What is correct basicity order of pyridine, pyridazine, pyrimidine and pyrazine ?

Pyridine is more basic as compared to pyridazine, pyrimidine and pyrazine because pyridazine, pyrimidine and pyrazine containing two nitrogen atoms which are exerted inductive effect to each other so availability of lone pair for donation is less.

But pyridazineis  more basic as expected, it may be due to electrostatic repulsion of the lone pairs of the vicinal nitrogens. This repulsion destabilizes the non-protonated structure and therefore makes protonation easier.

Related Questions:

(1) Give an explanation for the fact that Guanidine NH=C(CH3)2 is a stronger base than most of amines?

(2) Arrange in correct order of basic Character of aniline, pyrrol, pyridine and piperidine?

(3) What is correct basicity order of pyridine, pyridazine, pyrimidine and pyrazine ?

(4) Why pyridine is more basic than Pyrrole?

(5) Why pyrimidine is less basic than pyridine?

(6) Imidazole is more basic than pyridine? Why?

(7) Biological Important of Imidazole and structure:

(8) Pyridine is almost 1 million times less basic than piperidine? Why?

(9) Cyclohexylamine amine is the stronger base than Aniline? Why?

(10) Tetrahydroquinoline amine is the stronger base than Tetrahydroisoquinoline? Why?

Why pyridine is more basic than Pyrrole?

In case of Pyrrole  the lone pair electrons of the nitrogen atom is involved in conjugated system of pi electrons of five membered ring leading to greater stability of the molecule due to acquiring aromatic character. Hence less available for donation.

While in case pyridine already has a stable conjugated system of three double bonds in an aromatic ring, like benzene. Hence the lone pair electrons on the N atom in pyridine is localized and  more available for donation and  easily donated to a H⁺ ions. Therefore, pyridine is a stronger base than Pyrrole.

Related Questions:

Give an explanation for the fact that Guanidine NH=C(CH3)2 is a stronger base than most of amines?

Arrange in correct order of basic Character of aniline, pyrrol, pyridine and piperidine?

What is correct basicity order of pyridine, pyridazine, pyrimidine and pyrazine ?

Why pyridine is more basic than Pyrrole?

Why pyrimidine is less basic than pyridine?

Imidazole is more basic than pyridine? Why?

Biological Important of Imidazole and structure:

Pyridine is almost 1 million times less basic than piperidine? Why?

Cyclohexylamine amine is the stronger base than Aniline? Why?

Tetrahydroquinoline amine is the stronger base than Tetrahydroisoquinoline? Why?

Why pyrimidine is less basic than pyridine?

Pyrimidine is less basic than pyridine because (–I effect) negative inductive effect of nitrogen atom to another nitrogen atom that cause decreases electron density of each other. This makes it less willing to donate its lone pair. This is not count that number of lone pairs to explain basicity.

Related Questions:

Give an explanation for the fact that Guanidine NH=C(CH3)2 is a stronger base than most of amines?

Arrange in correct order of basic Character of aniline, pyrrol, pyridine and piperidine?

What is correct basicity order of pyridine, pyridazine, pyrimidine and pyrazine ?

Why pyridine is more basic than Pyrrole?

Why pyrimidine is less basic than pyridine?

Imidazole is more basic than pyridine? Why?

Biological Important of Imidazole and structure:

Pyridine is almost 1 million times less basic than piperidine? Why?

Cyclohexylamine amine is the stronger base than Aniline? Why?

Tetrahydroquinoline amine is the stronger base than Tetrahydroisoquinoline? Why?

How to prepare p-bromoaniline, knowing that aniline only gives the tris-brominated product; note that bromination of aniline does not stop at the monobrominated stage and cannot be moderated by using only one equivalent of bromine.

SOLUTION:

Moderating the activity of NH₂ by reacting of aniline with acetic anhydride

The activating influence of NH₂ has been reduced due to competing withdrawal of N-lone pair by carbonyl group:

Related Questions:

1. Why do not Friedel-Crafts reactions succeed on aromatic rings that are substituted either by a strongly electron-withdrawing group such as carbonyl (C=O) or by an amino group (-NH₂, NHR, -NR₂):
2. Why does not aniline undergo Friedel crafts reactions explain?
3. Why Friedel–Crafts alkylations often give polysubstitution products but Friedel–Crafts acylations do not.

What Is Mustard Gas?

Mustard gas is a colorless oily liquid whose vapor is a powerful irritant and vesicant, used in chemical weapons. Mustard gas, or sulphur mustard (Cl-CH₂CH₂)₂S, is a chemical agent that causes severe burning of the skin, eyes and respiratory tract. It can be absorbed into the body through inhalation, ingestion or by coming into contact with the skin or eyes

Sulphur Mustard:

Nitrogen Mustard:

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