Amines and Amides Flashcards
primary aliphatic amines
Primary aliphatic amines can be prepared by the reaction of ammonia with halogenoalkanes and by the reduction of nitriles.
aromatic amines
Aromatic amines, prepared by the reduction of nitro compounds, are used in the manufacture of dyes.
amines =
weak bases = lone electron pair on nitrogen atom can accept protons
primary aliphatic amines
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+
and so accepting a proton. They are
weak bases as only a low concentration of hydroxide ions is produced.
formation of ammonium ions
NH3 (aq) +H2O (l) ⇌NH4+(aq)+OH-(aq)
weak to strong base order
Aromatic amines < ammonia< primary amines< tertiary amines< secondary amines
amine + acid =
ammonium salts
amines
mine + acyl chloride or acid anhydride = amide
Naming amines:
e.g 4 carbon chain = butylamine
Amine attached to benzene ring = phenylamine
what are aromatic amines
Aromatic amines = only when nitrogen is direcetly bonded to benzene ring
content
Tertiary amines and amides do not experience hydrogen bonding
Amines can use their lone pairs to act as a nucelophile =electron pair donor
Amines convert CO2 and hydrogen sulfuide into less harmful products
Aliphatic amines –> ammonia –> aromatic amines = decreasing levels of pH
The more avaliable a lone pair is the stronger the base (more likely to accept a proton)
Aliphatic amine: An amine in which nitrogen is bonded only to alkyl groups
nucelophilic addition elimination
In nucelophilic addition elimination reactions the amine acts as a nucelophile
Chance of nucelophilic subsitution reactions occuring happens when excess halogenoalkane is used
cattionic surfaces
Quaternary ammonium ion salts can be used as cationic sufactants (soaps)
-surfactants = polar end and non-polar end
bonding in amines
-H2N – CH3 = methylamine (primary amine)
-hydrogen bonding is present between the molecules of methylamine
aromatic amines
-in aromatic amines the nitrogen lone pair is partially delocalised into the benzene ring, lowering base strength
naming amines
Amines = count the number of carbons directly attached to the nitrogen atom
-quaternary ammonium salts are not amines
phenylammonium chloride production
Phenylamine + HCl –> phenylammonium chloride (Water soluble ionic salt)
6 strong bases
-LiOH = lithium hydroxide
-NaOH = sodium hydroxide
-KOH = potassium hydroxide
-Ca(OH)2 = calcium hydroxide
-Sr(OH)2 = strontium hydroxide
-Ba(OH)2 = barium hydroxide
strength of bases
Dimethylamine is a stronger base than methylamine as it is secondary amine. Has a greater electron density on the nitrogen lone pair and therefore a greater ability to accept a proton (H+)
comparing strengths
-alkyl group release electrons away from alkyl group and towards the nitrogen atom (positive inductive effect)
-this inductive effect increases the electron density on the nitrogen atom (better electron pair donor_
-primary amine is stronger than NH3
-secondary amine is stronger than primary amine
-teritary amine is not a stronger base (less soluble in water)
teritary amines
-not stronger bases than secondary amines bc they are less soluble in wtaer
-teritary amines don’t have N-H bonds
Whats stronger propylamine or phenylamine:
Whats stronger propylamine or phenylamine:
-propylamine = lone pair on phenylamine is partially delocalised into the benzene ring
-propylamine has a greater eletron density on the nitrogen lone pair
-propylamine has a greater ability to accept H+
more alkyl groups
The more alkly groups attached to the amine the more strongly proton is attracted to the amine. The strength of bases is determined by how readily it will accept a proton
nucleophilic subsitution
Nucelophilic subsitution:
-haloalkane + ammonia = primary amine and ammonium salt
reduction of nitriles
-reducing nitriles via hydrogenation can produce amines
-requires LiAlH4 (reducing agent)
-R-C=N + reducing agent) –> R-CH2-NH2
production of aromatic amines
Production of aromatic amines:
-produced from the reduction of nitrobenzene using HCl and a tin catalyst
CH3Br –> C2H3N
KCN
alcohol
C2H3N –> C2H7N
nitrile –> amine
H2
Ni catalyst
Butylamine can also be prepared in a 2 step synthesis starting from 1-bromopropane
step 1 = CH3CH2CH2Br + KCN –> CH3CH2CH2CN + KBr
step 2 = CH3CH2CH2CN + 2H2 –> CH3CH2CH2CH2NH2
why is butylamine a stronger base than ammonia
-more alkly groups = lone pair on nitrogen increases electron density due to R group
-positive inductive effect
identify a substance that could be added to aqueous butylamine to produce a basic buffer solution
HCl
teritary amine isomer of butylamine
CH3CH2N(CH3)2
ionic salt =
more soluble in the body so can be used in medicinal treatments
give the reagents and equations needed for the nitration of benzene
Reagents = conc HNO3 + conc H2SO4
equation = HNO3 + 2H2SO4 –> NO2+ + H3O+ + 2HSO4-
reagents required for the reduction of nitrobeznene to phenylamine
Ni catalyst
H2
Give a use for J =
cationic surfatant / making dyes
why is J a weaker base than K
-lone pair on nitrogen
-delocalised into ring
-less avalable for protonation
name the compound (CH3)2NH
dimethylamine
(CH3)2NH can be formed by the reaction of excess CH3NH3 with CH3Br. Name and outline the mechanism
nucelophilic subsitution
suggest how the reaction conditions could be modified o minimise this contamination
use a large excess of NH3
give a reagent that could be used in a test-tube reaction to distinguish between benzene and cyclohexene
bromine water
benzene = no reaction
cyclohexene = brown to colourles
C6H5NH2 =
phenylamine
C6H5 =
phenyl
nitrogen =
lewis base (electron donor)
bronstey lowrd base = proton acceptor
amines =
higher boiling point due to hydrogen bonding
heavier molecules = less solubility
ammonia = base and acid
CH3NH2 + H2O –> CH3NH3+ + OH-
C6H5NH2 + HCl –> C6H5NH3+Cl-
C6H5NH3+Cl-
phenylammonium chloride
R group =
increases electron density on the nitrogen
impurity of propylamine
(C3H7)2NH
nitrile to amine =
reduction
H2/Ni catalyst
why is phenylammonium chloride soluble in water
ionic salt = soluble in water
1,6dibromohexane
Br(CH2)6Br
1,6,diaminohexane
H2N(CH2)6NH2
nitrile to amine
reduction reaction
true or false = amines are weak bases
true = lone pair electron on nitrogen can accept protons
alkyl groups =
positive inductive effect
push electron density towards nitrogen making it more available
reversible equations
CH3NH2 +H2O ⇌CH3NH3++OH-
NH3 (aq) +H2O (l) ⇌NH4+(aq)+OH-(aq)
bromoethane + ammonia equation
CH3CH2Br + 2NH3 —> CH3CH2NH2 + NH4Br
making buffer from an amine
Basic buffers can be made from combining a weak base with a salt of that weak basee.g. Ammonia and ammonium chloride
Methylamine and methylammonium chloride
Ethylamine and ethylammonium chloride
nitrile
-nitrile = C=N
-order of strength = phenylamine –< ammonia -> dimethylamine
-nucelophilic subsitution = introduce functional groups into a molecule
preparation of primary aliphatic amines
-nuceloohilic subsitution
-CH3Br + KCN –> CH3C=N + KBr
-CH3C=N + 4H2 –> CH3CH3NH2
preparation of aromatic amines
-reduction of nitro compounds using tin (Sn) and concentrated HCl
-nitrobenzene + 6H2 –> phenylamine + 2H2O
-using a large amount of excess ammonia increases the yield of the primary amine as there is a better chance that the halogenoalkane is formed
forming secondary amines
-halagoenoalkane + primary amines via an nucelophilic subsitution mechanism
-formation of diamines e.g dimethylamines + NH4X
forming tertiary amines
-diamines + halogenoalkane = triamines
quaternary ammonium salts
Quaternary ammonium salts = cationic surfactant
-forms salt N+ with 4 R groups
nitriles
-primary aliphatic amines can be prepared by the reduction of ammonia and halogenoalkanes + reduction of nitriles
-aromatic amines can be prepared by the reduction of nitro compounds
Halogenoalkanes react with cyanide in aqueous ethanol to form a nitrile
RBr + CN- –> RCN + Br-
RCN + 2H2 –> RCH2NH2
reduction of nitrile compounds
Reduction of nitrile compounds = more favourable = doesn’t continue to produce secondary amines. Nitriles = high atom economy
Production of primary aliphatic amines
-use H2 and Ni catalyst
Cyanide = toxic side effects
production of aromatic compounds
1) nitration of benzene
2) nitrobenzene to phenylamine
HNO3 + H2SO4
Use Sn and HCl as a reducing agent
C6H4N2O4 + 12H –> C6H8N2 + 4H2O
naming amides
secondary amides are named using an N to designate the alkyl group is on the nitrogen atom
CH3-CH2-C=O-NH-CH3 name
N-methylpropananmide
state one simple method of distinguishing the 2 solutions
pH meter
methylamine would have higher pH than ammonia as it is a stronger base
true or false - tertiary amines dont have N-H bonds
true
