organic paper 1 Flashcards
explain why there is an attraction between c=c double bond and br2
M1 C=C electron rich / area of high electron density
M2 Br-Br becomes polarised
M3 δ+ Br attracted to C=C
problem of distillation
Anti-bumping granules
1a no anti-bumping granules / add anti-bumping
granules
1b to create smaller bubbles / to prevent large
bubbles / to prevent mixture jumping into
condenser
Stage 2
Open system with no thermometer
2a system should be closed (above flask) to
prevent gases escaping
2b should be closed with (bung +) thermometer
2c to allow collection of propanone (only) / to
prevent distillation of other components / to
stay in suitable temperature range
Stage 3
The water direction in the condenser
3a water flows in wrong direction through
condenser / change water direction
3b condenser not cool enough / not full of water
3c product may not condense / comes through as
gas
explain why propanone has a lower bp than propan2ol
M1 propan-2-ol has stronger intermolecular forces
M2 propan-2-ol has hydrogen bonds between molecules
M3 propanone has dipole-dipole forces and/or van der
Waals’ forces
state the benefit to life on earth of ozone in the upper atmosphere
Absorbs (harmful) ultraviolet / uv (light / radiation)
suggest one reason why use of fcfs were not restricted for several years
- lack of evidence that ozone was being depleted
- lack of alternatives to CFCs
- commercial interest to continue to use CFCs
- hard to obtain international agreement
state and explain how cdc-11 is able to contribute to global warming
M1 absorbs infrared radiation
M2 molecule has polar bonds
naphtha to propene
M3 (thermal) cracking
M4 to make alkenes / propene / shorter molecules
crude oil to naphtha
M1 fractional distillation
M2 separated into mixtures of compounds with similar boiling
points / similar sized molecules
propene to polypropylene
M5 (addition) polymerisation
M6 molecules joined together or to produce long chain molecule
why poly(propene) is unreactive
no polar bonds (in chain) / non-polar
suggest why it’d benenfiial for some polymers to be biodegradable
to prevent build-up of waste (in landfill) OR
they can be broken down by natural processes
define the term enthalpy change
Heat (energy) change at constant pressure
explain why the value given for the o=o bond enthalpy is not a mean value
Oxygen / O2 is the only substance that has O=O bond
A student has samples of these four compounds but does not know which is which:
* butanoic acid
* 2-methylpropanal
* 2-methylpropanoic acid
* 2-methylpropan-1-ol
Step 1: Two of these compounds can be identified by simple chemical tests.
Step 2: The other two compounds, that contain the same functional group as each
other, can then be distinguished using a spectroscopic technique.
Describe how these two steps could be used to identify which compound is which.
Stage 1
Identifying aldehyde / 2-methylpropanal
1a Tollens’ or Fehling’s
1b silver mirror or orange-red precipitate
Stage 2
Identifying alcohol / 2-methylpropan-1-ol
2a acidified potassium dichromate
2b (orange to) green
2c tests done in suitable sequence to distinguish
aldehyde from alcohol,
Stage 3
Distinguishing the acids
3a using IR spectroscopy to distinguish the two
acids (or other suitable technique)
3b use finger-print region of IR spectrum (feature
of spectrum to use)
3c look for exact match to spectra of known
compounds (what the difference is)
Analysis of the products of this reaction shows the formation of a compound with the
empirical formula CCl2F
Give an equation to represent a termination step forming this compound.
Show the structural formula of the product in the equation.
*CCl2F → CCl2FCCl2F
The ethanol produced by fermentation of glucose may be regarded as a
carbon-neutral fuel.
Justify this statement. Include the relevant chemical equations in your answer.
M1 6CO2 + 6H2O → C6H12O6 + 6O2
M2 C6H12O6 → 2C2H5OH + 2CO2
M3 2C2H5OH + 6O2 → 4CO2 + 6H2O
M4 explains with reference to relevant equations that formation of
C6H12O6 takes in 6CO2 and fermentation and combustion of
ethanol gives out 6CO2
Coffee beans from South America are exported to Europe in an outer layer called
silverskin.
The waste silverskin can be fermented to produce a solution containing propanone,
ethanol and butan-1-ol
Suggest why ethanol produced in Europe using silverskin from South America is less
likely to be carbon-neutral than ethanol produced from crops grown in Europe
transport (from South America to Europe) produces CO2 /
has C emissions / has larger C footprint
There is a very low yield of butan-1-ol from but-1-ene in this manufacturing process.
Explain why
M1 formed from/on/via less stable carbocation
M2 (formed from) primary rather than secondary carbocation
A data book value for the enthalpy of combustion of cyclohexane is –3920 kJ mol−1
The student concluded that the temperature rise recorded in the experiment
was smaller than it should have been.
Suggest a practical reason for this
thermal energy / heat loss or
incomplete combustion or
evaporation
Give an equation for the complete combustion of octane
C8H18 + 12.5 O2 → 8 CO2 + 9 H2O
Give an equation for a reaction that removes nitrogen monoxide in
a catalytic converter.
2 NO + 2 CO → N2 + 2 CO2
The bond angle around the oxygen atom in methanol is slightly smaller than the
regular tetrahedral angle of 109.5°
Explain why this bond angle is smaller than 109.5°
Idea that lone pairs have greater repulsion than bonding pairs
Describe how to prepare 250 cm3 of an aqueous standard solution of
propanedioic acid containing an accurately measured mass of the acid.
Include essential practical details in your answer.
M1 weigh out sample in bottle / boat / container
M2 transfer to (conical) flask / beaker (or suitable container) and
wash all sample in or re-weigh bottle / boat / container or re
weigh bottle / boat / container
M3 dissolve sample in (deionised / distilled ) water (if volume of
water is specified, must be less than 250 cm3)
M4 add into volumetric flask with washings
M5 make up to mark / 250 cm3 in volumetric flask
M6 shake / invert (this should be to give a homogenous solution
rather than to dissolve
Give an equation to show the breakdown of one molecule of
1,2-dichlorotetrafluoroethane to form one chlorine radical and one other species.
CF2ClCF2Cl → *CF2CF2Cl + *Cl
Give two equations to show how chlorine radicals catalyse the decomposition of
ozone
M1 Cl* + O3 ⟶ ClO* + O2
M2 ClO* + O3 ⟶ Cl* + 2 O2
Why ultraviolet light is needed
provides energy to break (covalent) bond in chlorine / Cl2 or
to form chlorine free radicals
Suggest why the student chose not to carry out experiments at temperatures in the experiment
reaction would take too long / too slow / take a long time / very slow
mportance of percentage yield
idea of getting as much product as possible in the reaction /
idea of efficient conversion of reactants to products
Importance of percentage atom economy
idea of maximising the mass of reactants / atoms that ends up
in desired product or
idea of minimising the amount of by-products
Explain why pentan-2-ol has a higher boiling point than pent-1-ene.
M1 idea that pentan-2-ol has stronger intermolecular forces
M2 pent-1-ene has van der Waals’ forces (only)
M3 pentan-2-ol (also) has hydrogen bonds
Explain the differences between structural isomerism and stereoisomerism. Use examples to show how compounds with the molecular formula C4H8 exhibit
stereoisomerism and the three types of structural isomerism.
1a structural isomers = molecules with same
molecular formula but different structure
1b stereoisomers = molecules with same
structural formula but different
arrangement of atoms in space
2a lack of rotation around C=C
2b structures of E- and Z-but-2-ene
2c correct identity of E and Z isomers
3a different C chain, e.g. methylpropene &
but-1-ene / but-2-ene
3b different position of functional group e.g.
but-1-ene & but-2-ene
3c different functional group, e.g.
cyclobutane & but-1-ene / but-2-ene /
methylpropene
State what you would observe if bromine water was added to poly(chloroethene).
poly(chloroethene).
[3 marks]
Explain this observation.
M1 no reaction / yellow-orange
M2 polymer is saturated / does not contain double bond(s)
Ethanedioic acid is formed by the oxidation of ethane-1,2-diol (HOCH2CH2OH).
State suitable reagent(s) and a condition for this reaction.
M1 acidified potassium dichromate(VI) or
sulfuric acid & potassium dichromate(VI)
M2 reflux
Explain why nonane has a higher boiling point than 2,4-dimethylheptane.
M1 nonane has stronger / greater / more van der Waals’
forces between molecules
M2 nonane molecules pack closer together / more (surface)
contact
Four compounds, all colourless liquids, are
* butan-2-ol
* butanal
* butanone
* 2-methylpropan-2-ol
Two of these compounds can be identified using different test-tube reactions.
Describe these two test-tube reactions by giving reagents and observations in each
case.
Suggest how the results of a spectroscopic technique could be used to distinguish
between the other two compounds
Tollens’ reagent [or Fehling’s / Benedict’s]
Identifies butanal – silver mirror (or black ppt) [or orange/brick/red
ppt with Fehling’s]
(No reaction with other compounds)
Acidified potassium dichromate
Reacts with butanal and butan-2-ol – goes green
(No reaction with other compounds)
Sodium (not on specification but may be mentioned)
Reacts with butan-2-ol and 2-methylpropan-2-ol – fizzes
(No reaction with other compounds)
IR (infra-red) spectroscopy
If different functional groups: need to identify wavenumber and
bond of key functional group signal (e.g. (alcohol) O-H 3230-3550
or C=O 1680-1750 (cm–1)).
If same functional group, need idea of using fingerprint region to
look for match to known compounds / comparing region to
samples in a database
Mass spectrometry
If different, can use different Mr values with values of Mr given
butanone 72(.0), 2-methylpropan-2-ol = 74(.0), butan-2-ol = 74(.0),
butanal = 72(.0)
