14.2. Alkenes
A subsection of Chemistry, 9701, through 14. Hydrocarbons
Listing 10 of 191 questions
Benzene can be converted into cyclohexane. For this reaction name the type of reaction and identify the reagent and conditions needed. type of reaction reagent and conditions  State the bond angles in benzene and cyclohexane. bond angle in benzene bond angle in cyclohexane Explain your answers.  When benzene reacts with SO3, benzenesulfonic acid is produced. SO3H benzenesulfonic acid + SO3 The mechanism of this reaction is similar to that of the nitration of benzene. Concentrated H2SO4 is used in an initial step to generate the SO3H+ electrophile as shown. SO3 + H2SO4 SO3H+ + HSO4 – Draw a mechanism for the reaction of benzene with SO3H+ ions. Include all necessary curly arrows and charges. SO3H benzenesulfonic acid SO3H+  Write an equation to show how the H2SO4 catalyst is reformed. 3-dodecylbenzenesulfonic acid can be prepared from benzenesulfonic acid. 3-dodecylbenzenesulfonic acid SO3H SO3H C12H25 benzenesulfonic acid Suggest the reagents and conditions and name the mechanism for this reaction. reagents and conditions mechanism  When concentrated sulfuricacid is added to water, dissociation takes place in two stages. stage 1 H2SO4 H+ + HSO4 – stage 2 HSO4 – H+ + SO4 2– Ka2 = 1.0 × 10–2 mol dm–3 Ka2 is the acid dissociation constant for stage 2. Write the expression for the acid dissociation constant Ka2. Ka2 =  H2SO4 is considered a strong acid whereas HSO4 – is considered a weak acid. Suggest how the magnitude of the acid dissociation constant for stage1 compares to Ka2. Benzoic acid, C6H5CO2H, is a weak acid. A solution of 0.0250 mol dm–3 benzoic acid has a pH of 2.90. Calculate the Ka of benzoic acid.  Ka = mol dm–3  
9701_s19_qp_41
THEORY
2019
Paper 4, Variant 1
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Benzene can be converted into cyclohexane. For this reaction name the type of reaction and identify the reagent and conditions needed. type of reaction reagent and conditions  State the bond angles in benzene and cyclohexane. bond angle in benzene bond angle in cyclohexane Explain your answers.  When benzene reacts with SO3, benzenesulfonic acid is produced. SO3H benzenesulfonic acid + SO3 The mechanism of this reaction is similar to that of the nitration of benzene. Concentrated H2SO4 is used in an initial step to generate the SO3H+ electrophile as shown. SO3 + H2SO4 SO3H+ + HSO4 – Draw a mechanism for the reaction of benzene with SO3H+ ions. Include all necessary curly arrows and charges. SO3H benzenesulfonic acid SO3H+  Write an equation to show how the H2SO4 catalyst is reformed. 3-dodecylbenzenesulfonic acid can be prepared from benzenesulfonic acid. 3-dodecylbenzenesulfonic acid SO3H SO3H C12H25 benzenesulfonic acid Suggest the reagents and conditions and name the mechanism for this reaction. reagents and conditions mechanism  When concentrated sulfuricacid is added to water, dissociation takes place in two stages. stage 1 H2SO4 H+ + HSO4 – stage 2 HSO4 – H+ + SO4 2– Ka2 = 1.0 × 10–2 mol dm–3 Ka2 is the acid dissociation constant for stage 2. Write the expression for the acid dissociation constant Ka2. Ka2 =  H2SO4 is considered a strong acid whereas HSO4 – is considered a weak acid. Suggest how the magnitude of the acid dissociation constant for stage1 compares to Ka2. Benzoic acid, C6H5CO2H, is a weak acid. A solution of 0.0250 mol dm–3 benzoic acid has a pH of 2.90. Calculate the Ka of benzoic acid.  Ka = mol dm–3  
9701_s19_qp_43
THEORY
2019
Paper 4, Variant 3
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Propene, C3H6, reacts with H2O in the presence of an acid catalyst to form an alcohol with molecular formula C3H8O. Name this type of reaction. Name the catalyst used and state the conditions needed for this reaction to occur. catalyst conditions  Complete the table to show the numbers of sigma (σ) bonds and pi (π) bonds present in propene, C3H6, and C3H8O. σ π C3H6 C3H8O  The reaction of propene, C3H6, with H2O occurs in a two-step mechanism. In step1 C3H6 reacts with the catalyst, H+, to form a carbocation. Draw structures to identify the more stable and less stable carbocations which can form in step1. Explain your answer. more stable carbocation less stable carbocation explanation  Name the major organic product formed from the reaction of propene, C3H6, with H2O. 2-bromopropane reacts to form propene, hydrogen bromide and water under certain conditions. Name this type of reaction. Describe the reagents and conditions needed to favour this reaction. reagents conditions  
9701_s21_qp_21
THEORY
2021
Paper 2, Variant 1
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191