6.2 nitrogen compounds Flashcards
name the shape, bonding and bond angles in an ammonia molecule
pyramidal
covalent and hydrogen bonding
107 degrees
what is an amine?
amines are compounds derived from ammonia
what is meant by primary, secondary and tertiary amines?
primary - 2 hydrogens, 1 organic group attached to N
secondary - 1 hydrogen, 2 organic groups attached to N
tertiary - 3 organic groups attached N
what suffix is used when naming amines?
amine
what word comes before the amine suffix when naming amines?
the longest group attached to the nitrogen
eg. if a propyl group is the longest group attached to the N, its called propylamine
how do you name the other groups attached to the nitrogen?
other groups are names in alphabetical order
eg. EthylMethypropylamine
what do you put at the start of the name of a secondary amine?
N - …
what do you put at the start of the name of a tertiary amine?
N,N - …
what is a base?
substance which accepts protons in aqueous solution
amine + acid = ?
alkyl ammonium salt
ethylamine + hydrochloric acid = ?
ethylammonium salt
butylamine + nitric acid = ?
butylammonium nitrate
amine + water = ?
ammonium salt - N forms dative covalent bond with H and forms an ammonium ion
PREPARING ALIPHATIC AMINES: name the 3 ingredients
haloalkane
excess ethanolic ammonia
ethanol
PREPARING ALIPHATIC AMINES: what’s the first step?
- nucleophilic substitution between HALOALKANE and AMMONIA
- lone pair on ammonia accepts halogen
PREPARING ALIPHATIC AMINES: what are the conditions for the first step?
- sealed container with ethanol so ammonia doesn’t escape because its very volatile
PREPARING ALIPHATIC AMINES: what’s the second step?
- add excess ammonia to form amine and ammonium salt
- excess ammonia shifts equilibrium to the right to ensure no more substitution into di/tri/tetra amines and for max yield
PREPARING ALIPHATIC AMINES: give the overall equation for the preparation of ethylamine using bromoethane
CH₃CH₂Br + 2NH₃ ⇋ CH₃CH₂NH₂ + NH₄⁺Br⁻
PREPARING AROMATIC AMINES: name the ingredients
nitroarene
tin
concentrated HCl
sodium hydroxide - NaOH
PREPARING AROMATIC AMINES: name 3 conditions for the preparation
- reducing agent: mixture of tin and conc HCl –> [H]
- 100 degrees
- reflux
what is a nitroarene?
a benzene ring with a nitrate group attached (NO₂)
PREPARING AROMATIC AMINES: what happens during the reaction? how many hydrogens are needed?
the nitroarene is reduced
6 hydrogens are needed
- 2 replace the O₂ on the nitrate group
- four go to the water 2H₂O
PREPARING AROMATIC AMINES: what is the overall equation for the reaction?
nitrobenzene + 6[H] –> phenylamine + 2H₂O
PREPARING AROMATIC AMINES: what is added after 30 mins?
NaOH - added to neutralise excess acid
what two groups make up amino acids?
the amine group and the carboxyl group
what is an alpha amino acid?
simplest amino acid - one carbon in the centre with amine group and carboxyl group either side of it
which word can be used to describe the dual property of an amino acid?
AMPHOTERIC - acts as both a base and an acid
which is the simplest form of amino acid?
glycine
what is created when amino acid groups interact with each other? what interaction takes place?
a zwitterion is created when the H on the OH in the carboxyl group joins to the lone pair on the amine group
proton goes from carboxyl group to amine group
what is a zwitterion?
amine group is +ve and carboxyl group is -ve
so no overall charge
when do zwitterions form? what is this condition called?
at a certain pH depending on the R group
ISOELECTRIC POINT
what happens when you lower the pH/more H+ ions to an amino acid at the isoelectric point?
becomes POSITIVE
carboxyl group neutralises bc it accepts H+ ions
amine group remains positive
equilibrium shifts to the left towards carboxyl group
what happens when you increase pH/more OH- ions to an amino acid at the isoelectric point?
becomes NEGATIVE
amine group neutralises - donates H+ to OH- ions
carboxyl group remains negative
equilibrium shifts to the right towards the amine group
describe what an alpha amino acid is
an amino acid where the -COOH and -NH2 groups are on the same carbon
what is a condensation reaction involving amino acids?
when amino acids react to form peptides and peptide links
how are polypeptides made between two amino acids?
water is released from the H of an NH₂ group and the OH from the COOH group form water.
water is released and the two amino acids bonds together
which reaction takes place to break the peptide links between amino acids? what conditions are required?
HYDROLYSIS takes place.
peptides are hydrolysed in ALKALI or ACIDIC conditions (never only by water)
what is an acyl group?
R-C=O
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NR₂
what is a primary, secondary and tertiary amide?
primary - one carbon attached to the N
secondary - two carbons attached to the N
tertiary - three carbons attached to the N
how do you name amides?
suffix - amide
root - longest carbon chain
other groups are added as a prefix
what is optical isomerism?
when two molecules identically arranged in space are non-superimposable images of each other
the can’t be rotated to overlap onto each other
what is a chiral molecule?
molecules with no plane of symmetry
what is a chiral carbon?
a carbon atom with for distinct atoms or groups attached
chiral molecules exist in different forms called ______.
what are these forms?
enantiomers - different enantiomers rotate plane polarised light in opposite directions
what’s a racemate? what effect does it have on polarised light?
a 50:50 mixture of each enantiomer
a racemic mixture has no effect on polarised light because each enantiomer rotates oppositely and so cancel each other out.
what is involved in addition polymerisation?
a single monomer that forms a repeat chain
which two ways can polyester be formed by condensation polymerisation?
- two monomers: diol (two OH groups) and a dicarboxylic acid (two carboxyl groups)
- single monomer with both -OH and -COOH groups on it to self polymerise
how is a polyester formed from condensation polymerisation?
a H from the diol and a OH from the dicarboxylic acid are removed to form water and an ester linkage is formed.
for every 2 monomers, 2 ester linkages are formed.
which two ways can polyamides be formed by condensation polymerisation?
- two monomers: diamine (two amine groups) and a dicarboxylic acid
- a single monger with both an amine and carboxylic acid group on it (eg. alpha amino acid)
how is a polyamide formed from condensation polymerisation?
H from amine group and OH from carboxylic acid group are removed to form water and an amide link is formed
for every 2 monomers, 2 amide linkages are formed
give the structural formula for an ester linkage
O-C=O
give the structural formula for an amide linkage
O=C-NH
what is hydrolysis in terms of polymers?
breaking down polymers into its monomers
how is the slow hydrolysis process of polymers sped up?
by using acidic or alkali conditions
BASE hydrolysis of polyESTERS: what base is used? what products are obtained?
base used: NaOH/H₂O
carboxylate salt and diol formed
carboxyl groups deprotenate and Na+ is added to form salt ( COO⁻⁻Na⁺ )
ACID hydrolysis of polyESTERS: what acid is used? what products are obtained?
acid used: H⁺/H₂O
diol and dicarboxylic are formed (original monomers)
where is the ester linkage broken during hydrolysis?
between the C-O bond
O=C-/-O
BASE hydrolysis of polyAMIDE: what base is used? what products are obtained?
base used: NaOH/H₂O
carboxylate salt and diamine formed
carboxyl groups deprotenate with Na+ (COO⁻⁻Na⁺)
ACID hydrolysis of polyAMIDE: what acid is used? what products are obtained?
acid used: H⁺/H₂O diamie protenates (NH₃⁺) and dicarboxylic acid remains as original monomer
what chemical can be used for the synthesis of C-C bonds? what is the functional group?
cyanide :C⁻≡N: (negative charge on C)
functional group CN⁻
name two reactions/mechanisms in which can cyanide be used to synthesise C-C bonds. how does cyanide act in each reaction?
nucleophilic substitution with haloalkane
nucleophilic addition with carbonyl
cyanide acts as a NUCLEOPHILE
nucleophilic substitution using cyanide:
describe the mechanism
what are the condition?
mechanism:
- curly arrow from lone pair on C to the δ+ carbon in the carbon-halogen bond.
- curly arrow from carbon-halogen bond to δ- halogen
- carbon chain is lengthened by one with a nitrile group on the end + a halogen ion.
condition: ETHANOL and REFLUX
nucleophilic addition using cyanide:
describe the mechanism
what is the product formed?
- curly arrow from lone pair on C to the δ+ carbon in the C=O bond.
- INTERMEDIATE: curly arrow going from lone pair on :O⁻ in the C-O bond to the δ+ H in the H₂O
- curly arrow from H-O bond in water to δ- O.
- hydroxynitrile formed + :C≡N:
which two ways can a nitrile group be removed to be more useful?
- reduced to form amines
- hydrolysed to form carboxylic acids
industrial method of reducing the nitrile group:
- give the reducing agent
- give the conditions and catalyst
- give the general equation
reducing agent: hydrogen reducing agent
condition: high temp and high pressure
catalyst: nickel catalyst
RCN + 2H₂ –> RCH₂NH₂
what type of hydrolysis is used to remove the nitrile group?
acid hydrolysis
hydrolysis of nitrile:
- give the conditions
- give the two equations using ethanitrile
conditions: reflux with HCl
CH₃CN + 2H₂O + HCl –> CH₃COOH + NH₄Cl
CH₃CN –H⁺–> CH₃COOH
