1-Chloro-l-methylcyclopentane

When methylcyclopentene is treated with HCl, the isolated product is 1-chloro-l-methylcyclopentane. When methylcyclopentene is treated with concentrated sulfuric acid, however, methylcyclopentene is usually isolated rather than a different product. (This will be discussed in Chapter 12.) Briefly discuss why there is such a difference when sulfuric acid is a stronger acid than HCl. 

Using Markovnikov s rule, we predict that 2-iodo-2-methylpropane is the product in (a) and that 1-chloro-l-methylcyclopentane is the product in (b). 

Addition of HC1 to 1-isopropenyl-l-methylcyclopentane yields 1-chloro-1,2,2-trimethylcydohexane. Propose a mechanism, showing the structures of the intermediates and using curved arrows to indicate electron flow in each step. 

The hydride transfer reaction was found to have an activation energy of 9.9 Kcal/mole. Transfer from methylcyclopentane occurred much more easily than from methylcyclohexane where an Ea of 21.3 Kcal/mole was obtained. The difference between the two hydride donors can be rationalized by noting that solvolysis of the corresponding 1-chloro-l-methylcycloalkanes favors the cyclopentyl... 

Figure 28-2 Models of (a) cif-l-chloro-3-methylcyclopentane, (b) tram-1 -chloro- 3 -methylcyclopentane, and (c) ds-1 -chloro- 3 -methylcyclopentane (stereoview).

In a study of the reaetion between alkyl halides and the electrogenerated naphthalene radical anion, Sease and Reed [297] observed that only alkyl chlorides, such as 1-chloro-hexane and 6-chloro-l-hexene, are catalytically reduced 1-chlorohexane gives only n-hex-ane, whereas 6-chloro-l-hexene affords methylcyclopentane and 1-hexene. In an earlier paper [296], the reactions of 1-bromo- and 1-chlorobutane with the electrogenerated radical anions of rmn -stilbene and anthracene in DMSO were examined. Britton and Fry [298] elucidated the kinetics of the electron-transfer reaction between 1-chlorooctane and the phenanthrene radieal anion in DMF. 

The presence of by-products such as 1-chloro-ethyl acetate 3 and a small amoimt of ethyl acetate, suggests that the initial step is an intermolecular hydride ion transfer from cyclohexane or methylcyclopentane towards acetyl chloride-aluminium chloride complex to give 1-methylcyclopentene. From cyclohexane, the cyclohexyl cation isomerizes to 1-methyl-l-cyclopentyl carbenium ion which loses a proton. Then, the 1-chloro-ethylate-aluminium chloride... 

Draw structural representations of each of the following molecules (a) trans-l-chloro-2-ethylcyclopropane (b) cis-1-bromo-2-chlorocyclopentane (c) 2-chloro-l,l-diethylcyclopropane (d) frans-2-bromo-3-chloro-l,l-diethylcyclopropane (e) c/s-1,3-dichloro-2,2-dimethylcyclobutane (f) c(s-2-chloro-l,l-difluoro-3-methylcyclopentane. 

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