11.4. The reactions of chlorine
A subsection of Chemistry, 9701, through 11. Group 17
Listing 10 of 290 questions
Benzene reacts with chlorine gas to form chlorobenzene. This reaction can be described as the reaction between benzene molecules and Cl + ions. The Cl + ions are formed by adding a suitable catalyst to the chlorine gas. Give the name or formula of a catalyst that can be used for this reaction. The mechanism for this reaction is shown. Cl + Cl Cl x y step 1 step 2 diagram 1 diagram 2 diagram 3 H + The movement of a pair of electrons is represented by x in diagram 1. • State where this pair of electrons is before step 1 takes place. • State where this pair of electrons is after step 1 has taken place. The movement of another pair of electrons is represented by y in diagram 2. • State where this pair of electrons is before step 2 takes place. • State where this pair of electrons is after step 2 has taken place. There are six carbon atoms in diagram 2. State how many of these carbon atoms are sp hybridised, sp2 hybridised, and sp3 hybridised. sp hybridised sp2 hybridised sp3 hybridised Complete the equation for this reaction between benzene and chlorine. C6H6 + + The mechanism for this reaction is electrophilic substitution. Complete the following sentence. Write formulae in the gaps provided. During this reaction, the electrophile is and a atom in benzene is substituted by a atom. Chloroethane reacts with NaOH. Chlorobenzene does not. Name the mechanism of the reaction that chloroethane undergoes with NaOH, and identify the major organic product that is formed. mechanism major organic product Explain the difference in reactivity of chloroethane and chlorobenzene when treated with NaOH.
9701_w24_qp_42
THEORY
2024
Paper 4, Variant 2
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Allyl chloride is an important chemical used in the manufacture of plastics, pharmaceuticals and pesticides. Cl allyl chloride Give the systematic name of allyl chloride. Allyl chloride can be produced by many different methods. The most common method is chlorination of propene which proceeds via a free-radical substitution mechanism. Cl Cl 2 The initiation step in this reaction is the formation of chlorine radicals (Cl ●) from Cl 2 molecules. State the conditions required to initiate this reaction. The propenyl radical, CH2=CHCH2 ●, is formed in the first propagation step of the reaction. Write an equation to show the formation of CH2=CHCH2 ● in this propagation step. Explain why the free-radical substitution reaction gives a low yield of allyl chloride. Allyl chloride can also be formed by the following substitution reaction. Cl OH reagent X Suggest the identity of reagent X. A series of reactions starting from allyl chloride is shown. Cl Cl HO reaction 1 HCN and NaCN reaction 3 reaction 2 OH Cl CH3COO CH3COO CN CH3COO CH3COO Y Suggest a reagent that can be used in reaction1. In reaction2, the organic product of reaction1 is mixed with concentrated H2SO4 and an organic acid, and then heated under reflux. State the role of the concentrated H2SO4. Identify the organic acid used. role of the concentrated H2SO4 identity of the organic acid  State the name of the mechanism that occurs in reaction3. The organic product of reaction3 is Y. Y can be hydrolysed using excess aqueous H2SO4 to form Z. The molecular formula of Z is C4H8O4. Draw the structure of Z.  2-bromo-1-chloropropane, CH3CHBrCH2Cl, is the major product of the reaction of allyl chloride with HBr. Cl Cl HBr and Br major product Cl Br minor product Explain why 2-bromo-1-chloropropane is the major product of this reaction. 
9701_m19_qp_22
THEORY
2019
Paper 2, Variant 2
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State the electronic configuration of the iron atom. Apart from its electronic structure, state two properties of iron or its compounds that are characteristic of a transition element. Acidified solutions of iron(salts can be titrated using a dilute solution of potassium manganate(, KMnO4. Use the Data Booklet to calculate the standard cell potential and to write a balanced ionic equation for the reaction that takes place during the titration. Explain why no indicator is required for this titration. What colour change would you see at the end point? Use the reaction between Fe3+ ions and water molecules to explain the meanings of the terms ligand and complex formation. Use An important biological molecule containing iron is haemoglobin. What is the role of haemoglobin in the body? Use your answer to to explain why carbon monoxide is poisonous. In a possible industrial synthesis of ethanol, the complex Fe(CO)5 catalyses the reaction between carbon monoxide, hydrogen and methanol according to the following equation. 200 °C CH3OH + 2CO + H2 –––––→CH3CH2OH + CO2 300 atm Describe a test (reagents and observations) that would distinguish ethanol from methanol. reagents observation with methanol observation with ethanol Examiner's Use
9701_s05_qp_4
THEORY
2005
Paper 4, Variant 0
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Describe the observations you would make when concentrated sulfuric acid is added to separate portions of NaCl and NaBr. Write an equation for each reaction that occurs. NaCl : observation equation NaBr: observation equation By quoting relevant E o- data from the Data Booklet, explain how the observations you have described above relate to the relative oxidising power of the elements. By referring to relevant E o- data choose a suitable reagent to convert Br2 into Br −. Write an equation and calculate the E o- for the reaction.
9701_s09_qp_4
THEORY
2009
Paper 4, Variant 0
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A large number of organic compounds are soluble in both water and non-aqueous solvents such as hexane. If such a compound is shaken with a mixture of water and the non-aqueous solvent, it will dissolve in both solvents depending on the solubility in each. State what is meant by the term partition coefficient. When 100 cm3 of an aqueous solution containing 0.50 g of an organic compound X was shaken with 20 cm3 of hexane, it was found that 0.40 g of X was extracted into the hexane. Calculate the partition coefficient of X between hexane and water. If two 10 cm3 portions of hexane were used instead of a single 20 cm3 portion, calculate the total amount of X extracted and compare this with the amount extracted using one 20 cm3 portion. PCBs are highly toxic compounds released into the atmosphere when some plastics are burned at insufficiently high temperatures. In recent years PCB residues have been found in the breast milk of Inuit mothers in northern Canada. Foods, such as oily fish, seal and whale meat, which are high in fat, form an important part of the Inuit diet. Suggest why berries and drinking water are not contaminated by PCBs in the same way that oily fish, seal and whale meat are. Based on the information provided, what can you say about the partition coefficient between fat and water for PCB residues? The diagram shows the result of two-way paper chromatography. X starting point solvent 1 solvent How many spots were there after the first solvent had been used? Circle the spot that moved very little in solvent 2, but moved a greater distance in solvent 1. Draw a square around the spot that could be separated from the rest by using only solvent 1.
9701_s09_qp_4
THEORY
2009
Paper 4, Variant 0
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