the molecule. The entire molecule becomes insoluble in water due to this.</p><p>Water molecules create extensive hydrogen bonds with each other. However, Alkyl halides cannot form hydrogen bonds with water, which reduces their solubility in water. &lt;a href="https://www.shiksha.com/preparation/chemistry-ncert-solutions-class-12th-haloalkanes-and-haloarenes-4511-ns" target="_blank" rel="noopener"&gt;<em><strong>Haloalkane and Haloarene NCERT excercise</strong></em>&lt;/a&gt; discusses this question in further detail.</p><p><strong>(iii) Grignard reagents should be prepared under anhydrous conditions.</strong></p><p>Grignard reagents are very reactive organometallic compounds and they react readily with water to produce hydrocarbons. This destroys the Grignard reagent and makes it ineffective for its original purpose.</p><p><strong>The reaction with water not only destroy Grignard reagent but also it produces by products that can complicate the synthetic pathway.</strong></p><p>Preparing Grignard reagents under anhydrous conditions makes sure that they remain stable and effective for use in further reactions. Moisture-free conditions are important for the formation and utilization of reagents.</p><p>R-Mg-X + H-OH → R-H + Mg (OH)X</p><p>Do note that questions based on such equations from &lt;a href="https://www.shiksha.com/preparation/chemistry-organic-chemistry-tp" target="_blank" rel="noopener"&gt;<em><strong>organic chemistry</strong></em>&lt;/a&gt; are also be asked in the &lt;a href="https://www.shiksha.com/science/cuet-exam" target="_blank" rel="noopener"&gt;<em><strong>CUET exam</strong></em>&lt;/a&gt; which makes it important for students to remember it.</p><p><strong>Thus, Grignard reagents must be prepared under anhydrous conditions.</strong></p>

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