Pyridine: Structure, Properties, and Uses

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