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OCR A A-Level chemistry > module 6 > Flashcards

module 6 Flashcards

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1
Q

how many carbons will a primary, secondary, tertiary and quaternary amines have?

A

primary - 1
secondary - 2
tertiary -3
quaternary - 4

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2
Q

how do you name amines?

A

amino -

- amine

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3
Q

why are amines so reactive?

A

the lone pair of electrons on the nitrogen - due to N-H

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4
Q

what shape are amines around the N? Bond angle?

A

trigonal pyramid 107 due to lone pair on N

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5
Q

what kind of intermolecular forces do amines have? why?

A

hydrogen bonding due to polar N-H bond and lone pair of electrons on N atom

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6
Q

do amines have stronger intermolecular forces than alcohols? why?

A

No, N has lower electronegativity than O so weaker hydrogen bonding

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7
Q

how/when do amines act as bases?

A

the lone pair on the nitrogen atom accepts a proton

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8
Q

how/when do amines act as nucleophiles?

A

when they bond with an electron deficient C atom

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9
Q

what is the product from the basic action of an amine water?

A

RNH3+ - ammonium ion, which forms a salt with an anion

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10
Q

what is made when HCl reacts with methyl amine

A

methylammonium chloride

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11
Q

in order to be the strongest base, what must a particular amine have (compared to other amines)?

A

greatest electron density around N atom, making it a better electron pair donor (attracts protons more)

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12
Q

what effect do alkyl groups have on electron density and base strength?

A

positive inductive effect - increase electronic density around N - stronger base

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13
Q

place the following in order of base strength: NH3, primary amine, secondary amine, phenylamine

A

secondary amine> primary amine> NH3> phenylamine

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14
Q

how can primary amines form secondary and tertiary amines and quaternary ammonium ions? what are the problems with this method?

A

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

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15
Q

how would you maximise the yield of the primary amine?

A

use excess ammonia

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16
Q

what type of mechanism is the reaction of a haloalkane with a cyanide ion?

A

nucleophilic substitution

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17
Q

what conditions does this reaction require (haloalkane with cyanide ion) ? what product is formed?

A

ethanol as a solvent

a nitrile is formed

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18
Q

how do you get from a nitrile to a primary amine? why is this a purer method of synthesising amines?

A
  • reaction using Nick/hydrogen catalyst

- only the primary amine can be formed

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19
Q

what conditions are needed to form nitrobenzene from benzene?

A

conc. H2SO4 and HNO3 to form the NO2+ ion for electrophilic attack

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20
Q

how do you form an ammonium chloride salt from nitrobenzene? what conditions are needed

A

reduce nitrile using Tin/Hcl - forms an ammonium salt with Cl- ions
room temp

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21
Q

which mechanism is used for forming amides from acyl chlorides and amines?

A

nucleophilic addition/ elimination

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22
Q

what are the two functional groups of amino acids?

A

NH2 and COOH

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23
Q

are a-amino acids chiral? why?

A

yes, one carbon has 4 different groups - except glycine where R=H

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24
Q

define a zwitterion

A

ions which have both a permanent positive and negative charge, but are neutral overall

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25
Q

what will happen in an amine acid zwitterion

A

COOH deprotonated - COO-

NH2 protonated - NH3+

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26
Q

what happens to amino acids in acidic conditions?

A

gains a proton on NH2 group (becomes NH3+)

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27
Q

what happens to amino acids in alkaline conditions?

A

loses a proton from COOH group - COO-

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28
Q

what is the peptide/polyamide linkage

A

-CONH-

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29
Q

what property must a carbon atom have for the molecule to display optical isomerism about that carbon atom ?

A

4 different substituents attached to one carbon atom.

30
Q

what are the similarities and differences between two optical isomers?

A

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.

31
Q

what word is used to describe optically active molecules?

A

chiral

32
Q

what is condensation polymerisation

A

small molecules eliminated when polymer made from monomers (usually H2O)

33
Q

how many monomers are condensation polymers usually formed from?

A

two

34
Q

what properties do these monomers forming polymers have

A

each has two functional groups

35
Q

3 examples of condensation polymers?

A

polyesters
polyamides
polypeptides

36
Q

what linkage does a polyester have

A

ester linkage

37
Q

what molecule is eliminated in formation of a polyester

A

H2O

38
Q

what are the two monomers which form a polyester

A

diol and dicarbocylic acid or a molecule with both alcohol and a carboxylic acid functional group

39
Q

what is terylene used for

A

a fibre for making clothes

40
Q

what two monomers are used to form a polyamide

A

diamine and carboxylic acid

41
Q

what are some examples for polyamides?

A

Nylon, Kevlar

42
Q

if you are making Nylon in the lab, what monomers would you use and why? what molecule\ is eliminated

A

used hexane-1,6-diacyl chloride as the rate of reaction is much faster. Hcl is eliminated

43
Q

what is Kevlar used for?

A

in body armour (bullet proof vests, stab vests) helmets, oven gloves

44
Q

why are poly(alkenes) not biodegradable

A

non-polar C-H and C-C bonds

45
Q

why is it bad to burn poly(alkenes)

A

releases CO2, CO, C (soot) and other toxic chemicals from monomers

46
Q

where do most poly(alkenes) end up?

A

landfill sites

47
Q

why can condensation polymers be broken down

A

they have polar bonds

48
Q

how are condensation polymers broken down?

A

Hydrolysis (opposite of condensation)

49
Q

what is the difference between addition and condensation polymerisation?

A

condensation makes the polymer and eliminates a small molecule; addition polymerisation breaks C=C to form only one product (just the polymer)

50
Q

explain hydrogen boding between polyamides

A
  • 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
51
Q

why do polyesters not show hydrogen bonding?

A

all O-H bonds are removed during polymerisation

52
Q

what reagents are used for base hydrolysis

A

NaOH/H2O

53
Q

what reagents are used for acid hydrolysis

A

H+/H2O

54
Q

what type of mechanism is involved in the reaction between haloalkanes and cyanide ions

A

nucleophilic substitution

55
Q

what type of reaction is involved in the reaction between carbonyl compounds and cyanide ions

A

nucleophilic addition

56
Q

how can you form a carboxylic acid from a nitrile

A

acid hydrolysis

57
Q

what type of catalyst is used for a dreidel-crafts reaction

A

a halogen carrier (AlCl3)

58
Q

write an equation to form an electrophile that could be used to acylate benzene, starting with AlCl3 and ROCl

A

AlCl3 + RCOCl -> AlCl4- + RCO+ (+ on C)

RCO+ can attack benzene

59
Q

how could you use a Frieden-Crafts mechanism to add a methyl group to a benzene ring?

A

use a halogenalkane and AlCl3 to create electrophile that can attack benzene

60
Q

when purifying by recrystallisation why is the minimum volume of hot solvent used?

A

so that a saturated solution is created, so that as many crystals will fall out of solution as possible when it is cooled

61
Q

why is the solution filtered hot when purifying bay recrystallisation

A

to remove insoluble impurities and ensure that the crystals do not form in the filter paper

62
Q

why is the solution cooled in an ice bath when purifying b recrystallisation

A

to ensure that as many crystals as possible fall out of solution - yield is higher

63
Q

why are the crystals washed with cold water when purifying by recrystallisation

A

to remove soluble impurities

64
Q

how would you separate the crystals form the reaction mixture when purifying by recrystallisation

A

filter under reduced pressure using a Buchner funnel

65
Q

why might percentage yield be below 100%

A
  • 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
66
Q

in distillation setup, why is it necessary to have a continuous water flow around the condenser

A

so that the water remains cool In order for the mixture to be distilled

67
Q

describe a method that can be used to separate immiscible liquids

A
  • 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
68
Q

name two drying agents

A

magnesium sulphate and calcium chloride

69
Q

how is a drying agent used

A
  • 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
70
Q

what does re-distillation mean?

A

when a liquid is purified by using multiple distillations

71
Q

what are 3 key steps to purify an organic solid

A
  1. filtration under reduced pressure
  2. recrystallisation
  3. measurement of melting points
72
Q

how do you get from a nitrile to a primary amine?

A

reduce using a nickel catalyst and hydrogen

OCR A A-Level chemistry (3 decks)

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