Using any table ofchemical shift values give the approximate carbons indicated i

Question

Using any table ofchemical shift values give the approximate carbons indicated in the following compound? . 10. C-I3 NMR absorption values (chemical shift) for each of the b= 11. Using the mass spectrum below, answer the following questions: 100 T 57 80 60 91 40- 29 119 133 20 148 0.0t 160 80 m/z 0.0 40 120 a. What does m/z represent? b. Describe which peak represents the base peak. c. Describe which peak represents the molecular ion. d. Which peak is the M - 15 peak? What radical is typically lost to produce this? e. Which peak is the M-29 peak? What radical is typically lost to produce this? f. Given that this spectrum is from benzyl ethyl ketone, propose structures for the fragment ions a m/z 57 and 91.

Explanation / Answer

a) m/z indiacates the ratio between mass to charge of the fragmented ions.

b) The peak having maximum intensity in the mass spectrum is called as the base peak, which correspond to the fragmented ion which has maximum abundance. Thepeak having m/z 57 has maximum intensity and hence is the base peak.

c) the peak that appears at the extreme right of the mass spectrum is called as molecular ion peak, that provides the information regarding the molecular mass of the compound. The peak having m/z 148 is the molecular ion peak.

d)M+ - 15 peak, means a peak correspond to 15 unit less than that of molecular mass of the compound, i.e- 148 -15 = 133. This peak appears due to reomval of a water moleculae.

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