Basic-Gyan

We know that when a reaction is completed, all the reactants are completely converted into products. But the reactants do not directly convert into products. Rather, the reactants first convert to the transition state, and then from the transition state to the intermediate, then from the intermediate to the second transition state, and finally from the second transition state to the product.   Hence " Intermediates are defined as a molecular entity which is formed inbetween reactants and products (It is neither be a reactant nor a product) or inbetween two transition states ". Fig:- Reaction Energy Diagram   In a reaction mechanism (series of elementary reactions through which the overall reaction takes place), intermediate molecule is formed in one elementary step while consumed in another elementary step. Therefore, these intermediates are not present in the overall balanced equation. But still a part of every reaction. Intermediates tend to be extremely reactive due to the...

Comparison between transition state and intermediate Transition states are highly unstable while intermediate molecules are stable in nature.  Transition states are impossible to separate from the reaction mixture while intermediate molecules can be separated from the reaction mixture easily.  Transition states are having higher energy than compared to intermediate molecules.  Transition states have short lifetime (measured in femto-seconds) while the reaction intermediates have a finite lifetime (a few nanosecond or many days).  Transition states are formed in elementary reactions while intermediates are not formed in elementary reactions  Intermediates are formed in one elementary step of the reaction and then consumed in another elementary step of the reaction. While transition state is present in each step of a chemical reaction. Let's take a picture to clearly understand about transition state and intermediate and their formation; Let's have a look on a pic...

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 (pro...

As we know that when the reaction takes place, the reactants are converted into products, but what really happens, is that the reactants are directly converted into products. So the answer is no, it does not happen.  Then, what happens when the reaction occurs??? Generally, whenever a chemical reaction occurs, all the reactants are not directly converted into products. In an elementary reaction, first the reactant breaks their bond and forms an activated complex in the transition state and after that this activated complex is converted into product. Thus; ........" A Transition  state is define as a position of a molecule (may be reactant molecule but not always) in the reaction path at which it's potential energy is maximum as shown in below figure "........ OR  ......." We can say that transition state is an intermediate state which lies between the state where molecules are reactant and the state where molecules are products "........ We can say that the tota...

As we know that when the reaction takes place, the reactants are converted into products, but what really happens, is that the reactants are directly converted into products. So the answer is no, it does not happen.  Then, what happens when the reaction occurs??? Let's have a look What happens when there is a reaction??? Generally, whenever a chemical reaction occurs, all the reactants are not directly converted into products. In an elementary reaction, first the reactant breaks their bond and forms an activated complex in the transition state and after that this activated complex is converted into product.      A–B + C   ➝         A----B----C         ➝   A+B–C    Reactants     Activated Complex      Products  While in case of non-elementary reactions, inbetween two transition state one intermediate molecules may exists. These intermediate molecules ca...

Order of a reaction is an experimental term. It can not be directly determined by the observed rate law. In order to determine the reaction order, the rate expression must be known. That means, with the help of the dependence of the rate of reactions on the concentration of the reactants, we can easily determine the order of the reaction. Order of a reaction is defined as- " The summation of exponents of all the reactant's concentration term present in the rate law obtained from the rate determining step is called as an order of reaction ". Depending on the concentration of the reactants, the reactions may be first order reactions, second order reactions or pseudo first order reactions etc.   In this article, we will learn about pseudo first order reaction with the help of various examples of pseudo first order reactions. Here, we will learn that some reactions which are expected to be of high order follow first order kinetics.   Pseudo First Order Reaction A pseudo first...

Order of a reaction is an experimental term. It can not be directly determined by the observed rate law. In order to determine the reaction order, the rate expression must be known. The term ' Reaction Order ' (or sequence of reaction) refers to how the concentration of one or more reactants (chemicals) affects the rate of the reaction. The order of reaction refers to the relationship between the rate of a chemical reaction and the concentration of the species participating in it. Order of a reaction is defined as, " The summation of exponents of all the reactant's concentration term present in the rate law obtained from the rate determining step is called as an order of reaction ".  The rate equation can help you determine the order of the reaction. This equation shows the increase or decrease of a particular substance over time.  Depending on the concentration of the reactants present in rate equations, the reactions may be different types: zero order reactions,...

Order of a reaction is an experimental term. It can not be directly determined by the observed rate law. In order to determine the reaction order,  the rate law expression of the reaction must be known. Generally, The term ' Reaction Order ' (or sequence of reaction) refers to how the concentration of one or more reactants directly affects the rate of the reaction.   Thus, it  expresses how much the concentration of reactant can affect the rate of reaction.  ........." The Order Of The Reaction Can Be In The Form Of An Integer Or A Fractional Value. Its Value Can Also Be Zero ".......... Order Of A Reaction?? Reaction order for a chemical reaction is defined as;   " The sum of the exponents to which the concentration of reactants are raised in the rate law, is called as order of the reaction ".                                Or " The summation of exponents of all the reactant's conce...

"Gulberg"  &  "Waage" in 1867 studied the effect of concentration on the rate of reaction. In a chemical reaction, the concentrations of reactant and product molecules change over time. The above graph shows the variation in the concentrations of the reactants and products over time. As the reaction proceeds, the concentration of the molecules of the reactants decreases while that of the molecules of the products increases.  Affect on the Rate of reaction???? The rate of reaction also decreases with time. This is because the rate of a reaction is directly proportional to the concentration of the reactants. Therefore, as the concentration of the reactants decreases, the rate of the reaction also decreases with time.  Generally, the order of a reaction expresses how much the concentration of reactant can affect the rate of reaction.   Now, we understand about the order of a reaction or how one can found out the order of a reaction???? Order Of A Reaction Orde...

One or more molecules are involved in a chemical reaction. As a result, a chemical reaction occurs in one step or more than one step. Writing differential rate equation for one step reaction is easy but writing differential rate equation for more than one step reaction is the biggest problem. To solve the problem of writing differential rate equations for multistep reactions, we study the rate determination step. It helps us to write differential rate equation for a multistep reaction. One Step Reaction??  A single-step reaction which takes place in one single step is called an elementary reaction. The differential rate equation can be easily written for the initial reactions.  More Than One Step Reaction??  While the chemical reaction that involves a series of two or more steps is called a complex or complicated reaction or non-elementary reaction. The rate law cannot be easily written for non-elementary reactions. The rate law for these types of reaction is dependent on...

Let us now understand about the Molecularity of the reaction.  What is the molecularity of a chemical reaction and how is it defined? How are chemical reactions classified on the basis of molecularity ??? Chemical reactions occur when atoms, ions and molecules collide with each other to bring about a chemical change and form a new bonded molecule called a product. Therefore, it is important to know the number of reactive species that bring about a chemical change. This brings us to the concept of molecularity  of a reaction. ...." The molecularity of a reaction is equal to the sum of number of reactant molecules taking part in a balanced chemical reaction (or which takes part in an elementary step or rate determining step) "....... Molecularity of a reaction does not depend on the external factors such as temperature or pressure. Depending on the number of reactive molecules which means how many species (atoms, molecules or ions) are reacting with each other to form the pro...