Table of contents

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

26. Amines

Amine Alkylation

Organic Chemistry

26. Amines

Amine Alkylation

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Problem 64b

Textbook Question

In Section 10.12, we saw that S-adenosylmethionine (SAM) methylates the nitrogen atom of noradrenaline to form adrenaline, a more potent hormone. If SAM methylates an OH group attached to the benzene ring instead, it completely destroys noradrenaline's activity.
b. Which reaction is more apt to occur, methylation on nitrogen or methylation on oxygen?

Verified step by step guidance

Understand the context: The problem involves the methylation of noradrenaline by S-adenosylmethionine (SAM). Noradrenaline has functional groups that can be methylated, specifically the nitrogen atom and the oxygen atom of the hydroxyl group attached to the benzene ring. The question asks which site is more likely to undergo methylation.

Analyze the reactivity of the nitrogen atom: The nitrogen atom in noradrenaline is part of an amine group. Amines are nucleophilic due to the lone pair of electrons on the nitrogen, making them reactive toward electrophiles like the methyl group from SAM. This nucleophilicity makes the nitrogen a favorable site for methylation.

Analyze the reactivity of the oxygen atom: The oxygen atom in the hydroxyl group attached to the benzene ring is also nucleophilic due to its lone pairs of electrons. However, the hydroxyl group is part of a phenol structure, where the lone pairs on oxygen are partially delocalized into the aromatic ring. This delocalization reduces the nucleophilicity of the oxygen compared to the nitrogen.

Consider steric and electronic factors: Methylation on the nitrogen atom is more likely because the nitrogen is more nucleophilic and less hindered compared to the oxygen atom. Additionally, the methylation of the nitrogen atom leads to the formation of adrenaline, which is biologically significant, suggesting that the enzyme catalyzing this reaction is optimized for nitrogen methylation.

Conclude the comparison: Based on the nucleophilicity and the biological context, methylation on the nitrogen atom is more apt to occur than methylation on the oxygen atom of the hydroxyl group attached to the benzene ring.

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Key Concepts

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

Methylation Reactions

Methylation is a biochemical process where a methyl group (CH3) is added to a molecule, often affecting its function. In the context of organic chemistry, methylation can occur on various functional groups, such as nitrogen or oxygen. The reactivity and stability of the resulting compound depend on the nature of the atom being methylated and the surrounding chemical environment.

Functional Group Reactivity

Different functional groups exhibit varying reactivities due to their electronic and steric properties. Nitrogen atoms, especially in amines, are generally more nucleophilic than oxygen atoms in alcohols or phenols, making them more likely to undergo methylation. Understanding the reactivity of these functional groups is crucial for predicting the outcome of methylation reactions.

Biological Significance of Methylation

Methylation plays a vital role in biological systems, influencing the activity of hormones and neurotransmitters. For instance, the methylation of noradrenaline to form adrenaline enhances its potency as a hormone. Conversely, methylation on an oxygen atom can lead to loss of biological activity, highlighting the importance of the specific site of methylation in determining molecular function.

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