How to use the chemfig tags to draw an esterification scheme (@tags in charge env)?

Question

So for the love of me I cannot figure out chemfig. I tried for hours now to replicate a reaction mechanism and honestly regret not having just used photoshop. But here we are.

I cannot find out how to put the correct tags at the positions of my charges to replicate this. Wherever I put it it just displays the tag I set as characters in the figure and not as tag. I then tried to just use the position at the bond I already have, but shifting the arrow origin also isn't an option. Can you please help me? This is my code so far

\setchemfig{scheme debug=false}
\schemestart
\chemfig[atom sep=2em]{
    H-[0]C(-[2]H)(-[6]H)
    -[0]C(-[2]H)(-[6]H)
    -[0]C
    (=[@{DB}1]\charge{[circle]0=\|, 90=\|}{O})
    -[7]O
    -[0]H
}
\+
\chemfig{
\charge{[circle]45:3pt=$+$}{H}
}
\arrow{<=>}
\schemestop
\chemmove[]{
\draw[shorten <=5pt,shorten >=2pt] (DB) .. controls +(2:3) and +(10:5) .. (DB);
%   \draw(dnl)..controls +(90:1cm)and+(north:1cm)..(atoc);
%   \draw[shorten >=6pt](db)..controls +(north:5mm)and+(100:1cm)..(atoh);
}

This gets me here:

While we are at it: DO you know how to repair the bonds that go to the "charge Oxygen Atom"? For some reason the bond is extremely short especially in comparison to the others.

Answer 1

you need to define the starting and ending points (@{...}) of the arrows

\documentclass[border=2mm,12pt]{standalone}
\usepackage{amsmath}
\usepackage{chemfig}

\begin{document}

\setchemfig{scheme debug=false}
\schemestart
\chemfig[atom sep=2em]{H-[0]C(-[2]H)(-[6]H)-[0]C(-[2]H)(-[6]H)-[0]C(=[@{DB}1]@{DB2}\charge{0=\|, 90=\|}{O})-[7]O-[0]H}
\+
\chemfig{@{DB3}\charge{45:3pt=+}{H}}
\arrow{<=>}
\chemfig[atom sep=2em]{H-[0]C(-[2]H)(-[6]H)-[0]C(-[2]H)(-[6]H)-[0]\charge{100:5pt=\ $\oplus $}{C}(-[1]\charge{90=\|, 150=\|}{O}-H)-[7]O-[0]H}
\schemestop
\chemmove[]{
    \draw[red, shorten <=2pt,shorten >=-1pt] (DB) .. controls +(150:10mm) and +(140:5mm) .. (DB2);
      \draw[red,shorten <=3pt,shorten >=2pt](DB2)..controls +(0:10mm)and+(90:15mm)..(DB3);
}

\end{document}