[Tex/LaTex] Option [(a)] to get alphabet numbering when applied to enumerate doesn’t work

#enumeratelists

According to this popular guide http://texblog.wordpress.com/2008/10/16/lists-enumerate-itemize-description-and-how-to-change-them/, I should be able to apply an option [(a)] to get small case alphabet numbering. As it is below, I cannot:

\documentclass[12pt]{article}
\usepackage[version=3]{mhchem}

\date{}
\begin{document}

\begin{enumerate}[(a)]
\item {\bf \ce{CH3Br + KOH -> CH3OH + KBr}}
\end{enumerate}
\end{document}

Error message:

! LaTeX Error: Something's
wrong--perhaps a missing \item.

See the LaTeX manual or LaTeX
Companion for explanation. Type  H
<return>  for immediate help.  ...    

                                                   l.22 \item {
            \bf \ce{CH3Br + KOH -> CH3OH + KBr}} ?

Best Answer

This feature isn't part of 'standard' LaTeX, but is provided by the enumerate package.

You need to \usepackage{enumerate}.