ROUTERA


Chapter 10 Haloalkanes and Haloarenes

Class 12th Chemistry Chapter Assertion and Reason


Here are the options for the answers to each Assertion and Reason question:

Options: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
B) Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.
C) Assertion is correct, but Reason is incorrect.
D) Assertion is incorrect, but Reason is correct.


1.

Assertion (A): Haloalkanes are generally more reactive than alkyl halides.
Reason (R): The C–X bond in haloalkanes is weaker compared to other single bonds in organic compounds.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The C–X bond in haloalkanes is weaker, making them more reactive in nucleophilic substitution reactions.


2.

Assertion (A): Haloalkanes are non-polar molecules.
Reason (R): The electronegativity of halogens is similar to that of carbon.
Answer: D) Assertion is incorrect, but Reason is correct.
Explanation: Haloalkanes are polar because of the difference in electronegativity between carbon and halogens, creating a dipole moment. The statement about halogen electronegativity is correct, but it doesn't lead to non-polarity.


3.

Assertion (A): The boiling point of haloalkanes increases with the increasing size of the halogen.
Reason (R): Larger halogens have a greater number of electrons, leading to stronger van der Waals forces.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Larger halogens, such as iodine, result in stronger van der Waals forces due to their larger atomic size, leading to higher boiling points.


4.

Assertion (A): Chlorine is more reactive than iodine in nucleophilic substitution reactions.
Reason (R): The C–I bond is weaker than the C–Cl bond, making iodine less reactive.
Answer: D) Assertion is incorrect, but Reason is correct.
Explanation: The C–I bond is indeed weaker, but iodine is less reactive in nucleophilic substitution reactions due to its larger size, making the departure of the I– ion less favorable.


5.

Assertion (A): Haloarenes are generally less reactive than haloalkanes in nucleophilic substitution reactions.
Reason (R): The halogen in haloarenes is attached to the carbon in an aromatic ring, making the carbon-halogen bond stronger.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The resonance effect in haloarenes makes the C–X bond stronger, reducing the reactivity in nucleophilic substitution.


6.

Assertion (A): The solubility of haloalkanes in water is low.
Reason (R): Haloalkanes are polar molecules and can form hydrogen bonds with water.
Answer: C) Assertion is correct, but Reason is incorrect.
Explanation: Although haloalkanes are polar, they are not very soluble in water because they cannot form hydrogen bonds with water, as water is highly polar.


7.

Assertion (A): Grignard reagents are not reactive with haloalkanes.
Reason (R): Haloalkanes are stable and do not react with reactive substances like Grignard reagents.
Answer: D) Assertion is incorrect, but Reason is correct.
Explanation: Grignard reagents react with haloalkanes to form new carbon-carbon bonds, making the assertion incorrect.


8.

Assertion (A): The C–Cl bond in haloalkanes is weaker than the C–Br bond.
Reason (R): Chlorine is less electronegative than bromine, making the C–Cl bond weaker.
Answer: C) Assertion is correct, but Reason is incorrect.
Explanation: The C–Cl bond is stronger than the C–Br bond because bromine is larger, and thus the bond is weaker due to the less effective overlap of orbitals.


9.

Assertion (A): Haloalkanes are typically used as solvents in organic reactions.
Reason (R): Haloalkanes have high dielectric constants, making them suitable for dissolving a variety of organic compounds.
Answer: C) Assertion is correct, but Reason is incorrect.
Explanation: Haloalkanes are commonly used as solvents because of their ability to dissolve non-polar substances, but they do not have high dielectric constants.


10.

Assertion (A): Phenyl chlorides are less reactive in nucleophilic substitution reactions than alkyl chlorides.
Reason (R): The presence of the benzene ring in phenyl chloride stabilizes the transition state.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The resonance effect in phenyl chloride stabilizes the transition state, making the nucleophilic substitution reaction slower.


11.

Assertion (A): Haloalkanes undergo nucleophilic substitution reactions through the SN1 mechanism.
Reason (R): The reaction mechanism follows a two-step process where the bond between the carbon and halogen breaks first, forming a carbocation.
Answer: B) Both Assertion and Reason are correct, but Reason is not the correct explanation for Assertion.
Explanation: Haloalkanes undergo SN1 reactions, but the primary factor is the stability of the carbocation, not just the bond breaking mechanism.


12.

Assertion (A): Nucleophilic substitution in haloalkanes is faster with an alkyl group in the β-position.
Reason (R): The β-hydrogens can stabilize the transition state, facilitating the reaction.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Beta-hydrogen atoms stabilize the transition state via hyperconjugation, making the nucleophilic substitution reaction faster.


13.

Assertion (A): The presence of an electron-withdrawing group on the aromatic ring increases the reactivity of haloarenes in nucleophilic substitution reactions.
Reason (R): Electron-withdrawing groups increase the positive charge on the carbon atom to which the halogen is attached, making the bond easier to break.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Electron-withdrawing groups make the carbon attached to the halogen more electrophilic, increasing its reactivity in nucleophilic substitution.


14.

Assertion (A): The rate of nucleophilic substitution reactions in haloalkanes increases with the size of the halogen.
Reason (R): Larger halogens form weaker bonds with carbon, making it easier for the halogen to leave.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Larger halogens, such as iodine, form weaker bonds with carbon, making nucleophilic substitution reactions faster.


15.

Assertion (A): Haloalkanes undergo elimination reactions more readily in the presence of a strong base.
Reason (R): Strong bases abstract β-hydrogens, facilitating the formation of alkenes through elimination.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: A strong base removes β-hydrogens from the haloalkane, leading to the formation of alkenes via elimination.


16.

Assertion (A): Haloalkanes are typically less soluble in water than alcohols of similar molecular weight.
Reason (R): Haloalkanes lack hydrogen bonding, which is present in alcohols.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Alcohols can form hydrogen bonds with water, making them more soluble than haloalkanes, which lack such bonds.


17.

Assertion (A): Chlorination of methane leads to the formation of methyl chloride.
Reason (R): Chlorine reacts with methane in the presence of ultraviolet light to form methyl chloride through free radical substitution.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The free radical substitution mechanism leads to the formation of methyl chloride when methane is chlorinated under UV light.


18.

Assertion (A): The reaction between haloalkanes and nucleophiles is influenced by the solvent.
Reason (R): Polar protic solvents stabilize the leaving group, facilitating the reaction.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Polar protic solvents stabilize the leaving group (halogen) and enhance the nucleophilicity of the attacking nucleophile, increasing the rate of nucleophilic substitution.


19.

Assertion (A): Tertiary haloalkanes undergo nucleophilic substitution reactions faster than primary haloalkanes.
Reason (R): Tertiary carbocations are more stable, leading to faster nucleophilic substitution.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Tertiary carbocations are more stable than primary carbocations, making the nucleophilic substitution reaction faster for tertiary haloalkanes.


20.

Assertion (A): The C–Br bond in haloalkanes is stronger than the C–Cl bond.
Reason (R): Bromine is more electronegative than chlorine, resulting in a stronger bond.
Answer: C) Assertion is correct, but Reason is incorrect.
Explanation: The C–Br bond is weaker than the C–Cl bond because bromine is larger, and the bond strength decreases with increasing atomic size.

21.

Assertion (A): Haloalkanes are commonly used as solvents in organic reactions.
Reason (R): Haloalkanes are polar compounds, making them good solvents for other polar compounds.
Answer: C) Assertion is correct, but Reason is incorrect.
Explanation: Haloalkanes are polar, but they are not very effective solvents for polar compounds. They are often used to dissolve non-polar compounds due to their non-polar nature.


22.

Assertion (A): Chlorine reacts with methane in the presence of ultraviolet light to form methyl chloride.
Reason (R): Chlorine molecules absorb UV light and form free radicals, which initiate the substitution reaction.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: UV light causes chlorine molecules to form chlorine radicals, which then react with methane to form methyl chloride through a free radical mechanism.


23.

Assertion (A): The rate of nucleophilic substitution increases with the size of the halogen.
Reason (R): Larger halogens like iodine have a weaker bond with carbon, making it easier for the halogen to leave.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Larger halogens like iodine have a weaker C–X bond, making the halogen more easily displaced by nucleophiles.


24.

Assertion (A): Haloarenes are less reactive in nucleophilic substitution reactions compared to haloalkanes.
Reason (R): The aromatic ring in haloarenes exerts a resonance effect, stabilizing the carbon-halogen bond.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The resonance effect in the aromatic ring of haloarenes stabilizes the C–X bond, making it less reactive in nucleophilic substitution.


25.

Assertion (A): The boiling point of haloalkanes increases with the increasing size of the halogen.
Reason (R): Larger halogens have more electrons, leading to stronger London dispersion forces between molecules.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The larger the halogen, the stronger the London dispersion forces, which increases the boiling point of haloalkanes.


26.

Assertion (A): Tertiary haloalkanes undergo nucleophilic substitution faster than primary haloalkanes.
Reason (R): Tertiary carbocations are more stable and can form more easily than primary carbocations.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Tertiary carbocations are more stable, facilitating faster nucleophilic substitution in tertiary haloalkanes.


27.

Assertion (A): Haloalkanes with a longer carbon chain tend to be more reactive in nucleophilic substitution reactions.
Reason (R): Larger carbon chains lead to greater electron density around the carbon attached to the halogen, making the C–X bond more likely to break.
Answer: D) Assertion is incorrect, but Reason is correct.
Explanation: The length of the carbon chain does not directly influence reactivity in nucleophilic substitution. The reactivity depends more on factors like the stability of the leaving group and the type of halogen.


28.

Assertion (A): Haloalkanes have higher boiling points compared to alcohols of similar molecular weight.
Reason (R): Haloalkanes form stronger hydrogen bonds than alcohols, leading to higher boiling points.
Answer: D) Assertion is incorrect, but Reason is correct.
Explanation: Alcohols form hydrogen bonds, which are stronger than the dipole-dipole interactions in haloalkanes, leading to higher boiling points for alcohols.


29.

Assertion (A): Aqueous sodium hydroxide reacts with haloalkanes to form alcohols.
Reason (R): The hydroxide ion (OH-) from sodium hydroxide is a strong nucleophile and can replace the halogen in the haloalkane.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The hydroxide ion (OH-) replaces the halogen in a nucleophilic substitution reaction, forming alcohols.


30.

Assertion (A): The reactivity of haloalkanes decreases with the increasing number of halogen atoms.
Reason (R): More halogens on the carbon chain create steric hindrance, making the nucleophilic substitution slower.
Answer: D) Assertion is incorrect, but Reason is correct.
Explanation: The reactivity of haloalkanes generally increases with the number of halogen atoms due to the higher electronegativity of halogens. Steric hindrance may decrease reactivity, but it's not a consistent rule.


31.

Assertion (A): The presence of an electron-withdrawing group on the aromatic ring increases the reactivity of haloarenes in nucleophilic substitution reactions.
Reason (R): Electron-withdrawing groups increase the electrophilicity of the carbon attached to the halogen, making it more susceptible to nucleophilic attack.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Electron-withdrawing groups pull electron density away from the ring, increasing the partial positive charge on the carbon attached to the halogen, thereby enhancing reactivity in nucleophilic substitution.


32.

Assertion (A): The reactivity of haloalkanes is highest for methyl halides.
Reason (R): Methyl halides undergo nucleophilic substitution via the SN2 mechanism, where the nucleophile attacks the carbon from the opposite side of the halogen.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Methyl halides are more reactive because they are small and undergo SN2 reactions, where the nucleophile directly attacks the carbon, leading to faster substitution.


33.

Assertion (A): In an electrophilic aromatic substitution, haloarenes act as electron-withdrawing groups.
Reason (R): The halogen attached to the aromatic ring pulls electron density towards itself, making the ring less reactive to electrophilic attack.
Answer: C) Assertion is correct, but Reason is incorrect.
Explanation: While halogens are generally electron-withdrawing through induction, they are electron-donating via resonance, making the ring more reactive in electrophilic aromatic substitution.


34.

Assertion (A): Haloalkanes undergo elimination reactions in the presence of a strong base.
Reason (R): Strong bases deprotonate β-hydrogens, resulting in the formation of alkenes via the E2 mechanism.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Strong bases like KOH can deprotonate β-hydrogens, facilitating the E2 elimination mechanism to form alkenes.


35.

Assertion (A): Chlorination of alkanes forms a mixture of products.
Reason (R): Chlorine atoms react with hydrogen atoms in the alkane to form a variety of isomers.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Chlorine can substitute any hydrogen in the alkane, leading to the formation of a mixture of mono-, di-, and higher chlorinated products.


36.

Assertion (A): Haloalkanes with smaller alkyl groups are more reactive than those with larger alkyl groups.
Reason (R): Smaller alkyl groups allow for easier attack by nucleophiles due to less steric hindrance.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Smaller alkyl groups cause less steric hindrance, making it easier for nucleophiles to attack the electrophilic carbon.


37.

Assertion (A): Haloalkanes exhibit optical isomerism.
Reason (R): Haloalkanes can have chiral centers, resulting in non-superimposable mirror images.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: If the haloalkane has a chiral carbon, it can exhibit optical isomerism, resulting in two non-superimposable mirror images.


38.

Assertion (A): Alcohols can be synthesized from haloalkanes using NaOH.
Reason (R): The hydroxide ion (OH-) replaces the halogen in the haloalkane to form alcohols.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The hydroxide ion (OH-) from NaOH replaces the halogen in the haloalkane, resulting in alcohols.


39.

Assertion (A): The rate of nucleophilic substitution in haloalkanes increases with the leaving group ability.
Reason (R): A good leaving group stabilizes the transition state and facilitates the departure of the halogen.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: A good leaving group stabilizes the transition state, leading to a faster nucleophilic substitution reaction.


40.

Assertion (A): Haloalkanes are less soluble in water compared to alcohols of similar molecular mass.
Reason (R): Haloalkanes do not form hydrogen bonds, while alcohols can.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Alcohols can form hydrogen bonds with water molecules, increasing their solubility, whereas haloalkanes cannot form hydrogen bonds.


41.

Assertion (A): The reaction of a haloalkane with sodium cyanide results in the formation of nitriles.
Reason (R): The cyanide ion (CN-) is a strong nucleophile and displaces the halogen in haloalkanes.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Cyanide (CN-) is a strong nucleophile that replaces the halogen, forming nitriles in the process.


42.

Assertion (A): Haloalkanes are not used as anesthetics.
Reason (R): Haloalkanes are highly toxic and are not safe for inhalation.
Answer: C) Assertion is correct, but Reason is incorrect.
Explanation: Some haloalkanes, like halothane, are used as anesthetics, although they are toxic in high doses.


43.

Assertion (A): Allylic halides are more reactive in nucleophilic substitution reactions compared to alkyl halides.
Reason (R): The allylic position can stabilize the intermediate carbocation through resonance.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: The resonance stabilization of the carbocation intermediate in allylic halides increases their reactivity in nucleophilic substitution reactions.


44.

Assertion (A): The formation of an alkene from a haloalkane requires heating with a base.
Reason (R): Bases abstract a proton from a β-carbon, leading to the formation of a double bond via elimination.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: A base abstracts a proton from the β-carbon of the haloalkane, leading to the formation of an alkene via an elimination reaction.


45.

Assertion (A): Alkyl halides can be prepared by free radical halogenation of alkanes.
Reason (R): The free radical halogenation mechanism involves the homolytic cleavage of the halogen molecule to form free radicals.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Free radical halogenation involves homolytic cleavage of the halogen molecule to form radicals, which then react with alkanes to form alkyl halides.


46.

Assertion (A): Haloalkanes are highly soluble in organic solvents.
Reason (R): Haloalkanes are non-polar and can dissolve in a variety of non-polar solvents.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Due to their non-polar nature, haloalkanes dissolve easily in organic solvents that are also non-polar.


47.

Assertion (A): The solubility of haloalkanes in water increases with the electronegativity of the halogen.
Reason (R): More electronegative halogens increase the polarity of the molecule, making it more soluble in water.
Answer: D) Assertion is incorrect, but Reason is correct.
Explanation: The solubility of haloalkanes in water is not significantly affected by the electronegativity of the halogen; they are generally poorly soluble due to their non-polarity.


48.

Assertion (A): The reaction of alcohols with HX leads to the formation of haloalkanes.
Reason (R): Alcohols can undergo a nucleophilic substitution reaction with HX to replace the hydroxyl group with a halogen.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Alcohols undergo nucleophilic substitution with HX to form haloalkanes, where the -OH group is replaced by a halogen.


49.

Assertion (A): Halogen exchange reactions can be carried out using sodium iodide in acetone.
Reason (R): Sodium iodide in acetone favors the SN2 mechanism, where the iodide ion replaces the halogen atom.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Sodium iodide in acetone favors the SN2 mechanism, leading to halogen exchange and the formation of an iodide-containing product.


50.

Assertion (A): Allyl and benzyl halides undergo nucleophilic substitution faster than alkyl halides.
Reason (R): The carbocation intermediates in allyl and benzyl halides are stabilized by resonance.
Answer: A) Both Assertion and Reason are correct, and Reason is the correct explanation for Assertion.
Explanation: Allyl and benzyl halides undergo nucleophilic substitution faster because their carbocation intermediates are stabilized by resonance, making them more reactive.