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Chemistry A Level > Organics 6 > Flashcards

Organics 6 Flashcards

1
Q

Organics

A

The study of carbon compounds (except CO, CO2, CO3)

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2
Q

Carbon atoms have the unusual property of being able to …

A

… join with other carbon atoms to form chains

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3
Q

Homologous series of organic chemicals have

A
  • compounds with the same general formula
  • members with similar chemical properties
  • members that show a trend in physical properties
  • members which differ from each other by a CH2 unit
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4
Q

Function group

A

The part of the molecule that determines which homologous series it is a member of
• an atom or group of atoms which, when present in different molecules, causes them to have similar chemical properties

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5
Q

Highest precedent group…

A
  • taxes suffixes
  • all others take prefixes

RCOOH > aldehydes > ketones > alcohols > alkenes > halogenoalkanes

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6
Q

Alkanes

A
  • hydrocarbons that contain only single bonds
  • fully saturated
  • CnH2n+2
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7
Q

Hydrocarbons

A

Compounds of hydrogen and carbon only

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8
Q

Cycloalkanes

A
  • hydrocarbons joined in rings
  • saturated
  • two hydrogens less than the corresponding straight-chain alkane
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9
Q

Isomerism

A

When two molecules of the same molecular formula have a different arrangement of atoms

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10
Q

Structural isomerism

A

When atoms are arranged in a different order

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11
Q

Fuels

A
  • released heat energy when burned

* one of the main uses of alkanes; readily, highly exothermic

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12
Q

Crude oil

A
  • a mixture of a large number of hydrocarbon compounds

* undergoes fractional distillation to obtain fractions, then reformation to obtain fuels

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13
Q

Fractions

A

Consist of mixtures of hydrocarbons that boil within particular ranges

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14
Q

More useful fractions are those with

A
  • lower boiling ranges
  • generally occur in smaller proportions
  • higher demand
  • valuable
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15
Q

To solve the problem of supply and demand, we use

A

Catalytic cracking -> breaking C-C bonds
• 650°C (strong covalent bonds)
• Al2O3 catalyst

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16
Q

Cracking products

A

Alkanes break into smaller alkanes and alkanes, which can be used to make polymers

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17
Q

Engines

A
  • straight chain alkanes do not burn very evenly, causing ‘knocking’ in a car engine
  • cyclohydrocarbons burn more smoothly, giving fuel a higher octane number (more appropriate)
  • solved by reforming
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18
Q

Reforming - description

A
  • the process used to convert straight chained alkanes into ringed compounds (aromatic hydrocarbons)
  • 500°C, platinum/rhodium catalyst
  • e.g. benzene, methylbenzene
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19
Q

Reforming - definition

A

The processing of straight chain hydrocarbons into branched chain alkanes and cyclic hydrocarbons for efficient combustion

Aka. Isomérisation

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20
Q

Climate change

A
  • hydrocarbon fuels produce CO2 when they burn

* CO2 is a greenhouse gas

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21
Q

Greenhouse gases

A
  • when IR radiation from the sun hits the earth’s surface, it is absorbed and then re-radiated at a lower frequency
  • a greenhouse gas absorbs this and concerts it to heat energy, warming the atmosphere
  • burning fossil fuels increases the concentration of greenhouse gases in the atmosphere, causing climate change
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22
Q

Car engine pollutants

A
  • in an engine, the fuel and air mix is passed into the combustion chamber and ignited
  • powerful initial reaction is followed by less energetic processes
  • to achieve maximum power, the gases are expelled from the chamber before combustion is complete
  • results in CO and unburned hydrocarbons to be eject, causing pollution and smog
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23
Q

CO

A
  • poisonous

* binds almost irreversibly to Hb, reducing O2 transport around the body

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24
Q

Photochemical smog

A
  • unburned hydrocarbons tend to be react with the air, especially in the presence of sunlight
  • can cause serious breathing problems o
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25
Q

Sulfuric acid rain

A
  • fuels such as coal in power stations of contain sulfur
  • converted to sulfur dioxide in combustion
  • dilute sulfuric acid in atmosphere, dissolving
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26
Q

Nitric acid rain

A
  • combustion in engines tjs replace at high temperatures and has sparks, allowing atmospheric oxygen and nitrogen to form nitrous oxides
  • breaks the N2 triple bond
  • forms dilute nitric acid
  • forms NO-> toxic, smog
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27
Q

Pollutant carbon particulates

A
  • produced by Diesel engines and unturned petrol engines
  • caused global dimming (reflection of sun’s light)
  • breathing problems
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28
Q

Catalytic converters

A
  • rémove CO, NOx and unburned hydrocarbons form exhaust engines
  • help to combat engine pollutants
  • ceramic honeycomb coated w thin layer of catalyst metals (Pt, Pd, Rh) to give large SA
  • catalyst provides th resurface to enable oxidisers (e.g. nitrous oxides) to react w reductants (e.g. unburnt hydrocarbons) to form less harmful CO2, N2 and H2O
  • do not deal with CO2 effects
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29
Q

Reducing CO2

A
  • no fossil fuels

* alternative fuels

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30
Q

Alternative fuels

A
  • biofuels (biodiesel)

* alcohols formed from renewable resources

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31
Q

Biofuels

A
  • formed by plants that absorb atmospheric CO2 to form the plant materials that are used; renewable
  • carbon-neutral; no large-scale pollution
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32
Q

Bioethanol production

A
  • requires fertilisers and pesticides that have taken energy (from oil) to make
  • requires distillation
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33
Q

Biodiesel

A
  • smaller carbon footprint, does not require distillation

* reacting vegetable oils w/ alkali + methanol

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34
Q

Combustion of alkanes

A
  • react with oxygen to produce CO2 and H2O

* incomplète CO/C + H2O (less energy/mole)

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35
Q

Free radical substitution

A
  • halogénation (Cl/Br) if alkanes (halogen substitués H atoms)
  • because C-C and C-H relatively strong
  • alkanes are v. Unreactive; photochemical réaction caused by UV light
  • cyclical due to halogen regeneration at the termination stage
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36
Q

Free radical

A
  • a reactive species which possesses an unpaired electron
  • every time it finds another e-, it pings and creates another free radical
  • so reactive that can cause cancer
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37
Q

Simplified equation of free radical substitution

A
  • CH4 + X2 -> CH3X + HX
  • the réaction does not necessarily stop at one substitution can produce dihalogeno-, trihalogeno- and tetrahalogeno- etc. with excess halogen
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38
Q

Production of free radicals

A
  • homolytic fission
  • a covalent bond breaks, and the atoms originally joined by the bonds each take one electron
  • 2x unpaired electron shown as a dot ; no charge
  • shows by a single headed curly arrow
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39
Q

Initiation

A
  • only ever 1 stage

* halogen -uv-> 2x halogen free radicals

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40
Q

Why is it the halogen that undergoes homolytic fission?

A
  • always the halogen, because diatomic halogen bind has lower bind energy than C-H bond, so the UV light breaks it first preferentially
  • requires less energy to break
  • not enough to break C-H
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41
Q

Propagation

A
  • always two stages, with free radicals in reactants and products
  • halogen free radical + alkane -> alkane free radical + hydrogen halide
  • alkane free radical + halogen -> halogenoalkane + halogen free radical
  • hydrogen halide bond forms because it has a higher bond energy
  • chain reaction due to regeneration of halogen free radicals
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42
Q

Termination

A
  • can be any number of steps
  • reacts any free radicals to remove them
  • causation if free radical does not generate firther free radicals; chain is terminated
  • used structyral, not molecular formulae in equations
  • 2x halogen free radicals -> halogen (regeneration)
  • 2x alkane free radicals -> alkane (by-product)
  • Halogen free radical + alkane free radical -> halogenoalkane (product)
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43
Q

If a question asks for the halogen to be substituted into w middle carbon in the chain

A

It is important to show the free radical on the correct carbon at the propagation stages

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44
Q

Alkenes

A
  • hydrocarbons that contain one double bond
  • unsaturated
  • CnH2n
  • functional: C=C (one σ and one π)
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45
Q

Cycloalkenes

A
  • unsaturated

* CnH2n-2

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46
Q

Remember, when position isomers can occur…

A

… number need to be added to the name

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47
Q

σ bond

A
  • normal bond
  • electron cloud likes between the two atoms
  • firmed by one sp2 orbital from each (overlapping)
  • rotation can occur around the bond
  • end-on overlap (forms a denser cloud)
  • region of really high electron density (shared-pair)
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48
Q

π bond

A
  • electron cloud lying above and below the planes two atoms
  • side-on overlap of two p orbitals in each C atom
  • rotation is restricted (stopped)
  • weaker than the σ because it is not over the nuclei; doesn’t pull them together -> fast reaction
  • overlap is less efficient because the highest e- density is not directly between nuclei
  • resultant high e- density above and below the lines between the two nuclei
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49
Q

Nomenclature of alkenes

A
  • multiple double bonds are indicated by ‘diene’ or ‘triene’, stem ends in a
  • ‘en’ can go before other suffixes
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50
Q

Stereoisomerism

A
  • e.g. E-Z isomerism, cis-trans isomerism (geometric isomerism)
  • same structural formula, different spatial arrangement of atoms
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51
Q

E-Z isomerism

A
  • due to restricted rotation around C=C that doesn’t exist around C-C
  • needs two different groups/atoms attached to both end each of the double bonded Cs
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52
Q

Entgegen (E)

A
  • higher priority groups on opposite sides of E

* looks like a Z

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53
Q

Zussamen

A
  • higher priority groups on the same side of the C=C

* looks like an E

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54
Q

Naming E-Z isomers

A
  • determined the priority groups on both sides of the double bond
  • determined by atomic number
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55
Q

cis-trans isomerism

A
  • a specific case of E-Z isomerism

* two of the substituent groups are the same

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56
Q

If asked to name an organic reaction…

A

… think REDOX

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57
Q

Alkene reactions

A
  • more reactive than alkanes because of the double bond

* possible for the double bond to break, allowing each C to form a new bond (often energetically favourable)

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58
Q

Addition reactions in alkenes

A
  • a reaction where 2 molecules react to produce 1

* double bond breaks, 1 species joins each side

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59
Q

Alkene addition with hydrogen

A
  • hydrogenation
  • reagent: hydrogen (bombard)
  • conditions: nickel catalyst, heat
  • functional group: alkene -> alkane
  • réaction: addition/reduction (+H2)
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60
Q

Alkene addition with halogens

A
  • halogénation
  • reagent: Cl2/Br2 (dissolved in organic solvent)
  • conditions: room temp and pressure, not UV light
  • functional group: alkene -> dihalogenoalkane
  • mechanism: electrophilic addition
  • type of reagent: electrophile (Clδ+, Brδ-)
  • type of bond fission: heterolytic
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61
Q

Alkene addition with hydrogen halides

A
  • reagent: HCl/HBr
  • conditions: room temperature
  • functional group: alkene -> halogenoalkane
  • mechanism: electrophilic addition
  • type of reagent: electrophile (Hδ+)
  • type of bond fission: heterolytic
  • if the alkene is not symmetrical, the hydrogen adds to the carbon that’s already has the most hydrogen
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62
Q

Alkene addition with potassium managanate (VII)

A
  • acidified KMnO4
  • conditions: room temperature/cold -> not too vigorous
  • type of reaction: oxidation
  • observation: purple -> colourless
  • used to test for the alkene functional group; would not change for alkanes
  • functional group: alkene -> diol
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63
Q

KMnO4

A
  • acidified solution
  • oxidising agent
  • provides oxygen in conjunction with a water molecule to produce two -OH groups which add across the double bond
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64
Q

Alkene addition with bromine water

A
  • reagent BrOH (bromine dissolved in water)
  • conditions: room temperature
  • observation: orange -> colourless
  • also used to test for the alkene functional group
  • functional group: alkene -> halogenoalcohol
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65
Q

Alkene addition with steam

A
  • reagent: steam
  • conditions: 300-600°C, high pressure (70atm), conc. H3PO4 catalyst
  • functional group: alkene -> alcohol
  • reaction: hydration
  • industrial: no waste products; high atom economy, easier and cheaper
66
Q

Hydration

A
  • water is added to a molecule

* H + OH add

67
Q

Electrophilic addition premise

A

electron rich area in the double which allows the initial attack on the alkene by the electrophile

68
Q

Electrophile

A
  • a species attracted to an area of negative charge

* an electron pair acceptor

69
Q

Formation of carbocation in electrophilic halogénation of alkenes

A
  • alkenes pushes e-s in the π bond to bromine
  • induces à dipole because the π electrons repel the e- pair
  • Br2 becomes polar and electrophilic (Brδ+)
70
Q

Electrophilic addition of hydrogen halide to alkenes

A
  • Hδ+ is attracted to high e- density of double bind, drawing an e- pair out and forming a bond
  • bond between bromine and hydrogen breaks; both e-s go to bromine (heterolytic fission)
  • HBr is already polar due to electro negativities
  • a carbon will only have 3 bonds, creating positive charge - carbocation
  • bromide donates electron pair to carbocation, forming a bond
71
Q

When addition reactions involve larger alkenes…

A

…. there can be multiple possible intermediates, depending on which carbon the hydrogen from the hydrogen halide joins

72
Q

Markovnikov’s rule

A

During addition reactions, you predominantly form the most stable cation

73
Q

Carbocations are stabilised by..

A

… induction; the positive charge on the C attracts e-s from connecting atoms, causing the charge to spread

74
Q

Methyl groups have a

A

… higher inductive effect because they are higher in electron density (electron releasing, reduce charge on C)

75
Q

Which carbocation will be the most stable?

A
  • the more carbons attached to the positively charged carbon

* greater inductive effect

76
Q

Heterolytic bond fission

A
  • produces ions (which can be electrophiles or nucleophiles)
  • nucleophile
  • both electrons from the covalent bonding pair go to one atom
77
Q

Addition polymers

A

Formed when monomers containing double bonds are polymerised

78
Q

Polyalkenes

A

Are unreactive due to strong C-C and C-H bonds

79
Q

Éthene uses and properties

A
  • plastic bags
  • bottles
  • flexible
  • easily moulded
  • waterproof
  • chemical proof
  • low density
80
Q

Propène uses and properties

A
  • rope
  • carpet
  • stiffer
81
Q

Disposal of polyalkenes

A
  • no groups are susceptible to attack by water or natural organisms
  • not décomposed by natural processes
  • non-biodegradable, build your at landfills
82
Q

Recycling of polyalkenes

A
  • polymers sorted into type (automatically or with IR)
  • melted and remoulded
  • saves crude oil
  • expensive in energy and manpower
83
Q

Incinération of polyalkenes

A
  • burnt at a high temperature
  • used for energy generation
  • high temperature prevents poisonous gases entering the air (e.g. HCl)
  • emits greenhouse gases
  • volume of rubbish is greatly reduced
84
Q

Feedstock for cracking

A
  • decomposition
  • polymer is heated without oxygen
  • decomposes into smaller molecules that can be used as fuel
85
Q

Life cycle assessment

A
  • materials and energy used to make them
  • materials and energy used to maintain them
  • materials, space and energy used to dispose of them
86
Q

Improvements to disposal of polyalkenes

A
  • rénove any waste gases produced during incineration

* make plastics which are biodegradable (e.g. polyethanol)

87
Q

Halogenoalkanes

A

Functional group: halogen

88
Q

Classification

A

Depends on the number of carbon groups attached to the carbon with the halogen (X) group

89
Q

Preparation of halogenoalkanes

A
  • react the appropriate alcohol with the halogenating
  • chloro- : phosphorous pentachloride
  • bromo- : potassium bromide, 50% H2SO4
  • iodo- : red phosphorus w/ iodine
90
Q

Test for OH

A
  • phosphorus pentachloride (s) reacts with alcohols at room temperature
  • used to prep chloroalkanes

C2H5OH + PCl5 -> C2H5Cl + HCl + POCl3

91
Q

Preparation of bromoalkanes

A
  • heat under reflux
  • 50/50 mix
  • H2SO4 + KBr -> HBr + KHSO4
  • liberates hydrobromic acid
  • HBr + C3H7OH -> C3H7Br + H2O
92
Q

Preparation of iodoalkanes

A
  • heat under reflux
  • P + 3/2I2 -> PI3
  • PI3 + 3ROH -> 3RI + H3PO3
93
Q

PI3

A
  • (phosphorus(III) iodide)

* has a lone pair - trigonal pyramidal

94
Q

Conc. H2SO4 cannot be used …

A

… to make bromoalkanes or iodoalkanes as the halide ion is oxidised o the halogen

95
Q

Heating under reflux

A
  • stops solvent evaporating

* keeps réactions going

96
Q

Halogenoalkane reactions

A
  • v reactive!
  • carbon-halogen bond is polar due to the electronegativity of H (draws e-s away from the carbon to which it is attached, leaving it δ+)
  • δ+ attract negative ions, or molecules with negativity charged regions -> nucleophilic
97
Q

Nucleophile

A
  • a species attracted towards a region of positive
  • an electron pair donor
  • always have a lone pair
  • e.g. OH-, H2O, CN-, NH3
98
Q

Nucleophilic substitution

A

• swapping a halogen atom for another atom/ group of atoms

99
Q

Aqueous potassium hydroxide nucleophilic substitution

A
  • substitution with aqueous alkalis
  • halogen is substituted by an OH group
  • conditions: heat under reflux
  • functional group: halogenoalkane -> alcohol
  • role of reagent: nucleophile, OH-
  • products: alcohols + halide ion
100
Q

Why is OH- a stronger nucleophile than water?

A

It’s has a full negative charge leading to a stronger attraction to Cδ+

101
Q

Silver nitrate solution nucleophilic substitution

A
  • silver nitrate made by dissolving the solid in water
  • halide ions react with silver ions, producing a silver halide precipitate
  • precipitate only forms when the halide ion has left the halogenoalkane; rate of formation of precipitated used to compare halogenoalkane; rate of formation of precipitate used to compare halogenoalkane reactivity
102
Q

Ethanol as a cosolvent

A

in the presence of water, halogenoalkanes hydrolyse (poor nucleophile)
• much slower because water and halogenoalkanes are immiscible; low collision rate
• ethanol can interact both water (hydrogen bonding) and halogenoalkanes (polar and non-polar regions) acting as an emulsifier
• allows water and halogenoalkanes to mix, increasing reaction rate

103
Q

Hydrolysis

A

The splitting of a molecule by a reaction with water

104
Q

Comparing halogenoalkane

A
  • the quicker the precipitate is formed, the faster the substitution reaction, the more reactive the halogenoalkane
  • reaction rate depends on the C-X bond energy; the lower the energy the reaction
105
Q

Results of silver nitrate solution rate comparisons

A
  • chloroalkane: no precipitate forms
  • bromoalkane: precipitate forms after 15mins
  • iodoalkane: precipitate forms after 5 mins

Iodoalkanes > bromoalkanes > chloroalkanes

C-I is the weakest of the three; most easily broken

106
Q

Ammonia solution nucleophilic substitution

A
  • reagent: NH3 dissolved in ethanol
  • conditions: heating under pressure in a sealed tube
  • type of reagent: nucleophile NH3
  • products: amine + hydrogen halide
  • hydrogen halide then reacts with remaining ammonia to produce ammonia halide
  • further reaction can occur, leading to a lower yield of smoke; using excess ammonia prevents
107
Q

Why is ammonia a strong nucleophile

A

The nitrogen is highly electronegative

108
Q

Potassium cyanide nucleophile

A
  • reagent: KCN
  • conditions: ethanolic, heated under reflux
  • type of reagent: nucleophile (CN-)
  • products: nitrile
  • extends the carbon chain
109
Q

Nitrile

A

R-C=_ N

110
Q

Nucleophilic substitution 1 - mechanism

A
  • halogenoalkanes are susceptible to attack by nucleophiles
  • the halogen is electronegative draws bonding electron pair towards itself creating Cδ+
  • Cδ+ invites nucleophilic attack
  • 1st step is the slow step
  • carbocation is planar; nucleophilic attack from either side
111
Q

Nucleophilic substitution 2 - mechanism

A
  • transition state - not an actual substance, just a representation of the middle of the reaction
  • attaching a catalytic antibody attaching to TS to lower Ea
112
Q

How to tell which nucleophilic substitution mechanism will occur

A
  • consider carbocation states; 3° is the most stable and therefore best for Sn1
  • consider steric hindrance
  • 1°: Nu- lone pair not hindered
  • 3°: Nu- lone pair is sterically hindered by bulky methyl groups
  • 2° could be either
  • 1° does not do Sn1 because it would form an unstable primary carbocation
113
Q

Halogenoalkane élimination

A
  • reagent: KOH/NaOH in ethanol
  • role of reagent: base, OH-
  • condition: heat (boiling)
  • functional group: halogenoalkane -> alkene
  • products: alkene + hydrogen halide + water
  • structurally, the halogen and the H of the adjacent C are eliminated (unsymmetrical 2° and 3° can have structural isomers)
114
Q

How do halogenoalkane structure affect reaction?

A
  • 1° halogenoalkane tend towards substitution

* 3° halogenoalkane tend towards elimination

115
Q

Uses of halogenoalkanes

A
  • refrigerants, fire retardants, pesticides, aerosol propellants
  • chloro- , chlorofluoro- used as solvents
  • CH3CCl3 -> solvent used in dry cleaning
  • low flammability
  • many uses have been stopped due to toxicity and effect detrimental effect on ozone layer
116
Q

Test for halogenoalkanes

A
  • heated with aqueous NaOH (release halide ions)
  • RX + OH- -> ROH + X-
  • excess dilute nitric acid (removes remaining OH- ions)
  • AgNO3
  • Ag+ (aq) + X- (aq) -> AgX (s)
117
Q

Reactivity of halogenoalkanes

A
  • 3° halogenoalkanes react fastest because although there is no wait time for collision during Sn1
  • in Sn2 nucleophile must be correctly oriented and collide by coming from opposite
118
Q

Alcohols

A
  • functional group: OH
  • CnH2n+1OH
  • suffix: -ol
  • hydroxy- (used in RCOOH, remember to show number!)
119
Q

Carbonyl groups

A
  • involves in alcohol oxidation

* C=O

120
Q

Ketone

A
  • simplest: propanone
  • 5 or more means it’s necessary to add the number
  • -one
121
Q

Aldehyde

A
  • C=O is at the end of the carbon chain
  • no number needed
  • -al
122
Q

Properties of carbonyls

A
  • very flammable (like all other organic compounds); illustrated by whoosh bottle
  • used as fuels because they burn v. quickly
  • used as solvents because they evaporate v. quickly
  • liquid at room temperature because of the hydrogen bonding between molecules (higher BP to corresponding alkanes)
  • as chain length increases, dipole-dipole and H bonding loses relevance compound to London forces
123
Q

Small alcohols intermolecular forces

A
  • dipole-dipole
  • hydrogen
  • London

Soluble

124
Q

Large alcohols

A
  • dipole-dipole
  • hydrogen
  • much more London

Less soluble

125
Q

Combustion of alcohols

A
  • conditions: clean flame

* products: CO2 + H2O

126
Q

Alcohol reactions with sodium

A
  • observations: effervescence (H2), mixture gets hot, sodium dissolves, white solid produced
  • white solid = sodium alkoxide
  • uses: test for alcohols
127
Q

Sodium alkoxide

A

Ethoxide -> pale yellow solid, ionic properties, soluble

128
Q

Oxidation of alcohols - basics

A
  • loss of hydrogen
  • hydrogens attached to the C adjacent to the OH group must be lost
  • reagents: 0.3mol H2SO4 and K2Cr2O7 (aq)
129
Q

0.3mol H2SO4 + K2Cr2O7

A

[O] -> oxidising agent, is reduced

H2SO4 -> provides H+ ions, reduced to H2O

K2Cr2O7 -> easily controllable

(Cr2O7)2- + 14H+ + 6e- -> 2Cr3+ + 7H2O

130
Q

Partial oxidation of alcohols - primary

A
  • alcohol -> aldehyde
  • conditions: limited amount of dichromate (excess), warm gently
  • method: add one reagent dropwise to the other, distill off the aldehyde as it forms
  • orange solution -> green solution
  • Cr2O7)2- -> 2Cr3+
  • products: aldehyde + water
131
Q

Why must the aldehyde be distilled off?

A

To prevent further oxidation into a carboxylic acid

132
Q

Full oxidation of primary alcohols

A
  • doesn’t always happen, need other right conditions
  • excess dichromate, heat under reflux
  • products: RCOOH + water
  • orange solution -> green solution
  • Cr2O7)2- -> 2Cr3+
133
Q

Full oxidation of secondary alcohols

A
  • only H attached to the adjacent C, produces ketone, cannot oxidise further
  • excess dichromate, heat under reflux
  • products: ketone + water
  • orange solution -> green solution
  • Cr2O7)2- -> 2Cr3+
  • ketone can be distilled off because it is a volatile product in a involatile mixture (BPs of 50°C)
134
Q

Heating under reflux - diagram labels

A
  • open top to prevent pressure build up and explosion
  • Liebig condenser
  • cold water in at bottom and out at the top
  • pear-shaped flask
  • solvent, reactants and anti-bumping granules
  • heat (Bunsen/heating mantle)
135
Q

Anti-bumping granules

A
  • provide a large SA for bubbles to form on
  • prevents vigorous boiling and splashes caused by bumping by allowing smaller bubbles
  • smooth boiling
136
Q

Why use a heating mantle?

A

Flammable substances

137
Q

How does heating under reflux work?

A
  • as the reactants are heated, the volatile liquids boil off
  • converted back into liquid in the condenser and return to the flask
  • allows heating for longer, increasing reaction time
138
Q

Why can’t tertiary alcohols be oxidised with acidified dichromate?

A

There are no hydrogens attached to the carbon adjacent to the OH group

139
Q

Fehling’s (Benedict’s)

A
  • used to distinguish between carbonyls
  • reagent: contains Cu2+ ions (blue) + 2,3-dihydroxybutanedioic acid
  • conditions: heat gently
  • only aldehydes oxidise, reducing Cu2+ to copper(I) oxide (Cu2O)
  • observations -> blue solution -> red ppt
  • ketones do not react
140
Q

Tollens’

A
  • used to distinguish between carbonyls
  • ammoniacal silver nitrate
  • observations: aldehyde produces silver mirror through reduction of Ag+
141
Q

ammoniacal silver nitrate

A

Solution of silver nitrate, sodium hydroxide and ammonia solution

142
Q

General indicator of carbonyls

A
  • 2,4-DNPH

* produces a yellow-orange precipitate

143
Q

Alcohol elimination

A
  • reagent: conc. H3PO4 (acid-catalysed, dehydrating agent)
  • conditions: heat under reflux
  • functional group: alcohol -> alkene
  • some 2° and 3° alcohols can give more than one product, when the double bond forms between different carbon atoms (E-Z isomerism)
  • provides a possible route to polymers without using monomers derived from oil
144
Q

Dehydrating agents

A

Do what you think.. remove water molecules from larger molecules

145
Q

Na2SO4 anhydrous

A
  • insoluble in organic liquid
  • not react w/ organic liquid
  • drying agent
146
Q

Distillation

A

• used to separate an organic product from it’s reacting mixture

147
Q

Purification

A
  • solvent extraction
  • put the distillate of impure product into separating funnel
  • wash product with NaHCO3, inverting and releasing pressure from CO2 produced
  • wash product NaCl (aq)
  • allows layers to separate through inversion in the funnel, holding the stopper
  • run and discard aqueous layer
  • run organic layer into clean, dry conical flask; add 3 spatulas of anhydrous Na2SO4
  • devant liquid into distillation flask
  • distill for pure product
148
Q

NaHCO3

A

Neutralises any remaining reactant acid/acid catalyst

149
Q

NaCl (aq)

A

Helps separate organic layer from aqueous layer

150
Q

Solvent extraction

A

1) mix organic solvent and oil-water mixture in a separating funnel; separate oil layer
2) distil to separate oil from organic solvent
3) add anhydrous CaCl2
4) decent to remove

151
Q

Prior to purification

A

1) materials and reagents are mixed and heated under reflux

2) crudely distilled (w/out thermometer)

152
Q

After drying

A

1) filter liquid through small tuft of mineral wool into a pear-shaped flask
2) distill w/thermometer - bulb adjacent to still-head side-arm
3) collect product over particular temperature range

153
Q

Measuring BP

A
  • determines liquid purity and identifies product
  • distill/boil in a heating oil bath
  • constant and standard pressure
  • thermometer above the level of the surface of the boiling liquid; measuring the temperature of the saturated vapour
  • not very accurate -> several substances have the same BP
154
Q

General nomenclature

A
  • if the suffix starts with a vowel, remove e from stem
  • if it is a consonant, or multiple groups, do not remove e
  • functional groups take precedence over branched chains in giving lowest number
  • multiple functional groups or side are given in alphabetical order
155
Q

Chain isomers

A

Same molecular formula, different carbon skeleton structure

156
Q

Position isomers

A

Same molecular formula, different structures due to different positions of the same functional groups on the same carbon skeleton

157
Q

Functional group isomers

A
  • same molecular formula

* atoms arranged to give different functional groups

158
Q

Carboxylic acids

A
  • RCOOH
  • -oic acid
  • no number necessary because acid group is always at the end of the chain
  • can have -dioic acid
159
Q

Test for RCOOH

A
  • Na2CO3

* effervescence (CO2)

160
Q

Disadvantages of biofuels

A
  • less food crops may be grown
  • rain forests cut down to provide land
  • shortage of fertile soils

Chemistry A Level (12 decks)

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