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OCR A Jun 2017 Paper 2 Q4
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![The hydroxyl group, OH, is responsible for many properties of alcohols. (a) Methanol, CH3OH, is soluble in water because it has polar bonds. Pauling electronegativity values for carbon, oxygen and hydrogen are shown below. Element Carbon Oxygen Hydrogen Electronegativity 2.5 3.5 2.1 Use a labelled diagram to explain why methanol is soluble in water.Use displayed formulae showing one molecule of methanol and one molecule of water.Add partial charges d+ and d to show the two most polar bonds in a methanol molecule and the polar bonds in a water molecule. Show all lone pairs. Label the most important intermolecular bond between the molecules. [2]<br />
(b) Alcohol C is analysed using mass spectrometry. OH alcohol C (i) Give the systematic name of alcohol C.[1] (ii) The mass spectrum of alcohol C is shown below. Write structural formulae for the ions responsible for peak X and peak Y. X = Y = [2]<br />
10 (c)* Describe the oxidation reactions of butan-1-ol forming an aldehyde and a carboxylic acid. Explain, using a diagram, how the aldehyde can be produced in the laboratory by controlling the reaction conditions.[6]<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_QP_-_Paper_2_OCR_Chemistry_A_AS-Level_4-0.jpg)
![H032/02 Question Answer (a) Displayed formulae of CH3OH and H2O Mark scheme June 2017 Marks Guidance Must be displayed formulae AND CO AND OH polar bonds shown on CH3OH molecule with + andAND Both OH polar bonds shown on H2O molecule with + andTwo lone pairs shown on both oxygen atoms AND Hydrogen bond/H-bond labelled and in the correct position between the H on water and the oxygen lone pair on methanol(b) (i) 3-methylbutan-2-ol(ii) Peak X (m/z = 45) CH3CHOH+Peak Y (m/z = 88) 14 IGNORE + shown on other H atoms ALLOW hydrogen bond between the H on methanol (OH) and the oxygen lone pair on water + (too many H atoms) ALLOW 3-methyl-2-butanol ALLOW 3-methylbutane-2-ol ALLOW absence of hyphens IGNORE commas DO NOT ALLOW 2-methylbutan-3-ol C5H12O has lost C3H7 IGNORE C2H5O+ OR C2H4OH+ ambiguous DO NOT ALLOW unfeasible fragments e.g. C3H9 ALLOW correct structural OR skeletal OR displayed formula OR mixture of the above for both structures IGNORE C5H12O+ ALLOW C5H11OH+<br />
H032/02 Question (c)* Answer + CH3CH(CH3)CH(OH)CH3 OR CH3CH(OH)CH(CH3)2 Mark scheme June 2017 Marks Guidance Please refer to the marking instructions on page 5 of the mark scheme for guidance on how to mark this question. Level 3 (5-6 marks) A comprehensive explanation with all three scientific points covered thoroughly. There is a well-developed description with a logical structure including correct chemical equations and an explanation with a clear line of reasoning including a fully labelled diagram. Level 2 (34 marks) The candidate attempts all three scientific points but explanations are incomplete. OR Explains two scientific points thoroughly with no omissions. The description has a line of reasoning presented with some structure and includes correct structural formulae and an accurate diagram of a distillation apparatus. Level 1 (12 marks) A simple explanation based on at least two of the main scientific points 15 + charge (anywhere on structure) required for each response ALLOW one mark if both formulae are correct but with no charge/incorrect charge ALLOW one mark if both formulae are correct but incorrectly labelled X/Y Indicative scientific points 1. Oxidation reaction forming aldehydeacid/H+ AND dichromate/Cr2O7heat AND distillationorganic product is butanal/CH3CH2CH2CHOCH3CH2CH2CH2OH + [O]CH3CH2CH2CHO 2 +H2O 2. Oxidation reaction forming carboxylic acidacid/H+ AND dichromate/Cr2O7heat under refluxorganic product is butanoic acid/ 2 CH3CH2CH2COOHCH3CH2CH2CH2OH + 2[O]CH3CH2CH2COOH + H2O 3. Distillationdiagram of apparatus with condensercondenser has water flowcollection of organic productproduct is separated to prevent further oxidation (to carboxylic acid)<br />
H032/02 Question Mark scheme June 2017 Answer Marks Guidance OR The candidate explains one scientific point thoroughly with few omissions. The description may be communicated in an unstructured way but it includes the correct reagents and conditions for the formation of the aldehyde. There is an attempt at a logical structure with a line of reasoning. The information is in the most part relevant. 0 marksNo response or no response worthy of credit. Total 11 16<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_MS_-_Paper_2_OCR_Chemistry_A_AS-Level_4-0.jpg)
