10/20 Organic Chemistry (copy)

Chemistry - HL

10.1 Define homologous series.

• A homologous series is a series of compounds of the same family, with the • same general formula, which differ from each other by a common structural unit.

10.1 Define structural isomers.

Structural isomers are compounds with the same molecular formula but different arrangements of atoms.

10.1 List the corresponding stem to 1 to 6 \# of C atom in longest chain in naming organic compounds.

1: meth-
2: eth-
3: prop-
4. but-
5. pent-
6. hex-

10.1 List out the general formulas for:
Alkanes
Alkenes
Alkynes
Alchohols
Carboxylic
Acid

Alkanes:C(n) H(2n+2)
Alkenes:C(n) H(2n)
Alkynes: C(n) H(2n-2)
Alchohols: C(n) H(2n+ 1)OH
Carboxylic Acid: C(n) H(2n+ 1)COOH

10.1 List common features of compounds in the same homologous series/

-a group of similar compounds
-have similar chemical properties
-have a gradation/progression of physical properties
-have the same general formula

10.2 State the reaction these compounds undergo:
Alkanes (also state reactivity)
Alkenes (also state reactivity)
Alcohols
Halogenoalkanes
Polymers
Benzene

Alkanes:
• Alkanes have low reactivity and undergo free-radical substitution reactions.
*also undergoes combustion (both complete and incomplete)

Alkenes:
• Alkenes are more reactive than alkanes and undergo addition reactions.
*also undergoes combustion

Alcohols:
• Alcohols undergo nucleophilic substitution reactions with acids (also called esterification or condensation) and some undergo oxidation reactions.

Halogenoalkanes:
• Halogenoalkanes are more reactive than alkanes. They can undergo (nucleophilic) substitution reactions.

Polymers:
• Addition polymers consist of a wide range of monomers and form the basis of the plastics industry.

Benzene:
• Benzene does not readily undergo addition reactions but does undergo electrophilic substitution reactions.

10.2 Define nucleophile.

A nucleophile is an electron-rich species containing a lone pair that it donates to an electron-deficient carbon.

10.2 Explain the reactivity of alkanes.

-alkanes are relatively unreactive
-short/strong single bonds that are difficult to break
-only slightly polar bonds, so do all strong attract reagents

10.1 Explain the trends in boiling points of members of a homologous series.

10.2 Writing equations for the complete and incomplete combustion of propane.

complete combustion:
-reactant: oxygen
-product: CO2 + H2O

incomplete combustion:
-reactant: oxygen
-product: CO2 + H2O + C(s) + CO(g)

*all alkanes combust

Complete combustion:
C3H8 + 5O2 -\> 3CO2 + 4H2O

Incomplete combustion:
C3H8 + O2 -\> CO2 + CO + C + H2O
**incomplete combustion also makes CO(g) and C(s)
**dont need to balance incomplete combustions

-all real combustion is incomplete
-some fuels help facilitate complete combustion by producing oxygen

10.2 Writing equations for the complete combustion of methanol.

complete combustion:
-reactant: oxygen
-product: CO2 + H2O

2CH3OH + 3O2 -\> 2CO2 + 4H2O

10.2 State the type of reaction for FRCR, and its requirements.

-substitution reaction
-requires UV light or heat to occur

**produces a hydrogen halide and alkylhalide

10.1 Draw benzene, phenol, and benzoic acid.

.

10.2 Write out the free radical chain reaction mechanism for halogenation of an alkane with curly arrows.

Check notes.

10.2 Distinguish homolytic and heterolytic fission.

Homolytic fission:
-breaking a substance into 2 equal uncharged particles

Heterolytic fission:
-separation into unequal, charged particles.

10.2 List the type of reactions the following undergo and any requirements for them to occur:
alkenes
alkynes
hydrogenation of alkene
alkene + water
hydration
alcohol + carboxylic acid

alkenes and alkynes:
electrophilic addition reaction
-alkene/alkyne + hydrogen halid -\> \___alkane

hydrogenation of alkene to produce alkane:
-requires transition metal catalyst (e.g. Ni, Pt, Pd)
-heat

alkene + water: addition reaction to form alcohol
-requires phosphoric or strong acid catalyst
**concentrated H2SO4 is default for catalyst

hydration: electrophilic addition reaction
-requires concentrated acid (H2SO4 or H3PO4)
-requires catalyst

alcohol + carboxylic acid: esterification
-undergoes a condensation reaction
-product: ester
-naming: \___thl \_____noate
-requires concentrated H2SO4 catalyst
-requires heat under reflux

20.3 Define stereoisomers.

compounds with same structural formula but different arrangements of atoms in space;

20.3 State the instrument used to distinguish between each of the two enantiomers, and how they could be distinguished using this instrument.

polarimeter and (enantiomers) rotate plane of polarized light in (equal and) opposite directions;

20.3 State the structural features that give compounds the ability of having enantiomers.

chiral (carbon/centre/atom) / (tetrahedral) carbon surrounded by four different groups;
Accept chiral compound or chiral molecule.

20.3 Compare the physical and chemical properties of enantiomers.

Physical properties:
identical except for rotation of plane polarized light;
Accept "identical" as different optical properties assessed in (iii).
Do not accept similar.

Chemical properties:
identical unless they interact with other optically active/chiral compounds/reagents/solvents / identical with achiral compounds/reagents/solvents / OWTTE;
Allow different physiological effects/taste.

20.3 Explain why 1-chloro-but-2-ene shows geometrical isomerism.

no rotation possible due to double bond/pi bond;

10.1 State and explain the trend of the boiling points of the first five members of the alkene homologous series.

boiling points increase (from the first member to the fifth member);
increasing size of molecule/area of contact/number of electrons (from the first to the fifth member);
strength of intermolecular/van der Waals'/London/dispersion forces increase / more energy required to break the intermolecular bonds (from first member to fifth member);

10.1 Describe two features of a homologous series.

same general formula;
successive members differ by CH2;
same functional group / similar/same chemical properties;
gradual change in physical properties;
Accept specific physical property such as melting point, boiling point only once.

10.1 Describe a chemical test that could be used to distinguish between pent-1-ene and pentane.

add bromine water/bromine;
pentane no change/stays brown and pent-1-ene decolourizes bromine water/bromine;
OR
add acidified KMnO4KMnO4;
pentane no change/stays purple and pent-1-ene decolourizes acidified KMnO4KMnO4;
Accept any correct colour change.
Do not accept 'clear' instead of 'colourless'.

10.2 Ethyne, like ethene, undergoes hydrogenation to form ethane. State the conditions required.

nickel/Ni «catalyst»

high pressure
OR
heat

Accept these other catalysts: Pt, Pd, Ir, Rh, Co, Ti.
Accept "high temperature" or a stated temperature such as "150 °C".
\[2 marks]

10.2 State the characteristic reaction mechanism of benzene.

electrophilic substitution
OR
SE
\[1 mark]

10.2 Explain why but-2-ene is more volatile than C4H9OH

hydrogen bonding in compound C;
dipole-dipole forces in C / C is more polar;
C has greater molar mass/more dispersion/London/instantaneous induced dipole-induced dipole forces/van der Waal forces;
Accept converse argument.
Award [1 max] for stronger intermolecular forces.

10.2 Explain how the reaction of benzene with bromine provides chemical evidence that benzene does not contain three double bonds.

substitution rather than addition occurs / OWTTE;

10.2 Draw the listed functional groups:
-carbonyl
-hydroxyl
-carboxyl
-ester
-amide
-nitrile
-ethers

Check notes!

10.2 Draw the smallest ketone and the smallest aldehyde.

Check notes!

10.2 Describe the apparatus needed for esterification.

-requires heat under reflux: the mixture is heated but the vapours are returned to the solution to continue reacting

-bunsen burner to heat the solution
-put stopper on tube with a tall glass tube attached
-tall glass tube allows water to cool and condense back down (just high enough to water does not evaporate and escape)

-or can cover with aluminum foil (so that its not airtight)

20.3 Define enantiomers.

a pair of molecules that are non- superimposable mirror images.

20.3 Define racemix mixture.

a mixture that contains a 50:50 ratio of both enantiomers of a chiral molecule

20.3 Enantiomers are \_________________ \___________________.

Enantiomers are optically active.

20.3 List the characteristics of molecules that contain optical isomerism.

-chiral/asymmetric
-2 stereoisomers that are mirror images of each other (enantiomers)
-there are 2^n optical isomers for an organic molecule with n chiral centres

20.3 Compare the physical and chemical characteristics of 2 enantiomers.

-identical chemical properties (apart from reaction with other chiral molecules)
-same physical properties (apart from their interaction with plane polarised light)

20.3 List features of diastereoisomers.

-do not have opposite configurations at all of the chiral centres.
-no mirror images
-molecules that have more than one centre
**some diastereomers are optically active, some are not

20.3 Explain the Markovnikikov's rule.

-the more positive part of the reagent adds to the carbon with more hydrogens
-the carbon with more hydrogens will get even more hydrogens

-this is because the tertiary halogenoalkane is more stable
-therefore more likely to exist

20.3 Define, and list the characteristics of electrophiles and nucleophiles.

electrophiles: a substance that is attracted towards electrons
-electron deficient
-have a + charge or partially + charge
-acts as Lewis acids

nucleophiles: a substance that is attracted towards protons
-electron rich
-have negative or partial negative charge
-acts as Lewis base

20.3 List the stability of primary, secondary, and tertiary carbocation from the most stable to the least stable.

tertiary \> secondary \> primary
-tertiary carbocation is most likely to form and exist
-because the induced dipole of the alkyl groups reduces the charge of the carbocation

20.3 Outline the conditions required for a nucleophilic substitution to occur.

1) nucleophile: nucleus seeking
-have negative or partial negative charge
-have electron pair donors (lone pairs)
-Lewis base

2) Leaving group
-needs to be less electronegative than the nucleophile
-often has a larger atomic radius, so less electronegativity

2) Organic molecule (substrate)

20.3 Explain what determines the strength of nucleophiles.

The strength of nucleophile is defined by how quickly it reacts:
-strong nucleophiles \= faster reactions
-negative ions are stronger nucleophiles than neutral molecules
e.g. OH- is stronger than H2O
-larger atoms are stronger nucleophiles than smaller atoms (atomic radius)
e.g. Br- better than Cl-
-more electronegative atom \= weaker nucleophile
e.g. NH3 stronger than H2O

20.3 Sn2 mechanism is the \_____________ substitution reaction involving the \______________ rate law. It occurs fastest with \_____________ organic molecules, and slowest with \_____________ organic molecules. Sn2 is \_____________, meaning that any chiral molecule will maintain its optical activity.

-Sn2 mechanism is the nucleophilic substitution reaction
-involving the bimolecular rate law.
-occurs fastest with primary organic molecules, and slowest with tertiary organic molecules.
-Sn2 is stereospecific, meaning that any chiral molecule will maintain its optical activity.

20.3 Sn1 mechanism is the \_____________ substitution reaction involving the \______________ rate law. It occurs fastest with \_____________ organic molecules, and slowest with \_____________ organic molecules. Sn1 results in the \_____________ of optical activity, as the \___________ substance becomes a \_____________ \_______________.

-Sn1 mechanism is the nucleophilic substitution reaction
-involving the unimolecular rate law
-occurs fastest with tertiary organic molecules, and slowest with primary organic molecules.
-Sn1 results in the loss of optical activity, as the chiral substance becomes a racemic mixture.

20.3 Define protic solvents.

A protic solvent is a solvent that has a hydrogen atom bound to an oxygen, a nitrogen, or fluoride.

20.3 Compare where Sn1 and Sn2 mechanisms are favored.

Sn1:
-favored in polar, protic solvents

Sn2:
-favored in polar, aprotic solvents

10.1 2-chloro-2-methylbutane contains some molecules with a molar mass of approximately 106 gmol−1 and some with a molar mass of approximately 108 gmol−1. Explain the difference in molar mass.

chlorine can be 35Cl/Cl-35 or 37Cl/Cl-37;

Accept "chlorine can exist as two isotopes".

Answer must refer to chlorine rather than isotopes in general.

20.3 State the meaning of each of the symbols in SN2.

substitution and nucleophilic and bimolecular/two species in rate-determining step;
Allow second order in place of bimolecular.

20.3 State the type of bond fission that takes place in a SN1 reaction.

heterolytic/heterolysis

20.3 Suggest, giving a reason, the percentage of each isomer from the SN1 reaction.

around» 50% «each»
OR
similar/equal percentages

nucleophile can attack from either side «of the planar carbocation»

Accept "racemic mixture/racemate" for M1.
\[2 marks]

20.3 Draw three-dimensional representations of the two enantiomers.

.

20.3 Describe what happens to plane-polarized light when it passes through a solution of an optically active compound.

plane of polarization is rotated

Award zero if answer refers to plane-polarized light being bent.
\[1 mark]

20.3 A mixture of enantiomers shows optical rotation.
Suggest a conclusion you can draw from this data.

not a racemic mixture
OR
two enantiomers not equimolar
OR
mixture contains optically active impurity
OR
relative proportions of enantiomers in mixture can be determined
\[1 mark]

20.3 When one enantiomer undergoes substitution by alkaline hydrolysis approximately 75 % of the product molecules show inversion of configuration. Comment on the mechanisms that occur.

SN2 would give inversion of configuration «almost 100%»
OR
SN1 would give «approximately» 50% of each
so mechanism is a mixture of both mechanisms

20.3 Explain how the differentiation between the enantiomers is obtained using an apparatus.

polarimeter
Accept other alternative techniques such as "GC/HLPC/chromatography using a chiral column".Do not accept just "polarizer".

(ii)«plane-»polarized light passed through sample
analyzer/second polarizer determines the angle of rotation of the plane of polarized light
OR
each enantiomer will rotate plane «of plane-»polarized light in opposite directions «by the same angle»

Accept explanation related to other alternative techniques such as GC/ HLPC/chromatography using a chiral column.
Award [2] for "(+)/d rotates plane of polarization to the right AND (-)/l rotates plane of polarization to the left".

20.3 Outline how a polarimeter can distinguish between these isomers.

enantiomers rotate plane of (plane-) polarized light;
in opposite directions (by equal amounts);

20.3 State the conditions needed for a compound to show cis-trans.

restricted rotation around a (double) bond;
carbon atoms of the C\=C/carbon-carbon double bond (in alkene)/carbon atoms of the C-C/carbon-carbon single bond (in cycloalkane) must have two different atoms/groups of atoms / OWTTE;
Do not accept "functional groups" for "groups of atoms" in M2.

20.3 State what is meant by optical activity.

rotates the plane (of polarization) of plane polarized light;
Accept answers in which one of the "plane"s is missing.
c.i.

20.3 State what optical activity indicates about the structure of the molecule.

two isomers that are enantiomers/chiral/non-superimposable mirror images;

Accept "contains an asymmetric/chiral carbon" or "contains a carbon bonded to four different groups".
c.ii.

20.3 Optical activity can be detected using a polarimeter. Explain how this works.

polarizes light / polarized light source;
light passed through sample;
ANALYSER / SECOND polarizer detects whether plane of polarization rotated;

20.3 State and explain how the rates of the reactions in Sn1 and Sn2 are affected when the concentration of the sodium hydroxide is doubled.

Sn1:
no change as [OH−] does not appear in rate equation/in the rate determining step;

Sn2:
rate doubles as the rate is proportional to [OH−]/ OH- appears in the rate determining/
slow step / first order with respect to OH−OH−;

Award [1] if correctly predicts no rate change for SN1 and doubling of rate for SN2 of without suitable explanation.

20.3 Identify the isomer of C4H9Br that can exist as stereoisomers. Outline how a polarimeter will distinguish between the isomers, and how their physical and chemical properties compare.

2-bromobutane/B;
(plane-) polarized light shone through;
enantiomers rotate plane of plane-polarized light to left or right/opposite directions (by same amount);
Accept "turn" instead of "rotate" but not "bend/reflect".
physical properties identical (apart from effect on plane-polarized light);
chemical properties are identical (except with other chiral compounds);
Do not accept "similar" in place of "identical".

10.1 Compare the formation of sigma (σ) and pi (π) bonds between the carbon atoms in a molecule of ethyne.

σ bond:
end-on/axial overlap with electron density between the two carbon atoms/nuclei / end-on/axial overlap of orbitals so shared electrons are between atoms / OWTTE;
π bond:
sideways/parallel overlap of p orbitals with electron density above and below internuclear axis/σ bond / sideways/parallel overlap of p orbitals so shared electrons are above and below internuclear axis/σσ bond / OWTTE;
Marks can be scored from a suitable diagram.
Award [1 max] for stating end-on/axial overlap for σσ and sideways/parallel overlap for ππ only i.e. without mentioning electron density OR stating electron density between the two atoms/nuclei for σσ and above and below internuclear axis for ππ.

20.3 Define conformational isomers.

a form of stereoisomerism in which the isomers can be interconverted just by rotations about formally single bonds.

20.3 Explain the existence of geometrical isomerism in but-2-ene.

(but-2-ene exists as) cis-but-2-ene and trans-but-2-ene /
;
restricted rotation of C\=C/double bond;

20.3 Menthol occurs naturally and has several isomers. State the structural feature of menthol which is responsible for it having enantiomers.

chiral (carbon/centre/atom) / (tetrahedral) carbon surrounded by four
different groups;
Accept chiral compound or chiral molecule.

20.3 Suggest why, for some other halogenoalkanes, hydrolysis with NaOH is much more effective in alkaline rather than in neutral conditions.

hydroxide ion/OH− is a better nucleophile than water / hydroxide ion/OH− has negative charge;
undergo SN2 hydrolysis / RDS depends on attack of OH−/hydroxide ion (nucleophile);
Accept other suggestions that are chemically valid.

10.1 Discuss physical and chemical evidences, which suggest this is not the structure (C\=C and C-C bond) of benzene.

Physical evidence:
planar «X-ray»
equal C-C bond «lengths/strengths»
OR
regular hexagon
OR
«all» C-C have bond order of 1.5
OR
«all» C-C intermediate between single and double bonds

Chemical evidence:
undergoes substitution reaction «more readily than addition»
OR
does not discolour/react with bromine water
OR
substitution forms only one isomer for 1,2-disubstitution «presence of alternate double bonds would form two isomers»
OR
more stable than expected «compared to hypothetical molecule cyclohexa-1,3,5-triene»
OR
enthalpy change of hydrogenation/combustion is less exothermic than predicted «for cyclohexa-1,3,5-triene»

M1:
Accept "all C-C-C bond angles are equal".

10.1 Describe two differences, other than the number of atoms, between the models of ethane and ethene constructed from the kit shown.

Any two of:
Ethene: «carbon-carbon» double bond AND Ethane: «carbon-carbon» single bond
ethene has a shorter carbon-carbon bond «than ethane»

Ethene: planar/two-dimensional/2-D AND Ethane: tetrahedral «carbons»/three-dimensional/3-D
OR
Ethene: each carbon surrounded by three electron domains AND Ethane: each carbon surrounded by four electron domains
OR
different molecular geometries/shapes

rotation about carbon-carbon inhibited/blocked in ethene AND not in ethane

«H-C-C/H-C-H» bond angles different
OR
Ethene: «bond angles approximately» 120° AND Ethane: 109.5/109°

Do not accept "different number of atoms/hydrogens/bonds" etc.
Accept "Ethene: unsaturated AND Ethane: saturated" OR "Ethene: has a double bond AND Ethane: does not" OR "Ethene: two flexible bonds between carbon atoms AND Ethane: one".
Accept any reasonable physical description of the two different molecular models based on a variety of kits for M1.
For ethene, accept any bond angle in the range 117-122°.
Award [2] if any two of the concepts listed are shown in a correctly labelled or annotated diagram.
Award [1 max] for two correct statements for either molecule but with no comparison given to the other.
Award [1 max] for suitable unlabeled diagrams of both compounds.

10.1 Pyridine, like benzene, is an aromatic compound.
Outline what is meant by an aromatic compound.

bonds within ring have resonance
OR
contains delocalized «conjugated pi» electrons in ring

There must be reference to a ring or cyclic structure.
Accept "alternating single and double bonds in a ring".
Accept "ring which shows resonance/delocalization".
Accept "follows Hückel/4n +2 rule".
Do not accept "contains one or more benzene rings".
\[1 mark]

10.1 C5H12 exists as three isomers. Identify the structure of the isomer with the lowest boiling point and explain your choice.

C(CH3)4
Accept correct name 2,2-dimethylpropane.
Do not penalize missing H atoms.
weakest London/dispersion/van der Waals'/vdW/instantaneous induced dipole induced dipole forces because of smallest surface area/contact
OR
weakest London/dispersion/van der Waals'/vdW/ instantaneous induced dipole induced dipole forces because of least distortion of the electron cloud
OR
weakest London/dispersion/van der Waals'/vdW/ instantaneous induced dipole induced dipole forces because polarizability of electrons (in electron cloud) is less;
Accept other words to that effect but student must mention a correct IMF and a correct reason.

10.1 2,3 dimethyl butane + Br2 -\> 1-bromo 2,3 dimethyl butane + HBr
Outline why it would give a poor yield of the desired product.

random/further/multiple substitution (so low probability of desired product) / would give a mixture of many different products / OWTTE;

10.1 Describe, using an equation, how C4H9Br can be converted into C4H8Br2.

C4H9Br+Br2→C4H8Br2+HBr

10.1 Draw the ester functional group.

.

10.1 State the equation for the reaction of propanoic acid with water.

CH3CH2COOH+H2O⇌CH3CH2COO−+H3O+
CH3CH2COOH⇌CH3CH2COOH−+H+

⇌ required for mark.

10.1 State the meaning of the term isomers.

compounds with the same molecular formula but different arrangements of atoms / compounds with the same molecular formula but different structural formulas;

10.1 Explain why alkanes have low reactivity.

relatively strong bonds/high bond enthalpies so large amounts of energy must be provided for a reaction to occur;
non-polar bonds so not susceptible to attack / no C\=C so no addition reactions;

10.1 Outline the meaning of the term homolytic fission.

bond breaks and one electron (from the covalent bond) goes to each atom / OWTTE;

10.1 Outline two reasons why the polymers of the alkenes are of economic importance.

synthesis of materials not naturally available/plastics;
chemically unreactive materials produced;
wide range of uses/physical properties / versatile;
cheap;
large industry;
uses a limited natural resource;
Award [2] for any two.

10.1 Explain why monomers are often gases or volatile liquids, but polymers are solids.

monomers are smaller molecules / have smaller surface area than polymers;
Accept monomers have lower molecular mass.
with weaker intermolecular/Van der Waals'/London/dispersion forces;
Accept opposite argument for polymers.

20.3 Describe geometrical isomerism.

compounds with the same (molecular formula and) structural formula but different arrangements of atoms in space / OWTTE;

20.3 Describe the composition of a racemic mixture.

equimolar/50:50 mixture (of a pair) of enantiomers/both isomers;

10.2 Outline why the polymerization of alkenes is of economic importance and why the disposal of plastics is a problem.

plastics are cheap/versatile/a large industry / plastics have many uses / OWTTE;
plastics are not biodegradeable / plastics take up large amounts of space in landfill / pollution caused by burning of plastics / OWTTE;
Do not accept plastics cause litter.
Allow plastics don't decompose quickly / OWTTE.

20.2 Explain why the hydroxide ion is a better nucleophile than water.

OH- has a negative charge/higher electron density;
greater attraction to the carbon atom (with the partial positive charge) / OWTTE;
Do not allow just greater attraction.

20.1 Suggest how butan-1-ol could be synthesized in one step from butanoic acid.

«reduction with» lithium aluminium hydride/LiAlH4

20.1 State the reagents used in the nitration of benzene.

concentrated HNO3 AND concentrated H2SO4
"concentrated" must occur at least once (with either acid).

20.1 State an equation for the formation of NO2+.

HNO3 + 2H2SO4 ⇌ H3O+ + NO2+ + 2HSO4-

Accept: HNO3 + 2H2SO4 ⇌ NO2+ + HSO4- + H2O.
Accept: HNO3 + 2H2SO4 ⇌ H2NO3+ + HSO4-.
Accept single arrow instead of equilibrium sign.
Accept equivalent two step reactions in which sulfuric acid first behaves as strong acid and protonates nitric acid, before behaving as dehydrating agent removing water from it.

20.1 When the product CH2Cl is reacted with NaOH in a hot alcoholic solution, C2H3Cl is formed. State the role of the reactant NaOH other than as a nucleophile.

base
OR
proton acceptor

20.1 When one enantiomer undergoes substitution by alkaline hydrolysis approximately 75 % of the product molecules show inversion of configuration. Comment on the mechanisms that occur.

SN2 would give inversion of configuration «almost 100%»
OR
SN1 would give «approximately» 50% of each

so mechanism is a mixture of both mechanisms

20.1 (ii) Phenylamine, C6H5NH2, is produced by the reduction of nitrobenzene, C6H5NO2. Suggest how this conversion can be carried out.

«heat with» tin/Sn AND hydrochloric acid/HClaqueous alkali/OH-(aq)

10.2 Ethanol is a primary alcohol that can be oxidized by acidified potassium dichromate(VI). Distinguish between the reaction conditions needed to produce ethanal and ethanoic acid.

Ethanal: distill off product as it forms;
Accept distillation.
Ethanoic acid: (heat under) reflux / use excess oxidizing agent;

10.2 Deduce the half-equation for the oxidation of ethanol to ethanal.

CH3CH2OH→CH3CHO+2H+ +2e−

Half-equation required. Do not accept C2H5OH+2[O]→CH3CHO+H2O
Accept e for e−e−.

10.2 Deduce the overall redox equation for the reaction of ethanol to ethanal with acidified potassium dichromate(VI).

3CH3CH2OH(aq)+Cr2O2−7(aq)+8H+(aq)→2Cr3+(aq)+3CH3CHO(l)+7H2O(l)

correct reactants and products;
correct balancing;
M2 can only be scored if M1 correct.
Ignore state symbols.

10.2 (i) Outline two reasons why the polymerization of alkenes is of economic importance.

(i) (synthesis of) plastics/polymers/organic materials not naturally available / synthetic materials;
wide range of uses/physical properties / versatile;
large industry / many tons of plastics consumed by society / OWTTE;
Do not accept "useful" for M2.
Award [1 max] if specific addition polymer and its use is given.
Penalize reference to condensation polymers once only.

20.3 The reaction of propene with water can yield two possible products. Explain, in terms of the stability of the intermediate carbocations, why one is formed in much greater quantities than the other.

one product involves a primary carbocation and other a secondary carbocation;
secondary carbocation is more stable (than the primary carbocation, and hence this produces the major product);
alkyl groups reduce charge on carbon atom (through an inductive effect);
Positive inductive effect of alkyl groups alone not enough for M3.

10.1 Explain why 2-methylbut-2-ene is less soluble in water than 2-methylbutan-2-ol.

2-methylbutan-2-ol has hydroxyl/OH group;
Do not accept "hydroxide group".
Allow 2-methylbutan-2-ol is an alcohol.

20.3 Alkenes can undergo electrophilic addition reactions with bromine and with hydrogen bromide.
Explain how a bromine molecule is able to act as an electrophile.

as the bromine approaches the alkene an induced dipole is formed / OWTTE;

10.1 Explain why 1-bromopentane reacts by an SN2 mechanism whereas 2-bromo-2-methylbutane reacts by an SN1 mechanism.

the C bonded to the Br in 1-bromopentane is also bonded to two H atoms so can accommodate five groups around it in the transition state / OWTTE;
the C bonded to the Br in 2-bromo-2-methylbutane has three other (bulky) groups bonded to it so cannot accommodate five groups around it in the transition state / OWTTE;
2-bromo-2-methylbutane forms a tertiary carbocation which is stabilized by the positive inductive effect of the three alkyl groups / OWTTE;
1-bromopentane would form a primary carbocation (if it went by SN2SN2) which is much less stable as there is only one alkyl group exerting a positive inductive effect / OWTTE;

10.1 State and explain which of propan-1-ol, CH3CH2CH2OH, and methoxyethane, CH3OCH2CH3, is more volatile.

methoxyethane/ CH3OCH2CH3 as there are only dipole-dipole forces (and van der Waals' forces) between molecules;
propan-1-ol has hydrogen bonding between molecules;
hydrogen bonding is stronger than dipole-dipole forces;

10.1 Propan-1-ol, CH3CH2CH2OH, and hexan-l-ol, CH3(CH2)4CH2OH, are both alcohols. State and explain which compound is more soluble in water.

propan-1-ol/ CH3CH2CH2OH as it has a smaller hydrocarbon chain;
the longer (non-polar) carbon chain in hexan-1-ol decreases the attraction between the alcohol and the (polar) water molecules / OWTTE;