NH acidity

NH acidity of phthalimide: When exposed to potassium hydroxide, the potassium salt of phthalimide is formed.

NH acidity ( pK _s = 5.6) of sulfamethoxazole (a sulfonamide which is used in the chemotherapy of bacterial infections).

In organic chemistry, NH acidity is the tendency of nitrogen-containing amide derivatives to enter into a reaction that yields an amide anion with heterolytic breakage of an NH bond . At the same time, a proton is split off which, for example, reacts with a hydroxide anion to form water.

At first glance, the acidic effect of nitrogen-containing compounds is unexpected because amines are basic. In amide derivatives, for example sulfonamides , sulfonylureas , barbituric acid derivatives, thiazides or phthalimide , the protons on the amide nitrogen become significantly acidic due to the resonance interaction with the neighboring S = O or C = O double bonds and can become relatively acidic due to the action of a base simply split off. Some sulfonylureas are almost as acidic as acetic acid .

Drug Examples

The orally active antidiabetic glyburide ( pK _s = 5.3), the antiepileptic phenobarbital ( pK _s = 7.4) and the diuretic hydrochlorothiazide ( pK _s = 8.3) in addition sulfamethoxazole ( pK _s = 5.6) Other examples for drugs that have NH acidity.

Individual evidence

1. ^ Hans Beyer and Wolfgang Walter : Organische Chemie , S. Hirzel Verlag, Stuttgart, 1984, page 521, ISBN 3-7776-0406-2 .
2. ^ ^{A b} Carsten Schmuck, Bernd Engels, Tanja Schirmeister, Reinhold Fink: Chemistry for Medicine , Pearson Studies, p. 654, ISBN 978-3-8273-7286-4 .