Untitled Deck Flashcards
Why do primary aliphatic amines act as Bronsted-Lowry bases?
Because the lone pair of electrons on the nitrogen is readily available for forming a dative covalent bond with a H+ ion, allowing them to accept a proton.
Why are primary aliphatic amines stronger bases than ammonia?
Alkyl groups in primary aliphatic amines are electron-releasing, which pushes electrons towards the nitrogen atom, enhancing its ability to accept protons.
Why don’t primary aromatic amines form basic solutions?
In primary aromatic amines like phenylamine, the lone pair of electrons on the nitrogen delocalizes with the electrons in the benzene ring, making nitrogen less able to accept protons.
What happens when amines react with acids?
Amines react with acids to form ammonium salts.
Example Reaction: CH₃NH₂ (aq) + HCl (aq) → CH₃NH₃⁺Cl⁻ (aq) (Methylamine forms methylammonium chloride.)
What occurs when NaOH is added to an ammonium salt?
Addition of NaOH to an ammonium salt converts it back to the amine.
Why are ammonium salts formed in acid reactions soluble?
The ionic nature of the salts makes them soluble in water.
For example, phenylamine is not very soluble in water, but phenylammonium chloride is soluble.
What happens to ammonium salts if water is evaporated?
The salts form solid crystals due to strong ionic interactions.
How do alkyl groups affect the basicity of primary aliphatic amines?
Alkyl groups release electrons, increasing the electron density on nitrogen, making it a stronger base compared to ammonia.
What structural feature of aromatic amines reduces their basicity?
The lone pair of electrons on nitrogen delocalizes into the benzene ring, reducing its ability to accept protons.
What are the physical properties of ammonium salts formed by amines?
Ammonium salts are ionic, soluble in water, and form solid crystals if water is evaporated.
Why is phenylamine less soluble in water than its ammonium salt?
Phenylamine lacks strong ionic interactions, while phenylammonium chloride is ionic and thus more soluble.
How are primary amines formed through nucleophilic substitution?
Primary amines form when a haloalkane reacts with ammonia in a nucleophilic substitution reaction.
Example Reaction: CH₃CH₂Br + 2NH₃ → CH₃CH₂NH₂ + NH₄Br
What reagents and conditions are required to form primary amines from haloalkanes?
Excess ammonia dissolved in ethanol under suitable reaction conditions.
How can the amount of primary amine formed in nucleophilic substitution be maximized?
By using an excess of ammonia to limit further substitution reactions.
How are secondary amines formed in nucleophilic substitution?
Secondary amines form when a primary amine reacts with a haloalkane in the same mechanism as ammonia.
