91Ó°ÊÓ

Predict the product from reaction of the following substance (reddish brown=Br) with:

(a)${\mathbf{\text{PBr}}}_{\mathbf{3}}$

(b) Aqueous${\mathbf{\text{H}}}_{\mathbf{2}}\mathit{S}{\mathit{O}}_{\mathbf{4}}$

(c)${\mathbf{\text{SOCl}}}_{\mathbf{2}}$

(d)Dess-Martin periodinane

(e)${\mathbf{\text{Br}}}_{\mathbf{2}}\mathbf{ }\mathbf{,}\mathbf{}\mathit{F}\mathit{e}\mathit{B}{\mathit{r}}_{\mathbf{3}}$

Predict the product from reaction of the following substance with:

1. ${\mathbf{NaBH}}_4$; then ${\mathbf{H}}_3{\mathbf{O}}^{+}$
2. ${\mathbf{LiAlH}}_4$; then ${\mathbf{H}}_3{\mathbf{O}}^{+}$

3. $\mathbf{2}\text{ }{\mathbf{CH}}_3{\mathbf{CH}}_2\mathbf{MgBr}$; then ${\mathbf{H}}_3{\mathbf{O}}^{+}$

Name and assign R or S stereochemistry to the product (s) you would obtain by reaction of the following substance with ethylmagnesium bromide. Is the product chiral? Is it optically active? Explain.

Question: Evidence for the intermediate carbocations in the acid-catalyzed dehydration of alcohols comes from the observation that rearrangements sometimes occur. Propose a mechanism to account for the formation of 2,3-dimethyl-2-butene from 3,3-dimethyl-2-butanol.

Question:Acid-catalyzed dehydration of 2,2-dimethylcyclohexanol yields a mixture of 1,2-methylcyclohexane and isopropylidenecyclopentane. Propose a mechanism to account for the formation of both products.

Epoxides react with Grignard reagents to yield alcohols. Propose a mechanism.

Treatment of the following epoxide with aqueous acid produces a carbocation intermediate that reacts with water to give a diol product. Show the structure of the carbocation, and propose a mechanism for the second step.

Reduction of 2-butanone with NaBH₄yields 2-butanol. Is the product chiral? Is it optically active? Explain.

Draw structures corresponding to the following IUPAC names:

1. (Z)-2-Ethyl-2-buten-1-ol
2. 3-Cyclohexen-1-ol
3. trans-3-Chlorocycloheptanol
4. 1,4-Pentanediol
5. 2,6-Dimethylphenol
6. o-(2-Hydroxyethyl)phenol

The conversion of 3° alcohols into 3° alkyl halides under acidic conditions involves two cationic intermediates. For each reaction, draw the complete mechanism using curved arrows.