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According to the answer key, trimethylamine (iii) and ethanolamine (iv) are considered organic bases, whereas ammonium (i) and acrylamide (ii) are not:

ammonium; acrylamide; trimethylamine; ethanolamine

From my understanding, an organic base has an atom with a lone pair of electrons. Doesn't acrylamide (ii) have a lone pair of electrons and should thusly also be considered an organic base?

If I am using the wrong method to identify organic bases, what other method should I use?

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  • $\begingroup$ Nora, your understanding is correct. just remember that there are degrees of basicity. Amines are stronger bases than amides. An available electron pair makes a base, all that is needed is an appropriate acid. Check this for intra molecular acid base reactions with strange bases. www2.chemistry.msu.edu/faculty/reusch/VirtTxtJml/rearrang.htm $\endgroup$
    – jimchmst
    Commented Mar 6 at 18:48

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Organic bases are just organic compounds which act as bases. These primarily include amines.

Compound two is an amide. Amides are more acidic than amines, and they very rarely act as organic bases. They aren't classified as such.

The lone pair is not much available in an amide due to resonance, hence it acts as a base only when a strong acid is present. On the other hand, amide might act as an acid, donating proton. As $\ce{H+}$ comes out of the nitrogen in an amide, the negative charge is delocalized and hence the conjugate base is stabilized.

PS. This doesn't mean that an amide is much of an organic acid, either. They are both very weak bases and very weak acids.

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  • $\begingroup$ You contradict yourself not a base! a very weak base! $\endgroup$
    – jimchmst
    Commented Mar 6 at 18:31
  • $\begingroup$ @jimchmst By using the word very weak base I mean to say that it can't be treated as a base just like sodium hydroxide can't be treated as an acid. The words acid and base are often relative and interchangable in situations like these. Ethanol for example is more inclined towards the basic side and so it is a weak acid. It is just a matter of words. $\endgroup$
    – The Fright Of The Night
    Commented Mar 6 at 18:38
  • $\begingroup$ If it is a matter of words lets use them correctly. There are degrees of basicity and it depends on the acid it is reacting with. Add Al powder to a strong hydroxide solution to see how acidic it is. As for ethanol it definitely is an organic base but does not qualify under your answer or the tone of original question. Again you contradict yourself. $\endgroup$
    – jimchmst
    Commented Mar 6 at 19:04
  • $\begingroup$ That is what I mean. The terms acid and bases are relative and depend on the reagent added.So I used the word very weak base instead of "not a base" at the end $\endgroup$
    – The Fright Of The Night
    Commented Mar 7 at 1:54
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Organic base has an atom with a lone pair of electrons. This statement is not true considering the fact that the lone pair of the compound may be in resonance.

Consider the example of a carboxylic acid. They are organic bases under your definition as the oxygen has a lone pair. The second question is similar to a carboxylic acid. Consider the image:enter image description here

The first situation shows amide acting as a base.This leads to a highly unstable structure.This resonating structure will have no contribution to the hybrid. The second situation shows amide behaving as an acid. This leads to a stable structure. Hence as @TheFrightOfTheNight pointed out,the amides are acidic and so can't be called organic bases.

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    $\begingroup$ This alternative mesomeric structure with protonated amide isn't unstable, it's nonsensical. There's no resonance stabilisation of amide protonated on nitrogen. There is, if it gets protonated on oxygen, though. $\endgroup$
    – Mithoron
    Commented Jun 1 at 16:46
  • $\begingroup$ That's true. I edited my question stating that the structure has zero contribution to the hybrid. $\endgroup$
    – Nightwing
    Commented Jun 2 at 17:16

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