2024 Paper 3 Flashcards
(20 cards)
Ammonia reacts with bromoethane.
2NH3 + CH3CH2BR -> NH4BR + CH3CH2NH2
Explain by referring to the reaction mechanism the roles of ammonia in the formation for each of the products in the reaction (3)
- one molecule of ammonia acts as a nucleophile (1)
- to attack the carbon with a partial positive charge (1)
- a molecule of NH3 acts as a base (1)
- to remove a proton from the intermediate (1)
What conditions are needed for ammonia reacting with bromoethane?
A- heat in a sealed tube and ethanol
(As it needs to be a closed system and bromoethane is not soluble in water)
State the use of Grignard reagents in organic synthesis (1)
Extend/ increase the length of the CARBON chain
In their reactions, the Grignard reagent is best described as…
A- carbocation
B- electrophoresis
C- nucleophile
D - radical
C - nucleophile
Predict the organic product that forms when CH3CH2MgBr reacts with water. Justify your answer by considering the polarity of both CH3CH2MgBr and water. (2)
Ethane
Negative carbon (in Grignard reagent) is attracted to the partially positive hydrogen (in water)
which compound will form a tertiary alcohol when it reacts with a Grignard reagent followed by acid hydrolysis?
A- CO2
B- HCHO
C- CH3CHO
D- CH3COCH3
D- CH3COCH3
Hydrogen peroxide decomposes to form water and oxygen
2H2O2 (aq) -> 2H2O (l) + O2 (g)
Explain, using oxidation numbers, why the decomposition of hydrogen peroxide is classified as a disproportionation reaction (3)
Oxidation number of oxygen has changed from -1 (in H2O2) (1)
to -2 in water so it is reduced (1)
and zero in oxygen (O2) so it is oxidised(1)
Describe the test and the positive result that confirms the gas produced is oxygen (1)
Glowing splint (into bubbles of gas) and splint relights
The foam produced often has a slight yellow brown colour
Explain what causes this colour which is not caused by the detergent (2)
Aqueous solution of IODINE (1)
Formed when excess hydrogen peroxide oxidises the iodide ions (1)
Discuss the role of society, and chemists in particular, can play in order to contribute to a more sustainable use of polymers. (6)
Your answer should consider:
- different ways of dealing with waste polymers - how chemist can limit the problems caused by the disposal of polymers.
TREATMENT OF WSTE POLYMERS
M1: waste polymers can be recycled and sorted
M2: waste polymers can be incinerated to generate energy (e.g. electricity)
M3: polymers can be cracked/ thermally decompose to form monomers
LIMITING PROBLEMS OF DISPOSAL
M4: Chemists can develop new biodegradable polymers
M5: chemists can devise techniques to reduce emission of harmful gases from incineration of waste polymers
M6: By neutralising Cl/ SO2
What is the initiation step for cyclopentane into bromocyclopentane? (1)
Br2 -> 2Br’
‘= radical
Explain why the solvent ethanol is treated with anhydrous sodium sulfate before use in this reaction (2)
To dry the ethanol (1)
as presence of water would result in formation of some cyclopentanol (1)
Explain why TMS is used in mass spectrometry (2)
- acts as a standard reference point at 0ppm
- has 12 equivalent hydrogens to cause a strong peak
State what is meant by a ‘secondary amine’ (1)
Nitrogen (in amine) is attached to two carbon atoms
Using carbon 13 NMR how can we distinguish between the two alcohols, cyclohexane-1,2-diol and cyclohexane-1,3-diol (2)
1,2 = 3 peaks AND 3 diff environments
1.3= 4 peaks AND 4 different environments
Explain how chlorine can act as an electrophile even though a chlorine molecule is symmetrical (2)
Chlorine moves to the electron rich PI BOND (1)
Induces a partial positive charge on chlorine (1)
Name the type of reaction that occurs when chloroprene polymerises
Additional polymerisation
Explain why ethane-1,2- diol is soluble in water (2)
- both compounds have hydrogen bonds (1)
- the hydrogen bonds formed will be of similar strength (1)
State what is meant by a chiral carbon atom (1)
A carbon with 4 different atoms
