13. An introduction to AS Level organic chemistry
A section of Chemistry, 9701
Listing 10 of 507 questions
Copper is a transition element. It forms a wide variety of compounds. Define transition element. An aqueous solution of copper(sulfate, CuSO4, contains [Cu(H2O)6]2+ complex ions. If an excess of concentrated hydrochloricacid is added to this solution a ligand exchange reaction occurs and [CuCl 4]2– complex ions are formed. Complete Table5.1 to state the geometry, the coordination number of copper, and one bond angle in each of the two complex ions. Table 5.1 complex ion geometry coordination number bond angle [Cu(H2O)6]2+ [CuCl 4]2–  In an isolated Cu2+ ion the d-orbitals are all degenerate. In a complex ion such as [Cu(H2O)6]2+ the d-orbitals are non-degenerate. Define degenerate and non-degenerate in this context. degenerate non-degenerate  Explain why the solutions of the two complex ions in Table5.1 are different colours. Cu2+ forms a complex ion containing water molecules and ethanedioate ions, C2O4 2–, as ligands. The formula of the complex is [Cu(C2O4)2(H2O)2]2–. The ethanedioate ion is a bidentate ligand. Explain what is meant by bidentate. There are three stereoisomers with the formula [Cu(C2O4)2(H2O)2]2–. Complete the three-dimensional diagrams to show these three stereoisomers. stereoisomer 1 Cu stereoisomer 2 Cu stereoisomer 3 Cu  Use your answer to to answer this question. Stereoisomers 1, 2 and 3 show two different types of isomerism. Name these two types of isomerism. For each type of isomerism identify the pair of stereoisomers that demonstrate this isomerism. type of isomerism pair of stereoisomers and and  A solution contains 3.70 g of Na2[Cu(C2O4)2(H2O)2] dissolved in 100 cm3 of solution. A 25.0 cm3 sample of this solution is warmed and then oxidised by 0.0100 mol dm–3 acidified potassiummanganate(. The equation for the redox reaction is shown. 5C2O4 2– + 2MnO4 – + 16H+ → 10CO2 + 2Mn2+ + 8H2O Calculate the minimum volume of 0.0100 mol dm–3 acidified potassiummanganate(needed to oxidise all of the ethanedioate ions, C2O4 2–, in the 25.0 cm3 sample. Show all your working. [Mr: Na2[Cu(C2O4)2(H2O)2], 321.5]  minimum volume = cm3 Copper(nitrate, Cu(NO3)2, and bariumnitrate, Ba(NO3)2, both decompose when heated. Copper(nitrate decomposes at a lower temperature than barium nitrate. Suggest a reason for this difference. Explain your answer. 
9701_w22_qp_42
THEORY
2022
Paper 4, Variant 2
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Compound G, in which R– represents the rest of the molecule, was made for use as a tear gas in World War 2. Compound G was made by the following sequence of reactions. stage I stage II stage III R–CH3 R–CH2Cl R–CH2CN R–CHBrCN For stage I and for stage II, state the reagentand conditionused to carry out each change. stage I reagentconditionstage II reagentconditionSuggest the reagentand conditionnecessary to carry out stage III. reagentcondition R H C Br CN compound G Compound G was not actually used in World War 2 and stocks of it had to be destroyed safely. The following sequence of reactions was used in this process. stage IV stage V R–CHBrCN R–CHBrCO2H R–CH(OH)CO2H stage VI R–CH2CO2H For stage IV and for stage V state the reagentand conditionnecessary to bring about each reaction. stage IV reagentconditionstage V reagentconditionThe full sequence of stages I to VI involves some compounds which contain chiral centres. Explain what is meant by the term chiral centre. Draw displayed formulae for the isomers of one compound in the full sequence of stages I to VI which you consider to be chiral.
9701_s05_qp_2
THEORY
2005
Paper 2, Variant 0
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Questions Discovered
507