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OCR A Jan 2010 Paper 2 Q6
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![This question is about the six alcohols below. 14 butan-2-ol 2-methylpentan-3-ol propan-1-ol ethane-1,2-diol 2-methylpropan-2-ol propan-2-ol (a) Which alcohol is an example of a tertiary alcohol?[1] (b) Draw the skeletal formula for 2-methylpentan-3-ol. (c) Butan-2-ol and 2-methylpropan-2-ol are structural isomers. (i) What is meant by the term structural isomer ? [1][1] (ii) Draw another structural isomer of these two alcohols. [1] (d) Ethane-1,2-diol can be dissolved in water to act as an anti-freeze in car radiators. Explain why ethane-1,2-diol is very soluble in water.[2]OCR 2010<br />
15 (e) Ethane-1,2-diol is heated under reflux with ethanoic acid and a small amount of H2SO4 catalyst. Compound A is formed with molecular formula C6H10O4. Draw the structure of compound A. (f) Butan-2-ol is heated with H2SO4 catalyst.A mixture of three alkenes forms, B, C and D. The alkenes B and C are stereoisomers. (i) Draw the structures of the two stereoisomers B and C. [2] [2] (ii) What type of stereoisomerism is shown by B and C?[1] (iii) Draw the structure of the other alkene, D, that is formed in this reaction.OCR 2010 [1] Turn over<br />
(g) Alcohol E is one of the following alcohols. 16 butan-2-ol 2-methylpentan-3-ol propan-1-ol ethane-1,2-diol 2-methylpropan-2-ol propan-2-ol A student oxidises alcohol E by heating under reflux with excess acidified potassium dichromate(VI). An organic product F is isolated. The mass spectrum of the alcohol E is shown below. 100 80 60 40 20 relative intensity 0 10 15 20 25 30 35 m / z 40 45 50 55 60 The infrared spectrum of the organic product F is shown below. 100 transmittance 50 (%) 0 4000 3000 2000 1500 wavenumber / cm1 1000 500OCR 2010<br />
17 Name or draw the structures of the alcohol E and the organic product F. Write an equation for the reaction of alcohol E with acidified potassium dichromate(VI).Use [O] to represent the oxidising agent, acidified potassium dichromate(VI). In your answer, you should make clear how each structure fits with the information given above.[7]OCR 2010 [Total: 19] Turn over<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_2_QP_JAN10_question_6-0.jpg)
![(i) 2-Methylpropan-2-ol (cid:57) Expected Answers Mark Scheme January 2010 Marks ALLOW methylpropan-2-ol Additional Guidance F322 Question 6 (a) (b) (c) (i) Same molecular formula but different structural formulae (cid:57) O H (cid:57) (ii) CH3CH2CH2CH2OH OR (CH3)2CHCH2OH (cid:57) ALLOW OH OR OH 26 Formula must be skeletal AND not include any symbol except for OH ALLOW Same molecular formula but different arrangement of atoms OR Same molecular formula but different structures OR Same molecular formula but different displayed formulae DO NOT ALLOW Same molecular formula but different spatial arrangement of atoms ALLOW displayed formula ALLOW sticks (i.e. no H shown bonded to C) ALLOW DO NOT ALLOW OH shown as below OH sticks OK but OH is not OK OH sticks OK and OH is OK ALLOW correct ethers<br />
F322 Question (d) Expected Answers Has OH (bonds) OR has hydroxyl (groups) OR has hydroxy (groups) (cid:57) Forms hydrogen bonds with water (molecules) (cid:57) Marks (e) (f) (i) CH3COOCH2CH2OOCCH3 1 mark for each ester end of molecule (cid:57)(cid:57) CH3 CH3 CH3 C C C C CH3 (cid:57) (cid:57) (ii) E/Z (cid:57) (iii) CH3CH2CH=CH2 OR but-1-ene (cid:57) Mark Scheme January 2010 Additional Guidance ALLOW marks from a diagram of hydrogen bonding IGNORE reference to alcohol functional group DO NOT ALLOW forms hydrogen bonds ALLOW displayed formula OR skeletal formula ALLOW sticks CH3COOCH2CH2OH shows one of the two ester groups and scores one mark DO NOT ALLOW H3C CH3 H3C OH CH3 OH i.e. no ECF ALLOW cis-trans IGNORE geometric If but-1-ene given in part (i), ALLOW but-2-ene OR CH3CH=CHCH3 i.e. ECF from f(i) DO NOT ALLOW methylpropene: H3C H3C 27<br />
F322 Question From the evidence, candidates may have identified compound F as propanone, propanal or propanoic acid (cid:120) The mark scheme for F = propanone and propanal is shown in the Expected Answers column. (cid:120) The mark scheme for F = propanoic acid is shown in the Additional Guidance column. If F is propanone or propanoic acid, then maximum score = 7; but if F is propanal then maximum score = 6 Expected Answers Mark Scheme (g) Marks Additional Guidance January 2010 19 28 Mark scheme for F = propanone and propanal mass spec of E Remember to check the spectrum Quality of Written Communicationmass spec gives M+ or molecular ion of 60 OR mass spec gives parent ion of 60 OR highest m/z (ALLOW m/e) value is 60 (cid:57) m/z = 45 indicates loss of CH3 OR m/z = 45 indicates presence of CH3CHOH OR CH2CH2OH OR C2H5O (cid:57) IR of FRemember to check the spectrum IR shows no broad absorption between 2500 to 3300 cm1 so no OH bond OR no broad absorption between 2500 to 3300 cm1 so not a carboxylic acid (cid:57) IR shows absorption at 1700 cm1 due to a C=O bond OR absorption at 1700 cm1 indicates a ketone OR aldehyde present (cid:57) Identification and equation F is CH3COCH3 OR propanone (cid:57) E is CH3CHOHCH3 OR propan-2-ol (cid:57) CH3CHOHCH3 + [O] (cid:127)(cid:111) CH3COCH3 + H2O (cid:57) If F has been incorrectly identified as propanal, mark identification and equation as ECF, so max = 2 ALLOW E is CH3CH2CH2OH (cid:57) ALLOW: CH3CH2CH2OH + [O] (cid:111) CH3CH2CHO + H2O (cid:57) Total Mark scheme for F = propanoic acid mass spec of E Remember to check the spectrum QWCmass spec gives M+ or molecular ion of 60 OR mass spec gives parent ion of 60 OR highest m/z (OR m/e) value is 60 (cid:57) m/z = 45 indicates loss of CH3 OR m/z = 45 indicates presence of CH3CHOH OR CH2CH2OH OR C2H5O (cid:57) IR of F Remember to check the spectrum IR shows (broad) absorption somewhere between 3500 and 2500 cm1 suggests carboxylic acid OR OH bond (cid:57) IR shows absorption at 1700 cm1 due to C=O OR absorption at 1700 cm1 indicates a carboxylic acid (cid:57) Identification and equation F is CH3CH2COOH OR propanoic acid (cid:57) E is CH3CH2CH2OH OR propan-1-ol (cid:57) CH3CH2CH2OH + 2[O] (cid:127)(cid:111) CH3CH2COOH + H2O (cid:57)<br />
January 2010 Mark Scheme F322 Extra guidance for marking of Q6(g) If E has not been identified OR if F has been identified as a ketone or aldehyde, use the left-hand mark scheme If F has been identified as a carboxylic acid, use the right-hand mark scheme Mass spec These two marking points stand as independent marks whichever compounds have been identified. The positive sign for fragment ions is not required. IGNORE negative charge. The mass spec may well be on the actual spectrum. IR mark These stand as independent marks whichever compounds have been identified. The IR analysis may well be on the actual spectrum. Identification marks If both structure and name are given they must both be correct but allow propanol drawn with the correct structure because the position number of the OH has been clearly identified ALLOW ECF for identification of F e.g. if E is pentan-2-ol (cid:56) then an answer of pentan-2-one for F will be given a mark (cid:57) as ECF ALLOW identification marks for E and F from equation Equation mark ALLOW ECF for any correct equation showing the oxidation of any alcohol to the appropriate product. ALLOW molecular formulae in equations, i.e. C3H7OH + [O] (cid:111) C2H5CHO + H2O (cid:57) ; C3H8O + [O] (cid:111) C3H6O + H2O (cid:57) ; C3H7OH + [O] (cid:111) C2H5COH + H2O (cid:57) 29<br />](https://learnah.org/wp-content/uploads/2018/08/OCR_2_QP_JAN10_answer_6-0.jpg)
