17.1. Aldehydes and ketones
A subsection of Chemistry, 9701, through 17. Carbonyl compounds
Listing 10 of 304 questions
Ketones are widely used as solvents and as intermediates in the chemical industry. Ketones contain the reactive keto group, C O. Propanone, CH3COCH3, undergoes a reaction with hydrogen cyanide, HCN. What type of reaction is this? What reagents are used? Draw a diagram to show the dipole present in the propanone molecule. Propanone reacts with 2,4-dinitrophenylhydrazine reagent. H2N NO2 NO2 N H 2,4-dinitrophenylhydrazine Construct a balanced equation for the reaction between propanone and 2,4-dinitrophenylhydrazine. A similar type of reaction occurs between propanone and hydroxylamine, NH2OH. Draw the displayed formula of the organic product of this reaction. H3C H3C C O + H H N OH
9701_s11_qp_21
THEORY
2011
Paper 2, Variant 1
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Fermentation of sugars by bacteria or moulds produces many different organic compounds. One compound present in fermented molasses is 2-ethyl-3-methylbutanoic acid which gives a distinctive aroma to rum. (CH3)2CHCH(C2H5)CO2H 2-ethyl-3-methylbutanoic acid What is the molecular formula of 2-ethyl-3-methylbutanoic acid? How many chiral carbon atoms are present in a molecule of 2-ethyl-3-methylbutanoic acid? If none write ‘none’. A sample of 2-ethyl-3-methylbutanoic acid may be prepared in a school or college laboratory by the oxidation of 2-ethyl-3-methylbutan-1-ol, (CH3)2CHCH(C2H5)CH2OH. State the reagentthat would be used for this oxidation. Describe what colour change would be seen. reagentcolour change from to This reaction is carried out by heating the reacting chemicals together. What could be the main organic impurity present in the sample of the acid? Explain your answer. State whether a distillation apparatus or a reflux apparatus should be used. Explain your answer. A structural isomer of 2-ethyl-3-methylbutan-1-ol is 2-ethyl-3-methylbutan-2-ol, (CH3)2CHC(OH)(C2H5)CH3. What colour change would be seen if this were heated with the reagents you have given in ? Explain your answer as clearly as you can. An isomer of 2-ethyl-3-methylbutanoic acid which is an ethyl ester is a very strong smelling compound which is found in some wines. This ethyl ester contains a branched hydrocarbon chain and is chiral. Draw the displayed formula of this ethyl ester. Identify the chiral carbon atom with an asterisk (*).
9701_s11_qp_23
THEORY
2011
Paper 2, Variant 3
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Complete combustion of compound X gives carbon dioxide and water only. A sample of X is mixed with aqueous potassium(dichromate and boiled under reflux for one hour. The mixture is then distilled and the only organic substance present is collected. The organic substance collected reacts with sodium to give hydrogen, but does not react with 2,4-dinitrophenylhydrazine reagent and does not react with ethanol in the presence of concentrated sulfuric acid to give an ester. What can be deduced from this information?
9701_s12_qp_12
MCQ
2012
Paper 1, Variant 2
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Questions Discovered
304