What is the formula of the conjugate acid of dimethylamine, (CH3)2NH? What is the formula of its conjugate base? Trimethylamine has a similar structure to dimethylamine; why does it not have a conjugate base?
The correct answer and explanation is :
The formula of the conjugate acid of dimethylamine ((CH_3)_2NH) is ((CH_3)_2NH_2^+) (dimethylammonium ion).
The formula of the conjugate base of dimethylamine is ((CH_3)_2N^-) (dimethylamide ion).
Explanation:
Dimethylamine ((CH_3)_2NH) is a weak base because of the presence of a nitrogen atom with a lone pair of electrons that can accept a proton (H⁺). When it reacts with an acid, it gains a proton to form its conjugate acid, dimethylammonium ion ((CH_3)_2NH_2^+). This occurs as follows:
[
(CH_3)_2NH + H^+ \rightarrow (CH_3)_2NH_2^+
]
Conversely, dimethylamine can also lose a proton (though this is much less common) to form its conjugate base, dimethylamide ion ((CH_3)_2N^-):
[
(CH_3)_2NH \rightarrow (CH_3)_2N^- + H^+
]
Why Trimethylamine Does Not Have a Conjugate Base:
Trimethylamine ((CH_3)_3N) has a nitrogen atom bonded to three methyl groups. Unlike dimethylamine, it lacks a hydrogen atom directly attached to the nitrogen, which means it cannot lose a proton to form a conjugate base. Since conjugate bases are formed by deprotonation (removal of an H⁺), and trimethylamine has no such hydrogen, it does not have a conjugate base. However, it can accept a proton to form a conjugate acid, trimethylammonium ion ((CH_3)_3NH^+):
[
(CH_3)_3N + H^+ \rightarrow (CH_3)_3NH^+
]
Thus, while dimethylamine has both a conjugate acid and base, trimethylamine only has a conjugate acid.
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