pdfLaTeX + memoir class compile error

Question

I'm in the middle of writing my thesis, and was using KOMA-Script. The document compiles just fine. I stumbled upon the memoir class yesterday, and was thinking of giving it a try, so here I am trying to compile with this class instead of KOMA-Script. First compilation is OK. On second compilation, the document would not build

(./fourier/fourier.tex [98]
! Undefined control sequence.
<argument> ... C\protect \noexpand \protect \bond 
                                                  \protect \noexpand \protec...
l.1 \chapter
            {Homogénéisation numérique par transformée de Fourier rapide}
? 

It has apparently not connected to hyperlink (btw, I'm using memhfixc), since I've commented this one out. Here is the preamble of my document, any thoughts?

%\documentclass[draft, 11pt, a4paper, chapterprefix]{scrreprt}
\documentclass[draft, 11pt, a4paper]{memoir}
\usepackage[authoryear, round]{natbib}
\usepackage[french]{babel}
\usepackage[latin1]{inputenc}
\usepackage{pdfsync}
\usepackage[version=3]{mhchem}
\usepackage{pgf}

\usepackage{microtype}
\usepackage{txfonts} % Polices times

\usepackage[notref, notcite]{showkeys}

\usepackage{amsmath}
\usepackage{amssymb}
\usepackage[bvec]{sbmacros}
\usepackage{micromechanics}
\usepackage{pgfcad}


%\usepackage[breaklinks=true]{hyperref}
%\usepackage{memhfixc} % Pour assurer la compatibilité entre memoir et hyperref
%\newcommand{\url}[1]{\texttt{#1}}

% Options KOMA-Script
% \addtokomafont{caption}{\small}
% \pagestyle{headings}

Answer 1

I found the answer, for those who might be interested. I started to have serious doubts when I realized that the exact same problem occured when I used the KOMA-Script scrbook class instead of the KOMA-Script scrreprt class...

And I finally found that the mhchem package somehow conflicts with those packages. Since I didn't use this package much anyway, I got completely rid of it, and am now using memoir, no problem.