2- bromo-3,3-dimethylpentane

A-10. Draw the structures of all the alkenes, including stereoisomers, that can be formed from the E2 elimination of 3-bromo-2,3-dimethylpentane with sodium ethoxide (NaOCH2CH3) in ethanol. Which of these would you expect to be the major product ... 

Since compound A gives a single alkene on being treated with sodium ethoxide in ethanol, it can only be 3-bromo-2,4-dimethylpentane, and compound B must be 2,4-dimethyl-2-pentene. 

Scheme 6.3 Solvolysis of 2-bromo-2,3-dimethylpentane in methanol leads to formation of up to six different products via multiple mechanistic pathways.

As can be deduced from discussions presented above and in Chapter 5, it is very important to recognize that when designing reactions involving carbocations, both migration reactions and elimination reactions can complicate the outcome of intended SnI transformations. An example illustrating the potential formation of multiple side products is shown in Scheme 6.3 with the solvolysis of 2-bromo-2,3-dimethylpentane in methanol. 

Propose an S l mechanism for the solvolysis of 3-bromo-2,3-dimethylpentane in ethanol. 

We saw (Section 6-12) that the 8 2 reaction is stereospecific The nucleophile attacks from the back side of the electrophilic carbon atom, giving inversion of configuration. In contrast, the S l reaction is not stereospecific. In the 8 1 mechanism, the carbocation intermediate is sp hybridized and planar. A nucleophile can attack the carbocation from either face. Figure 6-10 shows the 8 1 solvolysis of a chiral compound, (S)-3-bromo-2,3-dimethylpentane, in ethanol. The carbocation is planar and achiral attack from both faces gives both enantiomers of the product. Such a process, giving both enantiomers of the product (whether or not the two enantiomers are produced in equal amounts), is called racemization. The product is either racemic or at least less optically pure than the starting material... 

Write structural formulas for the following organic compounds (a) 3-methylhexane, (b) 1,3,5-trichloro-cyclohexane, (c) 2,3-dimethylpentane, (d) 2-bromo-4-phenylpentane, (e) 3,4,5-trimethyloctane. 

The results of intramolecular Li-Barbier reactions (cyclization reactions) with 5-bromo-l-cyano-2,2-dimethylpentane and the corresponding 6-bromohexane were rather disappointing [22]. The expected 2,2-dimethylhexanone was formed in only 31% yield ... 

When 3-bromo-2,4-dimethylpentane is treated with sodium hydroxide, only one alkene is formed. Draw the product and explain why this reaction has only one regiochemical outcome. 

Four alkenes are formed from the El reaction of 3-bromo-2,3-dimethylpentane and methoxide ion. Draw the structures of the alkenes and rank them according to the amount that would be formed. I... 

Problem 9.20 How many products can result from the dehydrobromination of 3-bromo- 2,3-dimethylpentane Predict the major alkene product formed. Predict the alkene formed in the smallest amount. 

---