Amines, Amino Acids and Polymers Flashcards
preparation of aliphatic amines
substitution of halogen alkanes with excess ethanolic ammonia (add aqueous alkali)
what type of substitution of the preparation of aliphatic amines
nucleophillic, as the ammonia has a lone pair of electrons on the nitrogen atom, allowing substitution to occur with a haloalkane
why is ammonia in excess in the preparation of aliphatic amines
reduces further substitution of the amine to form secondary/tertiary amines
ammonia is very soluble in water, so why is ethanol used as a solvent and not water in the preparation of aliphatic amines
prevents any substitution of the haloalkane by water to form alcohols
preparation of aromatic amines
reduction of nitroarenes using tin and concentrated HCL (add aqueous alkali)
what conditions is the preparation of aromatic amines carried out under
nitrobenzene heated under reflux with Tin and conc HCL forming phenylammonium chloride, which is then reacted with excess NaOH to produce the aromatic amine, phenylamine. Tin and HCL act as reducing agent
what is an amine
ammonia molecule with 1 or more H atoms replaced with a carbon ring or chain
how do you classify amines
by the number of H substituted
primary, secondary, tertiary
what are N-substituted amines
when there are 2 or more different groups attached to the Nitrogen
eg. N-butylethylamine or 3-amino pentane
what do amines smell like
fish
reactions of amines
CH3CH2NH2 + HCL–>
CH3CH2CH2CH2NH2 + HNO3 –>
CH3CH2NH3+ + Cl-
CH3CH2CH2CH2NH3+ + NO3-
dative covalent bond between hydrogen atom and nitrogen
why are amines basic
have a lone pair of electrons so they are able to accept H+ ions from acids
most basic to least out of-
propylamine/aminopropane, ammonia and phenylamine
propylamine- positive inductive effect pushes electrons
ammonia
phenylamine- lone pair electrons donated into delocalised ring
what is an alpha amino acid
carbon attached to amino group is also attached to carboxylic group
what does amphoteric mean
can act as an acid or a base
what is a zwitterion
has high melting point due to electrostatic attraction
has intermediate values of pH (not always neutral)
is both positive and negative
RCH – (NH3+) – COO-
what is the isoelectric point
concentration of zwitterion that is highest
What happens when an amino acid is in an acidified solution
adds a hydrogen to the nh2 group
RCH – (NH3+) – COOH
what happens when an amino acid is in an alkaline solution
removes hydrogen from OH group
RCH – (NH2) – COO-
general formula for an amino acid
RCH(NH2)COOH
what are amides and what bond is present
R – CO – NH
peptide bond
preparation of an amide
acyl chloride + ammonia –> primary amide (primary substitution)
acyl chloride + primary amide –> secondary amide (secondary substitution)
how does cis trans isomerism arise in ….
double bond present between 2 carbons so can’t rotate
hydrogens present on both sides
2 different groups on each carbon
define structural isomerism
eg. chain, positional, functional group
same molecular formula but different structural formula
define stereoisomerism
eg. E/Z, optical
same structural formula but different arrangement in space
what causes steroeisomerism
a carbon with 4 different groups attached
chiral centre
mirror images are non-superimposable
what is optical steroisomerism
non-superimposable mirror images about a chiral centre
what is an enantiomer
pair of optical isomers
how do optical isomers differ
differ in chemical reactions
the isomers rotate plane polarised light in opposite directions- causing a difference in properties of the mirror image forms of a chiral compound
why is chirality important
biological receptors will only accept one enantiomers
can amino acids be switched around in tripeptides to form a different compound
yes
how can tripeptides be analysed using gas chromatography, coupled with mass spectroscopy
gas chromatography separates peptides
mass spectroscopy will fragment peptides
using a database compare the mass ion calculated
out of 2 polymers, one containing a C=O as well as being an ester, and one without, which is likely to be degradable
the one with a C=O present and the ester, as the bond absorbs radiation
and the ester linkage can be hydrolysed
what is it called when multiple monomers join together
polymerisation
benefits of polymers
can replace natural materials
cheaper
better suited to a particular use
negatives of polymers
non-biodegradable
alternatives to landfill for polymers
burning for energy- scrubbers needed to neutralise acidic gases
feedstock (make other chemicals)
recycling
difference between condensation polymers and addition polymers
condensation- polyamides eg. kevlar, nylon 6-6
addition- end in ene, 100% atom economy, need high pressure and temp
how are polyamides/polyesters hydrolysed
in alkaline or acidic conditions
should theoretically can be biodegradable but takes a
very long time in reality
