Category: Chemistry Notes PPT

Pyridine is a heterocyclic compound that is colorless fluid with a chemical formula C5H5N. It is a heterocyclic natural compound, also called Azine or Pyridine. The structure resembles benzene, with one methine bunch supplanted by a nitrogen particle. It has a sour, foul, and fish-like smell. Pyridine can be integrated from ammonia, formaldehyde, and acetaldehyde, or it tends to be produced using unrefined coal tar. It is a weak base and mixes with water. It is combustible and, when inhaled or ingested, is poisonous. A portion of the manifestations, when presented to Pyridine, are queasiness, asthmatic breathing, migraine, laryngitis, and coughing. 

Pyridine Structure 

Much the same as benzene, pyridine structure rings a C5N hexagon. Electron limitation in Pyridine structures reflects in the shorter C–N ring bond (137 pm for the C–N bond in Pyridine versus 139 pm for C–C bond in benzene). In comparison, the carbon-carbon relationships in the pyridine ring have a similar 139 pm length as in benzene. These bond lengths lie between the qualities for the single and twofold relationships and are typical of fragrant mixes. 

Resonance Structure of Pyridine

Three resonances of Pyridine structure can be found in Pyridine. All three resonances of Pyridine structures contain positively charged carbons. Electrophilic substitution reaction rates at Pyridine Structures are generally found lower than at benzene for electrophilic substitutes.

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Properties of Pyridine 

Physical Properties:

The simple derivatives of Pyridine are mostly stable and generally unreactive fluids with unpleasant penetrating odors. The atomic electric dipole second is 2.2 debyes. Pyridine is diamagnetic and has a diamagnetic defenselessness of −48.7 × 10−6 cm3·mol−1. The standard enthalpy of development is 100.2 kJ·mol−1 in the fluid phase and 140.4 kJ·mol−1 in the gas stage. At 25 °C, Pyridine has a thickness of 0.88 mPa/s and warm conductivity of 0.166 W·m−1·K−1. The enthalpy of vaporization is 35.09 kJ·mol−1 at the breaking point and normal pressure. The enthalpy of combination is 8.28 kJ·mol−1 at the dissolving point. 

The basic parameters of Pyridine are pressure 6.70 MPa, temperature 620 K, and volume 229 cm3·mol−1. In the heat go 340–426 °C, its vapor pressure p can be depicted with the Antoine equation. 

Log10p= A-{B/(C+T)}

Where T is temperature, A=4.16272, B1371.358 K and C=-58.496 K.

Chemical Properties:

Given the electronegative nitrogen in the pyridine ring, the atom is generally electron lacking. That is why it enters less promptly into electrophilic aromatic substitution responses than benzene derivatives. Correspondingly, Pyridine is progressively inclined to nucleophilic substitution, as confirmed by the simplicity of metalation by solid organometallic bases. The reactivity of the Pyridine structure can be recognized for three compound gatherings. With electrophiles, electrophilic substitution happens where Pyridine communicates fragrant properties. With nucleophiles, Pyridine responds at positions 2 and 4, and along these lines carries on like imines and carbonyls. The response with many Lewis acids brings about the expansion to the nitrogen particle of Pyridine, which is like the reactivity of tertiary amines. The capacity of Pyridine and its subsidiaries to oxidize, shaping amine oxides (N-oxides), is additionally a component of tertiary amines. 

The nitrogen focal point of the Pyridine structure includes an essential solitary pair of electrons. This single pair doesn’t cover with the sweet-smelling π-framework ring. Therefore Pyridine is necessary, having chemical properties like those of tertiary amines. Protonation gives pyridinium, C5H5NH+. The pKa of the conjugate corrosive (the pyridinium cation) is 5.25. The structures of Pyridine and pyridinium are nearly identical.

Different Pyridine Uses 

Pyridine is dissolvable and is added to ethyl liquor that makes it unfit for drinking. It is changed to items such as sulfapyridine, a medication dynamic against bacterial and viral contaminations; pyribenzamine and pyrilamine, as antihistaminic drugs; and piperidine, which is utilized in elastic preparation, and as a crude substance material; and water anti-agents, bactericides, and herbicides. Compounds not using Pyridine, however, containing its ring structure incorporate niacin and pyridoxal, both B nutrients; isoniazid, an antitubercular medication; and nicotine and a few different nitrogenous plant items. Pyridine uses in the chemical industries and enterprises as a significant crude material, used in dental consideration items for cleaning, used as a dissolvable which is appropriate for dehalogenation, Pyridine uses in pharmaceuticals, radiator fluid blends as a denaturant, Pyridine uses as a sulfonating specialist, used in colors and paints, disinfectant, a ligand in the chemical science.

Examples 

1. Which is the common derivative of Pyridine that is mostly found in mammals?

Through oxidation, Mammals synthesize nicotinic acid whose coenzyme forms are nicotinamide adenine dinucleotide (NAD).

2. Which plant is considered to be the natural source of Pyridine?

Pyridine is generally present in the leaves and roots of Atropa belladonna.

Fun Facts 

1. In our daily life, the products produced in roasting and canning processes include fried chicken, roasted coffee, potato chips, and fried bacon, etc.

2. Pyridine which was impure was without a doubt prepared by early alchemists. The heating of the animal bones and other organic matter was done first.

3. Pyridine traces can be sometimes found in Beaufort cheese, vaginal secretions, as well as black tea. 

Quick overview of Properties 

Common uses of Pyridine

1. In pharmaceutical companies

2. Used as dyes and paints

3. As a reducing and sulfonating agent

4. In dental firms, used as antiseptic

5. Raw material for various compound production

Pyridine Health Side Effects

Though pyridine is a useful compound, utilized in every potential field. But if consumed by humans, it might prove dangerous. The severity depends upon the amount of consumption and mode. Pyridine can enter the human body while breathing, drinking, or consuming anything that has the presence of that chemical. Once the intake is done, this chemical can irritate the nose, leading to coughs and wheezes. Due to which health problems like headaches, dizziness, fatigue happen, and major symptoms may even lead to death. And if pyridine consumption is through the mouth, more than 50% of it is absorbed into your body.  In some cases, skin allergy happens, due to which any future exposure leads to skin rashes. Pyridine is a flammable liquid and a fire hazard. 

Some ways to reduce exposure of pyridine to the human body and surroundings. 

• Perform enclosed operations wherever possible. 

• Any local exhaust or proper ventilation system must be observed at the site of chemical release

• Protective measures must be taken as wearing masks, safety equipment

• If exposed to pyridine, immediately wash the affected part and consult medical help

• Warning & hazardous information about chemicals must be notified in working areas. 

• Education and training about side effects and handling pyridine must be done properly for all employees working at the site. 

Studying Time & Strategy

Organic topics in chemistry must not be kept an option for students studying in exams. There are very high chances that such topics will come. One can expect questions based on organic topics and their properties. 

For studying, first, start with basic understanding and concept learning of aromatic compounds like benzene. Then understand how pyridine is derived by making some changes in benzene. Move further to study in detail its resonating structures, 3D conformers, crystal structures. Then students may study its physical, chemical properties along with its uses.

Pyridine topic is actually simple as compared to complex areas of chemistry. It won’t take more than 2-3 hours to study completely about it. However, the study time depends upon various factors such as background prerequisite, learning scope and grasping power.

If prepared properly for the exam, any student can score well in these organic topics. 

Questions asked about this topic:

1. Explain pyridine compound in details

2. What are the uses of pyridine

3. Give chemical formula and draw resonating structures of pyridine

4. Is pyridine a nucleophile? If yes, please explain in detail

5. What are the chemical properties of pyridine

6. Answer the following with respect to pyridine 

• Melting point 

• Boiling point 

• Acidic or Basic Nature

• Molecular formula

• Molecular weight

Due to nuclear instability, the nucleus exhibits the phenomenon of Radioactivity. It is the phenomena of the disintegration of heavy elements into comparatively lighter ones by emission in the form of radiation. It was discovered by Henri becquerel in 1896. Energy is lost due to radiation emitted out of the unstable nucleus of an atom. The driving force of this phenomenon is the force of repulsion also known as electrostatic force, and the forces of attraction of the nucleus which keep the nucleus together. The two forces are considered extremely strong in the natural environment.

The instability of the atom increases as the size of the nucleus increases because the mass of the nucleus becomes a lot when concentrated. This is the main reason that atoms of Plutonium, Uranium are extremely unstable and undergo the phenomena of radioactivity.  Emission and absorption are not noticed easily when it takes place in the atom.

Radioisotopes are radioactive isotopes of an element. They are the atoms containing an unstable combination of neutrons and protons or excess energy in their nucleus. The excess of energy can be used in any of the ways during those processes, the radionuclide is said to undergo radioactive decay.  

Radioactive decay is a property of naturally occurring elements and artificially produced isotopes of the elements. The rate at which a radioactive element decays is expressed in terms of its half-life which is the time required for one-half of any given quantity of the isotope to decay. We have discussed radioactive isotope definition, Radioisotopes, Half-life, Radioactive decay now we will discuss some application of radioactive isotopes.

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Laws of Radioactivity

• The rate of decay of the nucleus is independent of the temperature and pressure.

• It follows the law of conservation of charge.

• The emission of energy from radioactivity is accompanied by alpha, beta, and gamma particles.

• The rate of decay of radioactive substances is proportional to the number of atoms that are present at the time.

(Curie and Rutherford are the units of radioactivity.)

Uses of Radioactive Isotopes

• Radioisotopes used in medicine have short half-lives, which means they decay quickly and are suitable for diagnostic purposes; others with longer half-lives take more time to decay, which makes them suitable for therapeutic purposes.

• Radioactive isotopes have several other useful applications like they are used in medicine, for example, Cobalt-60 is extensively used as a radiation source to arrest the development of cancer. 

• Americium-241 an alpha emitter is used in domestic smoke detectors in the United States.

• Iodine-131 is found effective in treating hyperthyroidism. Another important radioactive isotope is carbon-14, which is used in a breath test to detect the ulcer-causing bacteria Heliobacter pylori.

• They are also used to measure the thickness of metal or plastic sheets, the precision of thickness is indicated by the strength of the radiations that penetrate the material being inspected.

Application of Isotopes

Isotopes of an element have the same atomic number but different mass numbers. Hydrogen is the first element present in the periodic table and has one proton. Hydrogen has three isotopes protium, deuterium, and tritium. The three isotopes are different because of the difference in the number of neutrons present in them. In protium, there is only proton and electron, whereas deuterium contains one neutron and tritium contains two neutrons.  Out of these three isotopes of hydrogen, tritium is radioactive in nature which emits low energy particles. Some radioactive isotopes examples are Tritium is used in  Boosting Nuclear weapons, Neutron initiator, Self-powered lighting, etc.

Another Radioactive isotopes example is Uranium, which is a weakly radioactive element with an atomic number 92 and symbol U. It has two isotopes U-235 and U-238. It is one of the heavy metals that can be utilized as a rich source of concentrated energy. Isotope U-235 is mostly used because it can be split readily and yield a large amount of energy when bombarded with a slow-moving neutron. Natural uranium is found as a mixture of two isotopes. U-238 accounts for 99.3% and U-235 around 0.7%.

Types of Radioactivity: Alpha, Beta, and Gamma Decay

Alpha Decay: ​The nuclear disintegration process that emits alpha particles is termed alpha decay. An example of alpha decay is uranium-238. The alpha decay of  U -238 is given as:

92U238    →   4He2   +  234Th90

In the above nuclear change, the uranium atom is transformed into an atom of thorium and gives off an alpha particle. The bottom number in a  symbol indicates the number of protons which signifies that the alpha particle has two protons in it that is lost by the uranium atom. The two protons also have a charge of  +2. The top number 4 indicates the mass number or the total of the protons and neutrons in the particle.

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Beta Decay: A beta particle is a type of decay in which a high-energy electron is emitted from the nucleus. Nuclei don’t contain electrons and yet during decay, an electron is emitted from a nucleus. At the equivalent time that the electron is being ejected from the nucleus, a neutron is becoming a proton. (It is unwise to picture this as a neutron breaking into two pieces are a proton and an electron.) That would be convenient for simplicity, but unfortunately, this is not what actually happens. For convenience, we’ll treat decay as a neutron splitting into a proton and an electron. The proton stays within the nucleus, increasing the number of the atom by one. The electron ejected from the nucleus and is the particle of radiation which is called beta.

In order to insert an electron in the equation and to add up properly, a nucleon number is to be assigned to an electron. The mass number assigned to an electron is zero (0), which is reasonable since the mass number is the
number of protons and neutrons, and an electron contains no protons and no neutrons. The number assigned to an electron may be a negative one (-1) because that permits a nuclear equation containing an electron to balance atomic numbers. In the example below Thorium is a nucleus that undergoes beta decay.

-1e0  or  -1β0

234Th90 → 0e-1 + 234Pa91

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Gamma Ray: Gamma-ray is produced in nuclear reactions of all types. In the alpha decay of U -238 nucleus, two gamma rays of different energies are emitted in addition to the alpha particle.

238U92  → 4He2  + 234Th90 + 20γ0

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Did You Know?

Radioactivity was discovered accidentally by Henry Becquerel in the year 1896. A Uranium compound was placed in a drawer containing photographic plates, wrapped in black paper. When the plates were examined thoroughly it was found that they were exposed. This exposure, later on, gave rise to the concept of Radioactive decay. The life of every radioactive element is finite.

Usually, the word ‘real gas’ refers to a gas that does not function as an ideal gas. The interactions between gaseous molecules can explain their behaviour. Such intermolecular interactions between gas particles are the explanation of why the ideal gas law does not adhere to real gases. A real gas can therefore be characterized as a non-ideal gas whose molecules occupy a given amount of space and are capable of interacting with one another. In this article, we will study the real gas definition, real gas equation, and ideal and real gases in detail.

 

Real Gas Definition

A real gas is defined as a gas that at all standard pressure and temperature conditions does not obey gas laws. It deviates from its ideal behaviour as the gas becomes huge and voluminous. True gases have velocity, mass, and volume. They liquefy when cooled to their boiling point. The space filled by gas is not small when compared to the total volume of gas.

 

Ideal and Real Gas Equation

An ideal gas is defined as a gas that obeys gas laws at all pressure and temperature conditions. Ideal gases have velocity as well as mass. They have no volume. The volume taken up by the gas is small as compared to the overall volume of the gas. It does not condense and triple-point does not exist.

 

The ideal gas law is the equation of the state of a hypothetical ideal gas, also called the general gas equation. Under many conditions, it is a reasonable approximation of the behaviour of several gases, but it has many limitations. In 1834, Benoît Paul Émile Clapeyron first described it as a variation of the empirical law of Boyle, the law of Charles, the law of Avogadro, and the law of Gay-Lussac. In an empirical form, the ideal gas law is also written:

 

pV=nRT

 

Real Gas Law

By explicitly including the effects of molecular size and intermolecular forces, the Dutch physicist Johannes van der Waals modified the ideal gas law to explain the behavior of real gases. The Van der Waal real gas equation is given below-

 

Real gas law equation,

 

= [frac {(P+an^2)} {V^2} = (V-nb) nRT]

 

Where a and b represent the empirical constant which is unique for each gas.

 

[frac {n^2} {V^2}] represents the concentration of gas. 

 

P represents pressure

 

R represents a universal gas constant and T is the temperature 

 

Ideal and Real Gases

The difference below shows the properties of real gas and ideal gas, and also the ideal and real gas behaviour.

 

Did You Know?

A factor known as compressibility factor Z is determined by the deviation of real gas from ideal gas and is defined as the ratio of the actual volume to the volume predicted by the ideal gas law at the same temperature and pressure Z = Actual volume/volume predicted by the ideal gas = v/RT/P     

 

But the ideal gas rate, Videal, is RT/P. The compressibility factor can therefore also be defined as the ratio of specific real gas volume to specific ideal gas volume, i.e.

 

Compressibility factor Z= [frac {V_{real gas}} {V_{ideal gas}}]

 

As we all know, at very low pressures and high temperatures, all gases act as ideal gases. So when the pressures are reduced, as the gas behaves as ideal, the value of Z tends to unite. 

 

It is to be remembered that, depending on the pressure and temperature, the value of Z can be less than unity or greater than unity. The compressibility factor chart shows the Z values corresponding to the pressure.

 

Liquefaction of Gases

The kinetic molecular theory of gases does neither predict nor explain the liquefaction of gases. According to both theory and the ideal gas law, gases crushed to extremely high pressures and chilled to extremely low temperatures should still behave like gases, albeit cold, dense ones. When gases are compressed and cooled, they invariably condense to become liquids, although light elements like helium require extremely low temperatures to liquefy (for He, 4.2 K at 1 atm pressure).

Liquefaction can be thought of as an extreme deviation from ideal gas behavior. When the molecules in a gas are cooled to the point that their kinetic energy is no longer adequate to resist intermolecular attraction forces, this phenomenon happens. The exact temperature and pressure combination required to liquefy a gas is highly dependent on its molar mass and structure, with heavier and more complicated molecules liquefying at higher temperatures. Because large coefficients suggest relatively strong intermolecular attractive interactions, substances with large van der Waals coefficients are generally easy to liquefy. Small molecules containing only light components, on the other hand, have low coefficients, indicating weak intermolecular interactions and making them difficult to liquefy. On a large scale, gas liquefaction is used to separate O₂, N₂, Ar, Ne, Kr, and Xe. After liquefying a sample of air, the mixture is warmed, and the gases are separated according to their properties.

Properties of Resorcinol 

Physical Properties – It shows following physical properties –

• It is white in color and solid at room temperature. 

• It is soluble in water, alcohol and ether.

• Its molar mass is 110 g/mol.

• It turns pink on exposure to air, light and iron. 

• It gives a faint benzene odor. 

• It is insoluble in chloroform and carbon disulfide. 

• Its melting point is 110℃.

• Its boiling point is 277℃.

• Its density is 1.28g/cm3.

Chemical Properties – It shows following chemical properties –

Production of Resorcinol 

Resorcinol is prepared from benzene. It crystallizes from benzene as colorless needles. Production of it from benzene takes place through several steps. It is a classic sulfonate fusion process. In this, benzene is treated with sulfuric acid at 100℃ which gives mono sulfonic acid. Which is converted to m-disulfonic acid with 65% oleum at 85℃. Now m-benzenedisulfonate melts in alkaline medium (NaOH) at 300℃ which gives resorcinol and sodium sulfite. Reaction is given below –

As the above reaction shows one step can be reduced by reacting SO3 directly to benzene. 

Applications of Resorcinol 

Large scale production of resorcinol itself shows its high demand in the market and usefulness. Few applications of resorcinol are listed below –

• It is used in acne treatment. 

• It is antiseptic and disinfectant so used in treatment of many chronic skin diseases such as eczema, psoriasis etc.

• It is used in shampoo as an anti-dandruff agent. 

• Its 2% solution has been used in the treatment of hay fever and whooping cough.

• It protects from UV -rays so used in sunscreens. 

• It is used in treatment of gastric ulcers.

• It is used in many medicated soaps as well.

• It is used in the production of diazo dyes, plasticizers and resins.

• It is used as an analytical reagent for qualitative determination of ketoses. 

• It is used in explosive materials as well.

• It is used in synthesis of raw materials for aerogel.

• As it can withstand a wide range of temperatures So,

•  it is used in the automotive industry as well. 

This was a brief on Resorcinol, if you are looking for study notes on other topics of Chemistry then register yourself on or download Learning App for Class 6-10, IIT-JEE and NEET.

It is common knowledge today that an atom consists of electrons, protons, and neutrons. Originally, an atom was thought to be the smallest unit (atomic meaning unbreakable) in existence, but that theory has since been proved redundant by the discovery of subatomic particles and research is still underway to find out if these subatomic particles still can be split further. The discovery and research of quarks is a step in that direction.

There have been many scientists who have proposed different models of the atom, right from the ancient Greeks and Indians. The Atom was then considered to be indivisible, but when JJ Thompson discovered negatively charged particles in the atom, the norm was challenged, and the scientific community set out on another expedition.

JJ Thomson proposed the Plum Pudding Model shortly after he observed the presence of negatively charged particles that he named electrons. So, if there was a negative charge and the atom was electrically neutral, there had to be a positive charge. He postulated that the atom was like a Pudding with the mass and positive charge distributed across its surface and electrons embedded in the pudding-like plums.

J. J. Thomson’s plum pudding model didn’t work well when he tried to explain some experiments about how elements have atoms. Ernest Rutherford, a British scientist, did an experiment and based on what he saw, he came up with a theory about the atoms of elements and came up with the Rutherford Atomic Model.

Rutherford carried out an experiment in which he bombarded a thin sheet of gold foil with α-particles and then analysed the track of these particles after they collided with the gold foil.

Rutherford induced alpha rays to collide with a gold foil. As a source of alpha rays, he used the radioactive element polonium. 

He did notice that the majority of the alpha rays passed through the gold foil in a straight line and only a few reflected in different directions. 

Apart from this, more observations were then obtained by Rutherford.

Observations and Conclusions from Rutherford’s Experiment

• This contradicted Thompson’s model as most of the atom was observed to be virtually made of space.

• Some of the alpha particles were deflected by the gold foil by very small angles giving rise to the conclusion that the positive charge is not uniformly distributed in the atom unlike what Thompson proposed but in reality, concentrated at a very small space most likely in the centre of the atom.

• Very few of the alpha particles were deflected back almost retracting the same path they were bombarded in, at an angle of 180 degrees which insinuated that the volume occupied by the positive charge is very minute compared to the entire atomic structure.

Rutherford’s Postulates and Their Salient Features Based on the Experimental Observations

• Based on the experimental observations, Rutherford most of the mass of the atom is due to positively charged particles (later called photons) concentrated at the centre of the atom. This volume was called the nucleus of the atom and the rest of the atomic space was mostly empty. It was later theorized and proved that the nucleus also consisted of uncharged particles called neutrons which had mass but bore no charge.

• The atom has no net charge and is ‘electrically neutral’ as there are equal numbers of positively and negatively charged particles in an atom. The electrons revolving around the nucleus are negatively charged and the dense nucleus consisting of protons are positively charged. A strong electrostatic force of attraction held these two entities together bound inside the atom.

Rutherford Atomic Model

Rutherford hypothesised the atomic structure of atoms based on the following findings. The Rutherford atomic model says:

• Positively charged particles and the majority of an atom’s mass were packed into a tiny space. The nucleus is the name he gave to this part of the atom.

• According to the Rutherford model, an atom’s nucleus is surrounded by negatively charged electrons. He also believed that the electrons that surround the nucleus travel at high speeds in circular paths. He coined the term “orbits” to describe these circular pathways.

• Because electrons are negatively charged and the nucleus is a highly concentrated mass of positively charged particles, the nucleus is held together by a strong electrostatic force of attraction.

Limitations

Electrons orbit the nucleus with predetermined trajectories, according to Rutherford. According to Maxwell, accelerating charged particles release electromagnetic radiation, thus an electron rotating around the nucleus should do the same.

This radiation would send energy from the electron’s movement, but it would also shrink its orbit. In the end, the electrons would all collapse into the nucleus.

It would take less than 10-8 seconds for an electron to break apart inside the nucleus as per the Rutherford model.

As a result, the Rutherford model didn’t agree with Maxwell’s theory and couldn’t explain why atoms were stable.

One of the flaws of the Rutherford model was that he didn’t think about how electrons in an atom were arranged. This left his theory unfinished.

The early atomic models were wrong, and even though they didn’t explain some experiments, they were the foundation for future quantum mechanics breakthroughs.

These drawbacks were further built on by Neil’s Bohr, James Chadwick and many scientists that came after him. Although these didn’t sufficiently explain all observed phenomena, the revolutionary experiments, and observations that they conducted changed man’s understanding of the atomic theory and formed the basis of today’s modern physics which has seen many applications throughout an array of industries and utilities.

What is Schmidt Reaction? 

The Schmidt reaction is an important name reaction of organic chemistry. In this reaction azide (conjugate base of hydrazoic acid) reacts with a carbonyl derivative (such as carboxylic acid, aldehyde, ketone) under acidic conditions to give amine or amides with release of nitrogen. It is a rearrangement reaction. That’s why it is also known as Schmidt rearrangement reaction. This reaction is very closely reacted to another name reaction called Curtius rearrangement. 

When Schmidt reaction takes place with carboxylic acid, it gives amine while when it takes place with ketone, it gives amides. Although in Schmidt reactions of both carboxylic acid and ketone, hydrazoic acid is used and nitrogen gets released. 

Schmidt Reaction with Carboxylic Acid –

Carboxylic acid + Hydrazoic acid 🡪 Primary amine + Carbon dioxide + Nitrogen 

Reaction –

Schmidt Reaction with Ketone –

Ketone + Hydrazoic acid 🡪 Amide + Nitrogen 

Schmidt reaction is named after Karl Friedrich Schmidt (1887 – 1971). As Karl Friedrich Schmidt 1st reported the reaction by converting benzophenone and hydrazoic acid to benzanilide in 1924. Although Schmidt reaction for carboxylic acid was not reported until 1991. 

Mechanism of Schmidt Reaction 

First, we are describing here the mechanism of Schmidt reaction with carboxylic acids. Mechanism of this reaction can be understood by following 5 steps –

Step 1. Formation of Acylium Ion – Schmidt reaction with carboxylic acid starts with formation of acylium ion. It is formed by protonation of carboxylic acid with removal of water molecule. Reaction is given below –

Step 2. Acylium Ion Reaction with Hydrazoic Acid – Acylium ion reacts with hydrazoic acid and forms protonated azido ketone. Reaction is given below –

Step 3. Rearrangement of Azido Ketone – Now azido ketone undergoes rearrangement with alkyl group (R) migrating over the C-N bond and with removal of nitrogen gas. Rearrangement of azido ketone forms protonated isocyanate. Reaction is given below –

Step 4. Formation of Carbamate – Water molecule attacks on the protonated isocyanate and forms carbamate. Reaction is given below –

Step 5. Deprotonation of Carbamate and Formation of Amine – Now carbamate undergoes deprotonation and forms carbon dioxide and amine. Reaction is given below –

Mechanism of Schmidt Reaction of Ketones 

Mechanism of Schmidt reaction of ketone can be understood by following steps through Beckmann rearrangement –

Step 1. Activation of Carbonyl Group of Ketone – The carbonyl group of ketone is activated by protonation for nucleophilic addition by the azide. Reaction is given below –

Step 2. Formation of Azidohydrin – Azidohydrin is formed by nucleophilic addition of nucleophile N3– at activated carbon of carbonyl group of ketone. Reaction is given below –

Step 3. Formation of Diazoiminium – Azidohydrin loses water molecules in an elimination reaction to give diazoiminium. Reaction is given below –

Step 4. Formation of Nitrilium Intermediate – One of the alkyl (or aryl) groups migrates from carbon of diazoiminium to nitrogen with loss of nitrogen to give a nitrilium intermediate as in the Beckmann rearrangement. Reaction is given below –

Step 5. Formation of Imidic Acid – Now a water molecule attacks on nitrilium intermediate and converts it into protonated imidic acid. 

Step 6. Formation of Amide – Now imidic acid undergoes loss of proton to arrive at its tautomer of the final amide. Reactions of step 5 and 6 are given below together –

In an alternative mechanism, reaction may occur in a similar manner as Baeyer – Villiger reaction to give protonated amide. 

Schmidt Reaction and Curtius Rearrangement 

Schmidt reaction and Curtius rearrangement are closely related reactions. In Curtius rearrangement reaction acyl azide is produced by the reaction of acid chloride with sodium azide and the acid chloride is formed by the reaction of carboxylic acid with SOCl2 . While in Schmidt reaction acyl azide is produced by reaction of the carboxylic acid with hydrazoic acid as discussed under the section – What is Schmidt Reaction?

For your better understanding we are giving here a brief explanation of Curtius rearrangement. 

Curtius Rearrangement – Theodor Curtius was doing various experiments with acyl azides. During these experiments he discovered that on thermal decomposition of an acyl azide, it gives isocyanate with loss of nitrogen gas. The isocyanate on reaction with alcohols gives carbamate and with water and amines gives primary amine and urea derivatives respectively. The reaction is given below –

Thus, Curtius rearrangement reaction is thermal decomposition of carboxylic azides (such as acyl azide) to give isocyanate. In Curtius rearrangement acyl azide can be prepared by either reaction of acid chlorides or acid anhydrides with sodium azide or trimethyl azide or direct reaction of carboxylic acid with diphenylphosphoryl azide. Reactions are given below –

This ends our coverage on the topic “Schmidt Reaction”. We hope you enjoyed learning and were able to grasp the concepts. We hope after reading this article you will be able to solve problems based on the topic and will not get confused between Curtius Rearrangement and Schmidt Reaction. If you are looking for solutions to NCERT Textbook problems based on this topic, then log on to website or download Learning App. By doing so, you will be able to access free PDFs of NCERT Solutions as well as Revision notes, Mock Tests and much more.