Q&A - Ask Doubts and Get Answers

Sort by :
Clear All
Q

13.24  Suggest the name of a Lewis acid other than anhydrous aluminium chloride which can be used during ethylation of benzene.

Lewis acid like anhydrous ferric chloride, stannic chloride,  etc. can be used instead of aluminium chloride.

13.23     Out of benzene, m–dinitrobenzene and toluene which will undergo nitration most easily and why?

Nitration is occurred by an electrophilic substitution reaction, in which an electron rich species is attacked by an electron deficient molecule known as an electrophile. In nitration  is used as an electrophile. Here methyl group is electron donating group and the nitro group is electron withdrawing group. So, benzene ring attached with the  group has high electron density and the ring which...

13.22     Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile, E+

          (b)         Toluene, p-H_{3}C-C_{6}H_{4}-NO_{2},p-O_{2}N-C_{6}H_{4}-NO_{2.} 

Electrophiles are electron deficient species, so they want a nucleophile which donates electrons to them. The higher the electron density on a benzene ring, the higher is the reactivity towards electrophile. since the methyl group is electron donating group it increases the electron density on the benzene ring. And more the number of EWG lesser reactive towards electrophile. therefore, the...

13.22     Arrange the following set of compounds in order of their decreasing relative reactivity with an electrophile, E+

         (a)      Chlorobenzene, 2,4-dinitrochlorobenzene, p-nitrochlorobenzene

Electrophiles are electron deficient species, so they want a nucleophile which donates electrons to them. The higher the electron density on a benzene ring, the higher is the reactivity towards electrophile.  is an electron withdrawing group, it deactivates the benzene ring towards electrophile by decreasing the electron density from the ring. Decreasing order of their reactivity with an...

13.19     Why does benzene undergo electrophilic substitution reactions easily and nucleophilic substitutions with difficulty?

In benzene, the -electrons are delocalised above and below of the ring. Thus it is an electron rich species. In nucleophilic substitution, the attacking species is an electron-rich in nature, so it becomes challenging to attack benzene because they are repelled by benzene. On the other hand, when the attacking agent is electrophile, which is electron deficient, are easily attracted by the benzene.

13.18     Arrange benzene, n-hexane and ethyne in decreasing order of acidic behaviour. Also give reason for this behaviour.

As the  character increases, the electronegativity of the carbon atom also increases. As a result, there is a development of partial charges in the C-H bond. increasing order of  character- More is the  character, more is the acidic nature of the compound. So, the decreasing order of acidic behaviour is- ethyne(50% ) >benzene(33% ) > hexane(25% )

13.15     What effect does branching of an alkane chain has on its boiling point?

On an increase in the branching of the alkane, the boiling point of the alkane is decreased. Alkane experience inter-molecular van der Waals forces. The strong is the force, strong will be the boiling point. When we increase the branching, the surface area of the molecule decreases, as a result, of the van der Waals force also decreases.

13.13         How will you convert benzene into

          (iv)       acetophenone

Benzene on reacting with an acyl chloride in the presence of anhydrous aluminium chloride gives acetophenone and hydrochloric acid as a by-product.

13.14     How will you convert benzene into

         (ii)      m- nitrochlorobenzene 

Benzene on treatment with conc. nitric acid and sulphuric acid gives nitrobenzene which on further treatment with chlorine in the presence of anhydrous aluminium chloride () gives m-nitrochlorobenzene.

13.13     How will you convert benzene into

       (i)        p-nitrobromobenzene 

Bromination of a benzene ring in the presence of anhydrous  and  gives bromobenzene and after that treating bromobenzene with conc. nitric acid in the presence of sulphuric acid followed by fractional distillation gives p-nitrobenzene.

13.12     Explain why the following systems are not aromatic?

         (iii)     Explain why the following systems are not aromatic (iii)

It disobeys the Huckle rule of (4n+2) electron. According to this rule, it has 2, 6, 10 .... number of  electron but it has 8  electrons.

13.12     Explain why the following systems are not aromatic?

          (ii)    

There is no complete conjugation of a  electron in the ring. And also it does not obey huckle rule [(4n+2) ]electron.

13.12     Explain why the following systems are not aromatic?

         (i)     

     

Not an aromatic compound because the -electrons in the ring are not in a complete conjugation. And it is a non-planner structure.

13.11     What are the necessary conditions for any system to be aromatic?

The necessary conditions for any system to be aromatic are - The cyclic compound should be a planner  The complete(continuous) delocalisation of -electrons in the ring Follow the Huckel rule- it states that, the ring has (4n+2)-electrons, where n =integer(n = 0, 1, 2, 3....)  

13.8     Write chemical equations for combustion reaction of the following hydrocarbons:

       (iv)     Toluene

Combustion means the reaction of the given compound with the dioxygen() gives  carbon dioxide, water molecule and produce some amount of heat.

13.8     Write chemical equations for combustion reaction of the following hydrocarbons:

       (iii)     Hexyne

Combustion means the reaction of the given compound with the dioxygen(O_2) gives  carbon dioxide, water molecule and produce some amount of heat.
 

 

13.8     Write chemical equations for combustion reaction of the following hydrocarbons:

         (ii)     Pentene 

Combustion means the reaction of a compound with the dioxygen(). Combustion reaction of the Pentene-

13.8     Write chemical equations for combustion reaction of the following hydrocarbons:

       (i)       Butane

Combustion means the reaction of a compound with the dioxygen()

13.5     An alkene ‘A’ on ozonolysis gives a mixture of ethanal and pentan-3- one. Write structure and IUPAC name of ‘A’.

In the process of ozonolysis, an ozonide, cyclic ring structure intermediate is formed, which undergoes cleavage to give the product. The compound A produce pentan-3-one and ethanal. So, the possible structure of A should be- Thus, by removing the ozone from ozonide we can get the parent alkene structure.

13.4     Write IUPAC names of the products obtained by the ozonolysis of the following compounds:

       (iii)     2-Ethylbut-1-ene 

Ozonolysis of 2-Ethylbut-1-ene  gives two products one is keto compound and another is aldehyde. 2-Ethylbut-1-ene  + O3                                                                                    (i)                                                              (ii) aldehyde The IUPAC name of the compound (i) is Pentan-3-one and the name of the (ii) compound is methanal.
Exams
Articles
Questions