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\begin{document}
\title{Preparation of Pear Essence (Propyl Acetate) (7A/PPE)}
\author{Sam White}
\date{07/11/2017}
%\date{\vhCurrentDate\\\vhCurrentVersion}
\maketitle

%\section{Aim}
%To prepare propyl acetate from propan-1-ol and acetic acid and then determine the percentage yield.

\section{Reaction Mechanism\footcite[Preparation of Esters, p.~1014]{klein-organic} and Overall Equation}
\begin{figure}[H]
        \centering
        \includegraphics[width=0.75\textwidth]{Mechanism.png}
        \caption{Mechanism for reaction \label{fig:mechanism}}
\end{figure}
\begin{figure}[H]
        \centering
        \includegraphics[width=0.55\textwidth]{Equation.png}
        \caption{Overall Equation for Reaction \label{fig:equation}}
\end{figure}

\section{Results and Analysis}
{\centering Boiling temperature of pure product: \SI{101}{\celsius}

Mass of pure product: \SI{4.43}{\gram}

}
%\begin{table}[h]
%    \caption{Masses recorded at end of experiment.}
%    \centering
%    \begin{tabular}{|c|c|}
%        \hline
%        Item & Mass / \si{\gram} \\
%        \hline
%        Empty Sample Bottle and Lid & 11.93 \\
%        \hline
%        Filled Sample Bottle and Lid & 16.36 \\
%        \hline
%        Mass of Propyl Acetate & 4.43 \\
%        \hline
%    \end{tabular}
%\end{table}

%\begin{equation} \label{eq:ppyl-acte-abbr}
%    \ce{CH3CH2CH2OH(l) + CH3COOH(l) <=>[H+] CH3COOCH2CH2CH3(l) + H2O(l)}
%\end{equation}

\subsection{Yield Calculation}
\begin{displaymath}
    \begin{aligned}
        \text{Moles of propan-1-ol at start of reaction} &= \frac{\SI{9.6}{\gram}}{(3(12.011) + 8(1.008) + 15.999) \text{ \si{\gram\per\mole}}}  \\
            &= \frac{\SI{9.6}{\gram}}{\SI{60.096}{\gram\per\mole}} = \SI{0.16}{\mole} \\
        \text{Moles of acetic acid at start of reaction} &= \frac{\SI{24}{\gram}}{(2(12.011) + 4(1.008) + 2(15.999))\text{ \si{\gram\per\mole}}}  \\
            &= \frac{\SI{24}{\gram}}{\SI{60.052}{\gram\per\mole}} = \SI{0.40}{\mole}
    \end{aligned}
\end{displaymath}

From the equation shown in figure~\ref{fig:equation} there is a 1:1 molar ratio between propan-1-ol and acetic acid, hence the acetic acid is in excess. The equation also shows a 1:1 molar ratio between the propan-1-ol and propyl acetate, hence the theoretical amount of propyl acetate produced is \SI{0.16}{\mole}.

\begin{displaymath}
    \begin{aligned}
        \therefore \text{Theoretical yield of propyl acetate} &= \SI{0.16}{\mole} \times (5(12.011) + 10(1.008) + 2(15.999)) \text{ \si{\gram\per\mole}}  \\
            &= \SI{0.16}{\mole} \times \SI{102.133}{\gram\per\mole} = \SI{16}{\gram} \\
            \therefore \text{Percentage yield} &= \frac{\SI{4.43}{\gram}}{\SI{16}{\gram}} \times \SI{100}{\percent} = \SI{27}{\percent}
    \end{aligned}
\end{displaymath}

This is quite low. This may be due to losses during the purification (e.g. containers were not washed after transfers and some product remained in the filter paper) and a consequence of the reversible nature of the reaction. %The mass of the reactants should have been measured to increase the accuracy and precision of the percentage yield.

%This could be due to losses during the purification steps performed (such transfer losses since the containers of the product were not washed after transfers and since a fair amount of product remained in the filter paper) as well as due to the reaction not proceeding entirely to completion since it is reversible. In addition the actual masses of the reactants should have been measured at the start of the experiment to allow a more accurate and precise percentage yield to be determined.
\subsection{Spectra}
%\subsubsection{Reactants}
\begin{table}[h]
    \caption{IR Spectrum of propan-1-ol.}
    \centering
    \begin{tabular}{|c|c|c|}
        \hline
        Wavenumber / \si{\per\centi\metre} & Strength & Assignment \\
        \hline
        2976.7 & Weak & \ce{CH3} Absorption \\
        \hline
        2936.0 & Weak & \ce{C-H2} Absorption \\
        \hline
        2962.3 & Weak & \ce{C-H3} Absorption \\
        \hline
        3319.0 & Weak and Broad & \ce{O-H} Absorption in Alcohol \\
        \hline
    \end{tabular}
\end{table}
\begin{table}[h]
    \caption{$^1$H NMR Spectrum of propan-1-ol.}
    \centering
    \begin{tabular}{|c|c|>{\centering}m{2.2cm}|m{7.9cm}|}
        \hline
        Chemical Shift / ppm & $J$-Coupling & Integral Area & Summary \\
        \hline
        Approx. 7.3 & Singlet & Not Integrated & Characteristic for \ce{CDCl3} (Solvent) \\
        \hline
        3.66 & Triplet & 0.99 & Two $\alpha$-protons to alcohol group. Coupled to two protons. \\
        \hline
        2.03 & Singlet &  3.00 & \ce{OH} proton. Exchange decoupled. \\ \cline{1-2} \cline{4-4}
        1.57 & Quintet (Unclear) & (Integrated together) & Additional splitting possibly obscured by adjacent peaks. Coupled to four or five protons. \\ \cline{1-2} \cline{4-4}
        1.00 & Triplet (Small right-hand peak) & & Coupled to two protons. \\
        \hline
    \end{tabular}
\end{table}
\begin{table}[h]
    \caption{IR Spectrum of acetic acid.}
    \centering
    \begin{tabular}{|c|c|c|}
        \hline
        Wavenumber / \si{\per\centi\metre} & Strength & Assignment \\
        \hline
        1703.9 & Strong & \ce{C=O} Absorption close to acid range (1725-1705 \si{\per\centi\metre}) \\
        \hline
        3032.6 & Weak and Broad & \ce{O-H} Absorption close to carboxylic acid range (3000-2500 \si{\per\centi\metre}) \\
        \hline
    \end{tabular}
\end{table}
\begin{table}[h]
    \caption{$^1$H NMR Spectrum of acetic acid.}
    \centering
    \begin{tabular}{|c|c|c|c|}
        \hline
        Chemical Shift / ppm & $J$-Coupling & Integral Area & Summary \\
        \hline
        10.67 & Singlet & 0.90 & Single proton in \ce{-COOH} group. Exchange decoupled. \\
        \hline
        Approx. 7.4 & Singlet & Not Integrated & Characteristic for \ce{CDCl3} (Solvent). \\
        \hline
        2.19 & Singlet & 3.00 & Three $\alpha$-protons to carboxyl group. \\ 
        \hline
    \end{tabular}
\end{table}

%\subsubsection{Product}
\begin{table}[h]
    \caption{IR Spectrum of Product.}
    \centering
    \begin{tabular}{|c|c|c|}
        \hline
        Wavenumber / \si{\per\centi\metre} & Strength & Assignment \\
        \hline
        1738.0 & Strong & \ce{C=O} Absorption in the ester range (1740-1710 \si{\per\centi\metre}) \\
        \hline
        2882.5 & Weak & \ce{C-H} Absorption \\
        \hline
        2970.5 & Weak & \ce{C-H} Absorption \\
        \hline
    \end{tabular}
\end{table}
\begin{table}[h]
    \caption{$^1$H NMR Spectrum of Product.}
    \centering
    \begin{tabular}{|c|c|c|p{7.9cm}|}
        \hline
        Chemical Shift / ppm & $J$-Coupling & Integral Area & Summary \\
        \hline
        Approx. 7.4 & Singlet & 0.030 & Characteristic for \ce{CDCl3} (Solvent) \\
        \hline
        4.14 & Triplet & 1.98 & Two protons (\ce{RCOO-C\underline{H}}). Coupled to two protons. \\
        \hline
        2.17 & Singlet & 3.28 & Three protons in unique environment \\
        \hline
        Approx. 1.8 & Quartet (Unclear) & 1.90 & Two protons coupled three or four protons: splitting pattern difficult to interpret. \\
        \hline
        1.06 & Triplet (Small right-hand peak) & 2.75 & Three protons coupled to two protons. \\
        \hline
    \end{tabular}
\end{table}
These spectra are consistent with propyl acetate as a product since the starting materials both had a broad peak corresponding to \ce{O-H} absorptions in their IR spectra, however this is absent in the product's IR spectrum. Also the NMR spectrum for the product shows it has four distinct hydrogen environments with the expected chemical shifts and (mostly) the expected splitting pattens for propyl acetate. In the IR spectra the \ce{C=O} absorption has shifted position from being at \SI{1703.9}{\per\centi\metre} in acetic acid to \SI{1738.0}{\per\centi\metre} in the product: this higher wavenumber is expected for the production of an ester.

%These spectra are consistent with the product made being propyl acetate since the IR spectrum clearly shows the \ce{C=O} bond in the correct range for an ester and appropriate \ce{C-H} bond absorptions while the $^1$H NMR spectrum shows the correct number of environments, appropriate chemical shifts and roughly correct splitting pattens and areas for propyl acetate. The lack of the broad \ce{O-H} peak in the IR spectrum (which is present in both reactants) also indicates the formation of propyl acetate and little/no reactant impurities. The ambiguity in the splitting pattens in the $^1$H NMR spectrum around 1.6 ppm as well as the deviations of the areas of the peaks from the expected values may be due to the presence of impurities in the product mixture and also possibly due to the solvent residual water peak at 1.5 ppm. 

\end{document}
