Which of the following is 'not' true about enantiomers ?
(A) They have the same chemical reactivity.
(B) They have the same specific rotation.
(C) They have the same melting or boiling point.
(D) They have the same refractive index.
CBSE CLASS 12 • CHEMISTRY • CHAPTER 06
Haloalkanes and Haloarenes
116 distinct questions across 148 board paper set appearances (2022–2026).
Why are haloarenes less reactive towards nucleophilic substitution reaction ? Give two reasons.
Assertion (A) : Aromatic primary amines can be prepared by Gabriel Phthalimide synthesis.
Reason (R) : Aryl halides do not undergo nucleophilic substitution with the anion formed by phthalimide.
Ethers are prepared by the dehydration of alcohols in presence of protic acids at $413\text{ K}$. Symmetrical and unsymmetrical ethers can also be prepared by Williamson synthesis. This reaction involves $\text{S}_\text{N}2$ attack of an alkoxide ion on primary alkyl halide. If a tertiary alkyl hali...
(b) (i) Write the names of alkyl halide and sodium alkoxide used to prepare tert-butyl ethyl ether.
Assertion (A) : Phosphorus halides are preferred over thionyl chloride for the preparation of alkyl halides from alcohols.
Reason (R) : Reaction of alcohols with thionyl chloride forms pure alkyl halides.
Polyhalogen compounds have wide application in industries and agriculture. DDT is also a very important polyhalogen compound. It is a :
(A) greenhouse gas
(B) fertilizer
(C) biodegradable insecticide
(D) non-biodegradable insecticide
(a) Account for the following :
(i) Allyl chloride is hydrolysed more readily than n-propyl chloride.
(ii) Isocyanides are formed when alkyl halides are treated with silver cyanide.
(iii) Methyl chloride reacts faster with $\text{OH}^-$ ion in $\text{S}_\text{N}2$ reaction than t-butyl chloride.
OR
...
Why are haloarenes less reactive towards nucleophilic substitution reaction ? How does the presence of nitro ($- ext{NO}_2$) group at ortho- and para-positions in haloarenes increase the reactivity towards nucleophilic substitution reaction ?
Which one of the following halides contains $\text{C}_{\text{sp}^2} - \text{X}$ bond ?
(A) Alkyl halide
(B) Allyl halide
(C) Benzyl halide
(D) Vinyl halide
(a) What type of nucleophilic substitution ($S_N1$ or $S_N2$) occurs in the hydrolysis of 2-Bromobutane to form $(\pm)$-Butan-2-ol ? Give reason. (b) What happens when chlorobenzene and methyl chloride are treated with sodium metal in dry ether ?
Assertion (A) : The boiling points of alkyl halides decrease in the order $ ext{RI} > ext{RBr} > ext{RCl} > ext{RF}$.
Reason (R) : The van der Waals forces of attraction decrease in the order $ ext{RI} > ext{RBr} > ext{RCl} > ext{RF}$.
A compound (A) with molecular formula $\text{C}_4\text{H}_9\text{I}$ which is a primary alkyl halide, reacts with alcoholic $\text{KOH}$ to give compound (B). Compound (B) reacts with $\text{HI}$ to give (C) which is an isomer of (A). When (A) reacts with $\text{Na}$ metal in the presence of dry eth...
Identify the Freon from the following compounds :
(A) $\text{CCl}_2\text{F}_2$
(B) $\text{CCl}_2\text{Br}_2$
(C) $\text{CH}_2\text{Cl} - \text{CHCl}_2$
(D) $\text{CHCl}_2 - \text{CHCl}_2$
Account for the following :
(a) The dipole moment of chlorobenzene is lower than that of cyclohexylchloride.
(b) Alkyl halides are immiscible in water.
(c) t-butyl bromide has lower boiling point than n-butyl bromide.
The synthesis of alkyl fluoride is best obtained from :
(a) Free radicals
(b) Swartz reaction
(c) Sandmeyer reaction
(d) Finkelstein reaction
Assertion (A) : Ammonolysis of alkyl halides is not a suitable method for the preparation of pure primary amines. Reason (R) : Ammonolysis of alkyl halides yields mainly secondary amines.
Assertion (A) : Nucleophilic substitution of iodoethane is easier than chloroethane.
Reason (R) : Bond energy of $\text{C} - \text{Cl}$ bond is less than $\text{C} - \text{I}$ bond.
The polarity of $\text{C} - \text{X}$ bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Alkyl halides are prepared by the free radical halogenation of alkanes, addition of halogen acids to alken...
An alkyl halide (A) of molecular formula $\text{C}_6\text{H}_{13}\text{Cl}$ on treatment with alcoholic $\text{KOH}$ gives two isomeric alkenes (B) and (C) of molecular formula $\text{C}_6\text{H}_{12}$. Both alkenes on hydrogenation give 2,3-dimethylbutane. Write the structures of (A), (B) and (C).
(a) (i) Why do tertiary alkyl halides undergo $\text{S}_\text{N}1$ reaction at a faster rate ? (ii) Define Enantiomers. (iii) Why is chloroform stored in dark coloured air tight bottles ?
Which of the following Grignard Reagent will be used to prepare a cyclohexane ring attached to $\text{CH}_2\text{OH}$ when treated with methanal ?
(A) $\text{CH}_3\text{MgBr}$
(B) A cyclohexane ring attached with $\text{CH}_2\text{MgBr}$
(C) A cyclohexane ring attached with $\text{MgBr}$
(D) A cyclo...
Benzene diazonium chloride on reaction with phenol in weakly basic medium gives
(A) Azobenzene
(B) Benzene
(C) Chlorobenzene
(D) $p$-hydroxyazobenzene
26. (a) Write the major product in the following reactions :
$$\text{Cyclohexene} + \text{Br}_2 \xrightarrow{\text{heat}} ?$$
(b) Define Racemic mixture.
(c) p-dichlorobenzene has a higher melting point as compared to its ortho and meta isomers. Why ?
26. (a) Write the major product in the following reaction :
$$\text{CH}_2\text{CH}_3$$
$$\text{NO}_2$$
$$+ \text{Br}_2 \xrightarrow{\text{heat}} ?$$
(b) Define Chirality.
(c) Why racemisation occurs in $\text{S}_\text{N}1$ reaction ?
(a) Write the major product in the following reaction :
$$\text{Chlorobenzene} + \text{CH}_3-\text{Cl} \xrightarrow[\text{dry ether}]{\text{Na}} ?$$
(b) What happens when 2-Bromobutane is made to react with alcoholic potassium hydroxide ?
(a) Write the IUPAC name of the given compound :
$ ext{CH}_3 ext{CH}( ext{CH}_3) ext{CH}( ext{Br}) ext{CH}_3$
(b) Define Racemisation.
(c) The boiling points of the alkyl halides with the same alkyl group decrease in the given order :
$ ext{RI} > ext{RBr} > ext{R}Cl > ext{RF}$
Explain the abov...
In the preparation of an alkyl halide from alcohol, which of the following reagents is preferred ?
(A) $ ext{PCl}_5$
(B) $ ext{SOCl}_2$
(C) $ ext{PCl}_3$
(D) $ ext{HCl/ZnCl}_2$
The reaction of an alkyl halide with sodium forming alkane is known as :
(A) Williamson synthesis
(B) Wurtz reaction
(C) Swarts reaction
(D) Friedel-Crafts reaction
Nitrobenzene on reduction with $ ext{Fe}$ and $ ext{HCl}$ will yield :
(A) Chlorobenzene
(B) Phenol
(C) Aniline
(D) Benzonitrile
Assertion (A) : Ammonolysis of alkyl halides involves the reaction of an alkyl halide with an ethanolic solution of ammonia.
Reason (R) : Ammonolysis is not a good method to prepare pure primary amines.
(a) Define the following terms :
(i) Enantiomers
(ii) Racemic mixture
(b) Give one difference between chiral and achiral molecules.
What happens when :
(a) n-butyl chloride is treated with alcoholic $ ext{KOH}$ ?
(b) Chlorobenzene is treated with $ ext{CH}_3 ext{Cl}$ in the presence of anhydrous $ ext{AlCl}_3$ ?
Write two differences between $\text{S}_\text{N}1$ and $\text{S}_\text{N}2$ reactions. Out of chlorobenzene and $2,4,6$-trinitrochlorobenzene, which one is more reactive towards nucleophilic substitution reactions ?
Which of the following will be the least reactive towards nucleophilic substitution reaction ?
(A) $\text{C}_6\text{H}_5-\text{CH}_2-\text{Cl}$
(B) 4-chlorotoluene structure
(C) $\text{CH}_3-\text{Cl}$
(D) Chlorocyclohexane
Give reasons for the following :
(a) Although chlorine is an electron-withdrawing group, yet it is ortho-, para-directing in electrophilic aromatic substitution reactions.
(b) Aryl halides cannot be prepared by reacting phenol with concentrated halogen acids or phosphorus halides.
(c) Chloroform ...
How will you obtain the following from benzenediazonium chloride ? Give chemical equations involved :
(a) Chlorobenzene
(b) Benzene
(c) Benzonitrile
Which of the following compounds is most reactive towards nucleophilic substitution reaction with aqueous $ ext{NaOH}$ ?
(A) Chlorobenzene structure
(B) 2,4-Dimethylchlorobenzene structure
(C) 1-Chloro-4-methoxybenzene structure
(D) 1-Chloro-2,4-dinitrobenzene structure
Give reasons for the following :
(a) Alkyl halides, though polar, yet their solubility in water is very low.
(b) $ ext{p}$-Dichlorobenzene has higher melting point than those of $ ext{o}$- and $ ext{m}$-isomers.
(c) $ ext{CH}_3 - ext{I}$ is more reactive than $ ext{CH}_3 - ext{Br}$ towards $ ext{S...
Consider the following compounds :
Chlorobenzene (I), $2,4,6$-trinitrochlorobenzene (II),
$2,4$-dinitrochlorobenzene (III), $4$-nitrochlorobenzene (IV)
The correct order of increasing ease of nucleophilic substitution reactions of these compounds is :
(A) $\text{I} < \text{IV} < \text{III} < \text{I...
Give reasons for the following :
(a) Haloalkanes react with $ ext{KCN}$ to form alkyl cyanides, while with $ ext{AgCN}$, they form isocyanides.
(b) Cyclohexyl-$ ext{CH}_2 - ext{Cl}$ is more reactive towards $ ext{S}_ ext{N}2$ displacement as compared to Chlorocyclohexane.
(c) Grignard reagents shou...
Williamson synthesis is an example of :
(A) Nucleophilic addition reaction
(B) Electrophilic substitution reaction
(C) Nucleophilic substitution reaction
(D) Electrophilic addition reaction
(ii) Define the following terms :
(I) Ambident Nucleophiles
(II) Racemic mixture
OR
(b) (i) Answer the following :
(I) Which isomer of $ ext{C}_4 ext{H}_9 ext{Br}$ is most reactive towards $ ext{S}_ ext{N}1$ reaction ?
(II) Predict the alkene that would be formed by dehydrohalogenation of $1$-Brom...
(ii) Define the following terms :
(I) Ambident Nucleophiles
(II) Racemic mixture
(a) Complete the equation :
$$\text{C}_6\text{H}_5\text{N}_2^+\text{Cl}^- + \text{H}-\text{C}_6\text{H}_4-\text{NH}_2 \longrightarrow$$
(b) How will you convert chlorobenzene to p-chloroaniline ?
(a) (i) (I) Which of the following is more reactive towards $\text{S}_{\text{N}}1$ reaction : 2-Bromo-2-methylbutane or 1-Bromopentane
(II) What type of halide is present in the following compound :
$\text{CH}_3 - \text{CH} - \text{C} = \text{CH}_2$
$\text{ | } \quad \text{ | }$
$\text{CH}_3 \quad \...
(a) "Haloalkanes react with KCN to form alkyl cyanides as the main product, whereas with AgCN, they form isocyanides as the main product." Explain the statement.
(b) Complete the given equation :
$$\text{Chlorobenzene} \xrightarrow[\Delta]{\text{Conc. } \text{H}_2\text{SO}_4}$$
(a) Why are haloarenes less reactive towards nucleophilic substitution reactions than haloalkanes ? Give two reasons.
(b) Explain the Finkelstein reaction.
Match the column I and column II:
Column I
A. $ ext{CH}_3 - ext{CH}( ext{CH}_2 ext{CH}_3) - ext{OH} + ext{H-Cl} \xrightarrow{ ext{heat}} ext{CH}_3 - ext{CH}( ext{Cl}) - ext{CH}_2 - ext{CH}_3 + ext{H-OH}$
B. $ ext{H}_3 ext{C} - ext{CH}( ext{Br}) - ext{C}_6 ext{H}_{13} + ^- ext{OH} \longrig...
Identify the secondary benzylic halide and primary alkyl halide from the following:
(i)
(ii)
(iii)
(iv)
A. (i) and (iii)
B. (iv) and (ii)
C. (iii) and (iv)
D. (i) and (ii)
Explain the following:
I. Toluene on treatment with $ ext{Cl}_2$ in sunlight gives benzyl chloride whereas when treated with $ ext{Cl}_2$ in dark gives o-chlorobenzene and p-chlorobenzene.
II. Finkelstein reaction is carried out in the presence of dry acetone.
III. neo pentylchloride has lower boil...
The synthesis of alkyl iodide is best done by :
(A) Swarts reaction
(B) Wurtz reaction
(C) Sandmeyer reaction
(D) Finkelstein reaction
Major product obtained when chlorobenzene reacts with methyl chloride and sodium in the presence of dry ether is :
(A) Toluene
(B) o-Dichlorobenzene
(C) Benzene
(D) Methane
What happens when :
(a) Bromobenzene is treated with Mg in the presence of dry ether ?
(b) Benzyl chloride is treated with aqueous $ ext{KOH}$ ?
(c) $2,4,6$-trinitrochlorobenzene is treated with warm water ?
The conversion of an alkyl halide into an alcohol by aqueous $ ext{NaOH}$ is classified as
(A) an addition reaction
(B) a substitution reaction
(C) a dehydrohalogenation reaction
(D) a dehydration reaction
The synthesis of alkyl fluoride is best accomplished by
(A) Sandmeyer reaction
(B) Finkelstein reaction
(C) Wurtz reaction
(D) Swarts reaction
Assertion (A) : Nucleophilic substitution reaction of chlorobenzene is easier than that of chloroethane.
Reason (R) : $ ext{C}- ext{Cl}$ bond in chlorobenzene has partial double bond character due to resonance.
Account for the following :
(a) The $\text{C} - \text{Cl}$ bond length in chlorobenzene is shorter than that in methyl chloride.
(b) Grignard reagents should be prepared under anhydrous conditions.
(c) In case of optically active alkyl halides, $\text{S}_\text{N}1$ reactions are accompanied by racem...
(a) Among the following, which will have inversion of configuration on reaction with aqueous alkali and why ?
(i) 1-chloropropane $\text{OR}$ (ii) 2-chloro-2-methylpropane
Assertion ($A$) : The boiling points of alkyl halides decrease in the order $\text{RI} > \text{RBr} > \text{RCl} > \text{RF}$.
Reason ($R$) : The van der Waals forces of attraction decrease in the order $\text{RI} > \text{RBr} > \text{RCl} > \text{RF}$.
Account for the following :
(a) Haloarenes are less reactive towards nucleophilic substitution reactions.
(b) $p$-dichlorobenzene has higher melting point than ortho and meta isomers.
(c) Tertiary alkyl halides are least reactive towards $ ext{S}_ ext{N}2$ reaction.
Which reagents are required for one step conversion of chlorobenzene to toluene ?
(A) $ ext{NaNO}_2 + ext{HCl}$
(B) $ ext{CH}_3 ext{Cl}/ ext{Anhydrous } ext{AlCl}_3$
(C) $ ext{CH}_3 ext{Cl}/ ext{Fe, Dark}$
(D) $ ext{CH}_3 ext{Cl}, ext{Na}, ext{Dry ether}$
Which reagents are required for one step conversion of Chlorobenzene to Diphenyl ?
(A) Chlorobenzene, $ ext{Na}$, Dry ether
(B) Benzene, Anhydrous $ ext{AlCl}_3$
(C) Chlorobenzene/$ ext{Fe}$, Dark
(D) $ ext{NaNO}_2 + ext{HCl}$
Which of the following haloalkanes react with aqueous $ ext{KOH}$ most rapidly by $ ext{S}_ ext{N}1$ reaction ?
(A) 2-Chlorobutane
(B) 1-Bromobutane
(C) 2-Bromo-2-Methylpropane
(D) 2,2-Dimethyl-1-Chloropropane
The synthesis of alkyl fluoride is best carried out by :
(A) Finkelstein reaction
(B) Swarts reaction
(C) Sandmeyer reaction
(D) Wurtz reaction
Which of the following haloalkanes is most reactive towards $\text{S}_\text{N}2$ reaction ?
(A) $\text{CH}_3 - \text{CH}_2 - \text{I}$
(B) $\text{CH}_3 - \text{CH}_2 - \text{Br}$
(C) $\text{CH}_3 - \text{CH}_2 - \text{Cl}$
(D) $\text{CH}_3 - \text{CH}_2 - \text{F}$
A compound (A) with molecular formula $ ext{C}_4 ext{H}_9 ext{I}$ which is a primary alkyl halide, reacts with alcoholic $ ext{KOH}$ to give compound (B). Compound (B) reacts with $ ext{HI}$ to give (C) which is an isomer of (A). When (A) reacts with $ ext{Na}$ metal in the presence of dry ether, it...
Identify the Freon from the following compounds :
(A) $ ext{CCl}_2 ext{F}_2$
(B) $ ext{CCl}_2 ext{Br}_2$
(C) $ ext{CH}_2 ext{Cl} - ext{CHCl}_2$
(D) $ ext{CHCl}_2 - ext{CHCl}_2$
Assertion (A) : Presence of $-\text{NO}_2$ group at ortho or para position increases the reactivity of haloarenes towards nucleophilic substitution reactions.
Reason (R) : Nitro group decreases the electron density over the benzene ring.
Assertion (A) : Presence of $- ext{NO}_2$ group at meta position increases the reactivity of haloarenes towards nucleophilic substitution reactions.
Reason (R) : $- ext{NO}_2$ group decreases the electron density over the benzene ring and thus facilitates the attack of nucleophile on haloarenes.
Assertion (A) : Presence of $- ext{NO}_2$ group at ortho and para positions decreases the reactivity of haloarenes towards nucleophilic substitution reactions.
Reason (R) : Nitro group decreases the electron density over the benzene ring.
Study the graph showing the boiling points of bromoalkanes and identify the compounds.
(Graph showing boiling points of bromoalkanes with bars 1 = 277 K, 2 = 346 K, 3 = 364 K, 4 = 375 K)
a. 1 = Bromomethane, 2= 2-Bromobutane, 3= 1-Bromobutane, 4= 2-Bromo-2-methylpropane
b. 1 =1-Bromobutane, 2= 2-B...
Various isomeric haloalkanes with the general formula $\text{C}_4\text{H}_9\text{Cl}$ undergo hydrolysis reaction. Among them, compound “A” is the most reactive through $\text{S}_\text{N}^1$ mechanism. Identify “A” citing the reason for your choice. Write the mechanism for the reaction.
b. Williamson's process is used for the preparation of ethers from alkyl halide. Identify the alkyl bromide and sodium alkoxide used for the preparation of 2-Ethoxy-3-methylpentane
c. An organic compound A which is a Grignard reagent is used to obtain 2-methylbutan-2-ol on reaction with a carbonyl compound 'B'. Identify A' and 'B'. Write the equation for the reaction between A and B.
Define the following terms : (a) Racemic mixture (b) Chiral carbon (c) Enantiomers
(a) Which halogen compound in the following pair will react faster in $S_N1$ reaction and why ?
$\text{CH}_3 - \text{CH} - \text{CH}_3$ or $\text{CH}_3 - \text{C} - \text{Br}$
$|$ $|$
$\text{Br}$ $\text{CH}_3$
(b) Why is the dipole moment of chlorobenzene lower than that of cyclohexyl chlori...
Which of the following Grignard reagent will be used with methanal to prepare a cyclohexane ring attached to a $\text{CH}_2 - \text{OH}$ group?
(A) Cyclohexane ring attached to $\text{CH}_2\text{MgBr}$
(B) Cyclohexane ring attached to $\text{CH}_2\text{CH}_2\text{MgBr}$
(C) Benzene ring attached to...
(b) Why does the presence of nitro groups at ortho- and para- positions in haloarenes increase their reactivity towards nucleophilic substitution reaction?
Account for the following : (a) n-butyl bromide has higher boiling point than t-butyl bromide. (b) Alkyl halides are insoluble in water. (c) Cyclohexyl chloride possesses higher dipole moment than chlorobenzene.
A primary alkyl halide would prefer to undergo __________.
(A) $\text{S}_{\text{N}}2$ reaction
(B) $\text{S}_{\text{N}}1$ reaction
(C) Electrophilic substitution reaction
(D) Racemisation
(a) Out of $(\text{CH}_3)_3\text{C} - \text{Br}$ and $(\text{CH}_3)_3\text{C} - \text{I}$, which one is more reactive towards $\text{S}_\text{N}1$ and why ? (b) Write the product formed when p-nitrochlorobenzene is heated with aqueous $\text{NaOH}$ at $443 \text{ K}$ followed by acidification.
Write the main products when : (any three) (a) Methyl chloride is treated with KCN. (b) 2,4,6-trinitrochlorobenzene is subjected to hydrolysis. (c) Methyl chloride is treated with sodium in the presence of dry ether. (d) n-butylchloride is treated with alcoholic KOH.
Assertion (A) : Nucleophilic substitution of iodoethane is easier than chloroethane.
Reason (R) : Bond enthalpy of C-I bond is less than that of C-Cl bond.
Write main product formed when : (a) Methyl chloride is treated with $\text{NaI/Acetone}$. (b) 2,4,6-trinitrochlorobenzene is subjected to hydrolysis. (c) n-Butyl chloride is treated with alcoholic $\text{KOH}$.
Write the main product formed when : (a) n-Butyl chloride is treated with alc. KOH. (b) 2,4,6-Trinitrochlorobenzene is subjected to hydrolysis.
Write main product formed when : (a) Methyl chloride is treated with NaI/Acetone. (b) 2,4,6-trinitrochlorobenzene is subjected to hydrolysis. (c) n-Butyl chloride is treated with alcoholic KOH.
(a) Arrange the isomeric dichlorobenzene in the increasing order of their boiling point and melting points.
(b) Explain why the electrophilic substitution reactions in haloarenes occur slowly and require more drastic conditions as compared to those in benzene.
Assertion (A) : Chlorobenzene is resistant to electrophilic substitution reaction.
Reason (R) : C-$Cl$ bond in chlorobenzene acquires partial double bond characters due to resonance.
(c) Why p-dichlorobenzene has higher melting point than those of ortho- and meta-isomers ?
Inversion of configuration occurs in
(a) $\text{S}_\text{N}2$ reaction
(b) $\text{S}_\text{N}1$ reaction
(c) Neither $\text{S}_\text{N}2$ nor $\text{S}_\text{N}1$ reaction
(d) $\text{S}_\text{N}1$ as well as $\text{S}_\text{N}2$ reaction
Assertion (A) : Chlorobenzene is resistant to nucleophilic substitution reaction at room temperature.
Reason (R) : $\text{C}-\text{Cl}$ bond gets weaker due to resonance.
Answer any 3 of the following : (a) Which isomer of $ ext{C}_5 ext{H}_{10}$ gives a single monochloro compound $ ext{C}_5 ext{H}_9 ext{Cl}$ in bright sunlight ? (b) Arrange the following compounds in increasing order of reactivity towards $ ext{S}_ ext{N}2$ reaction : 2-Bromopentane, 1-Bromopentane,...
Assertion (A) : Nucleophilic substitution reaction of an optically active halide gives a mixture of enantiomers.
Reason (R) : $\text{S}_ ext{N}2$ reactions of optically active halides are accompanied by inversion of configuration.
What happens when :
(a) 1-chlorobutane is treated with alcoholic KOH ?
(b) Chlorobenzene is treated with sodium in dry ether ?
Answer any three of the following : (a) p-nitrochlorobenzene undergoes nucleophilic substitution reaction faster than chlorobenzene. (b) Why is $(\pm)$-Butan-2-ol optically inactive, though it contains a chiral carbon atom ? (c) Why is chloroform kept in airtight dark coloured bottle ? (d) Write the...
Which of the following is not true about enantiomers?
(a) They have the same density.
(b) They have the same melting or boiling point.
(c) They have the same specific rotation.
(d) They have the same chemical reactivity.
Which of the following has the highest melting point?
(a) o-Dichlorobenzene
(b) m-Dichlorobenzene
(c) p-Dichlorobenzene
(d) All have the same melting point
Assertion (A): Nucleophilic substitution of iodoethane is easier than chloroethane.
Reason (R): Bond energy of C - Cl bond is less than C - I bond.
Show how you will synthesise : (a) 1-methylcyclohexan-1-ol from a suitable alkene. (b) Cyclohexylmethanol from methanal using a suitable Grignard reagent.
Which of the following belongs to the class of alkyl halides ?
(a) $\text{CH}_2 = \text{CH} - \text{Cl}$
(b) $\text{CH}_2 = \text{CH} - \text{CH}_2 - \text{CH}_2 - \text{Cl}$
(c) $\text{CH}_2 = \text{CH} - \text{CH}(\text{Cl}) - \text{CH}_3$
(d) $\text{CH} \equiv \text{C} - \text{CH}_2 - \text{Cl}$
The following questions are case-based questions. Read the case carefully and answer the questions that follow.
The polarity of C - X bond of alkyl halides is responsible for their nucleophilic substitution, elimination and their reaction with metal atoms to form organometallic compounds. Alkyl hali...
Answer the following questions: (i) What happens when bromobenzene is treated with Mg in the presence of dry ether? (ii) Which compound in each of the following pairs will react faster in $\text{S}_\text{N}^1$ reaction with $\text{OH}^-$? (1) $\text{CH}_2 = \text{CH} - \text{CH}_2 - \text{Cl}$ or $\...
An alkyl halide (A) of molecular formula $\text{C}_6\text{H}_{13}\text{Cl}$ on treatment with alcoholic KOH gives two isomeric alkenes (B) and (C) of molecular formula $\text{C}_6\text{H}_{12}$. Both alkenes on hydrogenation give 2,3-dimethylbutane. Write the structures of (A), (B) and (C).
When nitrobenzene is heated with tin and concentrated $\text{HCl}$, the product formed is :
(a) Image of Aniline
(b) Image of Anilinium chloride
(c) Image of Azobenzene
(d) Image of Chlorobenzene
Why is boiling point of o-dichlorobenzene higher than p-dichlorobenzene but melting point of para isomer is higher than ortho isomer ?
Write equations for the following : (a) Oxidation of chloroform by air and light (b) Reaction of chlorobenzene with $\text{CH}_3\text{Cl} / \text{anhyd. AlCl}_3$
Why haloarenes are not reactive towards nucleophilic substitution reaction ? Give two reasons.
(a) (i) Why do tertiary alkyl halides undergo S$_{N}$1 reaction at a faster rate? (ii) Define Enantiomers. (iii) Why is chloroform stored in dark coloured air tight bottles?
Why is chlorobenzene less reactive towards nucleophilic substitution reaction ?
OR (b) (i) Write the major alkene that would be formed by dehydrohalogenation of 2-Bromopentane. (ii) Which would undergo $\text{S}_\text{N}2$ reaction at a faster rate and why ? $\text{CH}_3 - \text{CH}_2 - \text{Br}$ and $\text{CH}_3 - \text{C}(\text{CH}_3)_2 - \text{Br}$. (iii) Why is chlorobenze...
Answer any three of the following : (a) Out of $\text{chlorobenzene-Cl}$ and $\text{chlorobenzene-CH}_2 - \text{Cl}$, which one is more reactive towards $\text{S}_\text{N}^2$ reaction and why ? (b) Out of chlorobenzene and p-nitrochlorobenzene which is more reactive towards nucleophilic substitution...
Give reason for the following: a. During the electrophilic substitution reaction of haloarenes, para substituted derivative is the major product. b. The product formed during $\text{S}_ ext{N}^1$ reaction is a racemic mixture. OR a. Name the suitable alcohol and reagent, from which 2-Chloro-2-methyl...
a. Identify the major product formed when 2-cyclohexylchloroethane undergoes a dehydrohalogenation reaction. Name the reagent which is used to carry out the reaction. b. Why are haloalkanes more reactive towards nucleophilic substitution reactions than haloarenes and vinylic halides? OR a. Name the ...