For aliphatic amide and amine. I know we can use $\ce{NaOH}$ because amide will give off $\ce{NH3}$, but what will amine yield if we test it with $\ce{NaOH}$?
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2$\begingroup$ Amines don't react with NaOH $\endgroup$– Aditya AnandCommented Feb 14, 2016 at 6:37
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$\begingroup$ In order to identify amines, you might want to search for the Hinsberg reaction. $\endgroup$– Klaus-Dieter WarzechaCommented Feb 14, 2016 at 7:40
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$\begingroup$ Pfft, if you have simply choice between amine and amide, then make solution and use basicity indicator. $\endgroup$– MithoronCommented Feb 14, 2016 at 14:54
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3 Answers
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From Wikipedia:
While the conjugate acid of an amine has a pKa of about 9.5, the conjugate acid of an amide has a pKa around −0.5. Therefore, amides don't have as clearly noticeable acid-base properties in water.
Therefore, if you are dealing trying to distinguish a water-soluble amide from a water-soluble amine, and neither molecule has other functional groups, you could simply dissolve them in water and then measure the pH. If it's alkaline, it's an amine. If the pH doesn't change much, it's an amide.
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Easiest way is to use TLC(thin layer chromatography) plate and stain with ninhydrin. Ninhydrin colors primary and secondary amines and amides only with vigorous heating when amide bond breaks.
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I do not know how to distinguish chemically between an amide and an amine based on the reaction with $\ce{NaOH}$ but I can tell you a different way to distinguish between the two kinds of compounds.
An amide on acidic hydrolysis will yield the corresponding carboxylic acid (i.e. with the same number of carbons) as follows. $$\ce{RCONH2->[\ce{H3O+}][\Delta] RCOOH}$$
The carboxylic acid produced can be tested for using the sodium hydrogencarbonate test, in which adding a pinch of $\ce{NaHCO3}$ produces a brisk effervescence due to the evolution of carbon dioxide gas.
$$\ce{RCOOH + NaHCO3->RCOONa + H2O + CO2 ^}$$
So basically, out of the two given compounds, the one that gives you a brisk effervescence when you first hydrolyse it in an acidic medium and then follow it with a pinch of $\ce{NaHCO3}$, is the amide, and the other is the amine.
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3$\begingroup$ You will have to be careful doing this and make sure that you remove all of the acid used for hydrolysis, before adding the hydrogencarbonate, otherwise you will get false positives. $\endgroup$– bonCommented Feb 14, 2016 at 11:44
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$\begingroup$ Yes, that is true. I did not see that earlier. $\endgroup$– user25546Commented Feb 20, 2016 at 1:45