NEET/JEE Coaching Scholarship
Get up to 90% Scholarship on Offline NEET/JEE coaching from top Institutes
NCERT Chapter 10 Chemistry class 12, "Haloalkanes and Haloarenes", provides a detailed explanation of organic compounds that contain halogens (fluorine, chlorine, bromine, and iodine) attached to carbon atoms and the principles and theories that govern their behaviour. These organic compounds are widely used in industry and daily life, such as chlorofluorocarbons (CFCs), pesticides, and pharmaceuticals. This chapter, Haloalkanes and Haloarenes, also deals with the chemical structure, nomenclature, properties, and reactivity of haloalkanes and haloarenes. This NCERT chapter also includes many key concepts such as the preparation methods, the mechanisms of substitution reactions, nucleophilic substitution and elimination reactions, types of halogenation, and the physical properties of these compounds, including their solubility, boiling points, and density.
Latest: JEE Main high scoring chapters | JEE Main 10 year's papers
Recommended: NEET high scoring chapters
The NCERT Exemplar Class 12 Chemistry Solutions Chapter 10 Haloalkanes and Haloarenes are designed by our subject experts to offer a systematic and structured approach to these important concepts and help students to develop a clear understanding of critical concepts through a series of solved examples and conceptual explanations. These solutions provide a valuable resource to enhance performance in board exams as well as in competitive exams like JEE Advanced, NEET, JEE Mains, etc. In this article, we will discuss detailed solutions to all the questions. Also, check NCERT Solutions for Class 12 for solutions to all questions chapter-wise.
Question:1
The order of reactivity of the following alcohols with halogen acids is
(A)
(B)
(C)
(i) (A) > (B) > (C)
(ii) (C) > (B) > (A)
(iii) (B) > (A) > (C)
(iv) (A) > (C) > (B)
Answer:
The alcohol reacts with the halogen acids in an order of
Hence the correct option is (ii) (C) > (B) > (A)
Question:2
The tertiary alcohol reacts the most with concentrated HCl, as the tertiary carbocation is the most stable. Therefore, for tertiary alcohol, the room temperature is enough for the reaction. However, for primary and secondary alcohols, there is a need for the presence of a catalyst
Hence option (iv) is correct.
Question:3
Identify the compound Y in the following reaction:
Answer:
(a) Dissolved or suspended in cold aqueous mineral acid, a primary aromatic amine turns into a diazonium salt, after treatment with sodium nitrite. The diazonium group is replaced by -Cl as soon as the cuprous chloride is added to the previously prepared diazonium salt. Hence, the ‘Y’ here in the equation is chlorobenzene.
Question:4
Toluene reacts with a halogen in the presence of iron (III) chloride giving ortho and para halo compounds. The reaction is
(a) electrophilic elimination reaction
(b) electrophilic substitution reaction
(c) free radical addition reaction
(d) nucleophilic substitution reaction
Answer:
(b) This type of reaction is called an electrophilic substitution reaction.
Question:5
Which of the following is a halogen exchange reaction?
(i)
(ii)
(iii)
(iv)
Answer:
(a) Halogen exchange reaction means one halide is replaced by the other. This reaction is also called the Finkelstein reaction.
Question:6
Which reagent will you use for the following reaction?
(i)
(ii)
(iii)
(iv)
Answer:
(a) Here, it is a free radical substitution reaction. That means this reaction happens in the presence of UV light/peroxides/ high temperature. These are all free radical generators.
Question:7
Arrange the following compounds in the increasing order of their densities.
(i) (a) < (b) < (c) < (d)
(ii) (a) < (c) < (d) < (b)
(iii) (d) < (c) < (b) < (a)
(iv) (b) < (d) < (c) < (a)
Answer:
(a) Density increases with an increase in molecular mass. The order of molecular masses is (a) < (b) < (c) < (d)
Hence option (i) (a) < (b) < (c) < (d) is correct.
Question:8
Arrange the following compounds in increasing order of their boiling points
(i)
(ii)
(iii)
(i) (b) < (a) < (c)
(ii) (a) < (b) < (c)
(iii) (c) < (a) < (b)
(iv) (c) < (b) < (a)
Answer:
Option (iii) (c) < (a) < (b) is correct. Here the given alkanes are isomeric. Therefore isomeric alkane’s boiling point decreases with increase in branching. When the branching of an alkane increases, the surface area decreases. This causes a decrease in intermolecular force.
Question:9
In which of the following molecules carbon atom marked with an asterisk (*) is asymmetric?
(i) (a), (b), (c), (d)
(ii) (a), (b), (c)
(iii) (b), (c), (d)
(iv) (a), (c), (d)
Answer:
(ii) An Asymmetric carbon atom is linked with four different groups or atoms with all of its four valencies. Here, the carbon atoms of (i), (ii), and (iii), all have linked with four different groups of atoms. Hence, those are asymmetric. Whereas, in (iv), the carbon atom is linked with two of its valencies with two similar hydrogen atoms. Therefore, it is not an asymmetric carbon atom.
Question:10
Which of the following structures is enantiomeric with the molecule (A) given below:
Answer:
(i) Here the structure (i) is the enantiomer of compound (A). Here the position two groups, i.e., CH3 and C2H5 in (i) is exactly reversed of the given sample (A) at the chiral carbon.
Question:11
Which of the following is an example of vic-dihalide?
(a) Dichloromethane
(b) 1, 2-dichloroethane
(c) Ethylidene chloride
(d) Allyl chloride
Answer:
(b) 1, 2-Dichloroethane is an example of a vic-dihalide. This is because ofthe presence of two Cl atoms on vicinal carbon atoms (adjacent).
Question:12
The position of -Br in the compound
(a) allyl
(b) aryl
(c) vinyl
(d) secondary
Answer:
(a) The given sample is an allylic compound. Here the Br atom is attached next to double-bonded carbon.
Question:13
Chlorobenzene is formed by the reaction of chlorine with benzene in the presence of
(a)
(b)
(c)
(d)
Answer:
(b) Here, the
Question:14
Ethylidene chloride is a/an ________.
(a) vic-dihalide
(b) gem-dihalide
(c) allylic halide
(d) vinylic halide
Answer:
(ii) Ethylidene chloride is a gem-dihalide. This is because the halogen atoms of
Question:15
What is A in the following reaction?
Answer:
(c) Here, according to Markownikow's rule, HCl will be attached to the doubly bonded carbons. Therefore, for the carbon atom that has a lesser number of hydrogens, the addition of a negative addendum will take place.
Question:16
A primary alkyl halide would prefer to undergo __________ .
(a)
(b)
(c)
(d) Racemisation
Answer:
(b)
Question:17
Which of the following alkyl halides will undergo
(a)
(b)
(c)
(d)
Answer:
(d)
Question:18
Which is the correct IUPAC name of ?
(i) 1-Bromo-2-ethylpropane
(ii) 1-Bromo-2-ethyl-2-methylene
(iii) 1-Bromo-2-methylbutane
(iv) 2-Methyl-1-bromobutane
Answer:
(c) The correct IUPAC name of the given compound is 1-Bromo-2-methyl butane.
Question:19
What should be the correct IUPAC name for diethyl bromomethane?
(a) 1-Bromo-1, 1-diethylmethane
(b) 3-Bromopentane
(c) 1-Bromo-1-ethylpropane
(d) 1-Bromopentane
Answer:
(b) The IUPAC name of Diethyl Bromomethane is 3-Bromopentane.
Question:21
Chloromethane on treatment with excess of ammonia yields mainly
(i) N,N- Dimethylmethanamine
(ii) N-methylmethanamine
(iii) Methanamine
(iv) Mixture containing all of these mixtures in equal proportion
Answer:
(iii) Chloromethane on treatment with an excess of ammonia yields mainly methenamine.
However, if the two reactants are present in the same amount, the mixture of the primary, secondary, and tertiary amine is obtained.
Question:22
Molecules whose mirror image is non-superimposable over them are known as chiral. Which of the following molecules is chiral in nature?
(a) 2-Bromobutane
(b) 1-Bromobutane
(c) 2-Bromopropane
(d) 2-Bromopropan-2-ol
Answer:
Question:23
The reaction of
(a)
(b)
(c) Any of the above two depending upon the temperature of the reaction
(d) Saytzeff rule
Answer:
(a) Reaction of
Benzylic halides are highly reactive in nature towards the
Question:24
Which of the carbon atoms present in the molecule given below are asymmetric?
(i) a, b, c, d
(ii) b, c
(iii) a, d
(iv) a, b, c
Answer:
(b) Carbon has four valencies. When all four valencies are attached to four different atoms or groups then the carbon is called asymmetric/ chiral carbon. Here, ‘b’ and ‘c’ are attached to four different atoms/ groups. Hence, these are asymmetric.
Question:25
Which of the following compounds will give a racemic mixture on nucleophilic substitution by
(i) (a)
(ii) (a), (b), (c)
(iii) (b), (c)
(iv) (a), (c)
Answer:
(a) As the alkyl halide in it contains asymmetric carbon, therefore, a mixture of an enantiomer is formed during the
Question:26
In the question arrange the compounds in increasing order of the rate of reaction towards nucleophilic substitution.
(i) (a) < (b) < (c)
(ii) (c) < (b) < (a)
(iii) (a) < (c) < (b)
(iv) (c) < (a) < (b)
Answer:
(iii)
Question:27
In the questions, arrange the compounds in increasing order of the rate of reaction towards nucleophilic substitution.
(i) (a) < (b) < (c)
(ii) (a) < (c) < (b)
(iii) (c) < (b) < (a)
(iv) (b) < (c) < (a)
Answer:
(iv) The rate of nucleophilic substitution decreases when there is an electron-releasing group at ortho or para positions.
Question:28
In the questions, arrange the compounds in increasing order of the rate of reaction towards nucleophilic substitution.
(i) (c) < (b) < (a)
(ii) (b) < (c) < (a)
(iii) (a) < (c) < (b)
(iv) (a) < (b) < (c)
Answer:
(iv) The reactivity of aryl halides increases with the increase in the electron-withdrawing group. Therefore, the more the number of electron-withdrawing groups, the more the rate of nucleophilic substitution.
Question:29
In the questions, arrange the compounds in increasing order of the rate of reaction towards nucleophilic substitution.
(i) (a) < (b) < (c)
(ii) (b) < (a) < (c)
(iii) (c) < (b) < (a)
(iv) (a) < (c) < (b)
Answer:
(c) Electron-releasing groups increase the reactivity of aryl halides, less the number of electron-releasing groups, the lower the rate towards nucleophilic substitution.
Question:30
Which is the correct increasing order of boiling points of the following compounds?
1-Iodobutane, 1-Bromobutane, 1-Chlorobutane, Butane
(a) Butane < 1-Chlorobutane < 1-Bromobutane < 1 -Iodobutane
(b) 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane < Butane
(c) Butane < 1-Iodobutane < 1-Bromobutane < 1-Chlorobutane
(d) Butane < 1-Chlorobutane < 1-Iodobutane < 1-Bromobutane
Answer:
(a) The intermolecular force of attraction will increase with the increase in surface area. As a result, the boiling point will also increase. As the boiling point increases with the molecular mass for the similar alkyl halide. The Iodine has the highest atomic mass. Therefore, the boiling point of 1-iodobutane is the highest.
Question:31
Which is the correct increasing order of boiling points of the following compounds?
1-Bromoethane, 1-Bromopropane, 1-Bromobutane, Bromobenzene
(a) Bromobenzene < 1-Bromobutane < 1-Bromopropane < 1-Bromoethane
(b) Bromobenzene < 1-Bromoethane < 1 -Bromopropane < 1-Bromobutane
(c) 1-Bromopropane < 1-Bromobutane < 1-Bromoethane < Bromobenzene
(d) 1-Bromoethane < 1-Bromopropane < 1-Bromobutane < Bromobenzene
Answer:
d) The boiling point increases with an increase in molecular mass for the same types of alkyl halide.
Question:32
Which of the statements are correct about the above reaction?
(i) (a) and (e) both are nucleophiles.
(ii) In (c) carbon atom is sp3 hybridized.
(iii) In (c) carbon atom is sp2 hybridized.
(iv) (a) and (e) both are electrophiles.
Answer:
(i), (iii)
Question:33
Which of the following statements are correct about this reaction?
(i) The given reaction follows
(ii) (b) and (d) have opposite configurations.
(iii) (b) and (d) have the same configuration.
(iv) The given reaction follows
Answer:
(i), (ii) In the given reaction, alkyl halide is primary in nature. Here, a transition state is observed in which one bond is broken and one bond is formed simultaneously i.e., in one step. So, it follows the
In this mechanism, the nucleophile attacks the carbon at
Question:34
Which of the following statements are correct about the reaction intermediate?
(i) Intermediate (c) is unstable because this carbon is attached to 5 atoms.
(ii) Intermediate (c) is unstable because the carbon atom is
(iii) Intermediate (c) is stable because the carbon atom is
(iv) Intermediate (c) is less stable than the reactant (b).
Answer:
(i), (iv) are correct options.
Question:35
Which of the following statements are correct about the mechanism of this reaction?
(i) A carbocation will be formed as an intermediate in the reaction.
(ii)
(iii) An unstable intermediate will be formed in which
(iv) Reaction proceeds through
Answer:
(i), (iv) are correct. As the given reaction is a tertiary halide, therefore
Question:36
Which of the following statements are correct about the kinetics of this reaction?
(i) The rate of reaction depends on the concentration of only (b).
(ii) The rate of reaction depends on the concentration of both (a) and (b).
(iii) Molecularity of the reaction is one.
(iv) Molecularity of the reaction is two.
Answer:
(i), (iii) is the correct statements.
Question:37
Haloalkanes contain halogen atom(s) attached to sp3 hybridized carbon atoms of an alkyl group. Identify haloalkane from the following compounds.
(i) 2-Bromopentane
(ii) Vinyl chloride (chloroethene)
(iii) 2-chloroacetophenone
(iv) Trichloromethane
Answer:
(i), (iv) are the haloalkanes from the above list.
Question:38
Ethylene chloride and ethylidene chloride are isomers. Identify the correct statements.
(i) Both the compounds form the same product on treatment with alcoholic KOH.
(ii) Both the compounds form the same product on treatment with aq.NaOH.
(iii) Both the compounds form the same product on reduction.
(iv) Both the compounds are optically active.
Answer:
(i), (iii) are correct.
Question:39
Which of the following compounds are gem-dihalides?
(i) Ethylidene chloride
(ii) Ethylene dichloride
(iii) Methylene chloride
(iv) Benzyl chloride
Answer:
(i), (iii) are Gem-dihalides.
Question:40
Which of the following are secondary bromides?
(a)
(b)
(c)
(d)
Answer:
(i), (iii) are secondary bromides.
Question:41
Which of the following compounds can be classified as aryl halides?
(i)
(ii)
(iii)
(iv)
Answer:
(i), (iv) are classified as aryl halides as there is a bond between a halogen atom and an atomic ring.
Question:42
Alkyl halides are prepared from alcohol by treating with
(i)
(ii)
(iii)
(iv) all the above
Answer:
(i), (ii) are correct options
Question:43
Alkyl fluorides are synthesized by heating an alkyl chloride/bromide in
presence of ____ or ____
Answer:
(ii), (iii) are correct options
Question:44
Answer:
Iodination reactions are reversible in nature as because HI is formed in the process. To keep the reaction in forward direction, we need to remove the HI by oxidation process by adding some oxidizing agents like
Question:45
Out of o- and p-bromobenzene, which one has a higher melting point, and why?
Answer:
p-Dibromobenzene has a higher melting point. Because, in a crystal lattice, the symmetry of p-bromobenzene makes it fit better. As a result, a higher temperature is required to break the bond between the molecules and hence the melting point is higher.
Question:46
Which of the compounds will react faster in
Answer:
Question:47
Why does iodoform have appreciable antiseptic properties?
Answer:
Because there are liberal free iodines, iodoform is an applicable antiseptic.
Question:48
Haloarenes are less reactive than haloalkanes and haloalkenes. Explain.
Answer:
This is because there is a resonance stabilization formed in the aryl ring. Where the C -Cl bond acts as a partial double bond because of resonance. Therefore, they are less reactive in nucleophilic substitution.
Question:49
Discuss the role of Lewis acids in the preparation of aryl bromides and chlorides in the dark.
Answer:
Aryl bromides and chlorides can be prepared in the presence of Lewis acid catalysts (iron or iron chloride) from the electrophilic substitution of arenas with bromine and chlorine respectively.
Question:50
If we mix NaBr and
Question:51
Which of the products will be the major product in the reaction given below? Explain.
Answer:
As per Markovnikov's rule B will be the major product
Question:52
Why is the solubility of haloalkanes in water very low?
Answer:
The solubility of the haloalkanes in water is low. This is because, to make a haloalkane soluble in water, we need energy. Which will help to overcome the attraction between the haloalkane molecules and also help to break the hydrogen bonds between water molecules.
Question:53
Answer:
The functional group present in this ring is ortho-para directing. This is because the density of electrons at that position is higher.
Question:54
(i) 1-Bromobut-2-ene: It is a primary halide.
(ii) 4-Bromopent-2-ene: Here Bromine is attached to the secondary carbon. Hence, it is a secondary halide.
(iii) 2-Bromo-2-methylpropane: Here Bromine is attached to the tertiary carbon. Hence, it is a tertiary halide.
Question:55
Answer:
(i) The rate of reaction with aqueous KOH of the compound ‘A’ only depends upon the concentration of ‘A’, therefore, the reaction mechanism is
Whereas, ‘B’ is optically active and is an isomer of ‘A’. Therefore, ‘B’ must be 2-Bromobutane. As the concentration of ‘B’ is responsible for the rate of reaction of ‘B’ with aqueous KOH, therefore, the reaction mechanism is
(ii) Because of the
Question:56
Toluene
Question:58
Which of the following compounds will have the highest melting point and why?
Answer:
The structure (II) has the symmetry of para-positions. Therefore, it fits into crystal lattice better than other isomers and has the highest melting point.
Question:59
Write down the structure and IUPAC name for neo-pentyl bromide.
Answer:
1-Bromo-2,2-dimethylpropane is the IUPAC name for neo-pentyl bromide.
Question:60
We can say pentane
Question:61
Here, two different alkenes such as methylene cyclohexane and 1-methylcyclohex-1-ene can be found.
Question:62
Which of the following haloalkanes reacts with aqueous KOH most easily? Explain by giving a reason.
(i) 1-Bromobutane
(ii) 2-Bromobutane
(iii) 2-Bromo-2-methylpropane
(iv) 2-Chlorobutane
Answer:
(iii) 2-Bromo-2-methylpropane
This complex will easily react with the aqueous KOH. Here, tertiary carbocation will be formed and this will be most stable.
Question:63
Why can aryl halides not be prepared by the reaction of phenol with HCl in the presence of
Answer:
In the presence of
Question:64
Which of the following compounds would undergo
Answer:
B will undergo
On the other hand, the carbonation formed during the reaction (A) is not a resonance situation.
Question:65
Allyl chloride is hydrolyzed more readily than n-propyl chloride. Why?
Answer:
Allyl chloride becomes highly reactive in nature due to the formation of carbocation by hydrolysis, which is very much stable due to resonance. In the case of n-propyl chloride, there will be no such stability exists due to carbocation.
Question:66
Why is it necessary to avoid even traces of moisture during the use of a Grignard reagent?
Answer:
It is necessary to avoid even traces of moisture because the Grignard reagents are highly reactive in nature. Those reagents can react with even traces of water and produce corresponding hydrocarbons.
Question:67
How do polar solvents help in the first step in
Answer:
Through the formation of carbocation, the mechanism of the
Question:68
Write a test to detect the presence of a double bond in a molecule.
Answer:
If a molecule contains a double bond, then it can be detected easily by the bromine water test and Baeyer’s test. The bromine water or aqueous
Question:69
Diphenyls are a potential threat to the environment. How are these produced from aryl halides?
Answer:
Diphenyls(ex: p,p ‘-dichlorodiphenyltrichloroethane., i.e DDT) are a serious threat to the environment. This is because those are chemically stable and soluble in fat. The long-term presence of it in the atmosphere is extremely dangerous.
Di-phenyls can be prepared from aryl halides by the following two methods:
Question:70
IUPAC name of DDT is 2, 2-bis (4-chlorophenyl)-1, 1, 1-trichloroethane that of benzene hexachloride is 1, 2, 3, 4, 5, 6-hexachlorocyclohexane.
They are non-biodegradable and toxic at the same time. They are soluble in fat and their concentration keeps increasing in the food chain. This is why their use is banned in India and other countries.
Question:71
Answer:
Alkyl halides respond in nucleophilic substitution as well as elimination (
However, by setting the reaction condition and the right choice of reagent, a particular product can be obtained. Normally, elimination reaction suits the strong and larger bases along with high temperature. Whereas substitution reaction is suitable for the weaker and smaller bases in lower temperatures.
Ex:
Nucleophilic Subsitution : Reagents used are nucleophilies like
Question:72
How will you obtain mono bromobenzene from aniline?
Answer:
Mono bromobenzene from aniline:
Question:73
When the nucleophile is attached to the carbon carrying -Cl, due to resonance a stabilised intermediate compound is found. As the
Question:74
tert-Butylbromide reacts with aq. NaOH by
Answer:
In general, the
On the other hand, due to its unstable in nature, n-butyl bromide does not form 1° n-butyl carbocation by ionization. Therefore, it follows the mechanism of
Question:75
Predict the major product formed when HCl is added to isobutylene. Explain the mechanism involved.
Answer:
The major product is 2-chloro-2-methylpropane
Question:76
Discuss the nature of the C – X bond in the haloarenes.
Answer:
Resonance effect: The C – X bond holds the nature of a partial double bond character and as a result, the C – X bond is very difficult to break.
(i) The C – X bond in haloarenes is extremely less reactive towards nucleophilic
(ii) In C – X bond, the C atom attached to the halogen is sp2 hybridized. Carbon that is sp2 hybridized with a greater s-character is more electronegative in nature and it can hold the electron pair of C – X bond more tightly than sp3 hybridized carbon in haloalkanes with less s-character.
Question:77
Ethanol can be converted into chloroethane with the help of
Question:78
A cyanide ion acts as a stronger nucleophile from the carbon end. This is because it will form a C – C bond which is more stable (a bond between two similar atoms) than a C – N bond.
Question:79
Match the compounds given in Column I with the effects given in Column II.
Column I | Column II |
i. Chloramphenicol | a. Malaria |
ii. Thyroxine | b. Anesthetic |
iii. Chloroquine | c. Typhoid fever |
iv. Chloroform | d. Goiter |
e.Blood substituent |
Answer:
(i) Chloramphenicol is a broad-spectrum antibiotic that is used to treat typhoid fever.
(ii) Thyroxine is a hormone secreted by the thyroid gland. When the thyroxine is secreted more, then the patient will notice an enlarged thyroid gland which is called goiter.
(iii) Chloroquine is used to prevent malaria parasite plasmodium vivax in the blood.
(iv) Chloroform is trichloromethane
Question:80
Match the items of Column I and Column II.
column I | Column II |
i. | a. vic-dibromides |
ii. Chemicals in fire extinguisher | b. gem - dihalides |
iii. Bromination of alkene | c. Racemization |
iv. Alkylidene halides | d. Saytzeff rule |
v. Elimination of HX from alkyl halide | e. Chlorobromocarbons |
Answer:
(i) When any mixture has two enantiomers in equal proportions, then there will be zero optical rotation observed. These kinds of mixtures are called racemic mixtures and this process of conversion of enantiomers into a racemic mixture is known as racemization. When alkyl halide follows SN1 mechanism then racemization is observed.
(ii) Chlorofluorocarbons are used in fire extinguishers.
(iii) Halogen atoms are present on the adjacent carbon atom in vic-dihalides. vic-dihalides are observed from the Bromination of alkanes.
(iv) Alkylidene halides are also known as gem-dihalides. Halogen atoms are present on the same carbon atom in the case of gem-dihalides.
(v) Elimination of HX from alkyl halide follows the Saytzeff rule. This rule states that “in dehydrohalogenation reactions, the preferred product is that alkene which has the greater number of alkyl groups attached to the doubly bonded carbon atoms”.
Question:81
Match the reactions given in column I with the types of reactions given in column II.
Column I | Column II |
i. | a. Aryl halide |
ii. | b. Alkyl halide |
iii. | c. Vinyl halide |
iv. | d. Allyl halide |
Answer:
(i) A halogen atom in alkyl halide is bonded to a carbon atom that is sp3 hybridized, where further addition of alkyl group may happen.
(ii) A halogen atom in allyl halide is bonded to a carbon atom next to
(iii) Halogen atoms in aryl halide are bonded to a carbon atom that is
(iv) Halogen atoms in vinyl halide is bonded to a
Question:82
Match the reactions given in column I with the types of reactions given in column II.
Answer:
(i) Here, substitution takes place when an electrophile
(ii) Here, according to Markownifoff’s rule, on the double-bonded carbons the addition of HBr takes place followed by electrophilic addition.
(iii) Here, the reactant is a secondary halide in nature and the hydroxyl ion will substitute the halogen. Here the reaction mechanism is
(iv) Here the aromatic ring and the halogen atom are attached directly. The halogen of the given compound is substituted by the
(v) It follows Saytzeff's rule, i.,e elimination reaction.
Question:83
Match the structures given in Column I with the names given in Column II.
Answer:
(i) A: 4-bromopent-2-ene.
(ii) B: 4-bromo-3-methylpent-2-ene.
(iii) C: 1-bromo-2-methylbut-2-ene.
(iv) D: 1 -bromo-2-methylpent-2-ene.
Question:84
Match the reactions given in Column I with the names given in Column II.
Answer:
(i) Alkyl arene is produced by the mixture of an alkyl halide and aryl halides when treated with sodium in dry ether. This reaction is called the Wurtz-Fittig reaction.
(ii) Analogous compound is found from the aryl halides when it is treated with sodium in dry ether. Here, two aryl groups are attracted together. This reaction is called the Fittig reaction.
(iii) Chlorobenzene or bromobenzene is formed from the diazonium salt when it is treated with cuprous chloride or cuprous bromide. This reaction is called Sandmeyer’s reaction.
(iv) In dry acetone, alkyl chlorides, and sodium iodide react with each other and form Alkyl iodides. The reaction is called the Finkelstein reaction.
Question:85
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): Phosphorus chlorides (tri and penta) are preferred over thionyl chloride for the preparation of alkyl chlorides from alcohols.
Reason (R): Phosphorus chlorides give pure alkyl halides.
Answer:
(ii) To convert alcohol to alkyl halide, thionyl chloride is the best halogen carrier. Because all the byproducts are in a gaseous state. As a result, a pure form of alkyl halide can be prepared.
Question:86
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and the reason is the correct explanation of the assertion.
(ii) Both the assertion and the reason both are wrong statements.
(iii) The assertion is correct but the reason is a wrong statement.
(iv) The assertion is wrong, but the reason is the correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of the assertion.
Assertion (A): The boiling points of alkyl halides decrease in the order:
Reason (R): The boiling points of alkyl chlorides, bromides, and iodides are considerably higher than that of the hydrocarbon of comparable molecular mass.
Answer:
(v) The order of boiling point :
As the halides are polar molecules, therefore, their boiling temperature is always more than the boiling temperature of the hydrocarbons.
Question:87
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and the reason is the correct explanation of the assertion.
(ii) Assertion and reason both are wrong statements.
(iii) The assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): KCN reacts with methyl chloride to give methyl isocyanide
Reason (R):
Answer:
(iv)
Alkyl Cyanide
Methyl cyanide is also obtained as
Question:88
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): Tert-butyl bromide undergoes a Wurtz reaction to give 2, 2, 3, 3-tetramethylbutane.
Reason (R): In the Wurtz reaction, alkyl halides react with sodium in dry ether to give hydrocarbons containing double the number of carbon atoms present in the halide.
Answer:
Option (i) is correct.
In the Wurtz reaction, alkyl halides react with sodium in dry ether to give hydrocarbon containing double the number of carbon atoms present in the halide.
tert-Butyl bromide undergoes a Wurtz reaction to give 2, 2, 3, 3-tetramethylbutane.
Question:89
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): The presence of a nitro group at the ortho or para position increases the reactivity of haloarenes towards nucleophilic substitution.
Reason (R): The Nitro group, being an electron-withdrawing group decreases the electron density over the benzene ring.
Answer:
(i) The nitro group is used to decrease the electron density in the ring as it is an electron-withdrawing group. As a result, this will cause nucleophilic substitution due to an increase in reactivity of haloarenes.
Question:90
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): In mono haloarenes, further electrophilic substitution occurs at ortho and para positions.
Reason (R): The halogen atom is a ring deactivator.
Answer:
(v) Due to the (+M) or (+R) effect, the halogens are usually ortho-para directing in nature. However, due to high electronegativity, they are also deactivating in nature.
Question:91
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): Aryl iodides can be prepared by a reaction of arenes with iodine in the presence of an oxidizing agent.
Reason (R): Oxidising agent oxidizes
Answer:
(iii) HI converts into
Question:92
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but reason is not the correct explanation of assertion.
Assertion (A): It is difficult to replace chlorine by -OH in chlorobenzene in comparison to that in chloroethane.
Reason (R): Chlorine-carbon (C – Cl) bond in chlorobenzene has a partial double bond character due to resonance.
Answer:
(i) There is a partial double bond formed due to resonance in between the benzene ring and halogen. As a result, it is difficult for the aryl halide to take part in nucleophilic substitution as compared to the alkyl halide.
Question:93
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): Hydrolysis of (-)-2-bromooctane proceeds with inversion of configuration.
Reason (R): This reaction proceeds through the formation of a carbocation.
Answer:
(iii) Here,
Question:94
In the following questions, a statement of Assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question:
(i) Assertion and reason both are correct and reason is the correct explanation of assertion.
(ii) Assertion and reason both are wrong statements.
(iii) Assertion is correct but reason is wrong statement.
(iv) Assertion is wrong but reason is correct statement.
(v) Assertion and reason both are correct statements but the reason is not the correct explanation of assertion.
Assertion (A): Nitration of chlorobenzene leads to the formation of m-nitrochlorobenzene.
Reason (R):
Answer:
(iv) Nitration of chlorobenzene results in ortho and para nitro chlorobenzene. Although, the nitro groups are meta-directing in nature.
Question:95
Primary alkyl halides prefer SN2 mechanism in which a nucleophile attacks at 180? to the halogen atom. A transition state is formed in which carbon is bonded to two nucleophiles and finally halogen atom is pushed out. Below is the mechanism-
Hence, in SN2 mechanism, substitution takes place. Tertiary alkyl halides follow SN1 mechanism. In this case, there alkyl halides form 3? carbocations. If the reagent used is a weak base then substitution occurs while if it is a strong base then instead of substitution elimination occurs.
The reagent used is aq. KOH. It is a weak base so, substitution takes place.
As alc. KOH is a strong base, so elimination competes over substitution, and alkene is formed
Question:96
Uses of halogen-containing compounds are as follows:
Dichloromethane is mainly used as a solvent. Although it can be used as a paint remover, finishing solvent, metal cleaner, propellant in aerosols, solvent in case of drug manufacturing, etc.
Trichloromethane is used as a fat solvent. However, it can be used as a solvent for iodine, alkaloids, and other substances.
Triiodomethane is used as an antiseptic.
But some compounds of this class are responsible for the exposure of flora and fauna to more and more UV light which causes destruction to a great extent. These are as follows
(i) Tetrachloromethane
• CCl3 is released into the air and starts depleting the ozone layer in the atmosphere. As a result, UV rays will come to the earth easily and humans will get affected. This will cause skin cancer, functional disorder, eye diseases, and also the damage in the immune system. These UV rays not only affect the human but also cause damage to plants, and other animals too.
(ii) Freons
• Freon-113, releases and will move to the top of the atmosphere. Here, it generates Cl atoms in order to damage the ozone layer. As a result of this depletion UV rays enter our atmosphere and become responsible for damage to a great extent.
(iii) p – p’ – Dichlorodiphenyltrichloroethane (DDT)
• DDT can not be destroyed and removed from the atmosphere because it is not completely biodegradable. It is soluble in fats and creates a chain. When DDT goes into the body of a human, then it will affect the reproductive system.
In order to get rid of the harmful effects of the following substances, i.e., freons, hydrofluorocarbons, and fluorocarbons, we should lower the use of these substances.
Question:97
Aryl halides are less reactive towards nucleophilic substitution reactions for the reasons mentioned as follows:
(i) In the case of haloarenes, the benzene ring is attached to the lone pair electron of the halogen in resonance. As a result, the C-Cl bond acts as a partial double bond and increases the strength of the bond. This bond is difficult to substitute by nucleophilic substitution method. Hence, they usually react less in the above-mentioned reaction.
(ii) In the case of haloarenes, the
Method to increase the reactivity:
The reactivity of the aryl halides can be increased when there is an electron-withdrawing group
So, in the case of o- and p-chlorobenzenes, the carbon atom bearing
Thus, the presence of electron-withdrawing groups at o- and p-positions (but not at m-positions) w.r.t. The halogen atom activates the aryl halides towards nucleophilic substitution reaction.
Chapter 6 General Principles and Processes of Isolation of Elements |
Chapter 10 Haloalkanes and Haloarenes |
In Class 12 Chemistry NCERT exemplar solutions chapter 10, the students will learn that both haloalkanes and Haloarenes are hydrocarbons with one or more hydrogen atoms replaced. Haloalkanes are more reactive than Haloarenes.
Every topic in this chapter helps students learn about their uses, such as, Haloalkanes are used as refrigerants and as propellants.
They are also used to generate plastic aerosols. Haloalkanes are used for dry-cleaning and so on.
Haloarenes are used as flame retardants; they are important components of fire extinguishers, used widely in pharmaceuticals.
They react with different metals such as sodium and magnesium. Overall, NCERT exemplifies the Class 12 Chemistry Solutions Chapter 10. Apart from being informative, it is also fun and interesting for all those chemistry lovers who love to find different reactions and compounds.
Chapter 1 | |
Chapter 2 | |
Chapter 3 | |
Chapter 4 | |
Chapter 5 | |
Chapter 6 | |
Chapter 7 | Alcohols, Phenols, and Ethers |
Chapter 8 | |
Chapter 9 | |
Chapter 10 |
NCERT Exemplar Class 12 Solutions
Must read the NCERT Solution subject-wise
Read more NCERT Notes subject-wise
Also, check the NCERT Books and the NCERT Syllabus here:
Haloalkanes and Haloarenes are both organic compounds. In Haloalkanes, one or more hydrogen atoms of an alkane have been replaced by halogen atoms (fluorine, chlorine, bromine, or iodine). In Haloarenes, one or more hydrogen atoms of an aromatic ring (like benzene) are replaced by halogen atoms.
Haloalkanes and Haloarenes are both organic compounds. In Haloalkanes one or more hydrogen atoms of an alkane have been replaced by halogen atoms (fluorine, chlorine, bromine, or iodine). In Haloarenes, one or more hydrogen atoms of an aromatic ring (like benzene) are replaced by halogen atoms.
Haloalkanes and Haloarenes are both organic compounds. In Haloalkanes one or more hydrogen atoms of an alkane have been replaced by halogen atoms (fluorine, chlorine, bromine, or iodine). In Haloarenes, one or more hydrogen atoms of an aromatic ring (like benzene) are replaced by halogen atoms.
Haloalkanes primarily undergo:
.
Application Date:24 March,2025 - 23 April,2025
Admit Card Date:04 April,2025 - 26 April,2025
Changing from the CBSE board to the Odisha CHSE in Class 12 is generally difficult and often not ideal due to differences in syllabi and examination structures. Most boards, including Odisha CHSE , do not recommend switching in the final year of schooling. It is crucial to consult both CBSE and Odisha CHSE authorities for specific policies, but making such a change earlier is advisable to prevent academic complications.
Hello there! Thanks for reaching out to us at Careers360.
Ah, you're looking for CBSE quarterly question papers for mathematics, right? Those can be super helpful for exam prep.
Unfortunately, CBSE doesn't officially release quarterly papers - they mainly put out sample papers and previous years' board exam papers. But don't worry, there are still some good options to help you practice!
Have you checked out the CBSE sample papers on their official website? Those are usually pretty close to the actual exam format. You could also look into previous years' board exam papers - they're great for getting a feel for the types of questions that might come up.
If you're after more practice material, some textbook publishers release their own mock papers which can be useful too.
Let me know if you need any other tips for your math prep. Good luck with your studies!
It's understandable to feel disheartened after facing a compartment exam, especially when you've invested significant effort. However, it's important to remember that setbacks are a part of life, and they can be opportunities for growth.
Possible steps:
Re-evaluate Your Study Strategies:
Consider Professional Help:
Explore Alternative Options:
Focus on NEET 2025 Preparation:
Seek Support:
Remember: This is a temporary setback. With the right approach and perseverance, you can overcome this challenge and achieve your goals.
I hope this information helps you.
Hi,
Qualifications:
Age: As of the last registration date, you must be between the ages of 16 and 40.
Qualification: You must have graduated from an accredited board or at least passed the tenth grade. Higher qualifications are also accepted, such as a diploma, postgraduate degree, graduation, or 11th or 12th grade.
How to Apply:
Get the Medhavi app by visiting the Google Play Store.
Register: In the app, create an account.
Examine Notification: Examine the comprehensive notification on the scholarship examination.
Sign up to Take the Test: Finish the app's registration process.
Examine: The Medhavi app allows you to take the exam from the comfort of your home.
Get Results: In just two days, the results are made public.
Verification of Documents: Provide the required paperwork and bank account information for validation.
Get Scholarship: Following a successful verification process, the scholarship will be given. You need to have at least passed the 10th grade/matriculation scholarship amount will be transferred directly to your bank account.
Scholarship Details:
Type A: For candidates scoring 60% or above in the exam.
Type B: For candidates scoring between 50% and 60%.
Type C: For candidates scoring between 40% and 50%.
Cash Scholarship:
Scholarships can range from Rs. 2,000 to Rs. 18,000 per month, depending on the marks obtained and the type of scholarship exam (SAKSHAM, SWABHIMAN, SAMADHAN, etc.).
Since you already have a 12th grade qualification with 84%, you meet the qualification criteria and are eligible to apply for the Medhavi Scholarship exam. Make sure to prepare well for the exam to maximize your chances of receiving a higher scholarship.
Hope you find this useful!
hello mahima,
If you have uploaded screenshot of your 12th board result taken from CBSE official website,there won,t be a problem with that.If the screenshot that you have uploaded is clear and legible. It should display your name, roll number, marks obtained, and any other relevant details in a readable forma.ALSO, the screenshot clearly show it is from the official CBSE results portal.
hope this helps.
Get up to 90% Scholarship on Offline NEET/JEE coaching from top Institutes
This ebook serves as a valuable study guide for NEET 2025 exam.
This e-book offers NEET PYQ and serves as an indispensable NEET study material.
As per latest 2024 syllabus. Physics formulas, equations, & laws of class 11 & 12th chapters
As per latest 2024 syllabus. Chemistry formulas, equations, & laws of class 11 & 12th chapters
Accepted by more than 11,000 universities in over 150 countries worldwide