Sage-Tips

Why is direct fluorination of alkanes not possible?

The reaction of alkanes with fluorine is difficult to control because the activation energy for hydrogen abstraction is so low. The initiation step involves the homolytic cleavage of the F-F bond. This is a high activation energy. But only a few F atoms need to form.

What is necessary for iodination of alkanes?

Iodination of an alkane is carried out in the presence of oxidizing agent because one of the products of this reaction is hydrogen iodide and this is a strong reducing agent and converts alkyl iodide back to an alkane.

Why direct iodination of benzene is not possible?

Explanation: However, direct iodination of benzene in this manner is not possible. This is because iodination of benzene in this manner produces HI as a side product. HI being a strong reducing agent, reduces the halobenzene back to benzene, and thus the reaction becomes reversible in nature.

Why photochemical fluorination is explosive?

Direct fluorination of toluene using elemental fluorine is not possible as traditional reactors cannot regulate the heat release. So the process is slowed down purposely. Of all the chemical elements, fluorine is the most reactive and most electronegative.

Why fluorination is explosive?

In addition, fluorination is very exothermic, the reaction enthalpy is -431 kJ/mol. The reaction heat cannot be eliminated from the reaction mixture quickly enough with the consequence that the temperature and thus the reaction rate steadily increase. As a result, an explosion occurs.

Why does iodination of methane take place in hio3?

Iodine reacts with methane molecules reversibly. To overcome this difficulty, iodination is generally carried out in the presence of strong oxidising agents like iodic acid (HIO3) which oxides HI formed during the reaction to iodine.

Which halogen reacts with alkane rapidly with explosion?

Fluorine is the most reactive. If no precautions are taken, a mixture of fluorine and methane explodes. The reaction between methane and chlorine is easily controllable, while bromine is even less reactive than chlorine.

Why is iodination difficult?

For Iodination, the reaction is endothermic with 12kJ/mol of energy absorbed. Therefore, it cannot be done using the conventional method using Lewis acid catalyst and requires strong oxidizing agents. This is because, I2 adds to the Benzene reversibly generating HI.

Can benzene be iodinated with i2 directly?

Benzene cannot be iodinated with I_(2) directly. However, in presence of oxidants such as HNO_(3), iodination is possible. The electrophiles formed in the case is.

Why fluorination of benzene is explosive?

Considering the exothermic rates of aromatic halogenation decreasing down the periodic table in the Halogen family, Flourination is the most exothermic and Iodination would be the least. Being so exothermic, a reaction of flourine with benzene is explosive!

Does the iodination of methane occur?

In the case of Iodine the energy of activation is so high that Iodination of methane does not occur.

Is direct iodination possible in methane?

Iodination of methane may, however, be carried out in the presence of an oxidizing agent such as HIO3, HNO3, HgO etc., which oxidizes the HI formed to iodine. …

Why does the free radical iodination of alkane (methane) fail?

Therefore, without going into all these aspects, simply put, C-I bond formation is difficult and therefore the rate of iodination is slow and the reaction is reversible, which means the direct free radical iodination of alkane (methane) will not go to completion.

What is the halogenation of alkanes?

Halogenation (mainly chlorination and bromination) of alkanes is carried out by free radical process, using halogen (Cl2 or Br2) in presence of a free radical initiator. There are other reagents also. Direct iodination using I2 in presence of a free radical initiator is, however, a more complex than chlorination or bromination.

What is the chemical reaction between alkane and iodine?

Chlorine radicals, which are essentially chlorine atoms formed as a product when chlorine gas undergoes homolytic fission in UV, attacks the alkane as an electrophile and strips away a H along with an electron. Iodine most probably undergo the same fission under UV since I-I bonds are weaker than Cl-Cl bonds.

What is the difference between iodination and flourination of alkanes?

However, practically, the flourination of alkanes happens at such a fast rate and releases such a huge amount of energy that it is really difficult to control such a reaction. Meanwhile, iodination is such a slow process and the reaction is endothermic (requires energy in order to happen).