Nitrogen chemistry Flashcards
difference between aliphatic and aromatic amine
If the R group is an alkyl group (methyl, ethyl, etc) then then it is an aliphatic amine; if it is an aryl group (benzene ring or phenyl) then it is an aromatic amine
how are amides formed
from the condensation reaction of carboxylic acids or acyl chlorides with ammonia or amines
why are amino acids said to be amphoteric
A basic amino (-NH2) group
An acidic carboxylic acid (-COOH) group
Due to the presence of both a basic and acidic group in amino acids,
what do amines react with strong acids to form
ammonium salts
what do you add to ammonium salt to convert it back into amine
Addition of NaOH to an ammonium salt will convert it back to the amine
how to form amine via nucleophilic substitution
reaction between a halogenoalkane with ammonia in a sealed tube.
One mole of halogenoalkane reacts with two moles of ammonia, producing a primary amine and an ammonium salt
how can amines be formed from the reduction of nitriles
LiAlH4 dry ether or H2 and Ni catalyst
how does amine react with water
amine acts as a base to form an alkaline solution
Lone pair on nitrogen accepts a hydrogen from water molecules releasing OH-
how does amine react with acids
amine acts as a base and accepts a proton to form a quaternary ammonium salt
why are aliphatic amines stronger bases than aromatic amines
benzene ring draw electron density away from the nitrogen making the lone pair less available for dative bonding with ammonia so decreasing amine basicity
alkyl groups push electron density towards the nitrogen atom making the lone pair more available and increase amine basicity
how can aromatic amines be produced
reduction of nitrobenzene using concentrated HCL and tin catalyst
what is condensation polymerisation
polymer is produced by repeated condensation reactions between monomers
how can condensation polymers be identified
monomers are linked by ester or amide bonds
Condensation polymers can be formed by:
dicarboxylic acids and diols
dicarboxylic acids and diamines
amino acids
what is an amide link
key functional group in a polyamide
-CONH
what is a zwitterion and how is it formed
an ion with both a positive (-NH3+) and a negative (-COO-) charge
An amino acid molecule can interact within itself to form a zwitterion
what does a solution of amino acids in water exist as
zwitterions with both acidic and basic properties
They act as buffer solutions as they resist any changes in pH when small amounts of acids or alkali are added
what happens when acid is added to zwitter ion
what happens when base is added to zwitter ion
The -COO- part of the zwitterion will accept an H+ ion to reform the -COOH group
The -NH3+ part of the zwitterion will donate an H+ ion to reform the -NH2 group
This causes the zwitterion to become a negatively charged ion
what is isoelectric point of an amino acid
pH can be slightly adjusted to reach a point at which neither the negatively charged or positively charged ions dominate and the amino acid exists as a neutral zwitterion
what does amino acid and alkali react to form such as sodium hydroxide
salt and water
H2NCHRCOOH + NaOH ⇌ H2NCHRCOO- Na+ + H2O
what does it mean that all amino acids but glycine are chiral
they are optically active so a solution of amino acids will rotate plane polarised light.
how can polypeptide chains in a protein by broken down into amino acids
The polypeptide chains in a protein can be broken down into their individual amino acids by prolonged heating with concentrated hydrochloric acid.
This breaks the peptide bonds between amino acids
how can the amino acids produced by hydrolysis be identified
simple chromatography
Using a suitable solvent, the individual amino acids will rise to different heights on the chromatography paper
As the amino acids are colourless, the chromatogram is sprayed with a developing agent so that the amino acid positions can be seen
Once the positions of the amino acids have been established, their Rf values can be calculated
why is dibutylamine more alkaline than butylamine
Butyl / alkyl groups are electron donating / are electron pushing / are electron releasing
Two (alkyl) groups in dibutylamine (but only one in butylamine)
Lone pair (of electrons) on the nitrogen more readily available / higher electron density on the nitrogen or NH2 or amine group / N more delta negative / N or NH, accepts a proton more readily
why penylamine is much less alkaline than butylamine solution
For the idea of the lone pair being withdrawn
towards the ring
Lone pair pulled into the ring
For the idea of the lone pair being less
available
how can you use chromatography with samples of amino acids to show which amino acid the protein contained
Spot (of hydrolysate) on paper/tlc/thin layer chromatogram
Spi aci
(1)
(1)
KP2 Marker spots of known amino-acids/measure Rf
КР3 Run in (suitable)
solvent/discussion of comparative solubilities in phases
(1)
KP4 (Spray with) ninhydrin (and heat) [Stand alone mark]
(1)
KP 5 Marker spots and the unknown spots correspond
ALLOW
Compare R values of marker spots with hydrolysate spots
