2 added 73 characters in body edited Sep 8 '14 at 20:30 Jannis Andreska 5,18911 gold badge3030 silver badges7676 bronze badges The unprotonated amino group ($$\ce{R-NH2}$$) does not protonate $$\ce{OH-}$$ because it is an extremely weak acid. Primary and secondary amines have a $$pK_a$$$$pK_a$$ of around 35, while the $$pK_a$$ of hydroxide is about 13-14 in aqueous solution. Deprotonating $$\ce{NH2}$$ groups requires much stronger bases in non-aqueous medium. Therefore, the carboxylic acid group of the amino acid is deprotonated in aqueous alkaline solution, as shown in the scheme from your textbook. The unprotonated amino group ($$\ce{R-NH2}$$) does not protonate $$\ce{OH-}$$ because it is an extremely weak acid. Primary and secondary amines have a $$pK_a$$ of around 35, while the $$pK_a$$ of hydroxide is about 13-14 in aqueous solution. Deprotonating $$\ce{NH2}$$ groups requires much stronger bases in non-aqueous medium. Therefore, the carboxylic acid group of the amino acid is deprotonated in aqueous alkaline solution, as shown in the scheme from your textbook. The unprotonated amino group ($$\ce{R-NH2}$$) does not protonate $$\ce{OH-}$$ because it is an extremely weak acid. Primary and secondary amines have a $$pK_a$$ of around 35, while the $$pK_a$$ of hydroxide is about 13-14 in aqueous solution. Deprotonating $$\ce{NH2}$$ groups requires much stronger bases in non-aqueous medium. Therefore, the carboxylic acid group of the amino acid is deprotonated in aqueous alkaline solution, as shown in the scheme from your textbook. 1 answered Sep 8 '14 at 20:03 Jannis Andreska 5,18911 gold badge3030 silver badges7676 bronze badges The unprotonated amino group ($$\ce{R-NH2}$$) does not protonate $$\ce{OH-}$$ because it is an extremely weak acid. Primary and secondary amines have a $$pK_a$$ of around 35, while the $$pK_a$$ of hydroxide is about 13-14 in aqueous solution. Deprotonating $$\ce{NH2}$$ groups requires much stronger bases in non-aqueous medium. Therefore, the carboxylic acid group of the amino acid is deprotonated in aqueous alkaline solution, as shown in the scheme from your textbook.