14.1. Alkanes
A subsection of Chemistry, 9701, through 14. Hydrocarbons
Listing 10 of 122 questions
Glycerol, CH2(OH)CH(OH)CH2OH, is widely used in the food industry and in pharmaceuticals. A series of reactions starting from glycerol is shown. CH2OH CH2OH C H OH COOH COOH C NC OH C Q P HOOC HOOC O reaction 1 reaction 2 NaCN and HCN Suggest the reagentand conditions for reaction1. Name the reaction mechanism for reaction2. Give the observation you would make when 2,4-dinitrophenylhydrazine is added to P. Q does not show optical isomerism. Explain why. When Q is heated with excess aqueous ethanoicacid in the presence of a catalytic amount of sulfuricacid, two reactions take place to form compound R. COOH COOH HOOC C OCOCH3 R Identify the two types of reaction that occur.  Glycerol can be used as a starting material in the manufacture of nitroglycerine, C3H5N3O9. Nitroglycerine decomposes rapidly on heating to form a mixture of gases. 4C3H5N3O912CO2+ 10H2O+ 6N2+ O2A sample of nitroglycerine decomposes, releasing 1.06 dm3 of O2at 850 K and 1.00×105 Pa. Calculate the mass of nitroglycerine that decomposes.  mass of nitroglycerine = g Calculate the total volume of gas released by this decomposition at 850 K and 1.00×105 Pa.  total volume of gas = dm3 Fats are compounds made from glycerol and unsaturated carboxylic acids. 4-pentenoic acid is an example of an unsaturated carboxylic acid. (CH2)2COOH H 4-pentenoic acid H H Give the molecular formula of 4-pentenoic acid. Draw the repeat unit of the addition polymer that can be formed from 4-pentenoic acid.  Unsaturated acids are often brominated before being added to soft drinks. Complete the mechanism for the addition of Br2 to 4-pentenoic acid. ● ● Include the structures of the intermediate and the product of the reaction. ● ● Include all charges, partial charges, lone pairs and curly arrows. In the mechanism, R has been used to represent (CH2)2COOH. H R Br Br H H  A reaction of another unsaturated carboxylic acid, T, is shown. Br C6H13 T HOOC Br C6H13 U HOOC T is one of a pair of geometrical (cis-trans) isomers. Draw the other geometrical isomer of T and explain why the molecules exhibit this form of isomerism.  Identify the reagent used to convert T to U. The C–Br bond has an absorption between 500 cm–1 and 600 cm–1 in an infrared spectrum. The infrared spectra for both T and U have absorptions between 2850 cm–1 and 2950 cm–1. These correspond to C–H bonds. Identify: ● ● two other absorptions that would be seen in the infrared spectra of both T and U ● ● one other absorption that would only be seen in the infrared spectrum of T. For each absorption, give the range of the absorption and the bonds that correspond to these absorptions. absorption 1 present in both spectra absorption 2 present in both spectra absorption only present in spectrum of T  
9701_m20_qp_22
THEORY
2020
Paper 2, Variant 2
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Carboplatin and satraplatin are used as anticancer drugs instead of cisplatin. carboplatin satraplatin Pt NH3 N H2 O O O O Cl Cl O O O NH3 NH3 O Pt Describe the action of cisplatin as an anticancer drug. Suggest the geometry of the platinum centre in the carboplatin complex. Suggest why carboplatin does not show cis-trans isomerism. Satraplatin is a neutral complex, containing the ligands CH3CO2 –, C6H11NH2, Cl – and NH3. Deduce the oxidation state of platinum in satraplatin. CompoundM is made from 1,3-dimethylbenzene in a two-step synthesis. 1,3-dimethylbenzene C8H6O4 Cl Cl O M L O step 1 step 2 Draw the structure of L.  Suggest reactants and conditions for each step of this synthesis. step 1 step 2  Write an equation for step2. A student investigates a possible synthesis of M directly from benzene using COCl 2 in the presence of an Al Cl 3 catalyst. Benzene initially reacts with COCl 2 as shown. reaction 1 COCl 2 + Al Cl 3 → Al Cl 4 – + Cl C O reaction 2 C6H6 + Cl C O → C6H5COCl + H+ Reaction 2 is the electrophilic substitution of Cl C O for H+ in benzene. Suggest a mechanism for reaction2.   + + +
9701_m21_qp_42
THEORY
2021
Paper 4, Variant 2
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The gas ethyne, C2H2, more commonly known as acetylene, is manufactured for use in the synthesis of organic compounds. It is also used, in combination with oxygen, in ‘oxy-acetylene’ torches for the cutting and welding of metals. Industrially, ethyne is made from calcium carbide, CaC2, or by cracking liquid hydrocarbons. When calcium carbide is reacted with water, ethyne and calcium hydroxide are formed. Construct a balanced equation for this reaction. Ethyne can also be obtained from ethene by using the following sequence of reactions. CH2CH2 HCCH ClCH2CH2Cl step 1 step 2 What types of reaction are step 1 and step 2? step 1 step 2 Suggest what reagent and conditions would be used in a laboratory in step 2. reagent conditions When ethyne is passed into water at 60 °C, in the presence of a little H2SO4 and Hg2+ ions, a pungent, colourless organic liquid, Q, with Mr of 44 is obtained. This is step 3. When Q is warmed with Tollens’ reagent in a test-tube, a silver mirror is formed. On acidification, the solution remaining in the test-tube is found to contain the organic compound R which has Mr of 60. This is step 4. Give the structural formulae of Q and R. HCCH step 3 Q step 4 R What type of reaction is step 3 and step 4? step 3 step 4 The standard enthalpy change of combustion of C2H2, ΔH o–– c, is –1300 kJ mol–1 at 298 K. Values of relevant standard enthalpy changes of formation, ΔH o–– f, measured at 298 K, are given in the table. substance ΔH o–– f / kJ mol–1 CO2–394 H2O–286 Write balanced equations, with state symbols, that represent the standard enthalpy change of combustion, ΔH o–– c, of C2H2, and the standard enthalpy change of formation, ΔH o–– f, of C2H2. Use the data above and your answer to to calculate the standard enthalpy change of formation, ΔH o–– f, of C2H2. Show clearly whether the standard enthalpy change of formation of C2H2 has a positive or negative value.
9701_s11_qp_21
THEORY
2011
Paper 2, Variant 1
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Questions Discovered
122