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OCR A Jun 2017 Paper 2 Q19
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![19 This question is about alcohols. 23 (a) Construct an equation for the complete combustion of an unsaturated alcohol with 5 carbon atoms.[1] (b) Many alcohols, including ethanol, are soluble in water. (i) Explain, with the aid of a diagram, why ethanol is soluble in water. Include relevant dipoles and lone pairs.[2] (ii) The solubility of hexan-1-ol and hexane-1,6-diol in water is shown below in Table 19.1. Alcohol hexan-1-ol hexane-1,6-diol Solubility in water / g dm3 5.9 500 Table 19.1 Explain the difference in solubility of hexan-1-ol and hexane-1,6-diol.[1]<br />
(c) Alcohols are important in organic synthesis and can be formed by the reduction of carbonyl compounds. (i) Complete the flowchart by filling in each box. 24 carbonyl compound reduction reagent(s):OH NaBr / H2SO4 compound K acid catalyst heat structural isomers [5]<br />
(ii) What is the name of compound K? 25[1] (d) Butan-1-ol can be oxidised to form two different organic products, depending on the reaction conditions used. Describe both oxidation reactions of butan-1-ol. For each reaction includethe structure of the organic product a balanced equation the essential reaction conditions. In your equations you may use [O] to represent the oxidising agent.[5]<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_QP_-_Paper_2_OCR_Chemistry_A_A-Level_19-0.jpg)
![June 2017 Guidance ALLOW multiples e.g. 2C5H10O + 14O2 (cid:127)(cid:111) 10CO2 + 10H2O ALLOW any equation involving an unsaturated alcohol with correct balancing e.g. C5H8O + 6.5O2 (cid:127)(cid:111) 5CO2 + 4H2O C5H6O + 6O2 (cid:127)(cid:111) 5CO2 + 3H2O C5H4O + 5.5O2 (cid:127)(cid:111) 5CO2 + 2H2O C5H2O + 5O2 (cid:127)(cid:111) 5CO2 + H2O IGNORE state symbols ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous DO NOT ALLOW (cid:71)+ on H atoms of alkyl group DO NOT ALLOW any marks for a diagram containing O2H If more than one hydrogen bond is shown they must all be correct to award the mark. H432/02 Question 19 (a) C5H10O + 7O2 (cid:127)(cid:111) 5CO2 + 5H2O (cid:57) Answer Mark Scheme Marks (b) (i) Diagram showing a water molecule and an ethanol molecule with at least one H(cid:71)+ and one O(cid:71) on BOTH molecules (cid:57) Hydrogen bond between one lone pair on O atom in one of the molecules and the H atom of another. AND Hydrogen bonding stated or labelled on diagram (cid:57) e.g. Hydrogen bond (cid:71)- O (cid:71)+ (cid:71)+ H (cid:71)- O ((cid:71)+) 22<br />
H432/02 Question Mark Scheme Marks Answer (ii) Hexane-1,6-diol has more OH groups (than hexan-1-ol) AND (hexane-1,6-diol) forms more hydrogen bonds with water (cid:57) (c) (i) Starting material from reduction reaction (cid:57) Reagent for reduction NaBH4 (cid:57) Product from reaction with NaBr/H2SO4 Br (cid:57) Structural isomers 23 June 2017 Guidance Statements MUST be comparative e.g. hexane-1,6-diol has two OH groups and hexan-1-ol has one -OH group ALLOW hydroxyl or hydroxy DO NOT ALLOW hydroxide/OH ALLOW ORA ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous Watch for missing methyl groups IGNORE H+ / acid or H2O or ethanol ALLOW sodium borohydride OR sodium tetrahydridoborate ALLOW LiAlH4<br />
H432/02 Question Answer Mark Scheme Marks Guidance ALLOW in either order June 2017 (cid:57) (cid:57) (ii) 3-methylcyclohexanol (cid:57) Structures of organic products (d) (cid:57) OH (cid:57) Equations CH3CH2CH2CH2OH + [O] (cid:127)(cid:111) CH3CH2CH2CHO + H2O (cid:57) CH3CH2CH2CH2OH + 2[O] (cid:127)(cid:111) CH3CH2CH2COOH + H2O (cid:57) Reaction conditions 24 ALLOW 3-methylcyclohexan-1-ol ALLOW 1-methylcyclohexan-3-ol IGNORE lack of hyphens, or addition of commas ANNOTATE WITH TICKS AND CROSSES Use of any primary alcohol containing 3, 5 or more carbons can be awarded up to 4 marks. ALLOW any combination of skeletal OR structural OR displayed formula as long as unambiguous IGNORE names DO NOT ALLOW CH3CH2CH2COH for the structure of the aldehyde. ALLOW CH3CH2CH2CO2H for the structure of the carboxylic acid. ALLOW marks for structures from equations as long as unambiguous. ALLOW molecular formulae in equations e.g. C4H10O + [O] (cid:127)(cid:111) C4H8O + H2O IGNORE incorrect structures in equations i.e. C4H10O + [O] (cid:127)(cid:111) C3H7COH + H2O C4H10O + 2[O] (cid:127)(cid:111) C4H8O2 + H2O C4H9OH + [O] (cid:127)(cid:111) C3H7CHO + H2O C4H9OH + 2[O] (cid:127)(cid:111) C3H7CO2H + H2O<br />
Answer Mark Scheme Marks Distillation to produce aldehyde/CH3CH2CH2CHO AND Reflux to produce carboxylic acid/CH3CH2CH2COOH (cid:57) June 2017 Guidance scores equation mark Conditions must be linked to aldehyde/carboxylic acid or correct products. Conditions may be written above arrow of equation. H432/02 Question Question (a) 20 Answer Empirical formula Mole Ratio C : H : O = 5.88 : 5.92 : 1.47 (cid:57) Empirical formula = C4H4O (cid:57) Molecular formula Molecular formula = C8H8O2 AND Evidence of 136 in working or from labelled peak in spectrum (cid:57) (b) Functional groups Phenol AND ketone (cid:57) Explanation Total 15 Marks 25 Guidance 1.0 : 23.50 16.0 ANNOTATE ANSWER WITH TICKS AND CROSSES ALLOW 70.58 12.0 : 5.92 ALLOW 4:4:1 if linked to C:H:O Alternative method for 3 marks: C: 13670.58/100 H: 12.0 1365.92/100 13623.50/100 1.0 16.0 O: DO NOT ALLOW any other functional groups for first marking point.<br />](https://learnah.org/wp-content/uploads/2018/08/June_2017_MS_-_Paper_2_OCR_Chemistry_A_A-Level_19-0.jpg)
