Chemistry Formulas and Reactions

Chemical notation requires specialized formatting for formulas, reactions, and molecular structures. This guide covers the essential packages and techniques for professional chemistry typesetting in LaTeX.

Key concept: LaTeX provides powerful packages like mhchem for chemical equations and chemfig for molecular structures. These packages handle subscripts, superscripts, arrows, and complex chemical notation automatically.Related topics: Mathematical notation | Scientific notation | Symbols and special characters

The mhchem Package

Basic Chemical Formulas

\documentclass{article}
\usepackage[version=4]{mhchem}

\begin{document}

\section{Chemical Formulas}

% Simple formulas
Water: \ce{H2O}

Sulfuric acid: \ce{H2SO4}

Methane: \ce{CH4}

% Complex formulas with charges
Hydronium ion: \ce{H3O+}

Sulfate ion: \ce{SO4^2-}

Ammonium: \ce{NH4+}

% Isotopes
Carbon-14: \ce{^14C}

Uranium-235: \ce{^235U}

Deuterium oxide: \ce{^2H2O}

% States of matter
Solid sodium chloride: \ce{NaCl_{(s)}}

Aqueous hydrochloric acid: \ce{HCl_{(aq)}}

Gaseous carbon dioxide: \ce{CO2_{(g)}}

Liquid water: \ce{H2O_{(l)}}

\end{document}

Chemical Equations and Reactions

\documentclass{article}
\usepackage[version=4]{mhchem}

\begin{document}

\section{Chemical Reactions}

% Simple reaction
\ce{2H2 + O2 -> 2H2O}

% Reversible reaction
\ce{N2 + 3H2 <=> 2NH3}

% Equilibrium with conditions
\ce{CaCO3_{(s)} <=>[\Delta] CaO_{(s)} + CO2_{(g)}}

% Multiple steps
\begin{align}
\ce{CH4 + 2O2 &-> CO2 + 2H2O} \\
\ce{2H2 + O2 &-> 2H2O} \\
\ce{C + O2 &-> CO2}
\end{align}

\section{Complex Reactions}

% Precipitation reaction
\ce{AgNO3_{(aq)} + NaCl_{(aq)} -> AgCl_{(s)} v + NaNO3_{(aq)}}

% Acid-base reaction
\ce{HCl_{(aq)} + NaOH_{(aq)} -> NaCl_{(aq)} + H2O_{(l)}}

% Oxidation-reduction
\ce{Zn_{(s)} + Cu^2+_{(aq)} -> Zn^2+_{(aq)} + Cu_{(s)}}

% Organic reaction with mechanism
\ce{CH3CH2OH ->[H2SO4][\Delta] CH2=CH2 + H2O}

% Enzyme-catalyzed reaction
\ce{glucose + O2 ->[enzyme] CO2 + H2O + ATP}

\section{Reaction Mechanisms}

% Nucleophilic substitution
\ce{R-X + Nu^- -> R-Nu + X^-}

% Addition reaction
\ce{CH2=CH2 + HBr -> CH3CH2Br}

% Elimination reaction
\ce{CH3CH2Br + OH^- -> CH2=CH2 + Br^- + H2O}

\end{document}

Advanced Chemical Notation

\documentclass{article}
\usepackage[version=4]{mhchem}
\usepackage{amsmath}

\begin{document}

\section{Advanced Chemical Notation}

% Coordination compounds
Hexaamminecobalt(III) chloride: \ce{[Co(NH3)6]Cl3}

Potassium hexacyanoferrate(II): \ce{K4[Fe(CN)6]}

% Transition states
\ce{A + B ->[TS] P}

% Catalysts above arrows
\ce{benzene ->[AlCl3] methylbenzene}

\ce{ethene + H2 ->[Ni][\Delta] ethane}

% Multiple arrows
\ce{A ->[k1] B ->[k2] C}

\ce{reactants <=>[\ce{k_{forward}}][\ce{k_{reverse}}] products}

% Electron configurations
Ground state oxygen: \ce{[He] 2s^2 2p^4}

Excited state carbon: \ce{[He] 2s^1 2p^3}

\section{Thermodynamic Notation}

% Enthalpy changes
\ce{CH4_{(g)} + 2O2_{(g)} -> CO2_{(g)} + 2H2O_{(l)}} \quad $\Delta H = -890$ kJ/mol

% Equilibrium expressions
\ce{N2_{(g)} + 3H2_{(g)} <=> 2NH3_{(g)}} \quad $K_c = \frac{[\ce{NH3}]^2}{[\ce{N2}][\ce{H2}]^3}$

% Rate expressions
Rate = $k[\ce{A}]^m[\ce{B}]^n$

\section{Biochemical Notation}

% Amino acids
Glycine: \ce{NH2CH2COOH}

Alanine: \ce{NH2CH(CH3)COOH}

% Phosphorylation
\ce{ATP + H2O -> ADP + Pi + energy}

% DNA bases
Adenine: \ce{C5H5N5}

Guanine: \ce{C5H5N5O}

\end{document}

Molecular Structures with chemfig

Basic Molecular Drawing

\documentclass{article}
\usepackage{chemfig}

\begin{document}

\section{Basic Molecular Structures}

% Simple molecules
Methane: \chemfig{C(-[1]H)(-[3]H)(-[5]H)(-[7]H)}

Water: \chemfig{H-O-H}

Ammonia: \chemfig{N(-[1]H)(-[5]H)(-[7]H)}

% Linear molecules
Ethane: \chemfig{H_3C-CH_3}

Propane: \chemfig{H_3C-CH_2-CH_3}

% Branched molecules
Isobutane: \chemfig{H_3C-CH(-[2]CH_3)-CH_3}

% Double bonds
Ethene: \chemfig{H_2C=CH_2}

Carbon dioxide: \chemfig{O=C=O}

% Triple bonds
Ethyne: \chemfig{HC~CH}

Hydrogen cyanide: \chemfig{H-C~N}

\section{Cyclic Structures}

% Cyclohexane
\chemfig{*6(------)}

% Benzene
\chemfig{*6(=-==-=)}

% Cyclopentane
\chemfig{*5(-----)}

% Substituted benzene
Toluene: \chemfig{*6(=-=(-CH_3)-=)}

Phenol: \chemfig{*6(=-=(-OH)-=)}

\end{document}

Complex Organic Structures

\documentclass{article}
\usepackage{chemfig}

\begin{document}

\section{Complex Organic Molecules}

% Glucose
Glucose: \chemfig{HO-[1,0.5,2]?<[7,0.7]OH>[1,0.7]?<[2,0.5]OH>[3,0.7]?<[4]OH>[4,0.7]?<[3,0.5]OH>[7,0.7]?(-[1,0.3]O-[7,0.3]?)}

% Caffeine
Caffeine: \chemfig{*6((-N*5(-(-CH_3)-N=-N(-CH_3)-))=N-=(-N(-CH_3))=*6(-(-=O)-N(-CH_3)-(-=O)-N=-=))}

% Cholesterol (simplified)
Cholesterol: \chemfig{*6((-*6(-----(-OH)))---(-*5(---(-*6(------))--))-(-(=)-(-[1])-([7]))---)}

\section{Functional Groups}

% Alcohol
Primary alcohol: \chemfig{R-CH_2-OH}

Secondary alcohol: \chemfig{R-CH(-[2]OH)-R'}

Tertiary alcohol: \chemfig{R-C(-[2]OH)(-[6]R')(-[7]R'')}

% Carbonyl compounds
Aldehyde: \chemfig{R-C(=[2]O)-H}

Ketone: \chemfig{R-C(=[2]O)-R'}

% Carboxylic acid derivatives
Carboxylic acid: \chemfig{R-C(=[2]O)-OH}

Ester: \chemfig{R-C(=[2]O)-O-R'}

Amide: \chemfig{R-C(=[2]O)-N(-[6]H)-H}

% Aromatic functional groups
Aniline: \chemfig{*6(=-=(-NH_2)-=)}

Benzoic acid: \chemfig{*6(=-=(-C(=[2]O)-OH)-=)}

\section{Stereochemistry}

% Wedge and dash bonds
Tetrahedral carbon: \chemfig{C(-[1,,,1]H)(-[3,,,2]Cl)(-[5]Br)(-[7]F)}

% Chair conformation
Cyclohexane chair: \chemfig{*6((-[2]H)(-[6]H)-(-[2]H)(-[6]H)-(-[2]H)(-[6]H)---)}

% Newman projection
Newman projection: \chemfig{*6((-H)(-H)(-H)-*6((-H)(-H)(-H)---)---)}

\end{document}

Reaction Schemes

\documentclass{article}
\usepackage{chemfig}
\usepackage[version=4]{mhchem}

\begin{document}

\section{Organic Reaction Schemes}

% SN2 reaction
\schemestart
\chemfig{H_3C-CH_2-Br}
\+
\chemfig{OH^{-}}
\arrow{->[SN2]}
\chemfig{H_3C-CH_2-OH}
\+
\chemfig{Br^{-}}
\schemestop

% Addition reaction
\schemestart
\chemfig{H_2C=CH_2}
\+
\chemfig{HBr}
\arrow{->}
\chemfig{H_3C-CH_2Br}
\schemestop

% Multistep synthesis
\schemestart
\chemfig{*6(=-=(-CH_3)-=)}
\arrow{->[KMnO_4][H^+, heat]}
\chemfig{*6(=-=(-C(=[2]O)-OH)-=)}
\arrow{->[SOCl_2]}
\chemfig{*6(=-=(-C(=[2]O)-Cl)-=)}
\arrow{->[NH_3]}
\chemfig{*6(=-=(-C(=[2]O)-NH_2)-=)}
\schemestop

\section{Biochemical Pathways}

% Glycolysis step
\schemestart
\chemfig{glucose}
\arrow{->[hexokinase][ATP, Mg^{2+}]}
\chemfig{glucose-6-phosphate}
\arrow{->[phosphoglucose isomerase]}
\chemfig{fructose-6-phosphate}
\schemestop

% Peptide bond formation
\schemestart
\chemfig{H_2N-CH(-[6]R_1)-C(=[2]O)-OH}
\+
\chemfig{H_2N-CH(-[6]R_2)-C(=[2]O)-OH}
\arrow{->[condensation][-H_2O]}
\chemfig{H_2N-CH(-[6]R_1)-C(=[2]O)-NH-CH(-[6]R_2)-C(=[2]O)-OH}
\schemestop

\section{Coordination Chemistry}

% Octahedral complex
Octahedral \ce{[Co(NH3)6]^3+}:
\chemfig{Co(-[0]NH_3)(-[60]NH_3)(-[120]NH_3)(-[180]NH_3)(-[240]NH_3)(-[300]NH_3)}

% Square planar complex
Square planar \ce{[PtCl4]^2-}:
\chemfig{Pt(-[0]Cl)(-[90]Cl)(-[180]Cl)(-[270]Cl)}

% Chelating ligand
EDTA complex:
\chemfig{(-[1]OOC-CH_2)_2N-CH_2-CH_2-N(-[7]CH_2-COO)_2}

\end{document}

Spectroscopy and Analytical Chemistry

NMR and IR Notation

\documentclass{article}
\usepackage[version=4]{mhchem}
\usepackage{siunitx}

\begin{document}

\section{NMR Spectroscopy}

% Chemical shifts
\ce{^1H} NMR (400 MHz, CDCl$_3$): $\delta$ 7.26 (s, 5H, Ph), 3.85 (s, 3H, OCH$_3$), 2.45 (t, 2H, CH$_2$)

\ce{^13C} NMR (100 MHz, CDCl$_3$): $\delta$ 170.2 (C=O), 128.5 (Ar-C), 55.2 (OCH$_3$), 34.1 (CH$_2$)

% Coupling constants
\ce{^1H} NMR: $\delta$ 6.95 (d, $J$ = 8.0 Hz, 2H), 4.12 (q, $J$ = 7.2 Hz, 2H)

% Two-dimensional NMR
COSY, HSQC, and HMBC correlations confirm the structure.

\section{IR Spectroscopy}

IR (KBr): $\tilde{\nu}$ = \SI{3300}{\per\centi\meter} (O-H stretch), \SI{1720}{\per\centi\meter} (C=O stretch), \SI{1600}{\per\centi\meter} (C=C stretch)

FT-IR (neat): \SI{2950}{\per\centi\meter} (C-H stretch), \SI{1735}{\per\centi\meter} (ester C=O), \SI{1250}{\per\centi\meter} (C-O stretch)

\section{Mass Spectrometry}

MS (EI, 70 eV): $m/z$ (\%) = 180 (M$^+$, 45), 152 (M$^+$ - CO, 100), 124 (M$^+$ - 2CO, 75)

HRMS (ESI): $m/z$ calculated for \ce{C10H12NO2} [M+H]$^+$ 178.0868, found 178.0865

\section{Elemental Analysis}

Anal. Calculated for \ce{C15H14N2O3}: C, 66.66; H, 5.22; N, 10.36. Found: C, 66.58; H, 5.18; N, 10.41.

\section{Crystallography}

Crystal data: \ce{C12H10N2O}, $M$ = 198.22, monoclinic, space group $P2_1/c$, $a$ = \SI{7.123}{\angstrom}, $b$ = \SI{15.456}{\angstrom}, $c$ = \SI{9.876}{\angstrom}, $\beta$ = 105.23°, $V$ = \SI{1045.2}{\angstrom\cubed}, $Z$ = 4.

\end{document}

Physical Chemistry Notation

Thermodynamics and Kinetics

\documentclass{article}
\usepackage[version=4]{mhchem}
\usepackage{amsmath}
\usepackage{siunitx}

\begin{document}

\section{Thermodynamics}

% Standard formation enthalpies
$\Delta_f H^\circ$ (\ce{H2O}, l) = \SI{-285.8}{\kilo\joule\per\mole}

$\Delta_f H^\circ$ (\ce{CO2}, g) = \SI{-393.5}{\kilo\joule\per\mole}

% Gibbs free energy
$\Delta G = \Delta H - T\Delta S$

For the reaction \ce{N2 + 3H2 <=> 2NH3}:
$\Delta G^\circ = -2 \times \SI{16.5}{\kilo\joule\per\mole} = \SI{-33.0}{\kilo\joule\per\mole}$

% Equilibrium constant
$K_p = \frac{P_{\ce{NH3}}^2}{P_{\ce{N2}} \cdot P_{\ce{H2}}^3}$

$\ln K = -\frac{\Delta G^\circ}{RT}$

\section{Chemical Kinetics}

% Rate laws
For \ce{A + B -> C}, the rate law is:
\[
\text{Rate} = k[\ce{A}]^m[\ce{B}]^n
\]

% Integrated rate laws
First order: $\ln[\ce{A}] = \ln[\ce{A}]_0 - kt$

Second order: $\frac{1}{[\ce{A}]} = \frac{1}{[\ce{A}]_0} + kt$

% Arrhenius equation
$k = A e^{-E_a/RT}$

$\ln k = \ln A - \frac{E_a}{RT}$

\section{Electrochemistry}

% Nernst equation
$E = E^\circ - \frac{RT}{nF} \ln Q$

At 298 K: $E = E^\circ - \frac{0.0592}{n} \log Q$

% Standard reduction potentials
\ce{Cu^2+ + 2e^- -> Cu} \quad $E^\circ = +\SI{0.34}{\volt}$

\ce{Zn^2+ + 2e^- -> Zn} \quad $E^\circ = -\SI{0.76}{\volt}$

% Cell notation
\ce{Zn | Zn^2+ (1 M) || Cu^2+ (1 M) | Cu}

$E_{\text{cell}}^\circ = E_{\text{cathode}}^\circ - E_{\text{anode}}^\circ = 0.34 - (-0.76) = \SI{1.10}{\volt}$

\section{Quantum Chemistry}

% Schrödinger equation
$\hat{H}\Psi = E\Psi$

% Hydrogen atom wavefunctions
$\Psi_{1s} = \frac{1}{\sqrt{\pi a_0^3}} e^{-r/a_0}$

% Molecular orbitals
For \ce{H2^+}: $\Psi_{\pm} = \frac{1}{\sqrt{2 \pm 2S}}(\phi_A \pm \phi_B)$

% Electronic configurations
\ce{C}: $1s^2 2s^2 2p^2$

\ce{Fe^3+}: $[\ce{Ar}] 3d^5$

\end{document}

Chemical Drawing Packages Comparison

Package Selection Guide

\documentclass{article}
\usepackage[version=4]{mhchem}
\usepackage{chemfig}
\usepackage{modiagram}

\begin{document}

\section{Package Comparison}

\begin{tabular}{|l|l|l|}
\hline
\textbf{Package} & \textbf{Best For} & \textbf{Examples} \\
\hline
mhchem & Chemical equations & \ce{H2SO4}, \ce{A + B -> C} \\
& Formulas with charges & \ce{NH4+}, \ce{SO4^2-} \\
& Reaction arrows & \ce{A <=> B} \\
\hline
chemfig & Molecular structures & Benzene rings, stereochemistry \\
& Organic molecules & Complex natural products \\
& Reaction schemes & Multi-step syntheses \\
\hline
modiagram & Molecular orbitals & MO diagrams \\
& Electronic structure & Energy level diagrams \\
\hline
\end{tabular}

\section{Molecular Orbital Diagrams}

% Simple MO diagram for H2
\begin{modiagram}[labels]
\atom[N]{left}{1s}
\atom[N]{right}{1s}
\molecule[N]{
1sigma = {0; pair}
}
\end{modiagram}

% More complex example for O2
\begin{modiagram}[labels]
\atom[O]{left}{2s, 2p = {;pair,up,up}}
\atom[O]{right}{2s, 2p = {;pair,up,up}}
\molecule[O2]{
2sigma = {0; pair},
2sigma* = {1.5; },
2piy = {-1; pair},
2piz = {-1; pair},
2pix = {0.5; up, up},
2pix* = {2; }
}
\end{modiagram}

\end{document}

Best Practices

Chemistry typesetting guidelines:

Use mhchem for equations - Handles subscripts, superscripts, and arrows automatically
Consistent notation - Follow IUPAC naming conventions
Proper spacing - Let packages handle chemical spacing
Clear structures - Use chemfig for complex molecules
State symbols - Always indicate physical states when relevant
Units and precision - Use siunitx for measurements and uncertainties

Professional Chemistry Document

\documentclass{article}
\usepackage[version=4]{mhchem}
\usepackage{chemfig}
\usepackage{siunitx}
\usepackage{amsmath}
\usepackage{booktabs}

% Custom commands for common notation
\newcommand{\conc}[1]{[\ce{#1}]}
\newcommand{\std}{\circ}

\begin{document}

\title{Synthesis and Characterization of Novel Organic Compounds}
\author{Chemistry Department}
\maketitle

\section{Experimental}

\subsection{Synthesis of Compound 1}

To a solution of \ce{benzaldehyde} (\SI{1.06}{\gram}, \SI{10.0}{\milli\mole}) in dry \ce{CH2Cl2} (\SI{20}{\milli\liter}) was added \ce{NaBH4} (\SI{0.38}{\gram}, \SI{10.0}{\milli\mole}) at \SI{0}{\celsius}. The reaction mixture was stirred for \SI{2}{\hour} at room temperature.

\schemestart
\chemfig{*6(=-=(-CHO)-=)}
\arrow{->[NaBH_4][CH_2Cl_2, rt]}
\chemfig{*6(=-=(-CH_2OH)-=)}
\schemestop

\subsection{Characterization}

\textbf{Compound 1}: Colorless oil. Yield: \SI{92}{\percent}.

\textbf{\ce{^1H} NMR} (400 MHz, CDCl$_3$): $\delta$ 7.38-7.28 (m, 5H, Ar-H), 4.68 (s, 2H, CH$_2$), 2.15 (br s, 1H, OH).

\textbf{\ce{^13C} NMR} (100 MHz, CDCl$_3$): $\delta$ 140.8, 128.4, 127.6, 126.9, 65.1.

\textbf{IR} (neat): $\tilde{\nu}$ = \SI{3330}{\per\centi\meter} (O-H), \SI{3030}{\per\centi\meter} (Ar-H), \SI{2924}{\per\centi\meter} (C-H), \SI{1496}{\per\centi\meter}, \SI{1454}{\per\centi\meter} (Ar).

\textbf{MS} (EI): $m/z$ (\%) = 108 (M$^+$, 25), 79 (100), 77 (85).

\section{Results and Discussion}

The reaction proceeded via a nucleophilic addition mechanism:

\begin{align}
\ce{C6H5CHO + BH4^- &-> C6H5CH2O^-BH3} \\
\ce{C6H5CH2O^-BH3 + H2O &-> C6H5CH2OH + B(OH)3 + H2}
\end{align}

The equilibrium constant for the hydride transfer is:
\[
K_{eq} = \frac{\conc{C6H5CH2O^-BH3}}{\conc{C6H5CHO}\conc{BH4^-}}
\]

Thermodynamic analysis shows $\Delta G\std = \SI{-15.2}{\kilo\joule\per\mole}$ for this transformation at \SI{298}{\kelvin}.

\end{document}

Quick Reference

Essential mhchem Commands

Command	Purpose	Example
`\ce{formula}`	Chemical formula	`\ce{H2SO4}`
`\ce{A + B -> C}`	Chemical equation	`\ce{2H2 + O2 -> 2H2O}`
`\ce{A <=> B}`	Equilibrium	`\ce{N2 + 3H2 <=> 2NH3}`
`\ce{^14C}`	Isotope	`\ce{^14C}`
`\ce{SO4^2-}`	Ion with charge	`\ce{SO4^2-}`

Common Chemical Notation

Notation	LaTeX Code	Result
Subscript	`\ce{H2O}`	H₂O
Superscript	`\ce{Ca^2+}`	Ca²⁺
State	`\ce{NaCl_{(s)}}`	NaCl₍ₛ₎
Arrow	`\ce{->}`	→
Equilibrium	`\ce{<=>}`	⇌

chemfig Basics

Element	Code	Description
Single bond	`-`	Single bond
Double bond	`=`	Double bond
Triple bond	`~`	Triple bond
Angle	`[angle]`	Bond angle
Ring	`*n(bonds)`	n-membered ring

Next: Learn about Music notation and scores for musical typesetting, or explore Circuit diagrams for electrical schematics.

Getting Started

LaTeX Basics

Text & Formatting

Mathematics

Figures & Tables

Specialized Notation

Bibliography & References

Advanced Topics

The mhchem Package

Basic Chemical Formulas

Chemical Equations and Reactions

Advanced Chemical Notation

Molecular Structures with chemfig

Basic Molecular Drawing

Complex Organic Structures

Reaction Schemes

Spectroscopy and Analytical Chemistry

NMR and IR Notation

Physical Chemistry Notation

Thermodynamics and Kinetics

Chemical Drawing Packages Comparison

Package Selection Guide

Best Practices

Professional Chemistry Document

Quick Reference

Essential mhchem Commands

Common Chemical Notation

chemfig Basics

Getting Started

LaTeX Basics

Text & Formatting

Mathematics

Figures & Tables

Specialized Notation

Bibliography & References

Advanced Topics

​The mhchem Package

​Basic Chemical Formulas

​Chemical Equations and Reactions

​Advanced Chemical Notation

​Molecular Structures with chemfig

​Basic Molecular Drawing

​Complex Organic Structures

​Reaction Schemes

​Spectroscopy and Analytical Chemistry

​NMR and IR Notation

​Physical Chemistry Notation

​Thermodynamics and Kinetics

​Chemical Drawing Packages Comparison

​Package Selection Guide

​Best Practices

​Professional Chemistry Document

​Quick Reference

​Essential mhchem Commands

​Common Chemical Notation

​chemfig Basics

The mhchem Package

Basic Chemical Formulas

Chemical Equations and Reactions

Advanced Chemical Notation

Molecular Structures with chemfig

Basic Molecular Drawing

Complex Organic Structures

Reaction Schemes

Spectroscopy and Analytical Chemistry

NMR and IR Notation

Physical Chemistry Notation

Thermodynamics and Kinetics

Chemical Drawing Packages Comparison

Package Selection Guide

Best Practices

Professional Chemistry Document

Quick Reference

Essential mhchem Commands

Common Chemical Notation

chemfig Basics