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Edexcel Chemistry A LEVEL - RM > TOPIC 6 - ORGANIC CHEM > Flashcards

TOPIC 6 - ORGANIC CHEM Flashcards

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1
Q

Test for purity of liquids

A

• Measure the boiling temp
. More purity = closer to databook bp value.
• Any impurities will raise the boiling temperature
To determine bp:
-substance heated above its bp, allowed to cool down and drawn into capillary tube and temp change.

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2
Q

extraction with a solvent in a separating funnel

A
  • Add the chosen solvent to form 2 layers in a separating funnel (2 seperate liq with 2 diff densities)
  • Add stopper and gently shake
  • Allow the contents to settle into two layers
  • Remove the stopper and allow the lower layer to drain into a flask and the upper into a different flask
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3
Q

Drying with anhydrous salt

A
  • Anhydrous calcium chloride to remove water and absorb moisture.
  • The drying agent (does not react with organic liq) can be removed by:
  • Filtration
  • Decanting
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4
Q

Simple Distillation

A
  • separate liqs with very diff bp
  • easier to set up and quicker
  • only used if 25’C difference in bp
    1. liq heated, liqs with low bp evaporates/boils off first and passes into condenser and collected in reciever seperately. Other liqs have higher bp evaporate off later.

if temp begins to rise indicates diff compound boiling.

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5
Q

Fractional distillation

A

used to seperate liq. with similar bp
- filled with glass beads/broken acts as an surface area which vapour leaving the column can condense.

  1. Crude oil is heated in a furnace which turns most of it into vapour
  2. Near the top is where the shorter chain molecules condense
  3. Near the bottom is where longer molecules are as they have a higher melting point
  4. Different columns have different temperatures where different length carbon chains condense
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6
Q

What is a hydrocarbon?

A

A compound that contains hydrogen and carbon only

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7
Q

What are saturated hydrocarbons?

A

Contain single bonds only. Hydrocarbons with the maximum amount of hydrogens possible

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8
Q

What are unsaturated hydrocarbons?

A

Contain 1 or more double bonds. Hydrocarbons without the maximum amount of hydrogens possible

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9
Q

empirical formula

A

The simplest whole number ratio of atoms in a compound

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10
Q

molecular formula

A

The actual number of atoms in each molecule

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11
Q

structural formula

A

Shows the arrangement of atoms carbon by carbon with the attached hydrogens and functional groups

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12
Q

skeletal formula

A

Shows the bonds of the carbon skeleton only, with any functional groups

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13
Q

displayed formula

A

Shows how all the atoms are arranged, and the bonds between them, drawn out

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14
Q

functional group

A

The group of atoms which gives an organic compound its characteristic properties and reactions

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15
Q

homologous series

A

A series of compounds with the same functional group and general formula and similar chemical properties, which differ by CH2 from the next member

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16
Q

general formula

A 
alkenes - CnH2n
alkanes - CnH2n+2
Haloalkane - CnH2n+1X
Alcohols - CnH2n+1OH
Aldehyde - CnH2n+1CHO
Carboxylic acids - CnH2n+1COOH
Ketone - CnH2nO carbonyl bond not at end of C chain

when naming it has to be alphabetical and always count and write position of C in one direction.

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17
Q

addition react

A

Joining two or more molecules together to form a larger molecule

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18
Q

polymerisation

A

Joining together lots of simple molecules, same REPEATING UNITS - MONOMERS to form a large molecule - POLYMER.

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19
Q

Cis-trans isomerism / E-Z ISOMERISM

A

occur in alkenes
Because the presence of C=C leads to restricted rotation, whereas in alkanes the atoms can rotate freely, without restriction.
due to overlap of p-orbitals = pi bond.
- TRIGONAL PLANAR 120’ - due to 3 areas of electron densities repel each other
E = TRANS
Z = CIZ
- atoms/groups on each side with higher priority with higher Mr/Ar to determine E-Z isomerism

  • Ethene do not exhibit e/z as atoms are same on either side
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20
Q

crude oil

A

mainly made up of Alkanes.
energy comes from burning fossil fuels, crude oil and natural gases.
- Fractional distillation takes place:
as chain length increases bp increases, volatility and viscosity, flammability and reactivity decreases.

21
Q

3 main processes used to convert crude oil into fuels?

A
  • Cracking
  • Reforming
  • Fractional distillation
22
Q

Cracking

A

The breakdown of longer chain molecules into smaller ones by heating with a catalyst. Because the demand for longer chain hydrocarbons is much less than the demand for shorter chain hydrocarbons, therefore cracking is used to turn longer chain into shorter chain hydrocarbons

  1. THERMALYTIC CRACKING
    - produces higher prop of alkanes and alkenes
    - 7000kPa
    - high temp 1200K
  2. CATALYTIC CRACKING :
    - produces aromatic compounds/cyclic rings and H2 gas
    - low temps and normal press
    - zeolite catalyst
23
Q

Reforming

A

conversion of straight chains alkanes/hydrocarbons into branched chain and cyclic hydrocarbons as they burn less efficiently when heated
- so heated with a catalyst Pt helps it burn more smoothly in engine
pentane = cyclopentane + H2
heptane = methylbenzene + 4H2

24
Q

fractional distill

A

separate liq into fractions b boiling and condensing with similar bp
near bottom, fractions with large moleculs and longer chains with high bp
near top fractions with smaller molecules with low bp
- rise higher up column and collected at the top. they condense and collect bottom fraction column
= RPKDFB down the column fractions
- incr in bp and decr in voltality and viscosity

25
Q

Polymerisation

A

C=C need high temp draw box around repeating unit and put same n next to it. and show bonds opening.
- not sustainable because it is NON-BIODEGRADABLE and non-polar bonds can not be hydrolysed (unreactive)

  • Polyethene - cling film, bin bags, insulation
  • Polypropene - plastic bags, cups
  • Polystyrene - packaging
  • Polychloroethene - wire and cable insulation, windows and flooring
  • PTFE - non-stick pans, garden tools
26
Q

POLYMER WASTE

  1. Recycling
  2. Incineration
  3. Chemical feedstock
A
  1. convert Pw into other materials. Process is long chop, wash, melt, mould etc done by hands
  2. Convert pw into energy. heat energy/ e- energy can release pollutants/toxic gases so harder to remove.
  3. Breakdown of Pw into gases (H2/CO2) produces feedstock used in other chemical reactions and make new polymers.
27
Q

Complete Combustion

A

all the atoms in the fuel are fully oxidised

28
Q

Incomplete combustion

A

Some of the atoms in the fuel are not fully oxidised due to INSUFFICIENT AMOUNT OF O2 PRESENT. produce C particulates soot, CO cause suffocation.

Also oxides of sulphur and nitrogen are produced and form acid rain which damages aquatic life, crops, forests. and air pollution NO & NO2

29
Q

Incomplete combustion

A

Some of the atoms in the fuel are not fully oxidised due to INSUFFICIENT AMOUNT OF O2 PRESENT. produce unburned C soot, CO cause suffocation.

Also oxides of sulphur and nitrogen are produced and form acid rain which damages aquatic life, crops, forests. and air pollution and spark plugs cause NO & NO2

30
Q

Catalytic converter : outline the stages of how NO & CO react in a catalytic convertor

A
  • in exhaust system CO & NO are absorbed onto the surface of the catalyst - metals platinum and rhodium on honeycomb mesh.
  • The catalyst weakens the bonds so CO2 and N2 can be made
  • Products desorbs from the surface
  • costs to cool gases and increas of Ea of particles
31
Q

Alternative fuels

A

need:

  • depletion of natural resources
  • global warming
  • non-renewable resources, finite- non-sustainable

BIOFUELS: Fuels obtained from living matter that has died recently.

  • Bio diesel - refining fats/oils
  • Bio alcohols - ferment of sugars
  • bio gas - breakdown of organic waste

CARBON NEUTRAL = no net release of carbon dioxide into the atmosphere

DISAD:

  • a lot of land is needed when u can use it for food
  • low yield
  • no cost in drilling - cost ingrowing, processing and transport
32
Q

Steps for FRS (free radical substitution) for alkanes

A

Radical - A species that contains an unpaired electron

Homolytic Fission - The bond breaks evenly and each bonding atom receives one electron from the pair - e- pair movement shown by curly arrow.

Reduce formation of by prod

-Initiation = Formation of radicals, usually as a result of bond breaking caused by ultraviolet radiation or 300’C
Cl2➝ 2Cl•

-Propagation = Two steps that when repeated many times convert the starting materials into products
•Cl + CH4 ➝ HCl + •CH3
•CH3 + Cl2 ➝ CH3Cl + •Cl
-Termination = Formation of a molecule from two radicals
•CH3 + •Cl ➝ CH3Cl
•CH3 + •CH3 ➝ CH3CH3

PROB:
- radicals form with anything
- many multiple subst will take place 
- many termination steps will take place
= multiple products
- extra work to separate wanted prod
33
Q

heterolytic fission

A

The bond breaks unevenly with one of the bonded atoms recieving both electons from the bonded pair.

produce Two ions, one + and one -

34
Q

electrophile

A
  • electron pair acceptors = H+

- are e- deficient so attack to e- rich areas c=c and this bond polaries H-Br bond more.

35
Q

Alkenes

A

Unsaturated hydrocarbons contain C=C.
Due sigma bond and pi bond (overlap sideways/axially)
not holding e- tight so more reactive then alkanes

ADDITION REACTIONS MAKE Them stable saturaed product.

TEST FOR ALKENES:
- Causes Bromine water to decolourises as C=C as broken and open and become saturated.

36
Q

ELECTROPHILIC ADDITION

A
  1. Alkene + H2 —> Alkane
    COND: nickel catalyst, 150’C
    - manufacture margarine from unsat veg oil.
  2. Alkene + X2 —> DIHALOGENOALKANE
    COND: rtp, bubble gas thro at rt
  3. Alkene + HX —-> Halogenoalkane
    COND: rtp, bubble gas thro at rt

HETERLOYTIC FISSION arrow from c=c to bond and X is S-

CARBOCATION FORMED - 3. carbocat is more stable (less energy to make it) than 1.
Alkyl gps push electrons away to other C atom and become slightly positive making + stable so spreads charge out more and more from 1, 2, 3

  • major prod formed from more stable cation attached to C with more H atoms in unsymmetrical alkene
  1. Alkene + H20 (steam) —> Alcohol
    COND: concen H3PO4, 300’C, HIGH PRESS
    HIGH YIELD - ONLY PROD FORMED.

a5. Alkene + KMnO4 ​[O] + H20 —> DIOL
COND: H2SO4 and reagant - KMnO4
purple –> colourless

37
Q

Halogenoalkanes

A

contain polar bond C S+ - H S-

Down Gp 7, electronegativities decrease of halogens this decreases bond polarity so bond length increases and bond strength derease. So C+ attracts more nucleophiles.

Greater the Mr of X in polar bond, lower bond enthalpy = broken easily and ROR is faster.

Nucleophile - Species that donate a lone pair of electrons to form a covalent bond with an electron-deficient atom. CN:- NH3: - OH: -

38
Q

Nucleophilic substitution

A
  1. Halogenoalkane + alkali(aq) —> alcohols
    : OH- is nucleophile
  2. Alcohol + + Halogen —> haloalkane

CHLORINATION:

  • PCl5 + alcohol = chloroalkane + POCl3 + HCl
  • white misty fumes and turns damp blue litmus red
  • for tertiary alcohol need to be mixed with HCl.

BROMINATION:
- KBr & 50% of concen H2SO4 and alcohol warmed
KBr + H2SO4 -> K2SO4 + 2HBr mixed with OH to produce bromoalkane

IODINATION:
 Red phosphorus
• Iodine
• REFLUX
iodoalkane and H3PO3 acid produced.
  1. Halogenoalkane + KCN = RCN + KX
    - KCN in ethanolic col. gd co - solvent
    - heat under reflux
    aldhelydes recat with KCN does not react immediately must be acidified to increase polarity.
  2. Haloalkane + NH3 = AMINE ( RNH2) + NH4X
    - gas sealed in tube
    - form primary amine.
39
Q

Practical: Rates of Hydrolysis

A

• This is nucleophilic substitution
• Water acts as the nucleophile
ALL DEPENDS ON BOND ENTHALPY - incr in Mr means the decr in bond strength - low bond enthalpy incr rate of hydrolysis

  1. Set up 3 Test tubes for each haloalkane each containing 1cm^3 of ethanol and 2 drops of haloalkane
  2. Place the test tubes in a water bath (60 C) along with a test tube of 0.1 moldm silver nitrates (let it reach a constant temperature)
  3. Quickly add 1cm^3 of silver nitrate to each tube
  4. Record the time taken for a precipitate to form.

rate of precip. forms shows stable of RX.
faster precip - less stable RX, more quickly hydrolysed.
C-I weakest. 3. react more rapidly.

40
Q

ELMINATION

A
  1. RX + KOH = ALKENE + H2O+ KBR
    :OH - ACTS AS BASE NOT NUCLEOPHILE.
    in ethanolic acid.
  2. Dehydration of alcohol = alkene + h20
    - h2so4
41
Q

ETHANOL PROD

biofuel - no net movement of CO2 during process of combustion

A
  1. Fermentation
    - starch broken down by enzymes in yeast - low temp 35’c and air kept out as anerobic resp
    and CO2 prd
    - slow react. as high can denature enzyme.
    - air kept out as oxid of ethanol can form ethanolic acid - vinegar
    - ditilled by fractional distill at 78’C AND INCONTINUOUS
  2. Hydration of alkene to ethanol
    - high % yield only one prod and contiuous
    - cracking and hydration.

SOLUBILITY OF ALCHOL:
- meth, eth and prop due to as alkyl chain increase solubility decrase and -OH bong forms H bonds.

42
Q

Why tertiary alcohol not oxidised?

A

because the carbon atom that carries the OH group does not have a hydrogen atom attached but is instead bonded to other carbon atoms. k

43
Q

advantages and disadvantages of simple distillation?

A

Maximum yield is obtained.

More time consuming due to due to the low pressure of rising steam.

44
Q

advantages and disadvantages of fractional distillation?

A

High Efficiency.
Easy to Use.
Expensive

45
Q

alcohols - CnH2n+1OH

Properties

A

saturated/ polar/ OH is functional gp is the characteristic part of alcohol molec.
1’ / 2’ / 3’ OH => has a functional gp attached to the C atom with no more than 1 alkyl gp
- bp incr in alchol as chain length incr due to more SA contacts - the stronger the induced dipole-dipole intermolecular forced and more energy required to overcome them = HIGHER THAN ALKANES due H bonding strongest and additional intermolecular force
- Volatility incr as bp decr - evaporation of the alcohol incr as chain length decr
- water molec are polar means methanol, ethanol and propanol are soluble in water. as alkyl chain incr the solubility decr and becomes immiscible

46
Q

ESTERIFICATION

A
  1. carboxylic acid + alcohol = ester + water
    - seperation needs to happen quickly as to prevent reversible reaction occurring
  2. acid anhydride + alcohol
47
Q

oxidation of 1’ OH

A

gentle heat to 1’ and acidified K2Cr2O7 . H2SO4 and partially oxidises to aldehydes and has to be distilled immediately to prevent further oxidation
orange to bottle green
further oxidation is under REFLUX cond - it is the constant heating/ boiling/ condensing of the reaction mixt ensures the reaction goes to completion as fully as possible fully as possible - condenser vertically used

48
Q

oxid of 3’ OH

A

heat under reflux and ketone produced

Edexcel Chemistry A LEVEL - RM (12 decks)

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