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A-Level Chemistry > 6.2 Nitrogen compounds, polymers and synthesis > Flashcards

6.2 Nitrogen compounds, polymers and synthesis Flashcards

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1
Q

how to name amine

A

primary: identify number of carbons in alkyl chain, suffix -amine (e.g. methylamine)
secondary: for shorter alkyl chain add prefix “N-alkyl” e.g. N-methyl propylamine
tertiary: add “N-“ prefix for each shorter alkyl chain (e.g. N-methyl N-ethyl propylamine

if amine group is side chain, add number before “-amine” suffix

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2
Q

why amines are bases

A

lone pair on N atom
accept hydrogen ions to form alkyl ammonium salts
reacts with acids

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3
Q

formation of ammonium ion example with methylamine and water

A

methylamine + water -> methylammonium ion + hydroxide ion

methylamine accepts hydrogen ion from H2O due to lone pair

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4
Q

phenylamine solubility

A

only slightly soluble due to non-polar benzene ring

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5
Q

how to classify amines

A

primary: attached to 1 alkyl group
secondary: attached to 2 alkyl groups
tertiary: attached to 3 alkyl groups

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6
Q

formation of primary amines conditions

A

ethanol as solvent (prevents substitution of haloalkane by water to produce alcohol)
excess ammonia used (reduces further substitution of amine group to secondary and tertiary amine)
not reflux as gas would escape

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7
Q

formation of primary (aliphatic) amines method

A

haloalkane + ammonia -> alkylammonium salt
alkylammonium salt + aqueous alkali -> amine + salt + water

NH3 has lone pair (acts as nucleophile to substitute with halogen in haloalkane)
to form alkylammonium salt
aqueous alkali added to form amine, salt, water

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8
Q

formation of secondary, tertiary, quaternary (aliphatic) amines

A

haloalkane + primary amine -> ammonium salt
ammonium salt + alkali -> secondary amine + salt + water

tertiary and quaternary formed by repeating processes (continuing reaction)

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9
Q

how to separate primary, secondary, tertiary amines

A

distill as more chains = more boiling point

primary has lowest boiling point, tertiary highest

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10
Q

formation of quaternary amine conditions

A

excess haloalkane
ethanol as solvent
don’t reflux

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11
Q

formation of primary amines with nitriles

A

reduce nitriles
H3C-CN + 4[H] -[LiAlH4] -> primary amines
Na (alcohol), LiAlH4 = reducing agent
can add hydrogen gas and Ni catalyst as well

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12
Q

formation of aromatic amines

A

heat nitro compounds (nitrobenzene) with tin + conc. HCl under reflux for 30 minutes
C6H5NO2 + 7[H]^+ + 6e^- -> C6H5NH3^+ +2H2O
nitrobenzene + 7[H]^+ + 6e^- -> phenylammonium ion + water
add sodium hydroxide to remove hydrogen ions from phenyl ammonium ion
C6H5NH3^+ + OH^- -> C6H5NH2 + H2O
phenyl ammonium + hydroxide -> phenylamine + water

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13
Q

chirality definition

A

atoms in the enantiomers are joined up in the same order but have different spatial arrangement
molecules that are non-superimposable mirror images on one another

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14
Q

what is required for chirality

A

chiral centre (4 different groups attached to a carbon atom)

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15
Q

chiral molecule features

A

non-superimposable images
enantiomers
form of stereo isomerism
carbon atom with 4 different groups attached

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16
Q

optical isomers

A

only with chiral centred isomers

optical isomers rotate plane-polarised light differently (one clockwise, one anti-clockwise)

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17
Q

racemic

A

racemic = racemate
mixture containing 1:1 mix of both optical isomers
no effect on plane-polarised light as they cancel each other out

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18
Q

amino acid general structure

A

carboxylic acid functional group
amine functional group
central hydrogen ion
varying R group

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19
Q

reaction of amino acid with acids

A

amine group is basic
accepts hydrogen atom to form ammonium salt + negative ion
amino acid + acid -> salt + negative ion

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20
Q

reaction of amino acid with aqueous alkali

A

carboxylic acid group is acidic

amino acid + aqueous alkali -> ammonium salt + water

21
Q

reaction of amino acid + alcohol

A

amino acid + alcohol -[concentrated sulfuric acid]-> ester + water
amine group is protonated due to acidic conditions

22
Q

polyamides uses

A

nylons: fishing nets, ropes, parachutes, fabrics, guitars
Kevlar: armour

23
Q

condensation polymerisation definition

A

joining of 2 monomers, the monomers having 2 different functional group

24
Q

functional groups in amide linkage

A

carboxylic acids

amine

25
Q

how polyamides can be formed

A

condensation reaction between:
2 different monomers e.g. dicarboxylic acid + diamine
1 monomer with 2 functional groups

26
Q

addition polymerisation definition

A

formation of a very long molecular chain, by repeated addition reactions of many unsaturated alkene molecules

27
Q

how to make polyesters

A

condensation reactions between carboxylic acid and alcohol groups
either 2 monomers, one with 2 alcohols and the other with 2 carboxylic acids
or 1 monomer with both groups

28
Q

hydrolysis definition

A

reaction where water is a reactant in a decomposition reaction

29
Q

acid hydrolysis of polyester

A

polyester + water -> diol + dioc acid

conc. acid catalyst under feflux

30
Q

base hydrolysis of polyester

A

polyester + water -> diol + dioate salt
NaOH(aq) catalyst
under reflux

31
Q

acid hydrolysis of polyamide

A

polyamide + water -> diamine salt + dioic acid

conc. acid catalyst under reflux

32
Q

base hydrolysis of polyamide

A

polyamide + water -> diamine + dicarboxylic salt

NaOH(aq) catalyst under reflux

33
Q

importance of biodegradable polymers

A

break down easily (e.g. in landfills, less expensive)
don’t need to recycle (which is difficult to mechanise and automate)
no longer need to combust and release toxic emissions

34
Q

degradable polymer definition

A

breaks down into smaller fragments exposed to heat, light or moisture

35
Q

biodegradable polymer definition

A

polymer that breaks down completely onto CO2 and water

36
Q

photodegradable polymer definition

A

becomes weak and brittle when exposed to sunlight

carbonyl groups in backbone of polymer make it photodegradable by bacteria

37
Q

formation of nitriles from haloalkanes

A

nucleophilic substitution of haloalkane with cyanide ion formed from NaCN or KCN in ethanol
adds length to carbon chain
e.g.
1-chloropropane + KCN -> butanenitrile + KCl

38
Q

formation of nitriles from carbonyls

A

nucleophilic addition of carbonyls with
cyanide ions (formed with NaCN/H+)
adds length to carbon chain when with aldehyde
aldehyde/ketone + CN- + H+ -> hydroxynitrile

39
Q

what is used instead of HCN and why in formation of nitriles

A

HCN too poisonous
increased reaction rate (KCN faster than HCN)
mixture of NaCN + H2SO4
improves safety, increases reaction rate

40
Q

reduction of nitriles

A

nitrile + 2H2 -[Ni]-> amine
e.g.
propanenitrile + 2H2 -[Ni]-> propylamine

41
Q

hydrolysis of nitriles

A

heat with dilute aqueous acid e.g. HCl
nitrile + 2H2O + HCl -> carboxylic acid + ammonium chloride (NH4Cl)
e.g.
butanenitrile + 2H2O + HCl -> butanoic acid + NH4Cl

42
Q

alkylation of benzene rings

A

haloalkane + benzene -[halogen carrier catalyst]-> alkylbenzene + HCl/Br

43
Q

acylation of benzene

A

benzene + acyl chloride -> [AlCl3]-> phenylketone/phenylaldehyde + HCl

44
Q

organometallic compound importance

A

compounds containing carbon-metal bond

important for increasing carbon chain length in organic compounds

45
Q

Grignard reagents

A

made by reacting magnesium with haloalkane dissolved in ether solvent
e.g.
bromoethane + Mg -> ethylmagnesium bromide
Grignard reagents react as carbanion e.g. CH3CH2-

46
Q

nucleophilic substitution of haloalkane and cyanide ion

A

ethanol as solvent (so hydroxide ions can’t act as nucleophile)
heat under reflux
CN- + haloalkane -> nitrile + halogen ion

47
Q

why nucleophilic addition of carbonyls with cyanide and optical isomerism

A

C=O is planar
CN- can attack from either side
forms both optical isomers
racemic mixture is formed

48
Q

other way of reducing nitriles

A

LiAlH4
lithium tetrahydridoaluminate (III)
nitrile + 4[H] -> primary amine

49
Q

acid hydrolysis of nitriles

A

reflux with dilute hydrochloric acid
nitrile + 2H2O + HCl -> carboxylic acid + ammonium chloride
e.g.
ethanenitrile + 2H2O + HCl -> ethanoic acid + ammonium chloride
CH3CN + 2H2O + HCl -> CH3COOH + NH4Cl

A-Level Chemistry (12 decks)

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