OCR A AS Specimen Paper 2 Q5 (with explained solutions) |

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OCR A AS Specimen Paper 2 Q5

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12 5 Alcohols are used in organic synthesis. (a) Pentan-2-ol can be prepared by the alkaline hydrolysis of 2-iodopentane. CH3CH(I)CH2CH2CH3 + NaOHCH3CH(OH)CH2CH2CH3 + NaI The reaction mixture is boiled for 20 minutes. (i) State the most appropriate technique that could be used to boil the reaction mixture for 20 minutes. . (ii) Describe the mechanism for the alkaline hydrolysis of 2-iodopentane. In your answer, include the name of the mechanism, curly arrows and relevant dipoles. [1] name of mechanism: . Specimen [4]OCR 2014 H032/02<br />
13 (b) Alcohols can be converted into haloalkanes in a substitution reaction. Plan an experiment to prepare approximately 0.1 mol of 2-bromopentane, CH3CHBrCH2CH2CH3, from pentan-2-ol, CH3CH(OH)CH2CH2CH3. Your plan should include a calculation of the mass of alcohol required and details of the chemicals to be used in the reaction.. [2] SpecimenOCR 2014 H032/02 Turn over<br />
14 (c)* Alcohols can be converted into alkenes in an elimination reaction. The elimination of H2O from pentan-2-ol forms a mixture of organic products. Give the names and structures of all the organic products in the mixture. Your answer should explain how the reaction leads to the different isomers.Specimen. [6]OCR 2014 H032/02<br />

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H032/02 Question (a) (i) Reflux (cid:57) (ii) Nucleophilic substitution (cid:57) Mark Scheme June 20XX Answer Marks Guidance Mechanism Curly arrow from lone pair on OH to (cid:71)+ carbon atom (cid:57) Curly arrow and dipole on CI bond (cid:57) Correct products (cid:57) The curly arrow must start from the oxygen atom of the OH and must start from either the lone pair or the negative charge (b) (Minimum) n(pentan-2-ol) required = 0.1 88 = 8.8 g (cid:57) React the alcohol with a mixture of NaBr AND H2SO4 AND warm (to distil off the product) (cid:57) DO NOT ALLOW attack by NaOH ALLOW HBr Specimen 14 P M T<br />
H032/02 Question (c)* Mark Scheme June 20XX Marks Guidance Indicative scientific points may include: Answer Please refer to the marking instructions on page 4 of this mark scheme for guidance on how to mark this question. Level 3 (56 marks) Applies knowledge of elimination reactions to provide the correct names and structures of all three alkenes AND Full, detailed explanation of formation of both types of isomers linked to the reaction, with clear understanding of both types of isomerism The explanations show a well-developed line of reasoning which is clear and logically structured. The information presented is relevant to the compounds drawn/named. Level 2 (34 marks) Applies knowledge of elimination reactions to provide the correct name and structure for pent-1-ene AND Correct structures of stereoisomers of pent-2-ene but full names missing or incorrect AND Explanation of formation of at least one type of isomers in some detail. The explanations show a line of reasoning presented with some structure. The information presented is in the most-part relevant to the compounds drawn/named. Level 1 (12 marks) Applies knowledge of elimination reactions to name and draw the structures of organic products. Either name OR Specimenthe elimination can produce a double bond in either the 1- or the 2- position (through combination of the hydroxyl group with a hydrogen from either the 1st or the 3rd carbon)this leads to the formation of structural isomers (pent-1-ene and pent-2-ene)pent-2-ene exhibits stereoisomerism / E/Z isomerism / cistrans isomerism because it has two different groups attached to each carbon atomthere are two possible isomers of pent-2-ene and three in total Names and structures of alkenes pent-1-ene Z or cis-pent-2-ene E or trans-pent-2-ene 15 P M T<br />
H032/02 Question Mark Scheme June 20XX Answer Marks Guidance structure should be correct for two compounds. AND Attempts to explain formation of one type of isomer. The information about isomerism is basic and communicated in an unstructured way. The relationship to the compounds drawn/named may not be clear. 0 marks No response or no response worthy of credit. Specimen Total 13 16 P M T<br />

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