Questions Paper 2 Flashcards
Explain why 2,2-dimethylpropane has a much lower boiling temperature than its
isomer pentane. (2 marks) 2022
branching results in fewer London forces
due to less surface area
Butylamine, C4H9NH2 , reacts with ethanoyl chloride.
2C4H9NH2 + CH3COCl → C4H9NHCOCH3 + C4H9NH3 + Cl-
Explain how this equation illustrates that butylamine acts as a nucleophile and as
a base.
Nucleophiles are electron pair donors
so the amine group attacks as a nucleophile by attacking Cs.positive of the acyl chloride
which produces hydrogen chloride
it’s a base because the amine group reacts with the acid
Esters can be hydrolysed by heating under reflux with aqueous acid or alkali.
Compare and contrast these two methods of hydrolysis for amyl acetate.
alkali are irreversible, using NaOH you produce sodium ethanoate and methanol
acids are reversible, using HCL you produce ethanoic acid and salt
Explain why benzene is resistant to bromination but ethene reacts readily
with bromine at room temperature. (2023) 4 marks
In Ethene (𝐶2𝐻4C2H4 )
The pi bond is localized between the two carbon atoms.
This creates a high electron density in one specific area.
The high electron density attracts electrophiles like Br₂, making it very reactive.
In Benzene (𝐶6𝐻6C 6H 6)
Instead of being between two atoms, pi bonds are delocalized across all six carbon atoms.
This means the electron density is spread out evenly across the ring.
Lower electron density makes benzene less attractive to electrophiles like Br₂, making it less reactive.
Discuss the different types of stereoisomerism that occur in organic compounds.
Use only molecules A and B as examples.
CHCl C(CH3)Br CH3CH(OH)COOH
A B
Include in your answer:
* how the different types of isomerism arise
* the naming of alkenes with the formula A
* the properties of isomers with the formula B
* diagrams of the different isomers.
Molecule A: CHCl=C(CH₃)Br
This molecule contains a C=C double bond, which prevents free rotation.
Each carbon in the double bond has two different groups, meeting the criteria for E/Z isomerism.
Molecule B: CH₃CH(OH)COOH (Lactic Acid)
It contains a chiral carbon (a carbon bonded to four different groups: -OH, -COOH, -CH₃, and -H).
This leads to two non-superimposable mirror images (enantiomers).
Explain why phenylamine is a weaker base than butylamine.
If nitrogen has a lot of electrons, it’s “rich” and can easily donate them to H⁺ → stronger base.
If nitrogen loses some of its electrons, it’s “poor” and less likely to donate → weaker base.
(a) Butylamine (C₄H₉NH₂) – Stronger Base
The butyl (-C₄H₉) group “pushes” electrons toward nitrogen.
This means nitrogen has more electron density, (base are proton acceptors)
Since nitrogen can donate electrons easily, butylamine is a stronger base.
Benzene is an electron-withdrawing group so it pulls electrons away from nitrogen, into the ring structure. so lone pair availability is reduced and aromatic amines are less basic
Explain why the butan-2-ol produced from a single optical isomer of
2-bromobutane, using this mechanism, is not optically active. 3 marks
If a mixture has equal amounts of both enantiomers (racemic mixture), the rotations cancel out, making it optically inactive.
The butan-2-ol is not optically active because the reaction makes equal amounts of two mirror-image forms (enantiomers). These cancel out, so it does not rotate light.
i) Compare and contrast the bromination of phenol with the bromination of benzene.
Both electrophilic substitution
No need of a halogen carrier with phenol (1)
oxygen’s lone pair of electrons interacts with the
benzene ring of delocalised electrons so
electrophilic attack more likely
(heating under reflux)
Explain why the use of this apparatus would give a very low yield of propanal.
the propanal is condensed back in
so propanal is further oxidised
State how the use of anti-bumping granules gives smoother boiling.
provide surface area for bubbles to form
Explain, by reference to the data and any intermolecular forces involved, the
difference in the boiling temperatures.
propanone and ethanoic acid
similar molar masses so the number of electrons is
similar/same resulting in similar London forces (1)
* propanone (and ethanoic acid) form
permanent dipole(-dipole) forces (1)
* (only) ethanoic acid forms (intermolecular) hydrogen
bonding (1)
* which is stronger so requires more energy to break
(giving a higher boiling temperature)
Give the reagent and essential condition for the formation of propylamine
from a nitrile.
Include an equation for the reaction.
CH3CH2CN + 4[H] → CH3CH2CH2NH2
LiALH4 dry ether
Phenol reacts faster than phenylmethanol in electrophilic substitution reactions. Suggest why this is so.
the lone pair of electrons on the oxygen of oh is donated into the delocalised electron structure of benzene and increases the electron density of benzene making it more susceptible to an electrophilic attack.
Explain why far more 1-bromo-2-chloropropane forms than
2-bromo-1-chloropropane.
because a secondary carbocation (intermediate) is formed (1)
* more stable than a primary (carbocation intermediate)
