Organic

CFC-11 is a greenhouse gas that can contribute to global warming. State and explain how CFC-11 is able to contribute to global warming. (2 marks)

absorbs infrared radiation

molecule has polar bonds

Catalytic Cracking

• High temperature - 450^oC

• Zeolite (aluminosilicate) catalyst

• Produces mainly branched alkanes and cyclic compounds with very few alkenes

  • Used primarily in motor fuels as branched compounds reduce ‘knocking’

Thermal Cracking

• High temperature - 700^oC

• High pressure - 7000 kPa

• Produces a high proportion of alkenes - the high temperature causes chain to break close to the end forming small alkenes such as ethene

• Free radical process - homolytic fission of carbon chain

Explain why there is an attraction between a C=C double bond and Br₂ (3 marks)

C=C electron rich / area of high electron density

Br-Br becomes polarised

δ+ Br attracted to C=C

Why a plasticiser is added (2 marks)

make it more flexible

this is because they get between the polymer chains and reduce intermolecular forces.

Chemists provided evidence that was used to support a ban on the use of chlorodifluoromethane as a refrigerant. Many refrigerators now use pentane as a refrigerant.

State the environmental problem that chlorodifluoromethane can cause.

Give one reason why pentane does not cause this problem. (2 marks)

• Causes ozone depletion/decomposition/damage

Accept hole in the ozone layer

• Pentane does not have C-Cl bonds

Accept does not produce Cl radicals

Accept does not contain chlorine

State a simple chemical test that distinguishes the propanoic acid from the propan-1-ol. Give one observation for the test with each substance. (3 marks)

add sodium carbonate/hydrogencarbonate

Propanoic acid: effervescence / bubbles not gives off (CO₂) gas

Propan-1-ol: no (visible) change/reaction

Use evidence from the rate equation to explain why Step 1 is the rate determining step. (1 mark)

Step 1 contains all the species in the rate equation / Step 1 includes CH₃COCH₃ and OH^- and these are also in the rate equation

The overall order of the reaction can be deduced from a piece of information in one of the column headings in the table. Identify this piece of information and deduce the overall order. (2 marks)

• Unit of k (is s^-1)

• Order 1/first

This question is about simple test-tube reactions to identify organic liquids.

Silver nitrate solution can be used to distinguish between propanoyl chloride and 1-chloropropane. Give the observations you would expect when a few drops of silver nitrate solution are added to separate samples of propanoyl chloride and 1-chloropropane. (2 marks)

propanoyl chloride:

• Misty / white / steamy fumes

(immediate) White precipitate forms

1-chloropropane:

• No visible change

White precipitate forms slowly

Three unlabelled bottles are known to contain either propan-1-ol, propanal, or propanone.

A sample of each liquid is warmed with a few drops of Fehling’s solution.

Identify the liquid that reacts with Fehling’s solution and give the expected observation.

Suggest a further simple test-tube reaction that can be used to distinguish between the remaining two liquids.

Give the expected observation with the liquid that reacts. (3 marks)

• Propanal AND blue solution gives a brick red precipitate

(Warm with) acidified potassium dichromate (VI)	add Na	warm with a named carboxylic acid with conc H2SO4
Propan-1-ol/alcohol AND (orange solution) goes green	Propan-1-ol/alcohol AND effervescence	Propan-1-ol/alcohol AND fruity smell

The figure below shows enthalpy of hydrogenation data for cyclohexene and benzene. It also shows predicted data for the theoretical molecule cyclohexa-1,3,5-triene.

Compare benzene and the theoretical molecule cyclohexa-1,3,5-triene in terms of:

• stability

• shape

• carbon–carbon bond lengths.

For each of these properties, suggest reasons for any differences. Use data from the figure above in your answer. (5 marks)

• Benzene is more stable than cyclohexa-1,3,5-triene

• 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 possible use for the amine formed in Step 2. (1 mark)

Manufacture of dyes/(cationic) surfactants/fabric softener

Allow to make hair/fabric conditioner

Benzene reacts with methanoyl chloride (HCOCl) in the presence of a catalyst. Give an equation for the overall reaction when benzene reacts with methanoyl chloride. Name the organic product. (2 marks)

• C₆H₆ + HCOCl → C₆H₅CHO + HCl

• Benzaldehyde

Amine A is formed in step 2 and amine B is formed in step 5. Explain why the yield of B in step 5 is less than the yield of A in step 2. (2 marks)

• In Step 5 further substitution / gives other amine products

• In Step 2 only one amine

Explain why amine B (previous flashcard) is a stronger base than amine A. (2 marks)

• In B Alkyl group is electron donating or positive inductive effect

Or In A lone pair on N partially delocalised

• Lone pair on N more available

Lone pair on N less available

A student hydrolyses a sample of endomorphin-2 (a peptide) to break it down into its constituent amino acids. The student analyses the resulting mixture by thin-layer chromatography, TLC.

State a reagent and the conditions needed for the hydrolysis. (2 marks)

• (aqueous) HCl/hydrochloric acid

• reflux/heat

Name a suitable developing agent. State why the developing agent is needed. (2 marks)

• ninhydrin

• amino acids are colourless / to make the amino acids visible

R represents a group that varies between different amino acids. R groups can interact and contribute to protein structure.

Explain why the strength of the interaction between two cysteine R groups differs from the strength of the interaction between a serine R group and an aspartic acid R group. Use the Data Booklet to help you answer this question. (4 marks)

• Two Cys R groups form a disulfide bridge/link stated or described

• Ser and Asp R groups form Hydrogen bonds

• Disulfide bridges are stronger than H bonds

• Because disulfide bridges are covalent bonds (while H bonds aren’t)

Deduce the type of interaction that occurs between a lysine R group and an aspartic acid R group. (1 mark)

Ionic bond