The Acyloin condensation

Introduction: The Acyloin Condensation

Today's post is about the Acyloin condensation.In the Acyloin condensation, two esters are reduced with sodium forming an; α-hydroxy ketone, which is also called an acyloin.

The Mechanism

The Source Code

 Here is the TikZ Source Code of the mechanism:

\documentclass[12pt,landscape]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}

\usepackage{tikz}
\usetikzlibrary{calc}
\usepackage{chemfig}


\begin{document}
%%
%%
\pagestyle{empty}
\begin{tikzpicture}
%% Title
\node at(0.7,1.3){\bf The Acyloin Condensation\rm};

%% Some Styling
%% For reaction arrows:
\tikzstyle{eqArrowSt}=[ thick,->, >={stealth} ]
\tikzstyle{markupStyle}=[ red,thick,dashed,->,>={stealth} ]
\tikzstyle{elMovement}=[ blue,opacity=0.7,->,>={stealth} ]

%% For radicals:
\tikzstyle{radStyle}=[ red ]

%% The reactants:
\node at (0,0) {\chemfig{R-[::30]@{R1E2}(=[::60]O)-[::-60]O|Me}};
\node at (-1,0){2};
\node at (1.5,0) {+};
\node at (3,0) {4~\chemfig{Na^0}};

%% The first reaction step:
\draw[ eqArrowSt ](3.8,0)--(6.2,0) node[ above, midway ]%%
 {-4[\chemfig{Na^\oplus}\chemfig{ ^\ominus OCH_3}]};
 
%% The intermediats:
\node at (9,0) {\chemfig{R-[::45](-[::90]Na^\oplus|O^\ominus)=[::-45](-[::45]O^\ominus|Na^\oplus)-[::-45]R}};

%% The second reaction step:
\draw[ eqArrowSt ](11,0)--(12.5,0) node[ above, midway ]%%
 {\chemfig{H_2O}};
 
%% The final product:
\node at (14.5,0) {\chemfig{%%
R-[::45](=[::90]O)-[::-45](-[::45]O|H)-[::-45]R}}; 

%% Show more detailed steps
%% Two radicals are build:
\draw[ eqArrowSt ](0.0,-1)--(0.0,-2.5) node[ right, midway]%%
{2~\chemfig{Na^0@{R1E1}}};%%

%% First electron movement:
\coordinate (R1r1) at ($(R1E2) + (0.05,-0.1)$);
\chemmove{\draw[ elMovement,rounded corners ](R1E1)--++(0.2,0.2)--(R1r1);}

%% Second electron movement:
\coordinate (R1r2) at ($(R1E2) + (0,0.25)$);
\chemmove{
\draw[ elMovement,rounded corners ]%%
 (R1r2)--++(0.3,0.2)--($(R1r2)+(0.2,1)$);}

%% Draw the first radical
\node at (0,-4.0) {\chemfig{R-[::45](-[::45]O|^\ominus)-[::-90]O|Me}};
\node[ radStyle ] at (-0.1,-4.1) {\Large $\cdot$\normalsize};

%% Draw the second radical with an xshift of 3cm
\begin{scope}[xshift=3cm]
\node at (0,-4.0) {\chemfig{R-[::45](-[::45]O|^\ominus)-[::-90]O|Me}};
\node[ radStyle ] at (-0.1,-4.1) {\Large $\cdot$\normalsize};
\end{scope}

%% Draw the electron movement between the two radical electrons:
\draw[ elMovement,rounded corners=10mm ] ($(-0.1,-4.1)+(0.1,0.1)$) --(1.5,-3.5)--%%
 ($(2.9,-4.1)+(-0.1,0.1)$);

%% Draw the next step of the reaction:
\draw[ eqArrowSt ](0,-6)--(0,-7.5);%%
\node at (0,-8) {\chemfig{R-[::45](-[::90]Na^\oplus|O^\ominus)(-[::135]MeO)-[::-45](-[::45]O^\ominus|Na^\oplus)(-[::0]OMe)-[::-45]R}};

%% Next Step under elimination of OMe:
\draw[ eqArrowSt ](3,-8)--(4.5,-8)node[above,midway]%%
{-[\chemfig{Na^\oplus}\chemfig{^\ominus OCH_3}]};%%
\node at (7.5,-8) {\chemfig{R-[::45](-[::90]Na^\oplus|O^\ominus)(-[::135]MeO)-[::-45](=[::45]O)-[::-45]R}};

%% Electron Movement:
\draw[ elMovement, rounded corners=5mm ] (1.2,-7) --(0.7,-6.8)-- (0.6,-8);

%% Another elimination of OMe:
\draw[ eqArrowSt ](9.5,-8)--(11,-8)node[above,midway]%%
{-[\chemfig{Na^\oplus}\chemfig{^\ominus OCH_3}]};%%
\node at (12.5,-8) {\chemfig{R-[::45](=[::90]O)-[::-45](=[::45]O)-[::-45]R}};

%% Another radical intermediate with two sodium atoms:
%% Next Step under elimination of OMe:
\draw[ eqArrowSt ](12.5,-7.6)--(12.5,-6.5);%%
\node at (12.5,-5.5) {\chemfig{R-[::45](-[::90]Na^\oplus O^\ominus)-[::-45](-[::45]O|^\ominus|Na^\oplus)-[::-45]R}};

%% Draw radical electrons:
\node[ radStyle ] at (13.2,-5.55) {\Large $\cdot$\normalsize};
\node[ radStyle ] at (11.7,-5.55) {\Large $\cdot$\normalsize};

%% Draw the electron movement:
\draw[ elMovement,rounded corners=5mm ] %%
(13.2,-5.55)--(13.0,-5.15)--(12.45,-5.55);
\draw[elMovement,rounded corners=5mm] %%
(11.7,-5.55) --(11.9,-5.15)-- (12.45,-5.55);

%% Reconnecting to the old (overall) path
\draw[ markupStyle ] (10.5,-5.5) -- (7,-5.5)--(7,-1.7);

%% Showing the keto-enol tautomerism
\draw[ thick,dashed,draw=black,>=stealth,-> ] (9,-1.4) -- (9,-3.2) -- (14,-3.2) --(14,-1.4);
\node at ( 11.5,-3.5 ) {keto form is preferred};
\end{tikzpicture} 

\end{document}