27 - Amines, amino acids and polymers Flashcards
aliphatic amine?
nitrogen attached to at least one straight or branched carbon chain
aromatic
nitrogen atom is attached to an aromatic ring
how to name amine with a NH2 group on carbon 1
alkyl chain - amine
how to name an amine with NH2 not on carbon 1
use prefix amino
how to name secondary or tertiary amines containing the same alkyl group on the nitrogen
di of tri indicates number of alkyl groups
how to name secondary or tertiary amines with different alkyl groups attached to the nitrogen atom
CH3NHCH2CH2CH3
CH3N(CH2CH3)CH2CH2CH3
N-substituted derivative
CH3NHCH2CH2CH3 N-methylpropylamine
CH3N(CH2CH3)CH2CH2CH3 N-ethyl-Nmethylpropylamine
Explain how amines act as bases?
- they have a lone pair on their nitrogen atom and it can accept a proton
- this forms a dative covalent bond between nitrogen and hydrogen
Amine + Salt
CH3CH2CH2NH2 + HCl
-> acids
CH3CH2CH2NH+CL-
neutralisation
CH3CH2NH2 + H2SO4
(CH3CH2NH3+)2SO4 2-
forming a primary amine
ammonia reacts with a haloalkane, forming an ammonium salt
ammonium salt is mixed with aqueous alkali to generate the amine from the salt
how to form propylamine + sodium chloride
salt formation
1-chloropropane + HN3 -> propylammonium chloride (salt)
amine formation
propylammonium + NaOH -> propylamine
what are the conditions to form a primary amine?
- ethanol is used as a solvent - this prevents substitution of the haloalkane by the water to produce alcohols
- excess ammonia - reduces further substitution of the group to form secondary and tertiary amines
forming a secondary/tertiary amine
ammonia and a haloalkane react to form a primary amine- however this reaction isn’t pure as the primary amine can react further with a haloalkane to form a secondary amine.
-> you still need to react with NaOH to generate the mine from its salt
How to form Dipropylamine and NaCl-
CH3CH2CH2Cl + CH3CH2CH2NH2 -> (CH3CH2CH2)2NH2+Cl-
Propylamine -> Dipropylammonium chloride
(CH3CH2CH2)2NH2+Cl- + NaOH -> (CH3CH2CH2)2NH + NaCl + H2O
How to form Tipropylamine and NaCl-
CH3CH2CH2Cl +(CH3CH2CH2)2NH -> (CH3CH2CH2)2NH+Cl-
Propylamine -> Dipropylammonium chloride
((CH3CH2CH2)2NH+Cl- + NaOH -> (CH3CH2CH2)2N + NaCl + H2O
how to prepare an aromatic amine
reduction of nitrobenzene
heat under reflux with tin and HCl (reducing agent)
-> it forms the ammonium salt (phenylammonium)
react with excess NaOH
-> forms phenylamine
what is an amino acid?
organic compund containing both amine NH2 and carboxylic acid COOH functional groups
-> body has 20
R is a variable side chain
what is an alpha amino acid
give its general formula
the amine group is attached to the alpha carbon - the second carbon atom, next to the carboxylic group
RCH(NH2)COOH
what is a beta amino acid
where the amino acid is attached to the third carbon
amino acids with aqueous alkalis
amino acid react with an aqueous alkali to form a salt and water
how do you esterify a amine acid
heat with alcohol in the presence of concentrated sulfuric acid
what is an amide
the products of reactions of acyl chlorides with ammonia and amines
primary amide
one carbon bonded to nitrogen
what is an optical isomer
it is found in molecules that contain a chiral centre (carbon attached to 4 different atoms)
this means there are two molecules that are non-superimosable mirror image structures (enantiomers)
what are two important condensation polymers?
give some starting materials
- polyesters and polyamides
- carboxylic acids and their derivatives are common starting materials
what is condensation polymerisation
the joining of monomers with loss of a small molecule, usually water or HCl.
what do you need for a condensation reaction
two functional groups
what bond holds monomers in a polyesters
monomers are joined by ester linkages
O
∥
C — O
two ways polyesters are made
- made from one monomer containing both a carboxylic acid and an alcohol group
- made from two monomers here one contains a two carboxylic acid groups and the other containing two alcohol groups
two examples of polyesters made from two monomers with two functional groups groups
- one monomer is a dial, with wo hydroxyl group
- one monomer is a dicarboxylic acid with two carboxylic acid groups
what is a polyamide
condensation polymers formed when monomers are joind by amide linkages in a long chain
what is a amide linkage
O O
∥
——– C — N ——-
|
H
how can polyamides be made
- from one monomer containg both a COOH (or acyl chloride) and an amine group
- from two monomers one containing two COOH (or acyl chlorides) and the other containing two amine groups
(CH3)3CCHBrCH3 has stereoisomers.
Explain the term stereoisomers and name this type of stereoisomerism
Same structural formula
AND
Different arrangement (of atoms) in space
OR different spatial arrangement (of atoms)
optical
bond angle of a primary amine
107- trigonal pyrmidal
what is a amine group attached to benzene
phenylamine
compare melting point of a primary amina and an alkane of a similar chain length
- relatively high due to hydrogen bonding between molecules
:N-H therefore h bonding
only true to primary, secondary and phenylamine
Tm and Tb of primary amines compared to secondary
low due to no hydrogen bonds
are amines soluble
yes
producing amines from a haloalkane
nucleophilic substitution - where N is the nucleophile in excess to prevent further subs
primary : R-X + NH3 -> R -NH2 + HX
ethanol is needed
secondary : R-X + R-NH2 -> R-NH-R
tertiary: R-X + R-NH-R -> R-N(R)-R
producing amines from nitriles
Reagents: LiAlH4 (ether) or H2 with Ni/Pt catalyst
R-CN + 2[H] -> R-C-NH2
reduction
producing amines from nitrobenzene
Reagents: Conc HCL and SN catalyst followed by NaOH
Benzen-NO2 + 6[H] -> benzene-NH2 + 2H2O
product is phenylamine
HCl does the reducing- however it causes a salt forming as lone pair on N accepts
NaOH prevents the salt from forming as it neutralises excess H+
amine in water
R-NH2 + H2O <=> R-NH3+ + OH-
forming an alkaline solution
lone pair on N accepts H+
primary amine and HCl
R-NH2 + HCl -> R-NH3+ + Cl-
forms a salt _______ ammonium chloride
ethylamine and nitric acid
C2H5NH2 + HNO3 -> C2H5NH3+ + NO3-
why doe most amino acids have optical isomerism
central carbon atom has 4 different groups bonded to it (ie chiral)
what is a zwitterion how does it affect properties
COOh of an amino acid donates H+ to the amine group. Lone pair on nitrogen accepts the H+. forming a positive and negative end - opositly charged poles so it is very soluble and a very high Tm (due to strong electrostatic attractions-like ionic substances)
overall it is uncharged
