[texhax] problem with a defined command

[A Emery]

I define the following commands

\newcommand{\beq}{\begin{align}}
\newcommand{\eeq}{\end{align}}
\newcommand{\besq}{\begin{subequations}}
\newcommand{\eesq}{\end{subequations}}

then use them as
\beq
x=sin(y)
\eeq

The response is

Runaway argument?
x=sin(y) \eeq
! Paragraph ended before \align was complete.
<to be read again>
                    \par

But this works
\beq
x=sin(y)
\end{align}

However, \besq and \eesq  work perfectly

any ideas?

thanks