Haloalkanes And Haloarenes Questions With Answers Pdf Download

Question 44.

Haloalkanes undergo nucleophilic substitution whereas haloarenes undergo electrophilic substitution. Explain. (Comptt. Delhi 2012)

Answer:

Haloarenes (say chlorobenzene) is a resonance hybrid of the following five structures :

Resonance leads to lowering of energy and hence greater stability. On the other hand, no such resonance is possible in haloalkanes. Halogens directly attached to benzene ring are o, p-directing in electrophilic subsitution reactions. This is due to greater electron density at these positions in resonance.

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Haloalkanes and haloarenes are hydrocarbons that have had one or more hydrogen atoms replaced with halogen atoms. The major distinction between haloalkanes and haloarenes is that the former are formed from open-chain hydrocarbons (alkanes), whilst the latter are derived from aromatic hydrocarbons.

Common names are an alternative nomenclature system that is often used for simple haloalkanes and haloarenes. In this system, the halogen is named as a suffix is used and preceded by the name of the parent alkane or arene. For example, CH3Cl is commonly known as methyl chloride, and C6H5Cl is commonly known as phenyl chloride.

Grignard reagents are formed when haloalkanes react with magnesium metal in the presence of fully anhydrous ether to generate organomagnesium halide. In the presence of an aqueous alkali solution or a moist silver oxide solution, haloalkane undergoes a nucleophilic substitution process, forming alcohols.

Some common reactions of haloalkanes and haloarenes include nucleophilic substitution, elimination, and oxidative addition. Nucleophilic substitution involves the replacement of a halogen atom by a nucleophile, such as a hydroxide ion or an alkoxide ion. Elimination involves the removal of a halogen atom and a hydrogen atom from adjacent carbon atoms to form an alkene. Oxidative addition involves the addition of a metal atom or ion to the halogen atom, resulting in the formation of a new metal-halogen bond.

Chemistry topic Haloalkanes and Haloarenes is an important lesson for students to master because various questions are asked from it. However, for assistance in CBSE Class 12 Chemistry board exam preparation here on this page, we have shared the direct link of Haloalkanes and Haloarenes Class 12 Important Questions with Solutions.

Due to various reasons, Class 12 students should be thorough with Haloalkanes and Haloarenes Class 12 important questions. A few reasons to solve CBSE Class 12 Chemistry Haloalkanes and Haloarenes important questions are -

Once a Class 12 student has studied their Haloalkanes and Haloarenes lesson completely can go for the important questions to practise. However, there are a few more times when a CBSE Class 12 student can utilise the PDF file of Haloalkanes and Haloarenes Class 12 Important Questions with Solutions

Download JEE Main 2019 (Jan) Chapter wise solved questions for Chemistry in PDF format prepared by expert IIT JEE Teachers at Mathongo.com. By solving JEE Main January 2019 chapterwise questions with solutions will help you to score more in your IIT JEE examination.

Expert Teachers at CBSETuts.com have collected haloalkanes and haloarenes previous year questions of Class 12 Chemistry. Haloalkanes and haloarenes important questions are solved in accordance with CBSE marking scheme. You will find Previous year board Haloalkanes and Haloarenes Questions from 2009 to 2019.

Question 6.

Haloalkanes undergo nucleophilic substitution reaction whereas haloarenes undergo electrophilic substitution reaction. Comment.

Answer:

Haloalkanes undergo nucleophilic substitution reactions due to high clectronegativity of the halogen atom. The C-X bond in haloalkanes is slightly polar, thereby the C atom acquires a slight positive charge in C-X bond. [lence C atom is a good target for attack for nucleophiles. Therefore C-X atom of haloalkanes is replaced by a nucleophile easily.

On the other hand in haloarenes, the halogen atom releases electron to the benzene nucleus relatively electron rich with respect to the halogen atom. As a result the electrophilic attack occurs at ortho and para positions. Hence haloarenes undergo electrophilic substitution reactions.

Question 1.

(a) Haloalkanes have higher boiling point than the parent alkane with same number of carbons because of strong inter molecular forces of attraction.

(b) The boiling point of haloalkanes decreases with the increase of halogen atoms.

(d) Halo alkanes are soluble in water.

Answer:

(a) Halo alkanes have higher boiling point than the parent alkane with same number of carbons because of strong inter molecular forces of attraction.

Question 14.

CCl4 > CHCl3 > CH2Cl2 > CH3Cl is the decreasing order of boiling point in haloalkanes. Give reason.

Answer:

The boiling point of chioro, bromo and iodoalkanes increases with increase in the number of halogen atoms. So the correct decreasing order of boiling point of haloalkanes is:

CCl4> CHCl3 > CH2Cl2> CH3Cl.

Question 15.

Arrange the following in increasing order of boiling point. Give reason.

(CH3CH2CH2Cl, CH3CH2Cl, CH3Cl)

Answer:

The correct order of boiling point of haloalkanes is:

CH3CH2CH2Cl > CH3CH2Cl > CH3Cl.

The boiling point of monoalkanes increase with the increase in the number of carbon atoms.

Question 16.

Why haloalkanes arc insoluble in water but soluble in organic solvents?

Answer:

Haloalkanes are polar covalent compounds, soluble in organic solvents, but insoluble in water because they are unable to form hydrogen bond with water molecules.

Question 13.

Compare the bond length C-X in haloarenes and C-X in haloalkanes.

Answer:

1. Due to this double bond character of C-X bond in haloarenes, the C-X bond length is shorter length and stronger than in haloalkanes.

2. Example:

Question 29.

Explain as to why haloarenes arc much less reactive than haloalkanes towards nucleophilic substitution reactions?

Answer:

Haloarenes are much less reactive than haloalkanes towards nucleophilic substitution reactions due to the following reasons:

2. The C-Cl bond length in haloalkanes is 177 pm while in haloarenes it is 169 pm. Since it is difficult to break shorter bond than a longer bond. Therefore, haloarenes are less reactive than haloalkanes towards nucleophilic substitution reactions.

Please refer to CBSE Class 12 Chemistry HOTs Haloalkanes And Haloarenes. Download HOTS questions and answers for Class 12 Chemistry. Read CBSE Class 12 Chemistry HOTs for Unit 10 Haloalkanes and Haloarenes below and download in pdf. High Order Thinking Skills questions come in exams for Chemistry in Class 12 and if prepared properly can help you to score more marks. You can refer to more chapter wise Class 12 Chemistry HOTS Questions with solutions and also get latest topic wise important study material as per NCERT book for Class 12 Chemistry and all other subjects for free on Studiestoday designed as per latest CBSE, NCERT and KVS syllabus and pattern for Class 12

Class 12 Chemistry students should refer to the following high order thinking skills questions with answers for Unit 10 Haloalkanes and Haloarenes in Class 12. These HOTS questions with answers for Class 12 Chemistry will come in exams and help you to score good marks

Question. Why do haloalkenes under go nucleophillic substitution whereas haloarenes under go electophillic substitution?

Answer: Due to more electro negative nature of halide atom in haloalkanes carbon atom

becomes slightly positive and is easily attacked by nucleophillic reagents. While in haloarenes due to resonance, carbon atom becomes slightly negative and attacked by electrophillic reagents.

We hope students liked the above HOTS for Unit 10 Haloalkanes and Haloarenes designed as per the latest syllabus for Class 12 Chemistry released by CBSE. Students of Class 12 should download the High Order Thinking Skills Questions and Answers in Pdf format and practice the questions and solutions given in above Class 12 Chemistry HOTS Questions on daily basis. All latest HOTS with answers have been developed for Chemistry by referring to the most important and regularly asked topics that the students should learn and practice to get better score in school tests and examinations. Studiestoday is the best portal for Class 12 students to get all latest study material free of cost. 006ab0faaa