Pinolenic acid (C17H29CO2H) is an unbranched carboxylic acid with three cis alkene

Chapter 15, Problem 15.74

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Pinolenic acid (C17H29CO2H) is an unbranched carboxylic acid with three cis alkene groups. It is found in pine nuts and is sometimes used in weight loss regimens as a hunger suppressant. Not every mass spectrometry technique requires ionization through ejection of single electrons; some instruments rely instead on milder ionization methods such as protonation or deprotonation to form charged species. Mass spectra of pinolenic acid were collected in positive ion mode (using conditions facilitating protonation) and in negative ion mode (using conditions facilitating deprotonation). A small amount of ozone was present in both experiments. Significant peaks in positive ion mode included m/z = 279, 211, 171, and 117. In the absence of ozone, however, only the peak at 279 remains (Anal. Chem. 2011, 83, 47384744). (a) Draw the structure of pinolenic acid as well as the ionic structures consistent with each of the peaks listed. (b) Predict m/z values for four significant peaks in negative ion mode, specifying the ion responsible for each peak.