amines Flashcards
What makes amines act as bases?
The lone pair on nitrogen can accept protons.
What affects the basic strength of amines?
Electron-donating or withdrawing groups attached to nitrogen.
Rank the base strength of different types of amines.
Aromatic amines < Ammonia < Primary amines < Tertiary amines < Secondary amines
Why are secondary amines stronger bases than primary amines?
Alkyl groups push electron density onto nitrogen, increasing its ability to accept protons.
Why are aromatic amines weaker bases?
The lone pair on nitrogen delocalizes into the benzene ring, reducing availability for protonation.
What happens when amines react with acids?
They form ammonium salts
How can an ammonium salt be converted back to an amine?
By adding NaOH (a strong base).
How do amines react with acyl chlorides?
they undergo nucleophilic addition-elimination to form amides.
What happens when amines react with halogenoalkanes?
They undergo nucleophilic substitution, forming secondary, tertiary amines, and quaternary ammonium salts.
How are primary amines made from halogenoalkanes?
: By heating with excess ammonia in ethanol.
Why is excess ammonia used?
To minimize further substitution and favor primary amine formation.
What is the issue with this method?
A mixture of primary, secondary, and tertiary amines is formed.
How can pure primary amines be made from nitriles?
By reducing them using LiAlH₄ in dry ether or H₂ with a Ni catalyst.
Why is reducing nitriles better than using halogenoalkanes?
It produces only primary amines with no unwanted by-products.
How can nitrobenzene be reduced to phenylamine?
By using tin (Sn) and hydrochloric acid, followed by NaOH.
What are the reaction steps for this process?
C6H5NO2+6[H]→C6H5NH2+2H2O
The amine is initially protonated to form𝐶6𝐻5𝑁𝐻3+𝐶𝑙−C6H5NH3+Cl−, then deprotonated with NaOH.
Why is phenylamine important in industry?
it is used to make dyes, drugs, and polymers.
What happens when an excess halogenoalkane reacts with an amine?
A quaternary ammonium salt is formed.
Why are quaternary ammonium salts useful?
They act as cationic surfactants, used in fabric softeners, hair conditioners, and detergents.
How do cationic surfactants work?
The positively charged head attracts to negatively charged surfaces (e.g., hair, fabrics), reducing static charge.
