Key Difference – Reactant vs Reagent
The two terms reactant and reagent are used in both organic and inorganic chemical reactions. Although the two terms have similar meanings, their role in a particular reaction differs from one other. The key difference between reactant and reagent is that reactants are the compounds that are consumed and directly involved in the reaction while reagents are used to measure the extent of a chemical reaction or to observe the reaction.
What is a Reactant?
A reactant is a substance that is directly involved in a chemical reaction. It initiates the chemical reaction and is consumed after the reaction. Particularly, there are two or more reactants in a chemical reaction. Even though solvents are involved in a chemical reaction, they are not considered as reactants. Similarly, catalysts are not consumed after the chemical reaction; therefore, they are not considered as reactants.
What is a Reagent?
A reagent in a chemical reaction facilitates the chemical reaction to occur, or it is used to detect, measure or examine the extent of reaction without being consumed at the end of the reaction. It can be a single compound or a mixture of chemical compounds. The role and the type of the reagent are very specific for a particular reaction. Different reagents are used for different reactions.
Examples of commonly used reagents and their functions:
Collin’s Reagent: To selectively oxidize primary alcohols to the aldehyde.
Fenton’s Reagent: To destroy organic compounds that are contaminants.
Grignard Reagent: To synthesize long chain organic compounds using alkyl/aryl halides.
Nessler’s Reagent: To identify the presence of ammonia.
Benedict’s Reagent: To detect the presence of reducing sugar(s). Other reducing substances also give a positive reaction.
Fehling’s Reagent: To differentiate between water-soluble carbohydrate and ketone functional groups.
Millon’s Reagent: To identify the presence of soluble proteins.
Tollen’s Reagent: To identify the presence of an aldehyde or alpha-hydroxyl ketone functional groups.
These chemical reagents can be grouped into two categories; organic chemical reagents and inorganic chemical reagents.
| Organic Reagents | Inorganic Reagents |
| Collins reagent | Nessler’s reagent |
| Fenton’s reagent | Benedict’s reagent |
| Grignard reagent | Fehling’s reagent |
| Millon’s reagent | |
| Tollen’s reagent |
Collin’s Reagent
What is the difference between Reactant and Reagent?
Definition:
Reactants are substances that initiate a chemical reaction and are consumed in the process.
Reagents are substances that facilitate a chemical reaction and have specific functions.
Consumption in Chemical Reaction:
Reactants are consumed in the chemical reaction; they become products after the chemical reaction.
Reagents are not necessarily consumed in a chemical reaction. They are used to detect, examine or to observe the extent of a chemical reaction or to identify certain functional groups.
Number of Compounds:
A reactant is a single compound.
A reagent can be a single chemical compound or a mixture of several chemical compounds.
| Reagent | Composition |
| Tollen’s reagent | A solution of silver nitrate (AgNO3) and ammonia (NH3) |
| Fehling’s solution | Equal volumes of Fehling’s A and Fehling’s B solutions.
Fehling’s A is a blue colored aqueous solution of copper(II) sulfate (CuSO4) Fehling’s B is a clear and colorless solution of aqueous potassium sodium tartrate and a strong alkali (commonly sodium hydroxide) |
| Collins reagent | A complex of chromium (VI) oxide (CrO3) with pyridine in dichloromethane
(CH2Cl2) |
| Grignard reagent | Product of the reaction of alkyl or aryl halide with magnesium metal (R-Mg-X) |
Necessity in Chemical Reactions:
Reactants are involved in all chemical reactions; it is a necessary component of a chemical reaction.
A reaction can occur even without a chemical reagent. In other words, not all chemical reactions necessarily required a chemical reagent.
Image Courtesy:
1. “Combustion reaction of methane” by JyntoRobert A. RohdeJacek FHJynto [CC BY-SA 3.0] via Commons
2. Collins reagent By Mephisto spa (Own work) [Public domain], via Wikimedia Commons
