Intermediate molecule

INTRODUCTION
"An intermediate is defined as a molecular entity which is formed inbetween the reactant and product molecules". intermediate molecules may be unstable (called reactive intermediates) or stable in nature and can be isolated from the reaction mixture. 
Intermediate molecules have finite lifetime. Intermediates represent by the minimum energy containing molecules (or depression) in the reaction-energy diagram. Hence, the lifetime of an intermediate molecules depend on the depth of depression. 
              Shallow depth - short lifetime 
                 Deep depth - long lifetime 
Some examples of reaction intermediates are carbo-cations, carnation, free radicals, carbenes, nitrenes and benzyme etc. Important to note that the intermediate is not formed in case of elementary reactions. 

So, we can say that intermediate are formed only in case of complex reactions (proceeds more than one elementary step). One more interesting thing is that an intermediate behaves like both reactant and product in a reaction. It behaves like a product for one elementary step while for other elementary step, it acts as reactant molecule.        

Thus, these intermediate molecules are produced in one elementary step and then consumed in other elementary step of a reaction mechanism. Intermediate molecules may not be a part of the overall chemical reactions, but are nonetheless a part of the reaction step in moving from the reactant to the products. 
As shown in the above figure, one intermediate molecule (minimum energy point) lies between two transition states (points having high energy). 
       It appears in reaction mechanism and disappear in overall balanced equation of reactions. For example; 
A balanced chemical equation,
                  A + B ➝ C +D
The reaction involved two elementary steps;
             Step1- A + B ➝ X*  
             Step2- X* ➝ C + D
Here,
         X* is called as reaction intermediate that is produced by step-1 and then consumed by step-2 and because of this it doesn't exist in the balanced chemical equation.


Hope you have found this article helpful!!
Do you have suggestions? Please write in comment box!!!
Feel free to comment if you have any queries!!

Comments

Post a Comment

Most Viewed Posts

Factors Affecting The Rate Of Reaction

Image
" Chemical Kinetics " also known as " Reaction Kinetics " which helps us to understand the rate of chemical reactions (or reaction rate) and tells us how these rates influenced by certain conditions.  For Examples :  Some reactions are happened at a faster rate (like in few second) while others are happened at a very slow rate (like in many days).  Rusting of iron - At a slow rate Wood combustion - At a fast rate  Nuclear explosion- At a fast rate Hence, the rate of reaction (at which a reaction goes to completion) can change according to the condition through which the reaction occurs.   In this article, we will learn about the factors which affects the rate of reaction . Rate Law Let us define a " Rate Law " which tell us about the rate of reaction and also tell us that these rates are affected by which parameters, " A rate law or a rate equation is a relationship between the reaction rate and the concentration of its reactants ". Thus, a reac
Read more