13.1. Formulas, functional groups and the naming of organic compounds
A subsection of Chemistry, 9701, through 13. An introduction to AS Level organic chemistry
Listing 10 of 266 questions
An organic ester, B, has the empirical formula C2H4O. An experiment by a student in a college gave a value of 87.5 for Mr of B. What is the molecular formula of B? ………………………… In the boxes below, draw the structural formulae of four isomers of B that are esters. W X Y Z The student hydrolysed his sample of B by heating with aqueous mineral acid and then separating the alcohol, C, that was formed. He heated the alcohol C under reflux with acidified dichromate(ions and collected the product D. A sample of D gave an orange precipitate with 2,4-dinitrophenylhydrazine reagent. A second sample of D gave no reaction with Tollens’ reagent. What group does the reaction with 2,4-dinitrophenylhydrazine reagent show to be present in D? ……………………………………… What does the result of the test with Tollens’ reagent show about D? ……………………………………… What is the structural formula of the alcohol C? Which of your esters, W, X, Y, or Z has the same structure as that of the ester B? ……………… Which, if any of your esters, W, X, Y, or Z is chiral? Explain your answer.
9701_w08_qp_2
THEORY
2008
Paper 2, Variant 0
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Compound R is a weak diprotic acid which is very soluble in water. A solution of R was prepared which contained 1.25 g of R in 250 cm3 of solution. When 25.0 cm3 of this solution was titrated with 0.100 mol dm–3 NaOH, 21.6 cm3 of the alkali were needed for complete reaction. Using the formula H2X to represent R, construct a balanced equation for the reaction between H2X and NaOH. Use the data above to calculate the amount, in moles, of OH– ions used in the titration. Use your answers to and to calculate the amount, in moles, of R present in 25.0 cm3 of solution. Calculate the amount, in moles, of R present in 250 cm3 of solution. Calculate Mr of R. Three possible structures for R are shown below. S T U HO2CCH=CHCO2H HO2CCH(OH)CH2CO2H HO2CCH(OH)CH(OH)CO2H Calculate the Mr of each of these acids. Mr of S = Mr of T = Mr of U = Deduce which of the structures, S, T or U, correctly represents the structure of the acid, R. R is represented by It is possible to convert S, T, or U into one another. State the reagentand essential conditions that would be used for the following conversions. S into T S into U T into S Give the structural formula of the organic product formed in each of the following reactions. T reacting with an excess of Na U reacting with an excess of Na2CO3 The acid S shows stereoisomerism. Draw structures to show this isomerism. Label each isomer. When one of the isomers of S is heated at 110 °C in the absence of air, a cyclic compound V, with molecular formula C4H2O3, is formed. The other isomer of S does not react at this temperature. Suggest the displayed formula of V.
9701_w13_qp_21
THEORY
2013
Paper 2, Variant 1
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Compound R is a weak diprotic acid which is very soluble in water. A solution of R was prepared which contained 1.25 g of R in 250 cm3 of solution. When 25.0 cm3 of this solution was titrated with 0.100 mol dm–3 NaOH, 21.6 cm3 of the alkali were needed for complete reaction. Using the formula H2X to represent R, construct a balanced equation for the reaction between H2X and NaOH. Use the data above to calculate the amount, in moles, of OH– ions used in the titration. Use your answers to and to calculate the amount, in moles, of R present in 25.0 cm3 of solution. Calculate the amount, in moles, of R present in 250 cm3 of solution. Calculate Mr of R. Three possible structures for R are shown below. S T U HO2CCH=CHCO2H HO2CCH(OH)CH2CO2H HO2CCH(OH)CH(OH)CO2H Calculate the Mr of each of these acids. Mr of S = Mr of T = Mr of U = Deduce which of the structures, S, T or U, correctly represents the structure of the acid, R. R is represented by It is possible to convert S, T, or U into one another. State the reagentand essential conditions that would be used for the following conversions. S into T S into U T into S Give the structural formula of the organic product formed in each of the following reactions. T reacting with an excess of Na U reacting with an excess of Na2CO3 The acid S shows stereoisomerism. Draw structures to show this isomerism. Label each isomer. When one of the isomers of S is heated at 110 °C in the absence of air, a cyclic compound V, with molecular formula C4H2O3, is formed. The other isomer of S does not react at this temperature. Suggest the displayed formula of V.
9701_w13_qp_22
THEORY
2013
Paper 2, Variant 2
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Questions Discovered
266