module 6 Flashcards
how many carbons will a primary, secondary, tertiary and quaternary amines have?
primary - 1
secondary - 2
tertiary -3
quaternary - 4
how do you name amines?
amino -
- amine
why are amines so reactive?
the lone pair of electrons on the nitrogen - due to N-H
what shape are amines around the N? Bond angle?
trigonal pyramid 107 due to lone pair on N
what kind of intermolecular forces do amines have? why?
hydrogen bonding due to polar N-H bond and lone pair of electrons on N atom
do amines have stronger intermolecular forces than alcohols? why?
No, N has lower electronegativity than O so weaker hydrogen bonding
how/when do amines act as bases?
the lone pair on the nitrogen atom accepts a proton
how/when do amines act as nucleophiles?
when they bond with an electron deficient C atom
what is the product from the basic action of an amine water?
RNH3+ - ammonium ion, which forms a salt with an anion
what is made when HCl reacts with methyl amine
methylammonium chloride
in order to be the strongest base, what must a particular amine have (compared to other amines)?
greatest electron density around N atom, making it a better electron pair donor (attracts protons more)
what effect do alkyl groups have on electron density and base strength?
positive inductive effect - increase electronic density around N - stronger base
place the following in order of base strength: NH3, primary amine, secondary amine, phenylamine
secondary amine> primary amine> NH3> phenylamine
how can primary amines form secondary and tertiary amines and quaternary ammonium ions? what are the problems with this method?
multiple substitutions; primary amine is a nucleophile that attacks the original haloalkane etc
- not efficient as low yield of primary amine due to multiple substitutions
how would you maximise the yield of the primary amine?
use excess ammonia
what type of mechanism is the reaction of a haloalkane with a cyanide ion?
nucleophilic substitution
what conditions does this reaction require (haloalkane with cyanide ion) ? what product is formed?
ethanol as a solvent
a nitrile is formed
how do you get from a nitrile to a primary amine? why is this a purer method of synthesising amines?
- reaction using Nick/hydrogen catalyst
- only the primary amine can be formed
what conditions are needed to form nitrobenzene from benzene?
conc. H2SO4 and HNO3 to form the NO2+ ion for electrophilic attack
how do you form an ammonium chloride salt from nitrobenzene? what conditions are needed
reduce nitrile using Tin/Hcl - forms an ammonium salt with Cl- ions
room temp
which mechanism is used for forming amides from acyl chlorides and amines?
nucleophilic addition/ elimination
what are the two functional groups of amino acids?
NH2 and COOH
are a-amino acids chiral? why?
yes, one carbon has 4 different groups - except glycine where R=H
define a zwitterion
ions which have both a permanent positive and negative charge, but are neutral overall
what will happen in an amine acid zwitterion
COOH deprotonated - COO-
NH2 protonated - NH3+
what happens to amino acids in acidic conditions?
gains a proton on NH2 group (becomes NH3+)
what happens to amino acids in alkaline conditions?
loses a proton from COOH group - COO-
what is the peptide/polyamide linkage
-CONH-
what property must a carbon atom have for the molecule to display optical isomerism about that carbon atom ?
4 different substituents attached to one carbon atom.
what are the similarities and differences between two optical isomers?
same atoms and bonds, but they are non-superimposable mirror images of one another. NOT IDENTICAL in chemical properties necessarily.
differ in the way they rotate plane polarised light - rotate plan of polarisation by the same angle but in different directions.
what word is used to describe optically active molecules?
chiral
what is condensation polymerisation
small molecules eliminated when polymer made from monomers (usually H2O)
how many monomers are condensation polymers usually formed from?
two
what properties do these monomers forming polymers have
each has two functional groups
3 examples of condensation polymers?
polyesters
polyamides
polypeptides
what linkage does a polyester have
ester linkage
what molecule is eliminated in formation of a polyester
H2O
what are the two monomers which form a polyester
diol and dicarbocylic acid or a molecule with both alcohol and a carboxylic acid functional group
what is terylene used for
a fibre for making clothes
what two monomers are used to form a polyamide
diamine and carboxylic acid
what are some examples for polyamides?
Nylon, Kevlar
if you are making Nylon in the lab, what monomers would you use and why? what molecule\ is eliminated
used hexane-1,6-diacyl chloride as the rate of reaction is much faster. Hcl is eliminated
what is Kevlar used for?
in body armour (bullet proof vests, stab vests) helmets, oven gloves
why are poly(alkenes) not biodegradable
non-polar C-H and C-C bonds
why is it bad to burn poly(alkenes)
releases CO2, CO, C (soot) and other toxic chemicals from monomers
where do most poly(alkenes) end up?
landfill sites
why can condensation polymers be broken down
they have polar bonds
how are condensation polymers broken down?
Hydrolysis (opposite of condensation)
what is the difference between addition and condensation polymerisation?
condensation makes the polymer and eliminates a small molecule; addition polymerisation breaks C=C to form only one product (just the polymer)
explain hydrogen boding between polyamides
- both C=O and N-H are polar bonds, as N’s electronegativity>H’s and O’s electronegativity > C’s
- Hydrogen bonding between H and O in different molecules
- uses lone pair of electrons on O atom
why do polyesters not show hydrogen bonding?
all O-H bonds are removed during polymerisation
what reagents are used for base hydrolysis
NaOH/H2O
what reagents are used for acid hydrolysis
H+/H2O
what type of mechanism is involved in the reaction between haloalkanes and cyanide ions
nucleophilic substitution
what type of reaction is involved in the reaction between carbonyl compounds and cyanide ions
nucleophilic addition
how can you form a carboxylic acid from a nitrile
acid hydrolysis
what type of catalyst is used for a dreidel-crafts reaction
a halogen carrier (AlCl3)
write an equation to form an electrophile that could be used to acylate benzene, starting with AlCl3 and ROCl
AlCl3 + RCOCl -> AlCl4- + RCO+ (+ on C)
RCO+ can attack benzene
how could you use a Frieden-Crafts mechanism to add a methyl group to a benzene ring?
use a halogenalkane and AlCl3 to create electrophile that can attack benzene
when purifying by recrystallisation why is the minimum volume of hot solvent used?
so that a saturated solution is created, so that as many crystals will fall out of solution as possible when it is cooled
why is the solution filtered hot when purifying bay recrystallisation
to remove insoluble impurities and ensure that the crystals do not form in the filter paper
why is the solution cooled in an ice bath when purifying b recrystallisation
to ensure that as many crystals as possible fall out of solution - yield is higher
why are the crystals washed with cold water when purifying by recrystallisation
to remove soluble impurities
how would you separate the crystals form the reaction mixture when purifying by recrystallisation
filter under reduced pressure using a Buchner funnel
why might percentage yield be below 100%
- product lost due to filtration, drying and weighing - spills, not all transferred from one piece of apparatus to the otoher
- product left disc;ved in solution - some does not crystallise. some left on filter paper. sample still wet
in distillation setup, why is it necessary to have a continuous water flow around the condenser
so that the water remains cool In order for the mixture to be distilled
describe a method that can be used to separate immiscible liquids
- pour the mixture into a separating funnel and some distilled water
- add stopper and invert the flask to mix the mixture
- equalise the pressure by opening the stopper as required
- continue shaking until there is no ‘whistle’ sound
- to collect the water in the lower layer, open the stopper and place a beaker under the spout
- use another beaker to collect the organic layer
- shake the liquid with some drying agent
name two drying agents
magnesium sulphate and calcium chloride
how is a drying agent used
- add deleted drying agent to organic product
- if drying agent forms clumps add some more until they are moving freely
- use gravity filtration to collect the dry product
- filtrate is the product
what does re-distillation mean?
when a liquid is purified by using multiple distillations
what are 3 key steps to purify an organic solid
- filtration under reduced pressure
- recrystallisation
- measurement of melting points
how do you get from a nitrile to a primary amine?
reduce using a nickel catalyst and hydrogen
