"if is logged in" doesn't work for me

Im trying to achieve the code hides part of the content from unregistered users but doesn't work for me and comes back with error this is the code i tried

if ( is_user_logged_in() ) {
echo '<div class="container_12">
<?php while ( have_posts() ) : the_post(); ?>
<?php woocommerce_get_template_part( 'content', 'single-product' ); ?>
<?php endwhile; // end of the loop. ?>
</div>}
else {
echo 'you must to log in to see the content';}
?>