Page 9 - phytochemistry II -pharmD general

II- Chemical Properties
❑ All alkaloids should contain at least one nitrogen atom (in addition to
C,H & O).

But some alkaloids are free from Oxygen atom. e.g.

nicotine and coniine

❑ The state or the type of nitrogen atoms as amines.

• Primary amine (R-NH2)
• Secondary amine (R2-NH)
• Tertiary amine (majority) (R3-N)
• Quaternary ammonium (R4-N+ ) e.g. d-Tubocurarine.
• Another form of nitrogen is N-oxide alk.

❑ Basicity of alkaloids

Generally, alkaloids are basic compounds due to the presence of N atoms, the
lone pair of electrons on the nitrogen atom of alkaloids is normally responsible for
its basicity.

but still some alkaloids are neutral (ricinine, colchicines) or amphoteric (morphine
& Narceine). why?

Factors that may influence the degree of basicity:

1- Structure of the molecule such as the degree of unsaturation of the
heterocyclic ring.

❑ Unsaturation decreases the basicity??

That alkaloids having piperidine as their basic nucleus are more basic than
alkaloids having pyridine as their basic ring.

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