The lignins are macromolecules that are major components of the many types of wood

Chapter 15, Problem 15.54

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The lignins are macromolecules that are major components of the many types of wood, where they bind cellulose fibers together in these natural composites. The lignins are built up out of a variety of small molecules (most having phenylpropane skeletons). These precursor molecules are covalently connected in varying ways, and this gives the lignins great complexity. To explain the formation of compound B below as one of many products obtained when lignins are ozonized, lignin model compound A was treated as shown. Use the following information to determine the structure of B. To make B volatile enough for GC/MS (gas chromatographymass spectrometry, Section 9.19), it was first converted to its tris(O-trimethylsilyl) derivative, which had M. + 308 m/z. [Tris means that three of the indicated complex groups named (e.g., trimethylsilyl groups here) are present. The capital, italicized O means these are attached to oxygen atoms of the parent compound, taking the place of hydrogen atoms. Similarly, the prefix bis indicates the presence of two complex groups subsequently named, and tetrakis (used in the problem below), means four.] The IR spectrum of B had a broad absorption at 3400 cm-1 , and its 1 H NMR spectrum showed a single multiplet at d 3.6. What is the structure of B?