Which formula best represents the form a primary amine takes in acidic solution?
A) RNH2
B) RNH-
C) RNH2-
D) RNH2+
E) RNH3+
The correct answer and explanation is:
The correct answer is E) RNH3+.
Explanation:
A primary amine, such as RNH2, consists of a nitrogen atom bonded to a single alkyl group (R) and two hydrogen atoms. In a neutral or basic environment, a primary amine exists in its neutral form, RNH2. However, when it is in an acidic solution, the amine can act as a base, accepting a proton (H+).
A primary amine has a lone pair of electrons on the nitrogen atom, which can readily accept a proton. When this happens in an acidic solution, the nitrogen atom becomes positively charged, resulting in the formation of RNH3+. This protonated form of the primary amine is the one that is prevalent in acidic conditions.
Let’s break it down:
- RNH2 (Option A) represents the neutral amine. In acidic conditions, it will accept a proton to form RNH3+, so it is not the correct form in acid.
- RNH- (Option B) represents a negatively charged amine, which is unlikely in acidic conditions since the solution would provide an abundance of protons, not favoring negative charges.
- RNH2- (Option C) indicates a doubly negatively charged amine, which does not occur in acidic environments.
- RNH2+ (Option D) is a mistaken representation, as it does not capture the typical protonation behavior of primary amines in acids, where they form RNH3+ rather than RNH2+.
Thus, in an acidic environment, the primary amine will be protonated to form RNH3+, which is the correct representation of its form in acidic solution.