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Alcohols SCT Page 1 of 20 (E) Name the Type of Structural Isomerism Shown by C and D

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Alcohols SCT Page 1 of 20 (E) Name the Type of Structural Isomerism Shown by C and D Q1. Alcohol A (CH3)2CHCH(OH)CH3 undergoes reactions separately with acidified potassium dichromate(VI) and with concentrated sulfuric acid. (a) Deduce the IUPAC name for alcohol A. ___________________________________________________________________ (1) (b) Draw the structure of the organic product, B, formed when A is oxidised in the reaction with acidified potassium dichromate(VI). (1) (c) Two isomeric alkenes, C and D, are formed when A is dehydrated in the reaction with concentrated sulfuric acid. Name the mechanism for this dehydration reaction. ___________________________________________________________________ (1) (d) Draw the structure of each isomer. Isomer C Isomer D (2) Alcohols SCT Page 1 of 20 (e) Name the type of structural isomerism shown by C and D. ___________________________________________________________________ (1) (f) List alcohol A, product B and isomer C in order of increasing boiling point. ___________________________________________________________________ (1) (g) Draw the structure of the isomer of A that is not oxidised by acidified potassium dichromate(VI). (1) (h) Draw the structure of the isomer of A that cannot be dehydrated to form an alkene by reaction with concentrated sulfuric acid. (1) (Total 9 marks) Alcohols SCT Page 2 of 20 Q2. (a) Propanoic acid can be made from propan-1-ol by oxidation using acidified potassium dichromate(VI). Propanal is formed as an intermediate during this oxidation. (i) State the colour of the chromium species after the potassium dichromate(VI) has reacted. ______________________________________________________________ (1) (ii) Describe the experimental conditions and the practical method used to ensure that the acid is obtained in a high yield. Draw a diagram of the assembled apparatus you would use. Conditions _____________________________________________________ ______________________________________________________________ Apparatus (4) (iii) Describe the different experimental conditions necessary to produce propanal in high yield rather than propanoic acid. ______________________________________________________________ ______________________________________________________________ (2) (b) Propan-1-ol is a volatile, flammable liquid. Give one safety precaution that should be used during the reaction to minimise this hazard. ___________________________________________________________________ (1) Alcohols SCT Page 3 of 20 (c) A student followed the progress of the oxidation of propan-1-ol to propanoic acid by extracting the organic compounds from one sample of reaction mixture. (i) Give a chemical reagent which would enable the student to confirm the presence of propanal in the extracted compounds. State what you would observe when propanal reacts with this reagent. Reagent _______________________________________________________ Observation ____________________________________________________ ______________________________________________________________ (2) (ii) Give a chemical reagent that would enable the student to confirm the presence of propanoic acid in the extracted compounds. State what you would observe when propanoic acid reacts with this reagent. Reagent _______________________________________________________ Observation ____________________________________________________ ______________________________________________________________ (2) (d) Predict which one of the compounds, propan-1-ol, propanal and propanoic acid will have the highest boiling point. Explain your answer. Prediction __________________________________________________________ Explanation _________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (3) (Total 15 marks) Alcohols SCT Page 4 of 20 Q3. This question concerns the oxidation of a primary alcohol. The experiment was carried out using the distillation apparatus shown in the diagram. The oxidation product was distilled off as soon as it was formed. (a) Suggest the identity of reagent P. ___________________________________________________________________ (1) (b) State the chemical change that causes the solution in the flask to appear green at the end of the reaction. ___________________________________________________________________ (1) (c) Give one reason why using a water bath is better than direct heating with a Bunsen burner. ___________________________________________________________________ ___________________________________________________________________ (1) (d) Suggest a reagent that could be used to confirm the presence of an aldehyde in the distillate. State the observation you would expect to make if an aldehyde were present. Reagent ___________________________________________________________ Observation _________________________________________________________ (2) (Total 5 marks) Alcohols SCT Page 5 of 20 Q4. There are seven isomeric carbonyl compounds with the molecular formula C5H10O. The structures and names of some of these isomers are given below. Structure Name pentanal 2-methybutanal 2, 2-dimethypropanal pentan-2-one (a) (i) Complete the table. (ii) Two other isomeric carbonyl compounds with the molecular formula C5H10O are not shown in the table. One is an aldehyde and one is a ketone. Draw the structure of each. isomeric aldehyde isomeric ketone (4) Alcohols SCT Page 6 of 20 (b) Pentanal, CH3CH2CH2CH2CHO, can be oxidised to a carboxylic acid. (i) Write an equation for this reaction. Use [O] to represent the oxidising agent. _____________________________________________________________ (ii) Name the carboxylic acid formed in this reaction. ______________________________________________________________ (2) (c) Pentanal can be formed by the oxidation of an alcohol. (i) Identify this alcohol. ______________________________________________________________ (ii) State the class to which this alcohol belongs. ______________________________________________________________ (2) (Total 8 marks) Alcohols SCT Page 7 of 20 Q5. There are four isomeric alcohols with the molecular formula C4H10O (a) Two of these are butan-l-ol (CH3CH2CH2CH2OH) and butan-2-ol. The other two isomers are alcohol X and alcohol Y. Draw the displayed formula for butan-2-ol. Alcohol X does not react with acidified potassium dichromate(VI) solution. Give the structure of alcohol X. Name the fourth isomer, alcohol Y. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (3) (b) The infrared spectrum of one of these isomeric alcohols is given below. Identify one feature of the infrared spectrum which supports the fact that this is an alcohol. You may find it helpful to refer to Table 1 on the Data Sheet. Explain how infrared spectroscopy can be used to identify this isomeric alcohol. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (3) Alcohols SCT Page 8 of 20 (c) British scientists have used bacteria to ferment glucose and produce the biofuel butan-1-ol. Write an equation for the fermentation of glucose (C6H12O6) to form butan-1-ol, carbon dioxide and water only. State one condition necessary to ensure the complete combustion of a fuel in air. Write an equation for the complete combustion of butan-1-ol and state why it can be described as a biofuel. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (4) (d) Butan-1-ol reacts with acidified potassium dichromate(VI) solution to produce two organic compounds. State the class of alcohols to which butan-1-ol belongs. Draw the displayed formula for both of the organic products. State the type of reaction that occurs and the change in colour of the potassium dichromate(VI) solution. ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ ___________________________________________________________________ (5) (Total 15 marks) Alcohols SCT Page 9 of 20 Q6. Ethanal is prepared by heating ethanol with potassium dichromate(VI) in the presence of sulfuric acid. Figures 1 and 2 show two possible ways of heating this reaction mixture. Figure 1 Figure 2 State which arrangement would not be suitable for the preparation of ethanal. Explain your answer. Arrangement ____________________________________________________________
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