Isopropylidenecyclopentane -

PROBLEM For each reaction, write the mechanism using curved arrows for the conversion of the alcohol into
17-33 the corresponding alkene with $\mathrm{POCl}_{3}$. In each case, explain the regiochemistry of the elimination.
(a)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0597.jpg?height=212&width=646&top_left_y=520&top_left_x=479)
(b)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0597.jpg?height=178&width=651&top_left_y=529&top_left_x=1187)
(c)
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0597.jpg?height=207&width=735&top_left_y=739&top_left_x=478)


Isopropylidenecyclopentane -

PROBLEM The trimethylsilyl (TMS) protecting group is one of several silicon protecting groups for alcohols.
17-34 For each reaction, draw the mechanism for the protection of ( $R$ )-3-bromo-1-butanol with the following silyl chlorides, using triethylamine as the base:
(a) tert-butyldimethylsilyl chloride (TBS-Cl)
(b) triisopropylsilyl chloride (TIPS-Cl)
(c) triethylsilyl chloride (TES-Cl)


Isopropylidenecyclopentane -

PROBLEM When the following alcohol is treated with $\mathrm{POCl}_{3}$ and pyridine, the expected elimination product
17-35 is formed. However, when the same alcohol is treated with $\mathrm{H}_{2} \mathrm{SO}_{4}$, the elimination product is 1,2-dimethylcyclopentene. Propose a mechanism for each pathway to account for these differences.
![](https://cdn.mathpix.com/cropped/2025_02_06_5556f7656cbdcaa0f9a7g-0597.jpg?height=171&width=958&top_left_y=1351&top_left_x=410)