Chemistry $^{3}$ : Introducing inorganic, organic and physical chemistry

Andrew Burrows, John Holman, Andrew Parsons

Chapter 21 Alkenes and alkynes: electrophilic addition and pericyclic reactions - all with Video Answers

Educators

Chapter Questions

07:22

Problem 1

Suggest mechanisms for the following electrophilic addition reactions. (Section 21.3)

Nicholas S.

Numerade Educator

07:26

Suggest reagents (a-h) for the following transformations. More than one step may be required for each transformation. (The relative stereochemistry of the products is shown, not the absolute stereochemistry.) (Sections $21.3$ and 21.4)

Nicholas S.

Numerade Educator

07:10

Problem 3

An outline of a racemic synthesis of $\alpha$-multistriatin, a pheromone of the elm bark beetle, is shown below. (Sections $21.3$ and 21.4)

Rajesh S.

Numerade Educator

05:35

Problem 4

Draw the product from reaction of prop-1-yne $\left(\mathrm{HC}=\mathrm{CCH}_{3}\right)$ with each of the following reagents (Sections $21.2$ and $21.5)$ :
(a) $\mathrm{HBr}(2$ equivalents);
(b) $\mathrm{NaNH}_{2}$ then $\mathrm{PhCH}_{2}$ Br followed by $\mathrm{Na} / \mathrm{NH}_{3}$ :
(c) $\mathrm{NaNH}_{2}$ then Etl followed by $\mathrm{H}_{2} / \mathrm{Pd} / \mathrm{C}$.

Nicholas S.

Numerade Educator

07:56

Problem 5

Linalool $\left(\mathrm{C}_{10} \mathrm{H}_{18} \mathrm{O}\right)$ is found in lavender flowers and is one of the constituents of lavender oil. It has a single chiral centre and both $R$ and $S$ enantiomers (see Section 18.4, p.845) are found in lavender oil. To determine the structure of linalool, the following reactions were carried out. (Sections $21.3$ and 21.4)
(a) Use the information in reaction 1 to determine the number of $\mathrm{C}=\mathrm{C}$ bonds in linalool.
(b) From the products in reaction 2, what are the two possible structures of linalool?
(c) Use the information in reaction 3 to determine the structure of linalool.
(Hint. Disiamyiborane reacts with a C=C bond in a hydroboration reaction.)
(d) Explain why the reaction of disiamylborane with linalool is chemoselective. (Hint. Consider the size of disiamylborane.)

Rajesh S.

Numerade Educator

07:51

Problem 6

Reserpine is a natural product that has been used in medicine to control high blood pressure and to relieve psychotic symptoms. Part of a 21-step synthesis of the natural product reserpine, published by the American chemist R. B. Woodward, is shown below. (Section 21.3)
(a) Give a reaction mechanism that explains how 4 is converted into 5. (Hint: the reaction) involves an intermediate bromonium ion).
(b) The first step in the conversion of 5 into 6 involves deprotonation of 5 and elimination of bromide ion to form an alkene. Suggest a structure of the intermediate alkene.
(c) Give a reaction mechanism that explains how 6 is converted into 7 . (Hint: the reaction involves an intermediate bromonium ion).

Rajesh S.

Numerade Educator