My chemical reaction latex codes look like this



\chemname{\chemfig{R-H}}{Alkane} \arrow(.{5.5}--){->[light,heat or catalyst]}[0,2,] \chemname{\chemfig{R-X}}{Haloalkane} \+ \chemfig{HX}

\chemfig{CH_4} \+ \chemfig{Cl_2} \arrow(.{5.5}--){->[light]}[0,2,] \chemfig{CH_3Cl} \+ \chemfig{HCl}

\chemfig{CH_3Cl}  \+ \chemfig{Cl_2} \arrow(.{5.5}--){->[light]}[0,2,] \chemfig{CH_2Cl_2} \+ \chemfig{HCl}

\chemfig{CH_2Cl_2}  \+ \chemfig{Cl_2} \arrow(.{5.5}--){->[light]}[0,2,] \chemfig{CHCl_3} \+ \chemfig{HCl}

\chemfig{CH_3Cl}  \+ \chemfig{Cl_2} \arrow(.{5.5}--){->[light]}[0,2,] \chemfig{CCl_4} \+ \chemfig{HCl}


It looks like this on compiling enter image description here

I thought adding \arrow{0}[,0] will fix it but it didn't actually i don't' know why :( . But i think it works for reaction containing benzene etc :(

  • +How to i balance the position of arrow of chemical reaction ?
  • How to i give blue color to Cl_2 atoms ? i thought of adding \colors but dont' know how it works :(
  • How do i show all arrow of same length ?
  • How to i show these reaction with arrow center so it looks very nice ?
  • How to i reduce the distance between names of compound and their names?

Thank you .

  • 1
    I'd do those kind of reactions either with the chemformula or the mhchem package. Both \ch (chemformula) and \ce (mhchem) can be used in amsmath's align environment for alignment – cgnieder Jun 23 '15 at 13:39
  • @clemens Thanks clemens . I am learning chemfig as many people recommended. Is it good to learn chemformula or mhchem? – aftershock Jun 23 '15 at 13:43
  • chemformula and mhchem are alternatives to each other but both can be used quite well together with chemfig – cgnieder Jun 23 '15 at 13:44
  • @clemens thanks can chemformula and mhchem works like chemfig . I mean for example drawing benzene ? – aftershock Jun 23 '15 at 13:45
  • No but they do other things very well where chemfig is not the ideal soultion. Why don't you have a look at them and decide for yourself? – cgnieder Jun 23 '15 at 13:49

Basically the answer is: have a look at TikZ anchors and how to use them with chemfig's \arrow:

\arrow(<node name>.<anchor>--<node name>.<anchor>)

All node names and anchors are optional. Those can be used with an invisible downarrow (angle: -90) to achieve alignment, e.g., by aligning the lower right-hand edge of the upper compound (south west) with the upper right-hand edge of the lower compound (north west):

\arrow(@c1.south east--.north east)

Here is an example alignment:

% \schemedebug{true} % shows (not only) the node names
  % line one
  A + B \arrow C + D
  \arrow(@c1.south east--.north east){0}[-90,.15]
  % line two:
  E + F \arrow G + H
  \arrow(@c3.south east--.north east){0}[-90,.15]
  % line three:
  I + J \arrow K + L

enter image description here

or with \schemedebug{true}:

enter image description here

Coloring can be done by placing braces around the atom and adding \color{blue}


As for the distance between compounds and names: I supsect you have used \chemname not in a group somewhere and have forgotten to reset it. Have a look at Placement of caption in \chemfig via \chemname command - how to reset spacing

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