6.2 Flashcards
what are amines
organic chemicals where one or more of the hydrogen atoms on ammonia have been replaced by alkyl chains
what is a primary amine
one hydrogen atom has been substituted on ammonia
RNH2
what is a secondary amine
two hydrogen atoms have been substituted on an ammonia
RNHR’
what is a tertiary amine
all three hydrogen atoms have been substituted on ammonia
RNR’R”
what is a quaternary amine
all three hydrogens substituted on ammonia and there is an R group on N’s lone pair
(will be positive)
how to name primary amines
alkyl group first amine suffix
how to name secondary amines
N- then smaller alkyl group then longest alkyl chain and suffix amine
how to name tertiary amines
N,N- to show there’s two smaller groups attached to the N, then follow with their names in alphabetical order, then add name of longest alkyl chain and suffix amine
how to name quaternary amines
name alkyls in alphabetical order (no longer a root) then ammonium (because it’s now an ion due to the dative covalent bond) then the negative ion it’s reacted to because it’s now a salt
why are amines basic
the lone pair on the N atom can accpet protons:
RNH2 + H+ —> RNH3+
what does amines’ basicity depend on
N’s ability to pick up protons:
the greater the electron density on the N the easier it can accept protons - affected by the groups attached to the nitrogen
what’s the affect of electron withdrawing substitute at on amines’ basicity
decrease basicity as they lower the electron density on the N, so it’s lone pair is less effective at accepting a proton
example of electron withdrawing substituent
benzene ring
what is an electron releasing substituents effect on the basicity of amines
and why?
increases basicity as the electron density on N is increased so the lone pair on N is more effective at accepting a proton
why? because the N is more electronegative than the C’s in the alkyl chains
example of electron releasing substituent
CH3
what can limit amines basicity other than the type of side groups
the chain length of side groups can get in the way of the lone pair, so the longer the chain length, the lower the basicity
how do you make a primary amine from a haloalkane
haloalkane heated in sealed tube with EXCESS ammonia(alc)
ammonia with react with the haloalkane to make an ammonium salt
additional ammonium molecule reacts to form the amine product and an ammonium halide salt (reversible) - excess ammonia is used to drive the equilibrium of this reaction to the right to increase the yield of primary amine
how are secondary, tertiary and quaternary amines made from the process with haloalkanes
secondary:
haloalkane reacts with primary amine, substituting the alkyl chain where a H is on the N, making a secondary amine and a hydrogen halide (acid)
eg:
CH3CH2Cl+CH3CH2NH2<—>(CH3CH2)2NH m. +HCl
tertiary:
same process leading to a tertiary amine and hydrogen halide acid
quaternary ammonium salt:
same process but only makes the quaternary ammonium salt (alkyl chains then N+ X-)
why can further substitution happen on amines
because they have a lone pair of electrons on the N that can act as a nucleophile
what type of reaction is the preparation of amines from haloalkanes
nucleophilic sub
how to make aromatic amines from benzene
electrophilic sub (nitration) c. HNO3 and c. H2SO4
then reduction reaction: 6[H] - 2 H’s on phenylamine and 4 in 2H2O
reflux @100°C and conc. HCl and Tin catalyst (to make reducing agent) are
then add NaOH (strong alkali) to neutralise excess HCl
this will produce phenyl amine and 2H2O (because there’s 2 O’s in nitro group)
what is an amino acid
class of compound with two functional groups: -COOH and -NH2
what is an alpha amino acid
an amino acid where both the amine and carboxylic acid functional groups are attached to the same carbon RCH(NH2)COOH
how are amino acids amphoteric
the amine group has a lone pair on the N which can act as a proton acceptor (base) and the carboxylic acid group is a weak acid that can donate a proton (acid)
what’s happens to amino acids in aqueous solutions
COOH donates a proton NH2 accepts a proton
how do alkalis react with amino acids
react with the COOH group to form a conjugate base (COO-) which combines with a positive ion to form a salt
how do acids react with amino acids
react with NH2 group to create a conjugate acid which then combines with a negative ion to form a salt
what’s the reaction between alcohols and amino acids
esterification
what’s a stereoisomer
molecules that have the same structural formula but different arrangements of atoms in space
what are optical isomers
molecules that are non-superimposible mirror images of eachother with the same chemical properties but interact with polarised light differently
what is a chiral molecule
has four different groups attached to a carbon atom
what are enantiomers
chiral molecules with their groups arranged differently so that they are optical isomers of eachother
what will optical isomers do to plane polarised light
rotate it, one will rotate light clockwise D, one anti-clockwise L
what do chiral centres look like on skeletal diagrams
mercedes logo or chicken foot
what is a zwitterion
when an amino acids two functional groups exchange a proton and make an internal salt, the two charges cancel eachother out so they have no charge
what is the isoelectric point
when there is no net electrical charge due to each zwitterion having an internal balance of charge
how are zwitterion formed
the COOH group donates a proton to the NH2 group
what happens if you change the pH away from the isoelectric point of a zwitterion
lower pH, lots of H+, only the the amine group is charged and becomes NH3+
higher pH, amine group returns to normal and only the COOH group is charged, becoming COO-
how will the carboxylic acid group on amino acids react
same as usual, with metal oxides alkalis carbonates and alcohols
how will the amine group on amino acids react
same as a normal base, will accept a proton when reacting with acids, will make an ammonium salt
what are amides
a class of compound with a functional group made of an acyl group which is directly attached to an amine
what’s a primary amide
an amide with two H’s and one acyl group attached to the N
what’s a secondary amide
an amide with one H one acyl group and one alkyl group attached to the N
what’s a tertiary amide
an amide with no H’s attached to the N
how to name primary amides
named by the amount of carbon atoms in the parent hydrocarbon chain attached to the functional group (biggest one) then suffix amide
how to name secondary amides
N-smaller chain then bigger parent chain and amide suffix
how to name tertiary amides
N,N- alphabetical order smaller groups then biggest group then amide suffix
what are polyamides
polymers made up of monomers joined by amide links
what does the repeating unit look like in polyamides
split functional group at beginning and end, C=O and N-H with trailing bonds
what is a racemic solution
a 50:50 mixture of enantiomers that has no effect on polarised light as the rotations of the two isomers cancel eachother out
what is polymerisation
a process in which small molecules called monomers join together into large molecules consisting of repeating units
what is addition polymerisation
monomers join up with the breaking of the C=C bonds all atoms in the monomer are used to form the polymer
what is condensation polymerisation
monomers join up with the removal of small molecules not all atoms in the monomer are used to form the polymer
how to make polyesters with two monomers
dicarboxylic acids and diols (COOH and OH on both ends for each, they esterify and release water, 2 per repeat unit)
how to make polyesters with one monomer
hydroxycarboxylic acid (OH and COOH on each end)
repeat unit only with split ester link of the ends and only one water produced per repeat unit
how are polyamides made with two monomers
reaction between dicarboxylic acid and a diamine
react to make an amide link
how are polyamides made with one monomer
amino acids react with eachother
how to name polyamides (nylons)
nylon- number of carbons in diamine chain, number of carbons in the dicarboxylic chain
how do you name polyamides when there’s no central amide link in the repeat unit
just Nylon-number of carbons
what happens when polyesters and polyamides react with water
nothing really, it’s very very slow
what’s acid hydrolysis of polyester
when reacted with an aqueous strong acid, it will split into a diol and dicarboxylic acid
slow rate of reaction
what’s alkali hydrolysis of polyester
when reacts with hot aqueous alkali
polyesters become a diol (alcohols not strong enough to react)
and the salt of the dicarboxylic acid (with the positive ion of the base) because the alkali will react with the carboxylic acid
fast rate of reaction
what’s acid hydrolysis of polyamides
add aqueous acid and forms
dicarboxylic acid and diammonium salt
(think about what the acid will do to both monomers)
faster rate of reaction
what’s the base hydrolysis of polyamides
add hot aqueous alkali (eg NaOH(aq) )
produces diamine and salt of the dicarboxylic acid
slower, but still fast rate of reaction
why is the hydrolysis of polyesters and polyamides important
it means they can biodegrade
how do you extend the carbon chain with haloalkanes
nucleophilic sub (backside attack), with CN- nucleophile:
haloalkane and KCN (alc) so that OH- doesn’t act as an nucleophile, reflux (because alcohol is volatile)
makes a nitrile (with C=_ N) and X-
what does the hydrolysis of a nitrile do
makes a carboxylic acid and an ammonium salt
needs to react with 2H2O and a strong acid like HCl
can be HCl(aq)
what does the reduction of a nitrile do
makes amines
needs H2(g) and Ni catalyst and 150°C
will need 2H2
(if with a reducing agent you need 4[H])
example of a reducing agent
LiAlH4
how do you extend the carbon chain with carbonyls
nucleophilic addition
carbonyls and KCN react under reflux (and dilute acid which can be water as it releases H+)
CN- attacks the delta positive carbon, and the C=O pi bond is broken, making it O-, which a lone pair accepts a proton making a hydroxynitrile
why can hydroxynitriles have optical isomers
becuase the CN- nucleophile can attack the C from above or below as the C=O bond is planar, makes two different enantiomers
why must you separate optical isomers
could need higher dowsed to get desired affect
possible bad side effects
people could take legal action
how can you avoid having racemic solutions
use: natural chiral molecules, stereoselective reactions, catalysts for one isomer, enzymes/bacteria that are stereoselective
how to extend the carbon chain via alkylation
use haloalkane anhydrous AlCl3 and something with a benzene ring
electrophilic substitution with carbocation electrophile R+ (alkyl group)
AlCl3 steals the halogen and then it will react with the left over H+ at the end to regenerate the catalyst
how to extend the carbon cabin via acylation
use acyl chloride and anhydrous AlCl3 and aromatic substance
reflux at 50°C
electrophile RC+=O (acyl chloride without the Cl-)
catalyst regenerates as it always does
what’s a dimer
has a functional group on each end
describe recrystallisation in a practical
dissolve in minimum amount of hot solvent, cool the solution and filter the solid, scratch with a glass rod, wash with cold solvent and dry, collect pure crystals
