Chapter 9, Problem 1LGP

Given the following information, elucidate the structures of compounds A and B. Both compounds are soluble in dilute aqueous $\text{HCl}$, and both have the same molecular formula. The mass spectra of A and B have $\text{M}{\text{.}}^{+}149$. Other spectroscopic data for A and B are given below. Justify the structures you propose by assigning specific aspects of the data to the structures. Make sketches of the NMR spectra.

(a) The IR spectrum for compound A shows two bands in the 3300-3500 cm^−-1 region. The broadband proton-decoupled ${}^{\text{13}}\text{C NMR}$ spectrum displayed the following signals (information from the DEPT ${}^{\text{13}}\text{C}$ spectra is given in parentheses with the ${}^{\text{13}}\text{C}$ chemical shifts).

$A{\text{: }}^{\text{13}}\text{C NMR: δ 140 }\left(\text{C}\right)\text{, 127 }\left(\text{C}\right)\text{, 125 }\left(\text{CH}\right)\text{, 118 }\left(\text{CH}\right)\text{, 24 }\left({\text{CH}}_{\text{2}}\right)\text{, 13 }\left({\text{CH}}_{\text{3}}\right)$

(b) The IR spectrum for compound B shows no bands in the 3300-3500 cm^−-1 region. The broadband proton-decoupled ${}^{\text{13}}\text{C NMR}$ spectrum displayed the following signals (information from the DEPT ${}^{\text{13}}\text{C}$ spectra is given in parentheses with the ${}^{\text{13}}\text{C}$ chemical shifts):

$B{\text{: }}^{\text{13}}\text{C NMR: δ 147 }\left(\text{C}\right)\text{, 129 }\left(\text{C}\right)\text{, 115 }\left(\text{CH}\right)\text{, 111 }\left(\text{CH}\right)\text{, 44 }\left({\text{CH}}_{\text{2}}\right)\text{, 13 }\left({\text{CH}}_{\text{3}}\right)$