Ressonância Magnética Nuclear

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214 Chapter 10 USING NUCLEAR MAGNETIC RESONANCE SPECTROSCOPY TO DEDUCE STRUCTURE H 5 61. (a) CH₃ CH(CH₃)₂ OSO₂R (b) CH₃ C(CH₃)₂, via H shift: CH₃ CH(CH₃)₂ H + H CH₃ CH₃ C(CH₃)₂ CH(CH₃)₂ product (c) Follow all possible El mechanisms to the first with D in the starting molecule: H HD + D D shift + CH₃ CH₃ CH(CH₃)₂ CH(CH₃)₂ -H+ H D CH₃ CH(CH₃)₂ + CH₃ CH(CH₃)₂ "Major product" is now a mixture of these two species. According to these three pathways, some of the major product formed will have an alkene D instead of an alkene H. The molecules with alkene D will not show an NMR signal near δ = 5. So, the δ = 5 signal for the major product as a whole will be reduced in intensity compared with the major product from nondeuterated starting material. This result was good evidence for the involvement of hydride shifts in what were previously thought to be simple El reactions. 62. Write out your given information first. Believe me. it helps. A + E E has 2 complex NMR signals and 2 peaks B + KOH F (C₁H₈O); F has 2 'H NMR singlets and 3 peaks C + G (C₁H₈O); G has 2 complex ¹H NMR signals and 2 peaks D + G C and D have identical ¹H NMR spectra Starting materials may be optically active; products are not. What can we say for sure? Well, if C and D are different compounds but have identical NMR they're enantiomers (think about it). If they both give G after reaction, either G is or it is a meso compound. Next question. What kind of chemical reactions are we talking about here? Each