What's wrong here? ! Extra }, or forgotten \right.<template> }$}\ifmeasuring@ \savefieldlength@ \fi \set@field \endtemplate \end{align}

Question

This Error-Message is not understandable for me, what's wrong here?

! Extra }, or forgotten \right.<template> }$}\ifmeasuring@ \savefieldlength@ \fi \set@field \endtemplate \end{align}

The following looooong equation causes the error above:

\RequirePackage[patch]{kvoptions} 
\documentclass
%[draft]
{DissOnlineLatex}
%\usepackage[ngerman]{babel}
\usepackage[T1]{fontenc}
\usepackage{lmodern}
\usepackage{graphicx}
\usepackage{subfigure}
\usepackage{amsmath,amssymb}
\usepackage{amsthm}
\usepackage{amsfonts}
\usepackage{tabularx}
\usepackage{rotating}
\usepackage{longtable}
\usepackage{lscape}
\usepackage{setspace}
%\usepackage[obeyspaces]{url}
\usepackage[style=chem-angew,backend=biber,]{biblatex}%bibtex8,
\usepackage{csquotes}
\usepackage{hyperref}
\usepackage[printonlyused]{acronym}
\bibliography{Literatur.bib}
\onehalfspacing
\usepackage{fancyhdr}
\usepackage[version=3]{mhchem}
\usepackage{eurosym}

\newcommand{\Natural}{{\mathbb{N}}}

\renewcommand{\topfraction}{1.0}
\renewcommand{\bottomfraction}{1.0}
\renewcommand{\floatpagefraction}{1.0}
\renewcommand{\dbltopfraction}{1.0}
\renewcommand{\dblfloatpagefraction}{1.0}

\begin{document}
\begin{align}
\Delta{f}&=4\ln{10}\cdot{\epsilon_{0}c^2}\cdot{}\nonumber
\\
&\left(\left(\frac{\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}{N_{A}e^2\lambda_{av}^2}\cdot{\Delta{m_{e}}}\right)^2
+\left(\frac{m_{e}\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}{N_{A}^{2}e^2\lambda_{av}^2}\cdot{\Delta{N_{A}}}\right)^2\right.\nonumber{}
\\
\left.&+\left(\frac{2m_{e}\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}{N_{A}e^3\lambda_{av}^2}\cdot{\Delta{e}}\right)^2
+\left(\frac{2m_{e}\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}{N_{A}e^2\lambda_{av}^3}\cdot{\Delta{\lambda_{av}}}\right)^2\right.\nonumber{}
\\
\left.&+\left(\frac{m_{e}\sum_{A}{(\Delta\lambda)_{A}}}{N_{A}e^2\lambda_{av}^2}\cdot{\Delta{\varepsilon}}\right)^2
+\left(\frac{m_{e}\sum_{A}{\varepsilon}}{N_{A}e^2\lambda_{av}^2}
\cdot{\Delta(\Delta{\lambda)_{A}}}\right)^2\right)^{\frac{1}{2}}
\end{align}
\end{document}

Answer 1

The error is in the lines that start with

\left.&+\left

because you can't have \left on one side of & and the matching \right on the other side.

However, there's a better way for doing this, with split and more careful alignment:

\documentclass{report}
\usepackage{amsmath}

\begin{document}

\begin{equation}
\begin{split}
\Delta{f}={}&4\ln{10}\cdot{\epsilon_{0}c^2}\cdot{}
\\
&\Biggl( % to be closed at the end
  \left(
    \frac{\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}
         {N_{A}e^2\lambda_{av}^2}
    \cdot
    \Delta{m_{e}}
  \right)^2
  +
  \left(
    \frac{m_{e}\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}
         {N_{A}^{2}e^2\lambda_{av}^2}
    \cdot
    \Delta{N_{A}}
  \right)^2
\\
&\hphantom{\Biggl(}
  {}+
  \left(
    \frac{2m_{e}\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}
    {N_{A}e^3\lambda_{av}^2}
    \cdot
    \Delta{e}
  \right)^2
  +
  \left(
    \frac{2m_{e}\sum_{A}{\varepsilon(\Delta\lambda)_{A}}}
         {N_{A}e^2\lambda_{av}^3}
    \cdot
    \Delta{\lambda_{av}}
  \right)^2
\\
&\hphantom{\Biggl(}
  {}+
  \left(
    \frac{m_{e}\sum_{A}{(\Delta\lambda)_{A}}}
         {N_{A}e^2\lambda_{av}^2}
    \cdot
    \Delta{\varepsilon}
  \right)^2
  +
  \left(
    \frac{m_{e}\sum_{A}{\varepsilon}}
         {N_{A}e^2\lambda_{av}^2}
    \cdot
    \Delta(\Delta{\lambda)_{A}}
  \right)^2
\Biggr)^{\frac{1}{2}}
\end{split}
\end{equation}

\end{document}

The indentation helps in reading the input, but is not essential.

As you notice, I used ={}& in order to put the alignment point at the right of the equals sign; then the third and fourth line start with an \hphantom, so the + signs are at the right of the big parenthesis.

Using ^{1/2} instead of ^{\frac{1}{2} is possibly better.

The example uses a standard class, but it should work also with the one you're loading.