Chapter 24 - Amines and Heterocycles Flashcards
Higher the pKa, higher the _____.
basicity
Rank the following in increasing basicity:
ammonia, tertiary amine, primary amine, secondary amine, arylamine
arylamine < ammonia < 1º < 3º < 2º
more resonance = more acidic
Amides (RCONH2) are _____ _____, in contrast with amines.
not basic
Primary and secondary amines can act as very _____ _____.
weak acids
The proton from N–H can be removed by a sufficiently strong ( acid / base ).
base
Any electron withdrawing group in the ortho or para position of an arylamine will _____ the basicity.
decreases
(–CN & –NO2 are strongest)
(–Cl & –Br work well, too)
Any electron donating group in the ortho or para position of an arylamine will _____ the basicity.
increases
–NH2, –OCH3, –CH3
Primary amines can be prepared with the reduction of nitriles (–CN) and amides (–CONH2) with _____.
LiAlH$
Arylamines can be prepared from _____ of an aromatic compound and _____ of the nitro group.
nitration; reduction (= gain of H)
Reduction by catalytic hydrogenation over platinum is suitable if…
no other groups can be reduced.
C=O ==> CH2OH
Ammonia and other amines are good _____.
nucleophiles
Azide ion (N3-) displaces a _____ ion from a primary or _____ alkyl halide to give an alkyl azide (RN=N+=N-)
halide; secondary
1º or 2º alkyl halide gains azide ion from _____. It is reduced with _____ to form the amine.
NaN3; LiAlH4
Gabriel amine synthesis looks like a(n) _____ when trying to form a(n) _____ _____.
angel; primary amine
Reductive amination uses a 1º, 2º, or 3º amine and _____ to turn the _____ into an amine.
NaBH4; carbonyl
Carboxylic acid derivatives can be converted into _____ _____ with loss of one carbon atom by both Hofmann rearrangement and Curtius rearrangement.
primary amines
Hofmann rearrangement involves a(n) _____ _____.
primary amide
Curtius rearrangment involves a(n) _____ _____.
acyl azide
Hofmann rearrangement is when a primary amide (RCONH2) is treated with _____ and _____.
Br2 (or Cl2); base
Curtius rearrangement is when a(n) –R group from the C=O carbon atom migrates to the neighboring _____.
nitrogen
Curtius rearrangement reaction occurs when an acyl azide…
is heated.
Primary and secondary amines can be acylated by _____ _____ _____
nucleophilic acyl substitution
Hofmann elimination converts an amine into…
an alcohol
Hofmann elimination requires a better leaving group, so –NH2 must be converted to…
a quaternary ammonium salt (+N(CH3)3 I-)
Hofmann elimination requires a better leaving group, so –NH2 must be converted to a quaternary ammonium salt with…
excess iodomethane (CH3–I)
Hofmann elimination uses _____ (H2O, heat) to make the positive nitrogen atom leave.
Ag2O (silver oxide)
Hofmann elimination lets the alkene form…
where there is less steric hinderance
Diazonium replacement takes place through…
radical pathways
N–CH3 gives a sharp three-H singlet at…
2.2 to 2.6
1º and 2º amines are identified by characteristic N–H stretching absorptions at…
3300 to 3500 1/cm
A compound with an odd number of N atoms has…
an odd-numbers molecular weight
Alkylamines cleave at the C–C bond nearest the nitrogen (alpha-cleavage) to yield and alkyl radical and…
a nitrogen-containing cation
Diazonium coupling reactions: electrophilic diazonium ion (+N≡N) reacts with the electron-rich ring of…
a phenol or arylamine
Diazonium coupling reactions: usually occur at the _____ position.
para
Diazonium coupling reactions: usually occur at the para position but goes _____ if para is blocked.
ortho
To make a diazonium salt, you must react a primary arylamine with…
HNO2 / H2SO4
Sandmeyer reaction: reaction of an arenediazonium salt with the corresponding copper(I) halide to yield…
aryl chlorides and bromides
The reagents to go from arenediazonium salt to aryl chloride are…
HCl / CuCl
The reagents to go from arenediazonium salt to aryl iodide are…
NaI (direct reaction)
The reagents to go from arenediazonium salt to aryl bromide are…
HBr / CuBr
The reagents to go from arenediazonium salt to aryl nitrile (ArCN) are…
KCN / CuCN
The reagents to go from arenediazonium salt to phenol are…
Cu2O, H2O / Cu(NO3)2
The reagents to go from arenediazonium salt to a single H-bond are…
H3PO2
