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7.E: Alkenes: Structure and Reactivity (Exercises)

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    61712
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    These are the homework exercises to accompany the Textmap for McMurry's Organic Chemistry textbook.

    7.2 Calculating Degree of Unsaturation

    7.2 Exercises

    Questions

    Q7.2.1

    Calculate degrees of unsaturation (DoU) for the following, and propose a structure for each.

    A – C5H8

    B – C4H4

    Q7.2.1

    Calculate the degree of unsaturation (DoU) for the following molecules

    A – C5H5N

    B – C5H5NO2

    C – C5H5Br

    Q7.2.3

    The following molecule is caffeine (C8H10N4O2), determine the degrees of unsaturation (DoU).

    Solutions

    S7.2.1

    S7.2.2

    A = 4, B = 4, C = 3

    S7.2.3

    6 DoU

    7.4 Cis-Trans Isomerism in Alkenes

    7.4 Exercises

    Questions

    Q7.4.1

    Which of the following can have cis/trans isomers? Draw their isomers.

    (CH3CH2)CH=CH2, (CH3CH2)2C=CHCH3, (CH3CH2)CH=CHCH3

    Q7.4.2

    Name the following compounds, with cis/trans nomenclature.

    Solutions

    S7.4.1

    The last compound in the list can be a cis/trans isomer.

    S7.4.2

    A – trans-4-methyl-2-hexene

    B – cis-2,5-dibromo-3-hexene

    7.5 Alkene Stereochemistry and the E, Z Designation

    7.5 Exercises

    Questions

    Q7.5.1

    Order the following in increasing priority.

    A) –H, –Cl, –OH

    B) –CH3, CH2OH, CH2CH3

    C) –C≡CH, –CH=CH2, –CH=O

    Q7.5.2

    Label the following as E or Z conformations.

    Solutions

    S7.5.1

    A) –H < OH < Cl (highest priority)

    B) –CH3 < CH2CH3 < CH2OH (highest priority)

    C) –CH=CH2 < C≡CH < CH=O (highest priority)

    S7.5.2

    A – Z

    B – Z

    C – E

    7.6 Stability of Alkenes

    7.6 Exercises

    Questions

    Q7.6.1

    Which is the more stable alkene in each pair?

    Solutions

    S7.6.1

    A – 2

    B – 1

    7.8 Orientation of Electrophilic Additions: Markovnikov's Rule

    7.8 Exercises

    Questions

    Q7.8.1

    Predict the product(s) for the following reactions:

    Q7.8.2

    In each case, suggest an alkene that would give the product shown.

    Solutions

    S7.8.1

    S7.8.2

    7.9 Carbocation Structure and Stability

    7.9 Exercises

    Questions

    Q7.9.1

    Draw the cationic intermediates that are seen in the following reactions:

    Solutions

    S7.9.1

    7.10 The Hammond Postulate

    7.10 Exercises

    Questions

    Q7.10.1

    Consider the second step in the electrophilic addition of HBr to an alkene. Is this step exergonic or endergonic and does the transition state represent the product or the reactant (cation)? Draw out an energy diagram of this step reaction.

    Solutions

    S7.10.1

    Exergonic and the transition state (second step) represents the reactant (cation).

    As shown to go from intermediate cation to final product the step is exergonic.

    S7-10-1.png

     

    7.11 Evidence for the Mechanism of Electrophilic Additions

    7.11 Exercises

    Questions

    Q7.11.1

    The following reaction shows a rearrangement within the mechanism. Propose a mechanism that shows this.

    Solutions

    S7.11.1

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