Amines Flashcards
Hofmann ammonolysis reagents
1). Ethanolic NH3
2). NaOH
Hofmann ammonolysis follows
Sn2 mechanism
Reactivity order of Hofmann ammonolysis
primary > secondary > tertiary
RI > RBr> RCl
Gabriel Phthalimide Synthesis used to prepare
primary aliphatic amines
Hoffmann exhaustive methylation
Amine is reacted with CH3I
Physical properties of lower aliphatic amines
they are gases with fishy odour and soluble in water due to H-bonding.
Physical properties of primary amines with 3 or more carbon atoms
they are liquid and still higher ones are solid.
Physical properties of aniline and other arylamines
they are usually colorless but get colored on storage due to atmospheric oxidation
The boiling point and solubility in water of Amines is lower than
those of alcohols of similar molar mass due to weaker H- bonding in Amines.
The order of bp of isomeric amines
1°>2°>3°
Electrophilic aromatic substitution (SEAr) is
Electrophilic aromatic substitution (SEAr) is an organic reaction in which an atom that is attached to an aromatic system (usually hydrogen) is replaced by an electrophile.
In bromination of Aniline what is the reagent?
Bromine water (3 eq. of Br2) , And forms 2,4,6 - tribromoaniline
color of 2,4,6 - tribromoaniline
white ppt
what is the reagent for monobromination
Acetic anhydride (CH3CO)2O and a (base) pyridine
Solvent used in monobromination is
Br2, CH2COOH (solvent)
3rd step for monobromination
hydrolyses
Nature of aniline
basic
How does nitration of aniline occur?
Aniline is reacted with acidic (HNO₃ + H₂SO₄)
Ratio of Nitration products — o-, m-, p-
2:47:51 %
when is Anilinium ion is formed
When acid base reaction occure between aniline and (HNO₃ + H₂SO₄)
Process of sulphonation of aniline
1). H₂SO₄
After the formation of salt
2). Heat at temp. 453-473K
Use of Sulphonilic acid
Used in making dyes
Sulphonilic acid resonate as
Zwitter ion (positive and negative charges in a molecule)
Why does Aniline do not show Friedel Crafts reactions?
Aniline gets deactivated due to salt formation.
What is the temperature for mononitration during acid base reaction?
10-degree Celsius
What is Heinsberg’s test?
It is used to distinguish among 1°, 2°, 3° Amines.
Heinsberg’s reagent
Benzenesulphonyl chloride
How do we distinguish between amines through Heinsberg’s test?
1° amines give soluble product, a salt.
2° amines give insoluble product
3° amines do not give product.
Which amines give carbylamine reaction?
1° aliphatic and aromatic
Reagents of carbylamine reaction
CHCl₃ + KOH (ethanolic)
Products of carbylamine reaction
RNC + 3KCl + 3H₂O
RNC compounds name and property
Named as isocyanides and they are foul smelling.
:CCl₂ is
Dichlorocarbene an electrophile
Hoffmann mustard oil reaction
test for 1° amines
reagent-
1.) CS₂
2.) HgCl₂
Product of Hoffmann mustard oil reaction with reactant (CH₃-CH₂-NH₂) Ethylamine + CS₂
CH₃-CH₂-N=C=S (ethyl isothiocyanate) which smells like mustard oil
Which one is more basic? Cyclic amines or open chain amines
Cyclic amines are slightly more basic than open chain amines.
3° amines are
non- resolvable i.e., cannot be separated to give pure enantiomers, due to amine inversion
Of which hybridization N shows inversion
All sp³
Amine Inversion α
Steric hindrance (bulky groups)
and
1/EN of boundary atoms
What is Nucleophilic acyl substitution reaction?
The reaction of an acid chloride/ anhydride with 1° or 2° amines to give substituted amides.
1° Aliphatic Amine with HNO₂ at low temperature gives
clear solution (ROH) with evolution of N₂ gas.
2° Aliphatic Amine with HNO₂ gives
insoluble yellow oily liquid (R₂N-N=O) N-nitrosamine
3° Aliphatic Amine with HNO₂ gives
clear solution (ammonium salt)
Why does diazotization of 1° aliphatic amines considered a bad reaction?
Because it leads to a mixture of product.
1° Aromatic Amine with HNO₂ gives
Gives Diazonium cation (resonance stabilized)
2° Aromatic Amine with HNO₂ gives
Insoluble yellow oily liquid
3° Aromatic Amine with HNO₂ gives
o- and p- substituted nitrosoaniline
Diazonium ion on reaction with
1). HBF₄ 2). NaNO₂, Cu, with heat
gives
Nitrobenzene
Diazonium ion on reaction with H₃PO₂ gives
Benzene + H₃PO₃
Diazonium ion on reaction with CH₃CH₂OH gives
Benzene + CH₃CHO + Benzene ethoxide (by product)
Diazonium cation couples only with
strongly activated benzene rings, e.g., Phenols, anilines, naphthol, etc. because diazonium ion itself is a weak electrophile.
Why does coupling occurs at para position?
due to steric hindrance at ortho
when does coupling reaction occur at ortho?
when para position is occupied
why are products of coupling reaction called dyes?
they are colored due to extended conjugation
In which medium does coupling of phenols occur?
Slightly alkaline medium
Why does phenol ionize to phenoxide?
Because phenoxide is more reactive.
What is formed in strongly alkaline medium when OH⁻ attacks as Nu: ?
Diazotate (Ph-N=N-O⁻)
Why coupling does not occur with aniline in strongly acidic medium?
because aniline gets protonated to anilinium ion (C6H5NH3+)
Organol brown and orange red dye are formed by
Diazonium ion + naphthol
2- or β-naphthol gives orange red
1- or 2- naphthol gives organol brown
How is methyl red formed
Anthranilic acid reacted with 1). HNO₂
2). N,N- dimethylamine
When benzenediazonium chloride is heated with fluoroboric acid, fluorobenzene is formed. The reaction is called -
Balz Schiemann reaction
The product formed by a reaction of an aldehyde with a primary amine is
Schiff’s base
The conversion of benzene diazonium chloride to bromobenzene can be accomplished by
Gattermann reaction
Condition of coupling with aniline
pH : 4-5 (not strongly acidic)
Nitration of chlorobenzene give
2-chloronitrobenzene and 4-chloronitrobenzene
Benzenediazonium chloride is converted to phenol by
warming with water
