chemfig: arbitrary structural formulas of molecules
mhchem: chemical equations and especially stoichiometry
Conveniently, you can also include all packages in one command.
\usepackage{amsmath,amssymb,amstext}
Equations
Any chemical equations are created with the \ce{} command. For indices and superscripts, the typical LaTeX commands are omitted. Example:
\ce{C6H12O6 + 6O2 -> 6CO2 + 6H2O}
Furthermore, there are various arrow types that can indicate, among others, the equilibrium or reversibility of a reaction. Example:
-> % Reaction to the right
<- % Reaction to the left
<-> % Resonance arrow
<--> % Reaction in both directions
<=> % Equilibrium arrow
<=>> % Equilibrium on the right side
<<=> % Equilibrium on the left side
Structural Formulas
For structural formulas, one works with the \chemfig{} command. Within the curly braces, the structural formula is defined. In the parentheses, the attached atoms/molecules are noted, while in square brackets before them, the bond angles are specified. For bond angles, there is a specific unit from 1 to 8, which corresponds to 45° to 360°. Example:
% Molecular formulas
\ce{C4H10}
% Structural formulas
\chemfig{H-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)-H}
% In this variant, the name of the molecule is below the structural formula.
\chemname{{H-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)-C(-[2]H)(-[6]H)-H}}{Butane}
% Skeletal formula
\chemfig{-[1]-[-1]-[1]}
% Condensed formula
\ce{CH3(CH)2CH3}