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9.E: Alkynes: An Introduction to Organic Synthesis (Exercises)

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    61714
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    These are the homework exercises to accompany the Textmap for McMurry's Organic Chemistry textbook.

    9.1 Naming Alkynes

    9.1 Exercises

    Questions

    Q9.1.1

    Name the following compounds:

    Q9.1.2

    How many isomers are possible for C5H8? Draw them.

    Q9.1.3

    Draw the following compounds:

    A) 4,4-dimethyl-2-pentyne

    B) 3-octyne

    C) 3-methyl-1-hexyne

    D) trans 3-hepten-1-yne

    Q9.1.4

    Do alkynes show cis-trans isomerism? Explain.

    Solutions

    S9.1.1

    A – 3,6-diethyl-4-octyne

    B – 3-methylbutyne

    C – 4-ethyl-2-heptyne

    D – cyclodecyne

    S9.1.2

    2 possible isomers

    S9.1.3

    9-1-3 sol.png

    S9.1.4

    No. A triply bonded carbon atom can form only one other bond and has linear electron geometry so there are no "sides". Allkenes have two groups attached to each inyl carbon with a trigonal planar electron geometry that creates the possibility of cis-trans isomerism.

    9.4 Hydration of Alkynes

    9.4 Exercises

    Questions

    Q9.4.1

    What alkyne would you start with to gain the following products, in an oxidation reaction? Keep in mind resonance.

    9-4qu.png

    Q9.4.2

    Propose a reaction scheme for the following compound starting from the alkyne and showing required reagents and intermediates.

    Solutions

    S9.4.1

    9.4.png

    S9.4.2

    9.5 Reduction of Alkynes

    9.5 Exercises

    Questions

    Q9.5.1

    Usng any alkyne how would you prepare the following compounds:

    pentane, trans-4-methyl-2-pentene, cis-4-methyl-2-pentene.

    Solutions

    S9.5.1

    9.5.png

    9.7 Alkyne Acidity: Formation of Acetylide Anions

    9.7 Exercises

    Questions

    Q9.7.1

    If OH- has a pKa of 14.00 in water, what pKa be required to deprotonate OH-?

    Solutions

    S9.7.1

    Need a stronger base, or a compound with a pKa > 14.00 to deprotonate.

    9.8 Alkylation of Acetylide Anions

    9.8 Exercises

    Questions

    Q9.8.1

    Give the possible reactants for the following formations:

    Q9.8.2

    Propose a synthetic route to produce 2-pentene from propyne and an alkyl halide.

    Solutions

    S9.8.1

    S9.8.2

    9.8(2).png

    9.9 An Introduction to Organic Synthesis

    9.9 Exercises

    Questions

    Q9.9.1

    Starting at 3-hexyne predict synthetic routes to achieve:

    A – cis-3-hexene

    B – 3,4-dibromohexane

    C – 3-hexanol

    Q9.9.2

    Starting with acetylene and any alkyl halides propose a synthesis to make (a) pentanal and (b) hexane.

    Solutions

    S9.9.1

    S9.9.2

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