Organic 2026 Paper 2

define overall order

all the powers added together

explain why an enzymes catalyst the hydrolysis of enantiomer G and not F /2

enzyme active site is stereospecific, and is complementary to enantiomer G only

suggest a simple way to detect if ethanoic acid has reacted with alcohols, and suggest why conc. H2SO4 and NaHCO3 are added

• detection - esters are sweet smelling

• conc. H2SO4 catalyst

• NaHCO3 to neutralise excess acid

State why mass spectrometry using electrospray ionisation is not a suitable method to distinguish between the isomers/ 1

same Mr

explain the purpose of adding a small amount of cold ethanol to pure aspirin after being filtered under reduced pressure /1

removes soluble impurities

describe a difference in appearance between crude aspirin and pure aspirin

pure is larger crystals, shinier

apart from safety, why is KCN used to form hydroxynitriles rather than HCN

KCN dissociates better, HCN too weak

calculating percentage yield when reactants to products 2:1

divide amount of reactant by 2

involving a hydrogen atom, state the type of bond formed to guanine from cisplatin, and identify an atom in guanine that could form this bond /2

• hydrogen bond

• oxygen, nitrogen

in a ligand substitution reaction where a guanine atom bonds to platinum by displacing the water molecule. state the type of bond formed, and identify an atom in guanine that could bond to platinum in this way

dative covalent

nitrogen/oxygen

state and explain one risk associated with the use of cisplatin /2

• killing healthy cells

• may attach to DNA in normal cells

explain how cytosine forms hydrogen bonds with guanine /3

• H of NH2 at top bonds to lone pair of O on G

• lone pair on N bonds to H of NH on guanine

• lone pair on O bonds to lower H of NH2 of guanine

describe how you could distinguish two stereoisomers /2

shine plan polarised light

rotated equally in opposite directions

why can an expression of equilibrium be written without water?

conc. virtually constant

useful properties of Si(CH3)4

inert

peak very upfield

volatile - easy to remove

why might D2O be used in NMR rather than CCl4, and why instead of water /2

• is polar, good solvent for amino acids

• no hydrogens

what does amino acids exist as when solid?

zwitterions

carboxylic acid + NaOH

COO^-Na⁺

outline why column chromatography is able to separate a mixture of compounds /3

• stationary phase is silica beads

• mobile phase is solvent

• separation based on solubility in solvent or affinity to stationary phase

write an equation for the fragmentation of the molecular ion of alanine to give an ion that produces the peak m/z = 44. draw the displayed formula

lysine has 2 NH2 groups whereas alanine has 1. in a polar stationary phase of column chromatography, explain why lysine leaves the column after alanine /2

lysine has double positive charge

greater affinity for stationary phase

why might it be important to where gloves when handling a TLC plate?

prevents contamination

outline the steps needed to locate the positions of the amino acids on the TLC plate and determine their Rf values /4

• spray with ninhydrin

• measure distance from initial pencil line to spots

• measure distance from initial pencil line to solvent front

• divide spot value by solvent front distance

suggest a suitable reagent for the hydrolysis of a protein

concentrated HCl

Suggest why it was necessary to use two different solvents to separate the amino acids /1

some did not separate in the first OR some amino acids has the same Rf with the first solvent

state one environmental disadvantage of producing hydrogen by electrolysis /1

CO2 produced, is a greenhouse gas

what is the problem caused by having water in and out the wrong way in a reflux condenser?

water does not fill condenser, condenser is not cool enough

when reacting ethyl ethanoate and ethanol to form an ester, suggest why two layers form in the separating funnel

ethyl ethanoate is insoluble

suggest why Na2CO3 is used when forming an ester

to neutralise excess acid catalyst

what is phenyl benzenecarboxylate

explain how carbon dioxide causes global warming

C=O bonds vibrate and absorb infrared radiation

IR emitted by earth does not escape

give the reagents and conditions for the base hydrolysis of an ester

NaOH, aqueous

conditions for nucleophilic sub to form a nitrile

KCN, ALCOHOLIC

name the type of compound shown by the formula RCOOK

carboxylate salt

Suggest why aqueous ethanol is a suitable solvent when heating coconut oil with KOH

dissolves both oil and KOH

state the reagent for dehydration

conc. H2SO4

suggest why chemists design production methods with fewer steps and a high percentage atom economy /2

• better yield

• less waste

why is it necessary to reweigh the weighing boat after tipping out the solid /1

in order to calculate the exact mass added to reaction mixture

compare benzene and the theoretical molecule cyclohexa-1,3,5-triene in terms of stability, shape, carbon-carbon bond lengths /5

• Benzene is more stable than cyclohexatriene

• The enthalpy of hydrogenation of benzene is (152 kJ mol-1) less/less exothermic

• Due to the delocalisation of electrons in benzene

• Both are planar/hexagonal

  • Benzene has equal C-C bond lengths or regular hexagon whereas Cyclohexa-1,3,5-triene has bonds of different/varied length or the hexagon is distorted/irregular

state a potential use of 3,4-dimethylphenylamine

to manufacture cationic surfactants

6[H] → 2H2O

what does an ethanoate group indicate?

COO

The enthalpy of hydrogenation of cyclohexa-1,3-diene is not exactly double that of cyclohexene.

Suggest a value for the enthalpy of hydrogenation of cyclohexa-1,3-diene and justify your value /3

(-239 to -121)

double bonds are alternating/separated by single bonds

allows some delocalisation of p orbitals

give reasons for each of these steps of recrystallisation:

• the minimum quantity of hot water was used

• the flask was left to cool before crystals were filtered off

• the crystals were compressed in the funnel

To ensure the hot solution would be saturated / crystals would form on cooling

Yield lower if warm / solubility higher if warm

Air passes through the sample not just round it

why is the lone pair on N of phenylamine less available?

it is delocalised into the ring

what makes a molecule show E-Z isomerism ? /2

• restricted rotation around C=C

• different groups attached to C in C=C

The cyclohexene separated in Question 02.2 was obtained as a cloudy liquid.

The student dried this cyclohexene by adding a few lumps of anhydrous calcium chloride and allowing the mixture to stand.

Give one observation that the student made to confirm that the cyclohexene was dry. /1

cloudy liquid goes clear

explain why non polar hydrocarbons are not biodegradeable /1

carbon-carbon bonds are not susceptible to attack by nucleophiles

explain how carbon dioxide causes global warming /2

C=O bonds vibrate

absorb IR so it does not escape from atmosphere

energy transferred to other molecules by collisions in atmosphere

State why a dicarboxylic acid can be distinguished from two diols by high resolution mass spectrometry using electrospray ionisation /1

different precise molecular masses

explaiin why the reduction of butan-2-one with KCN forms a racemic mixture /3

• planar C=O bond

• equal chance of attack from above and below

• produced equal quantities of both enantiomers

why is the lid needed for TLC /2

prevents solvent from evaporating

so solvent can rise up plate

Predict which one of the compounds, propan-1-ol, propanal and propanoic acid will have the highest boiling point. Explain your answer /3

• propanoic acid

• contains H bonds

• compared to stronger IMFs in propanoic acid

draw the structure of propanoic anhydride /1

sugg

suggest one possible environmental disadvantage of producing hydrogen by electrolysis /1

greenhouse gases emitted in production

explain the origin of hydrogen bonds in the secondary structure /4

• nitrogen and oxygen are very electronegative

• so, C=O and N-H are polar

• H bonds form between O and H

• lone pair on oxygen oxygen is attracted to delta negative H’

methanol + vegetable oil (any ester)

glycerol + methyl esters (biodiesel) - separate esters, not linked