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Unraveling the Chemistry of Fe-HCl Mixture: Reactions Products and Applications

Reaction between Fe and HCl


Have you ever wondered what happens when iron (Fe) is mixed with hydrochloric acid (HCl)? In this article, we will explore the extensive reactions that take place when these two substances are combined, examining the products formed, the type of reaction that occurs, the balancing method and titration procedure used, and much more.

Additionally, we will also discuss the various applications of the Fe-HCl mixture, including deprotection of oximes, selective oxidative hydrolysis of nitroalkanes/nitroalkenes, and reduction of aromatic primary amines.

Reaction Description

When Fe is mixed with HCl, the following products are formed: hydrogen gas (H2) and ferrous chloride (FeCl2). This is an exothermic reaction where Fe displaces the hydrogen portion of HCl, forming FeCl2 and releasing H2 gas.

Reaction Classification

The reaction can be classified as a single-displacement and redox reaction since Fe is oxidized from its elemental state to +2 oxidation state, while hydrogen in HCl is reduced to form H2 gas. The reaction can be expressed as:

Fe + 2HCl → FeCl2 + H2

Balancing the Reaction

To balance this reaction, we can use mole numbers.

There are two moles of HCl reacting with one mole of Fe. Thus, to balance the reaction, we need to place two Fe atoms on the reactant side:

Fe + 2HCl → FeCl2 + H2

Titration Procedure

The above reaction occurs without changing the experimental pH, preventing the use of a titration procedure.

Net Ionic Equation

The net ionic equation for this reaction can be written as:

Fe(s) + 2H+(aq) + 2Cl(aq) → Fe2+(aq) + 2Cl(aq) + H2(g)

Conjugate Pairs

Since Fe cannot donate or accept H+ ions, there are no conjugate pairs present in the reaction.

Intermolecular Forces

Intermolecular forces play a crucial role in chemical reactions. In the case of the Fe-HCl reaction, the dipole-dipole interaction between HCl molecules is stronger than the London dispersion forces among Fe atoms and H2 molecules.

No hydrogen bonding occurs since HCl is not involved in a reaction with water.


The enthalpy of the Fe-HCl reaction is negative, indicating that it is an exothermic reaction.

Heat is released on the product side, leading to increased stability.

Buffer Solutions

Buffer solutions are useful in controlling pH in reactions. The Fe-HCl reaction produces a strong acid, making it a suitable reducing agent. It also acts as an oxidizing agent since Fe is oxidized to FeCl2.

Complete Reaction

The complete reaction of Fe-HCl produces ferrous chloride and evolution of H2 gas:

Fe(s) + 2HCl(aq) → FeCl2(aq) + H2(g)

Uses of Fe-HCl mixture

Deprotection of Oximes

The Fe-HCl mixture has several applications in organic chemistry. One of its uses is in the deprotection of oximes.

Oximes are organic compounds that contain a C=N-O functional group. Deprotection of this group can be achieved through the reaction of oximes with acid.

FeCl2·4H2O is an effective deprotection reagent for oximes, leading to the formation of nitriles.

Selective Oxidative Hydrolysis

Another application of the Fe-HCl mixture is in the selective oxidative hydrolysis of nitroalkanes or nitroalkenes, producing aldehydes and ketones.

The selective nature of the reaction can be attributed to the reduction of FeCl2 to Fe, which prevents over-oxidation of the aldehydes and ketones produced.

Reduction of Aromatic Primary Amines

Finally, the Fe-HCl mixture can also be used in the reduction of aromatic primary amines to produce cyclic amines.

FeCl2·4H2O is a mild reducing agent, which makes it ideal for reductions that require specific conditions.


Fe-HCl is an essential reaction in organic chemistry, leading to the formation of ferrous chloride and H2 gas. The reaction is exothermic, redox, and single-displacement.

The mixture has several applications, including deprotection of oximes, selective hydrolysis of nitroalkanes or nitroalkenes, and reduction of aromatic primary amines.

From this article, you have learned how the Fe-HCl mixture works and how it can be used.

Its properties and applications make it an indispensable reagent for organic chemists to have in their toolkits.


In summary, the Fe-HCl mixture reacts to produce ferrous chloride and hydrogen gas through an exothermic, redox, and single-displacement reaction.

It has various applications, including deprotection, selective oxidative hydrolysis, and reduction of organic compounds.

Its properties and applications make it a valuable reagent in organic chemistry.


  • What are the products of the Fe-HCl reaction?
  • What kind of reaction is the Fe-HCl mixture?
  • What are the uses of the Fe-HCl mixture?

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