13. An introduction to AS Level organic chemistry
A section of Chemistry, 9701
Listing 10 of 507 questions
A student obtained the following results when analysing an organic compound, H. The student allowed test 5 to go to completion and then investigated the product of test 5 with the following result. Calculate the molecular formula of H. What can be deduced about the nature of H by the following tests? test 3 test 4 What functional group would have given a positive result in test 6? What functional group is shown to be present in H by tests 5 and 6? test observation test 1 test 2 test 3 test 4 test 5 test 6 relative molecular mass C, 66.7%; H, 11.1%; O, 22.2% Br2 decolourised H2evolved green colour observed no reaction % composition by mass reactions with Br2reaction with Nareaction with warm Cr2O7 2–/H+ reaction with 2,4-dinitrophenylhydrazine On testing a sample of H, the student found that it was not chiral. H did, however, show cis-trans isomerism. How does cis-trans isomerism arise in an organic molecule? Use all of the information above to draw labelled, displayed formulae of the stereoisomers of compound H.
9701_s05_qp_2
THEORY
2005
Paper 2, Variant 0
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Commercial paint and varnish removers contain a mixture of dichloromethane, CH2Cl2, and methanol, CH3OH. What would be observed when the following reactions are carried out? In each case, give the name or formula of the reaction product which is responsible for the observation you have made. CH2Cl2 is reacted with NaOHand AgNO3and the mixture left to stand. observation product responsible CH3OH is mixed with PCl5. observation product responsible CH3OH is reacted with sodium. observation product responsible When CH2Cl2 is heated under reflux with an excess of NaOH, a compound W is formed. W has the following composition by mass: C, 40.0%; H, 6.7%; O, 53.3%. Use this information and the Data Booklet to show that the empirical formula of W is CH2O. Compounds with the empirical formula CH2O can have the molecular formula C2H4O2. Two possible structural formulae for compounds with molecular formula C2H4O2 are HCO2CH3 and H2C=C(OH)2. In the boxes below, draw displayed formulae for three further structural isomers with the molecular formula C2H4O2. Do not attempt to draw any structures containing rings or O–O bonds. X Y Z Identify which of your compounds, X, Y, or Z, will react with the following reagents. In each case, state what you would observe. solid NaHCO3 compound observation Tollens’ reagent compound observation One of the three compounds, X, Y, or Z, shows stereoisomerism. Draw displayed, labelled structures of the stereoisomers of this compound.
9701_s07_qp_2
THEORY
2007
Paper 2, Variant 0
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Use Chemists use skeletal or partial-skeletal formulae to represent larger structures. For example the structure CH3 CH2 CH2 CH2 CH2 H2C H2C CH C C H OH may also be represented as follows. CH3 H H OH Oestradiol is one of the hormones that controls the reproductive cycle in female mammals. CH3 H H H H HO HO oestradiol On the above structure of oestradiol, circle one chiral centre. What is the total number of chiral centres in the oestradiol molecule? Complete the following part-structures (which have the -OH groups removed) to show the products obtained when oestradiol is reacted with the stated reagents. sodium metal CH3 H H H Examiner’s Use Br2CH3 H H H NaOHCH3 H H H CH3COCl CH3 H H H hot acidified K2Cr2O7 CH3 H H H
9701_s07_qp_4
THEORY
2007
Paper 4, Variant 0
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Ethanedial is used in the production of fabrics which have permanent creases. O O C H ethanedial C H Ethanedial undergoes many of the reactions of aldehydes. Ethanedial reacts with Tollens’ reagent. What would you see if you carried out this reaction? What is the structural formula of the organic compound formed? Ethanedial reacts with hydrogen cyanide, HCN, to give compound F. What is the structural formula of F? What type of reaction is this? What is the structural formula of the compound formed when F is heated with an aqueous mineral acid such as dilute sulphuric acid? Ethanedial can be oxidised and reduced. What is the structural formula of the organic compound formed when ethanedial is heated under reflux with an excess of acidified potassium dichromate(? What is the structural formula of the compound formed when ethanedial is reduced? What reagent would be used for this reduction? When ethanedial is reacted with NaOH and the product treated with a mineral acid such as dilute sulphuric acid, the following reaction sequence takes place. I CHOCHO + NaOH → HOCH2CO2Na II HOCH2CO2Na + H+ → HOCH2CO2H + Na+ What type of reaction is the overall change? An isomer of ethanedial exists which reacts with sodium metal to give hydrogen. Suggest the displayed formula of this isomer.
9701_s08_qp_2
THEORY
2008
Paper 2, Variant 0
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Questions Discovered
507