Today's Post is about aromatic compounds and benzene:

 Here is the corresponding TikZ source code (using chemfig):

\documentclass[12pt,a4paper,landscape]{article}
\usepackage[latin1]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage{tikz}
\usetikzlibrary{shadows}

\usepackage{chemfig}


\begin{document}
\pagestyle{empty}
\begin{tikzpicture}
%% Make a Background:
\draw[ fill = blue!50!white!50!gray, rounded corners, drop shadow ]%%
 ( -1, 1 ) rectangle ( 14, -14 );

%% Some Styling:
\tikzstyle{titleStyle}=[yellow!50!brown]

%% Kekule Structures:
\node[ titleStyle ] at ( 0, 0 ) {Kekule};
\node at ( 2, -2 ){\chemfig{*6(=-=-=-)}};
\node at ( 6, -2 ){\chemfig{*6(-=-=-=)}};
\draw[<->,thick] ( 3.5, -2 ) -- ( 4.5, -2 );

%% So the Kekule Structures give the following net state:
\node at ( 8.5, -2 ) {=};
\node at ( 10.8, -2 ) {\chemfig{*6(-------)}};
\draw[ dashed ] ( 10.8, -2 ) circle ( 1cm );

%% Draw the Dewar-Benzene also:
\node[ titleStyle ] at ( .7, -3.5 ){Dewar-Benzene};
\node at ( 2, -5 ){\chemfig{*4(-?[a]--=)--=^[::90]-[::90]}};


%% Ladenburg-Benzene:
\node[ titleStyle ] at ( 6.5, -4 ){Ladenburg-Benzene}; 
\node[very thick] at( 6, -5 ){\chemfig{%%
    >[::60,,,,line width=.01mm,line join=round]?[a]<[:-60]?[b]-[:180,,,,line width=2.5mm,line join=round]?[c]-%%(-?[a])%%-(-?[b])-(-[?[c]])%%
}};
\begin{scope}[yshift=-0.6cm]
\node[very thick] at( 6, -5 ){\chemfig{%%
    -[::60]?[a](-[::30])-[:-60]?[b](-[::150,,,,,line width=2mm])-[:180,,,,,line width =2mm]?[c](-[::-90,,,,,line width=2mm])-%%(-?[a])%%-(-?[b])-(-[?[c]])%%
}};
\end{scope}

%% Take care of the bad joints in the Ladenburg-Benzene:
%% Define Coordinate Points to colour black:
\coordinate (A) at (5.38,-5.4);
\coordinate (B) at (6.62,-5.4);
\coordinate (C) at (5.38,-6.7);
\coordinate (D) at (6.62,-6.7);

%% Fill The Coordinates With black Circles:
\draw[fill=black] (A) circle (1.2mm);
\draw[fill=black] (B) circle (1.2mm);
\draw[fill = black] (C) circle (1.2mm);
\draw[fill = black] (D) circle (1.2mm);

%% Typical Reactions of Aromatic Compounds
%% 
%% The Friedel-Crafts-Acylation
\node[ titleStyle ] at (1.5,-7.5) {Friedel-Crafts alkylation};

%% Reactants of the Friedel-Crafts-Alkylation
\node at (1,-9) {\chemfig{*6(=-=-=-)}};
\draw[ >=stealth, very thick, -> ] (3,-9)--(5,-9);%%
\node at ( 4, -8.5 ) {\chemfig{[:112.5]R-[::45]-[::45]X}};
\node at (4,-9.5) {\chemfig{AlCl_3}(kat.)};

%% Products of the Friedel-Crafts-Alkylation
\node at (8,-9) {\chemfig{[:180]*6(=-=-=-)-[::210]-[::-45]R }};
\node at (9.2,-9) {+};
\node at (10.7,-9){\chemfig{H-Cl}};

%% Hückel's rule:
\node[fill = blue!50!gray,rounded corners,drop shadow,general shadow={blue!50!black,opacity=0.9}] at ( 10, -6 ){$[\pi - e^\ominus]=4n+2$};

\end{tikzpicture}
\end{document}