[Tex/LaTex] Curved double arrow in tikz

chemfigmhchemtikz-pgf

High all, this is related to a previous question I asked (see here). I would like to make the double arrow between the alcohol and the amine curved (annotated with blue nodes above and below the arrow):

Here is the code used to generate the image:

\documentclass[10pt,a4paper]{article}
\usepackage[utf8]{inputenc}
\usepackage{amsmath}
\usepackage{amsfonts}
\usepackage{amssymb}
\usepackage[left=0.00cm, right=0.00cm]{geometry}
\usepackage{tikz}
\usepackage{chemfig}
\usepackage{mhchem}
\usetikzlibrary{calc,fadings,decorations.markings}
\usetikzlibrary{decorations.pathreplacing,calc,positioning,shapes.multipart}
\tikzset{two parallel arrows/.style={decorate,decoration={show path construction,
            lineto code={
                \draw [-latex] ($(\tikzinputsegmentfirst)!#1!90:(\tikzinputsegmentlast)$) 
                -- ($(\tikzinputsegmentlast)!#1!-90:(\tikzinputsegmentfirst)$); 
                \draw [latex-] ($(\tikzinputsegmentfirst)!#1!-90:(\tikzinputsegmentlast)$) 
                -- ($(\tikzinputsegmentlast)!#1!90:(\tikzinputsegmentfirst)$); 
    }}},two parallel arrows/.default=2pt}
\usetikzlibrary{calc,fadings,decorations.markings}
\newcommand\setpolymerdelim[2]{\def\delimleft{#1}\def\delimright{#2}}
\def\makebraces[#1,#2]#3#4#5{%
    \edef\delimhalfdim{\the\dimexpr(#1+#2)/2}%
    \edef\delimvshift{\the\dimexpr(#1-#2)/2}%
    \chemmove{%
        \node[at=(#4),yshift=(\delimvshift)]
        {$\left\delimleft\vrule height\delimhalfdim depth\delimhalfdim
            width0pt\right.$};%
        \node[at=(#5),yshift=(\delimvshift)]
        {$\left.\vrule height\delimhalfdim depth\delimhalfdim
            width0pt\right\delimright_{\rlap{$\scriptstyle#3$}}$};}}
\setpolymerdelim()
\definecolor{mainColor}{RGB}{255,51,76} 
\begin{document}
\begin{tikzpicture}
\setchemfig{atom sep=2em}
\linespread{0.7}
% ---------------- LABELS ----------------
\node[mainColor] (alkyne) at (0,0) {Alkyne};
\node[below] at (0,-0.15) {{\footnotesize \chemfig{-C~C-}}};
\node[mainColor] (haloalkene) at (2,3) {Haloalkene};
\node[align=left] at (2.8,2.1) {{\footnotesize \chemfig{C(-[:-120])(-[:120]R)=C(-[:60]X)-[:-60]}}};
\node[mainColor] (haloalkane) at (0,6) {Haloalkane};
\node[align=left] at (1.8,6) {{\footnotesize \chemfig{-C(-[:90]R1)(-[:-90]R2)-C(-[:90]X)(-[:-90]R3)-}}};
\node[mainColor] (alkane) at (-1,3) {Alkane};
\node at (0.2,3.3) {\footnotesize\chemfig{-C(-[:90]H)(-[:-90]H)-C(-[:90]H)(-[:-90]H)-}};
\node[mainColor] (tertiaryalcohol) at (0,8) {3$^\circ$ Alcohol};
\node at (1.5,7.8) {\footnotesize\chemfig{(-[:-90]R2)(-[:-150]R1)(-[:-30]R3)-[:90]OH}};
\node[mainColor] (alkene) at (-3.3,3) {Alkene};
\node at (-3.2,2) {\footnotesize\chemfig{H-[:-60]C(-[:-120])=C(-[:60]H)-[:-60]}};
\node[mainColor] (ketone) at (-4.5,0) {Ketone};
\node at (-4.5,-0.6) {\footnotesize\chemfig{R1-C(=[:90]O)-R2}};
\node[mainColor] (alcohol) at (-7,3) {Alcohol};
\node[mainColor] (glucose) at (-7,5.5) {Glucose};
\node at (-7,6.5) {\footnotesize\setchemfig{cram width=2pt}
    \chemfig{HO-[2,0.7,2]?<[7,0.7](-[2,0.5]OH)-[,,,,
        line width=2pt](-[6,0.7]OH)>[1,0.7](-[6,0.7]OH)-[3,0.7]
        O-[4]?(-[2,0.3]-[3,0.7]HO)}};
\node[mainColor] (ester) at (-7,-1) {Ester};
\node at (-6.2,-1.3) {\footnotesize{\chemfig{R1-C(=[:90]O)-O-R2}}};
\node[mainColor] (carboxylicacid) at (-10.5,1) {Carboxylic Acid};
\node at (-12.5,1) {\footnotesize{\chemfig{R-[:30]C(=[:90]O)-[:-30]OH}}};
\node[mainColor] (aldehyde) at (-10.5,2.5) {Aldehyde};
\node at (-10.5,3.4) {\footnotesize{\chemfig{R-[:30]C(=[:90]O)-[:-30]H}}};
\node[mainColor] (amide) at (-10.5,-1) {Amide};
\node at (-12.5,-1) {\footnotesize{\chemfig{R1-C(=[:90]O)-N(-[:-90]H)-R2}}};
\node[mainColor] (amine) at (-9.25,0.25) {Amine};
\node at (-8.75,-0.5) {\footnotesize{\chemfig{H-N(-[:60]R1)-[:-60]R2}}};
\node[mainColor] (amine2) at (-10.5,4.5) {Amine}; % LABEL FOR AMINE
\node[mainColor] (cellulose) at (-10.5,5.5) {Cellulose};
\node at (-11,6.7) {\footnotesize{\setchemfig{cram width=2pt}
        \chemfig{-[@{left}]O-[0,0.7]?<[7,0.7](-[2,0.5]OH)-[,,,,
            line width=2pt](-[6,0.7]OH)>[1,0.7](-[@{right}])-[3,0.7]
            O-[4]?(-[2,0.3]-[3,0.7]HO)}
        \makebraces[20pt,20pt]{\!\!n}{left}{right}}};
\node[mainColor,align=center] (acidchloride) at (-12.55,2.5) {Acid\\Chloride};
\node at (-12.5,3.4) {\footnotesize\chemfig{R-[:30]C(=[:90]O)-[:-30]Cl}};
\node[mainColor] (amide2) at (-12.55,4.5) {Amide};
% BOXES FOR PRIMARY (1 DEGREE) AND SECONDARY (2 DEGREE) ALCOHOL
\node[rectangle split,rectangle split horizontal, rectangle split parts=2, draw, anchor=center,
below=0pt of alcohol] (degrees) {1$^\circ$ \nodepart{two} 2$^\circ$};
\draw[decorate,decoration=brace] (degrees.south east) -- 
(degrees.south west) coordinate[midway,below=2pt] (brace);
\draw (degrees.south east) +(-85:0.5) node {\footnotesize\chemfig{-[:30,0.7](-[:90,0.7]OH)-[:-30,0.7]}};
\draw (degrees.south west) +(-120:0.5) node {\footnotesize{\chemfig{R-[:30]-[:-30]OH}}};
% ---------------- ARROWS ----------------
\draw[-latex] (alkyne) -- node[above,midway,sloped] {{\footnotesize \ce{HX}, \ce{X2}}} (haloalkene); 
\draw[-latex] (haloalkene) -- node[above,midway,sloped] {{\footnotesize \ce{H2}, \ce{Pd}/\ce{C}}} (haloalkane);
\draw[-latex] (alkyne) -- node[above,midway,sloped] {{\footnotesize \ce{H2}, \ce{Pd}/\ce{C}}} (alkane);
\draw[-latex] (alkane) -- node[above,sloped,midway] {{\footnotesize \ce{X2}, UV light}} (haloalkane);
\draw[-latex] (alkene) -- node[midway,above] {{\footnotesize \ce{H2}, \ce{Pd}/\ce{C}}} (alkane);
\draw[-latex] (alkyne) -- node[above,midway,sloped] {{\footnotesize \ce{H2O}, \ce{H2SO4}, \ce{HgSO4}}} (ketone);
\draw[-latex] (degrees.east) ..controls +(0:1) and +(90:1) .. node[xshift=0.2cm,yshift=-0.1cm,above,midway,sloped] {\footnotesize \ce{H+}/\ce{Cr2O^{2-}_{7}}} (ketone);
\draw[two parallel arrows] (alcohol) -- node[below,midway,sloped,align=center] {\footnotesize {dil. \ce{NaOH}}\\\footnotesize{acetone solv.}} node[above,midway,sloped] {\footnotesize\ce{HX}} (haloalkane);
\draw[-latex] (haloalkane) -- node[midway,left,align=right] {\footnotesize\ce{H2O} with\\\footnotesize dil. \ce{NaOH}\\\footnotesize{acetone solv.}} (tertiaryalcohol);
\draw[-latex] (alkene) -- node[midway,above,sloped] {\footnotesize\ce{HX}, \ce{X2}} (haloalkane);
\draw[two parallel arrows] (alcohol) -- node[above,midway] {\footnotesize Conc. \ce{H+}} node[below,midway] {\footnotesize\ce{H2O}, dil. \ce{H+}} (alkene); 
\draw[-latex] (glucose) -- (alcohol);
\draw (brace) -- node[right,midway,align=left] {\footnotesize{conc.}\\\footnotesize\ce{H2SO4}\\\footnotesize{reflux}} (ester);
\draw[-latex] (degrees.west) -- node[midway,above,sloped,align=center] {\footnotesize{limited}\\\footnotesize \ce{H+}/\ce{Cr2O^{2-}_{7}}} (aldehyde);
\draw[-latex] (aldehyde) -- node[midway,right,align=left] {\footnotesize \ce{H+}/\ce{Cr2O^{2-}_{7}}} (carboxylicacid);
\draw (carboxylicacid) -- node[midway,left,align=right,xshift=-2mm] {\footnotesize{heat}\\\footnotesize{DCC reflux}} (amide);
\draw[two parallel arrows,blue] (alcohol.north west) -- node[midway,below,sloped] {\footnotesize\ce{NH3}} node[above,midway,sloped] {\footnotesize{\ce{NaNO2}, dil. \ce{HCl}}} (amine2.east); %CURVED DOUBLE ARROW DESIRED HERE
\draw[-latex] (cellulose) -- node[midway,above,align=center] {\footnotesize{cellulase or}\\\footnotesize{conc. \ce{H+}}} (glucose);
\draw[-latex] ([xshift=60pt]glucose.east) node[right] {{\ce{CO2 +H2O}}} -- node[midway,above] {\footnotesize{light}} node[midway,below] {\footnotesize{chlorophyll}} (glucose);
\draw[-latex] ([xshift=60pt]glucose.east) .. controls +(180:1.75) and +(-90:1).. +(-1.5,1) node[above] {\ce{O2}};
\draw[-latex] ([xshift=-10pt]carboxylicacid.north) .. controls +(90:0.7) and +(-90:0.7) .. node[midway,above] {\footnotesize\ce{SOCl2}} (acidchloride.south);
\draw[-latex] (acidchloride.east) .. controls +(45:0.5) and +(-45:0.5) .. node[midway,above right] {\footnotesize\ce{NH3}} (amide2.east);
% ---------------- ADDITIONAL DECORATIONS ----------------
\draw[-latex] (glucose) .. controls +(-90:1) and +(180:1) .. (-6,4.5) node[right] {\ce{CO2}};
\draw[-{Latex[harpoon]}] (carboxylicacid) to[out=0,in=90,looseness=1.6] (ester);
\draw[-{Latex[harpoon]}] ([xshift=-4pt]ester.north) -- ++ (0,1);
\draw[-{Latex[harpoon]}] (amine) to[out=180,in=90,looseness=1.6] (amide);
\draw[-{Latex[harpoon]}] ([xshift=-4pt]amide.north) -- ++ (-0,0.75);
\node at (-9,8.3) {\textbf{Note:} All organic compounds can undergo combustion reactions};
% ---------------- ADDITION POLYMERS ----------------
\node[align=center,mainColor] (additionpolymer) at (-1.5,1.5) {Addition\\Polymers};
\draw[-latex] (alkene.south east) +(0,0.1) .. controls +(0:0.5) and +(90:0.5) .. (additionpolymer.north);
\draw[-latex,densely dashed] (haloalkene.south) .. controls +(-110:3) and +(-60:0.7) .. (additionpolymer.south);
\end{tikzpicture}
\end{document}

Things I have tried include changing the lossness value, changing it to a bezier curve and defining a new decoration with looseness value or a bezier curve.

I have annotated the relevant sections in the above code. But I am essentially asking for how to draw arrows for something like this:

Best Answer

This is just for fun. Both Raaja's answer and Symbol 1's answer are great. However, the paths in Raaa's answer are not precisely parallel, and the ones in Symbol 1's answer cannot be colored individually (at least not in an obvious way). So here is something that allows one to record paths and then parallel transport them and so on. This solution makes use of decorations, so for very curvy paths it can lead to dimension too large errors, a limitation the above-mentioned answers do not have. This proposal can be used as follows. You need first to record the path, e.g.

\path[record path={name=AB}] (A) to[bend left] (B);

Then there will be two paths, one called top and the other bottom, which emerge from the above path by parallel transport. They can be reconstructed as follows:

 \draw[-latex,reconstruct top=AB];
 \draw[red,-latex,reconstruct bottom=AB];

Here is the full code with further examples, including a pattern between these paths. The only library that is needed for this stuff is decorations.markings, patterns and bending are just for the examples and optics.

\documentclass[tikz,border=3.14mm]{standalone}
\usetikzlibrary{decorations.markings,patterns,bending}
\newcounter{parrow}

\tikzset{
  record path/.style={
    /utils/exec=\tikzset{parrow/.cd, #1},
    decorate,
    decoration={
      markings,
      mark=at position 0 with {
        % init counter "parrow".
        \setcounter{parrow}{1}
        %\typeout{\pgfdecoratedpathlength}
        % record coordinates (parrowt-<name>-1) and (parrowt-<name>-1).
        \path 
          (0,\pgfkeysvalueof{/tikz/parrow/dist}/2) coordinate
            (parrowt-\pgfkeysvalueof{/tikz/parrow/name}-\number\value{parrow})
          (0,-\pgfkeysvalueof{/tikz/parrow/dist}/2) coordinate
            (parrowb-\pgfkeysvalueof{/tikz/parrow/name}-\number\value{parrow});
        % store step length (without unit) in \mystep globally.
        \pgfmathsetmacro{\mystep}{(\pgfdecoratedpathlength-4pt)/int(1+(\pgfdecoratedpathlength-4pt)/2pt)}
        \xdef\mystep{\mystep}
      },
      mark=between positions 2pt and 1 step \mystep pt with {
        % for every step, record coordinates (parrowt-<name>-<parrow>) and (parrowb-<name>-<parrow>)
        \stepcounter{parrow}
        \path
          (0,\pgfkeysvalueof{/tikz/parrow/dist}/2) coordinate
            (parrowt-\pgfkeysvalueof{/tikz/parrow/name}-\number\value{parrow})
          (0,-\pgfkeysvalueof{/tikz/parrow/dist}/2) coordinate 
            (parrowb-\pgfkeysvalueof{/tikz/parrow/name}-\number\value{parrow});
      }
    }
  },
  reconstruct top/.style={
    % insert a path along recoreded coordinates (parrowt-<name>-<n>), where <n> = 1 to <parrow>
    insert path={
      plot[variable=\t, samples at={1,...,\number\value{parrow}}, smooth] (parrowt-#1-\t)
    }
  },
  reconstruct bottom/.style={
    % insert a path along recoreded coordinates (parrowt-<name>-<n>), where <n> = <parrow>-1 to 1
    insert path={%
      plot[variable=\t, samples at={\number\value{parrow}, \the\numexpr\value{parrow}-1,...,1}, smooth] (parrowb-#1-\t)
    }
  },
  parrow area/.style={
    % insert a closed path
    insert path={
      (parrowt-#1-1) [reconstruct top=#1] -- 
      (parrowb-#1-\number\value{parrow}) [reconstruct bottom=#1]  --
      (parrowt-#1-1)
    }
  },
  % init keys
  parrow/.cd,
  dist/.initial=3.14pt,
  step/.initial=2pt,
  name/.initial={}
}

\begin{document}

\begin{tikzpicture}[font=\sffamily, nodes={circle,draw}]
  \path (0,0) node (A) {A} 
        (3,1) node (B) {B} 
        (3.2,-1) node(C) {C} 
        (5,0) node (D) {D};

  % A to B
  \path[record path={name=AB}] (A) to[bend left] (B);
  \draw[-latex, reconstruct top=AB];
  \draw[red, -latex, reconstruct bottom=AB];

  % B to C
  \path[record path] (B) to[out=-90,in=160] (C);
  \path[pattern=north east lines, parrow area];
  \draw[-latex, reconstruct top];
  \draw[red, -latex, reconstruct bottom];

  % C to D
  \path[record path={name=CD, dist=5pt}] (C) to[bend left] (D);
  \fill[yellow, parrow area=CD];
  \draw[blue, -latex, reconstruct top=CD];
  \draw[orange, -latex, reconstruct bottom=CD];
\end{tikzpicture}
\end{document}

Related Solutions

[Tex/LaTex] Create curved TikZ single arrow

This is due to the large curvature with thick linewidth. TikZ makes some inner calculations before putting the arrow heads such as measuring the finishing angle and going a little backwards to make sure the arrow head joins the lineend nicely etc. I think in this example you can get away with small corrections. I've added tiny extensions in the angle that I want to place the arrow head in the examples.

I really recommend using nodes and coordinates for referring to known points. Also to avoid the repetitions you can create custom styles. ++ syntax is used for adding some coordinate to the last point of the current path. Finally arc (start angle:end angle:xrad and yrad) is sufficient.

\documentclass{article}

\usepackage{tikz}
\usetikzlibrary{shapes.arrows}

\begin{document}

\begin{tikzpicture}[
rotor/.style={inner sep=3pt,outer sep=0,fill opacity=0.3,minimum width=2cm,circle},
crossline/.style={gray,line width=3pt,opacity=0.5,line cap=round}
]

% cross
\draw[crossline] (-2,0) -- (2,0);
\draw[crossline] (0,-2) -- (0,2);

%rotors
\node[rotor,fill=blue,draw=blue] (n1) at (-2,0) {};
\node[rotor,fill=blue,draw=blue] (n2) at (2,0)  {};
\node[rotor,fill=red,draw=red]   (n3) at (0,-2) {};
\node[rotor,fill=red,draw=red]   (n4) at (0,2)  {};

% rotation direction arrows
\draw [->,line width=5pt] (n1) ++(140:5mm) arc (-220:40:5mm) --++(110:2mm);
\draw [->,line width=1pt] (n2) ++(140:5mm) arc (-220:40:5mm);
\draw [<-,line width=2.5pt] (n3) ++(138:5mm) --++(60:-1pt) arc (-220:40:5mm) ;
\draw [<-,line width=2.5pt] (n4) ++(138:5mm) --++(60:-1pt) arc (-220:40:5mm);

% rotors asterisk to indicate front and side
\draw plot[mark=asterisk,mark size=5pt,mark options={color=red}] coordinates {(-2,0)};
\draw plot[mark=asterisk,mark size=5pt,mark options={color=green}] coordinates {(2,0)};
\draw plot[mark=asterisk,mark size=5pt,mark options={color=cyan}] coordinates {(0,-2)};
\draw plot[mark=asterisk,mark size=5pt,mark options={color=red}] coordinates {(0,2)};

% translation direction
\node[fill=black,single arrow,minimum height=3cm] (arrow)  at (0,-3.5){};

\end{tikzpicture}
\end{document}

enter image description here

[Tex/LaTex] How to define the default vertical distance between nodes

I don't really get the question so I hope this is what you wanted. If you include a full document (such that we copy paste and see the problem on our systems) things are much more easier.

Here, you can change the default setting within a scope but your block style had a node distance which was resetting every time it is issued. I've made it 2mm such that we can see the difference easier.

\documentclass[tikz]{standalone}
\usetikzlibrary{arrows,shapes.geometric,positioning}

\begin{document}
\begin{tikzpicture}[decision/.style={diamond, draw, text width=4.5em, text badly centered, node distance=3.5cm, inner sep=0pt},
                    block/.style   ={rectangle, draw, text width=6em, text centered, rounded corners, minimum height=4em, minimum height=2em},
                    cloud/.style   ={draw, ellipse, minimum height=2em},
                    line/.style    ={draw,-latex'},
                    node distance = 1cm, 
                    auto]
    \node [block] (1st) {1st};
    \node [block, right= of 1st]  (2nd1) {2nd1};
\begin{scope}[node distance=2mm and 10mm]%Here we change it for everything inside this scope
    \node [block, above= of 2nd1] (2nd2) {2nd2};
    \node [block, below= of 2nd1] (2nd3) {2nd3};
    \node [block, right= of 2nd1] (3rd1) {3rd1};
    \node [block, above= of 3rd1] (3rd2) {3rd2};
    \node [block, above= of 3rd2] (3rd3) {3rd3};
\end{scope}
    \node [block, below= of 3rd1] (3rd4) {3rd4};
    \node [block, below= of 3rd4] (3rd5) {3rd5};

    \path [line] (1st) -- (2nd1);
    \path [line] (2nd1) -- (2nd2);
    \path [line] (2nd1) -- (2nd3);
    \path [line] (2nd2) -- (3rd3);
    \path [line] (2nd1) -- (3rd1);
    \path [line] (1st) -- (2nd1);
\end{tikzpicture}
\end{document}

enter image description here

Best Answer

Related Solutions

[Tex/LaTex] Create curved TikZ single arrow

[Tex/LaTex] How to define the default vertical distance between nodes

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