1 (275)

Prévia do material em texto

224 Chapter 11 ALKENES; INFRARED SPECTROSCOPY AND MASS SPECTROMETRY (g) H CH=CH₂ CH₃CH₂CH₂ CH₂CH₃ C CH₃CH₂ H CH₂CH₂CH₃ C CH₃ H H (S) CH₂CH₃ (Z) CH₃ H III CH₃CH₂ H CH₂CH₂CH₃ H CH₃ CI CH=CH₂ CH₃CH₂ CH₂CH₂CH₃ C H CH₂CH₃ H CH₃ CH₂CH₂CH₃ H (R) (Z) CH₃ H III H CH₂CH₃ CH₂CH₂CH₃ 42. The energy of the E2 transition state for I-bromopropane is similar to that for 2-bromopropane. because the products are the same (propene). So the E2 rate constants for these two compounds will be similar. However. being primary, will have a faster competing SN2 reaction than will the secondary 2-bromopropane. Overall. it is reasonable to estimate that the actual E2 rate for 1-bromopropane will be intermediate between the rates for bromoethane and 2-bromopropane. 43. H H H H CH₃ H H CH₃ CH₃ H CH₃ CH₃ CH₂CH₃ CH₃CH₂ CH₃ CH₃CH₂ CH₃ CH₃ CH₂CH₃ Br Br Br Br 2R.3R 2R.3S These are probably not the most stable conformations because all contain three gauche interactions between alkyl groups or bromine. For the R.R isomer. a better conformation would probably be H Br CH₃ CH₃ CH₂CH₃ H The others would be similar. 44. Referring to problem numbers in Chapter 7: > (25c) Comparable amounts (25d) (CH₃)₂C= V These are the only elimination product mixtures in these problems.