Why are NH 3 and CH 3 NH 2 no longer nucleophiles when they are protonated?

Hey, everyone. And welcome back in today's video. We're going to answer the following question. Why are the protein ated di ethyl amine and ethyl amine no longer nuclear files? Let's draw these two structures. That's really important for our analysis. The first structure is di ethyl amine. So that means the two ethyl groups are bonded in nitrogen just as the structure suggests, two ch, three ch two groups are bonded to nitrogen which is bonded to hydrogen. That's the first structure we're analyzing. And the second one simply has an ethyl group bonded to nitrogen that has two hydrogen atoms bond. It'd let's recall that nitrogen in each case, has three bonds so that there must be a lone pair on nitrogen in each case to satisfy the architectural right. Nigeria must have three bonds in a low impaired. That's what we see in each case. The problem states that we are protein ating them. So we want to take a look at their protein ated forms. If you protein eight, each of them, the lone pair on nitrogen will accept that proton. So we're going to show how the lone pair accepts that proton. In each case, and we got the following two structures. The first one will accept a proton and then we will have two hydrogen atoms bonded to nitrogen. So we can say NH two Because Nige in forms four bonds, it used its lone pair in the formation of that nitrogen hydrogen bond. So there's no more lone pair. Andijan will have a formal positive charge. Similarly, for the second one, ni Jin will accept an additional hydrogen using its lone pair to create that Candyland nitrogen hydrogen bond and essential national will have a formal positive charge. This is really important for us. So the initial to a means they had lone pairs, the final protein ated structures have no lone pairs. So the answer to this question is clear if we remember that nuclear files, our electron pair donors whenever we want to create a bond between our nuclear file and electro file, because there is no more lone pair on nitrogen atom. In each case, that's why the two protein ated amines are no longer nuclear files. And therefore, we may conclude that the correct answer to the multiple choice question is a the nitrogen atoms no longer have lone pairs of electrons. And therefore, that's why they are no longer nuclear files because nuclear files must have electron pairs to donate them in forming a bond between a nuclear file and an electro file. That will be it. Thank you for watching.

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1. A Review of General Chemistry5h 5m
2. Molecular Representations1h 14m
3. Acids and Bases2h 46m
4. Alkanes and Cycloalkanes4h 17m
5. Chirality3h 39m
6. Thermodynamics and Kinetics1h 22m
7. Substitution Reactions1h 48m
8. Elimination Reactions2h 30m
9. Alkenes and Alkynes2h 9m
10. Addition Reactions3h 19m
11. Radical Reactions1h 58m
12. Alcohols, Ethers, Epoxides and Thiols2h 42m
13. Alcohols and Carbonyl Compounds2h 17m
14. Synthetic Techniques1h 26m
15. Analytical Techniques:IR, NMR, Mass Spect7h 3m
16. Conjugated Systems6h 13m
17. Ultraviolet Spectroscopy51m
18. Aromaticity2h 34m
19. Reactions of Aromatics: EAS and Beyond5h 1m
20. Phenols55m
21. Aldehydes and Ketones: Nucleophilic Addition4h 56m
22. Carboxylic Acid Derivatives: NAS2h 51m
23. The Chemistry of Thioesters, Phophate Ester and Phosphate Anhydrides1h 10m
24. Enolate Chemistry: Reactions at the Alpha-Carbon1h 53m
25. Condensation Chemistry2h 9m
26. Amines1h 43m
27. Heterocycles2h 0m
28. Carbohydrates5h 53m
29. Amino Acids4h 20m
30. Peptides and Proteins2h 42m
31. Catalysis in Organic Reactions1h 30m
32. Lipids 2h 50m
33. The Organic Chemistry of Metabolic Pathways2h 52m
34. Nucleic Acids1h 32m
35. Transition Metals6h 14m
36. Synthetic Polymers1h 49m

3. Acids and Bases

Reaction Mechanism

Organic Chemistry

3. Acids and Bases

Reaction Mechanism

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3:17 minutes

Problem 1

Textbook Question

Why are NH₃ and CH₃NH₂ no longer nucleophiles when they are protonated?

Verified step by step guidance

Understand the concept of nucleophilicity: Nucleophiles are species that donate a pair of electrons to form a bond with an electrophile. They must have a lone pair of electrons available for donation.

Examine the structure of NH3 (ammonia) and CH3NH2 (methylamine): Both molecules have lone pairs of electrons on the nitrogen atom, making them nucleophiles in their neutral forms.

Consider what happens during protonation: When NH3 or CH3NH2 is protonated, a hydrogen ion (H⁺) is added to the molecule. This results in the formation of NH4⁺ (ammonium ion) and CH3NH3⁺ (methylammonium ion), respectively.

Analyze the electron availability after protonation: In the protonated forms, the nitrogen atom no longer has a lone pair of electrons available for donation because the lone pair is now involved in bonding with the added hydrogen ion.

Conclude why they are no longer nucleophiles: Since nucleophilicity depends on the availability of a lone pair of electrons for donation, NH4⁺ and CH3NH3⁺ cannot act as nucleophiles because their nitrogen atoms lack free lone pairs after protonation.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Nucleophilicity

Nucleophilicity refers to the ability of a species to donate an electron pair to an electrophile, forming a chemical bond. Nucleophiles are typically electron-rich species, such as amines like NH3 and CH3NH2, which have lone pairs of electrons that can be used for bonding. When these nucleophiles are protonated, they become positively charged, which significantly reduces their electron density and ability to donate electrons.

Protonation

Protonation is the addition of a proton (H+) to a molecule, resulting in the formation of a positively charged species. In the case of NH3 and CH3NH2, protonation leads to the formation of NH4+ and CH3NH3+, respectively. This process alters the electronic structure of the molecules, making them less capable of acting as nucleophiles due to the increased positive charge that repels electron donation.

Charge and Reactivity

The charge of a molecule significantly influences its reactivity and ability to participate in chemical reactions. Neutral nucleophiles, like NH3 and CH3NH2, can readily attack electrophiles due to their electron-rich nature. However, once protonated, the resulting cations (NH4+ and CH3NH3+) are stabilized by their positive charge, which makes them less reactive towards electrophiles, effectively rendering them non-nucleophilic.

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