Given here are \({ }^{1} \mathrm{H}-\mathrm{NMR}\) and \({ }^{19} \mathrm{C}-\mathrm{NMR}\) spectral data for nine compounds. Each compound shows strong absorption between 1720 and \(1700 \mathrm{~cm}^{-1}\), and strong, broad absorption over the region \(2500-3300 \mathrm{~cm}^{-1}\). Propose a structural formula for each compound. Refer to Appendices 4,5, and 6 for spectral correlation tables. $$ \begin{aligned} &\text { (a) } \mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{13} \text { C-NMR } \\ \hline 0.94(\mathrm{t}, 3 \mathrm{H}) & 180.71 \\ 1.39(\mathrm{~m}, 2 \mathrm{H}) & 33.89 \\ 1.62(\mathrm{~m}, 2 \mathrm{H}) & 26.76 \\ 2.35(\mathrm{t}, 2 \mathrm{H}) & 22.21 \\ 12.0(\mathrm{~s}, 1 \mathrm{H}) & 13.69 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (b) } \mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{19} \text { C-NMR } \\ \hline 1.08(\mathrm{~s}, 9 \mathrm{H}) & 179.29 \\ 2.23(\mathrm{~s}, 2 \mathrm{H}) & 47.82 \\ 12.1(\mathrm{~s}, 1 \mathrm{H}) & 30.62 \\ & 29.57 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (c) } \mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{4}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{13} \text { C-NMR } \\ \hline 0.93(\mathrm{t}, 3 \mathrm{H}) & 170.94 \\ 1.80(\mathrm{~m}, 2 \mathrm{H}) & 53.28 \\ 3.10(\mathrm{t}, 1 \mathrm{H}) & 21.90 \\ 12.7(\mathrm{~s}, 2 \mathrm{H}) & 11.81 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (d) } \mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{4}\\\ &\begin{array}{cr} \hline{ }^{1} \text { H-NMR } & { }^{19} \text { C-NMR } \\ \hline 1.29(\mathrm{~s}, 6 \mathrm{H}) & 174.01 \\ 12.8(\mathrm{~s}, 2 \mathrm{H}) & 48.77 \\ & 22.56 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (e) } \mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{2}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{13} \text { C-NMR } \\ \hline 1.91(\mathrm{~d}, 3 \mathrm{H}) & 172.26 \\ 5.86(\mathrm{~d}, 1 \mathrm{H}) & 147.53 \\ 7.10(\mathrm{~m}, 1 \mathrm{H}) & 122.24 \\ 12.4(\mathrm{~s}, 1 \mathrm{H}) & 18.11 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (f) } \mathrm{C}_{3} \mathrm{H}_{4} \mathrm{Cl}_{2} \mathrm{O}_{2}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{19} \text { C-NMR } \\ \hline 2.34(\mathrm{~s}, 3 \mathrm{H}) & 171.82 \\ 11.3(\mathrm{~s}, 1 \mathrm{H}) & 79.36 \\ & 34.02 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (g) } \mathrm{C}_{5} \mathrm{H}_{8} \mathrm{Cl}_{2} \mathrm{O}_{2}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{13} \text { C-NMR } \\ \hline 1.42(\mathrm{~s}, 6 \mathrm{H}) & 180.15 \\ 6.10(\mathrm{~s}, 1 \mathrm{H}) & 77.78 \\ 12.4(\mathrm{~s}, 1 \mathrm{H}) & 51.88 \\ & 20.71 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (h) } \mathrm{C}_{5} \mathrm{H}_{9} \mathrm{BrO}_{2}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{13} \text { C-NMR } \\ \hline 0.97(\mathrm{t}, 3 \mathrm{H}) & 176.36 \\ 1.50(\mathrm{~m}, 2 \mathrm{H}) & 45.08 \\ 2.05(\mathrm{~m}, 2 \mathrm{H}) & 36.49 \\ 4.25(\mathrm{t}, 1 \mathrm{H}) & 20.48 \\ 12.1(\mathrm{~s}, 1 \mathrm{H}) & 13.24 \\ \hline \end{array} \end{aligned} $$ $$ \begin{aligned} &\text { (i) } \mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{3}\\\ &\begin{array}{cc} \hline{ }^{1} \text { H-NMR } & { }^{13} \text { C-NMR } \\ \hline 2.62(\mathrm{t}, 2 \mathrm{H}) & 177.33 \\ 3.38(\mathrm{~s}, 3 \mathrm{H}) & 67.55 \\ 3.68(\mathrm{~s}, 2 \mathrm{H}) & 58.72 \\ 11.5(\mathrm{~s}, 1 \mathrm{H}) & 34.75 \\ \hline \end{array} \end{aligned} $$

Short Answer

Expert verified
Based on the provided NMR data and strong absorptions in the IR spectrum, the proposed structural formulas for the 9 compounds are: (a) \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}\) $$ CH_3CH_2CH_2COOCH_3 $$ (b) \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}\) $$ tert{-}ButylCOOH $$ (c) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{4}\) $$ HOOCCH_2CH(OH)COOCH_3 $$ (d) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{4}\) $$ HOOCCH(OH)COOCH_3 $$ (e) \(\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{2}\) $$ CH_2=CHCOOH $$ (f) \(\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{Cl}_{2} \mathrm{O}_{2}\) $$ ClCH_2COOCH_3 $$ (g) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{Cl}_{2} \mathrm{O}_{2}\) $$ ClCH_2CH=C(Cl)COOH $$ (h) \(\mathrm{C}_{5} \mathrm{H}_{9} \mathrm{BrO}_{2}\) $$ BrCH_2CH_2CH_2COOH $$ (i) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{3}\) $$ CH_3CH(OCH_3)COOH $$

Step by step solution

01

(a) Interpret the NMR data for compound a and propose a structural formula

Given: \(\mathrm{C}_{5} \mathrm{H}_{10} \mathrm{O}_{2}\) From the NMR data: 1H NMR: 0.94 (t, 3H) 1.39 (m, 2H) 1.62 (m, 2H) 2.35 (t, 2H) 12.0 (s, 1H) 13C NMR: 180.71 33.89 26.76 22.21 13.69 Since the 1H NMR at 12.0 ppm is a singlet (1H), it suggests the carboxylic acid proton which corresponds to the strong absorption in the IR spectrum, between 1720 and 1700 cm⁻¹. Also, the 1H NMR at 0.94 ppm is a triplet (3H) and the 13C NMR has a chemical shift at 13.69 ppm, indicating a methyl group at the end of the molecule. The remaining hydrogens can be combined to form a four carbon chain with an ester group to satisfy the oxygen atoms required. The proposed structural formula is: $$ CH_3CH_2CH_2COOCH_3 $$
02

(b) Interpret the NMR data for compound b and propose a structural formula

Given: \(\mathrm{C}_{6} \mathrm{H}_{12} \mathrm{O}_{2}\) From the NMR data: 1H NMR: 1.08 (s, 9H) 2.23 (s, 2H) 12.1 (s, 1H) 13C NMR: 179.29 47.82 30.62 29.57 The 1H NMR at 12.1 ppm is a singlet (1H), suggesting a carboxylic acid proton. The 1H NMR at 1.08 ppm is a singlet (9H), indicating three methyl groups. From the 13C NMR, there is no carbon shift at 13-14 ppm indicating the three methyl groups are on one carbon, making this a tert-butyl group. The remaining 2 protons with the chemical shift at 2.23 ppm are part of a methylene group adjacent to the carboxylic acid. The proposed structural formula is: $$ tert{-}ButylCOOH $$
03

(c)-(i) Solution Summary for the Remaining Compounds

Following the same analysis pattern as compounds a and b using the provided NMR data and strong absorptions in the IR spectrum, the proposed structural formulas for the remaining compounds are: (c) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{4}\) $$ HOOCCH_2CH(OH)COOCH_3 $$ (d) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{O}_{4}\) $$ HOOCCH(OH)COOCH_3 $$ (e) \(\mathrm{C}_{4} \mathrm{H}_{6} \mathrm{O}_{2}\) $$ CH_2=CHCOOH $$ (f) \(\mathrm{C}_{3} \mathrm{H}_{4} \mathrm{Cl}_{2} \mathrm{O}_{2}\) $$ ClCH_2COOCH_3 $$ (g) \(\mathrm{C}_{5} \mathrm{H}_{8} \mathrm{Cl}_{2} \mathrm{O}_{2}\) $$ ClCH_2CH=C(Cl)COOH $$ (h) \(\mathrm{C}_{5} \mathrm{H}_{9} \mathrm{BrO}_{2}\) $$ BrCH_2CH_2CH_2COOH $$ (i) \(\mathrm{C}_{4} \mathrm{H}_{8} \mathrm{O}_{3}\) $$ CH_3CH(OCH_3)COOH $$

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