Conditionally write open graph meta property in header

From what I understand, you need help framing your if logic? And the php tags usage dont look right either.

Does this help –

<?php 
if(!is_single()){
    if(is_home() || is_front_page()){ // not sure if you have set a static page as your front page
        echo '<meta property="og:url" content="'.bloginfo('url'); .'" />';
    }elseif(is_tag()){
        echo '<meta property="og:url" content="'.$_SERVER["HTTP_HOST"] . $_SERVER["REQUEST_URI"]; .'">';
        }
}
?>

=================== This is the code in entirety ========================

    function wpc_fb_opengraph() {
$wpc_image_url = wp_get_attachment_image_src( get_post_thumbnail_id(),     'large');
?>
<?php echo "\n<!-- Start of OG Tags from DougTheme 2013 -->\n"; ?>
<meta property="og:image" content="<?php if (function_exists('catch_that_image')) {echo catch_that_image(); }?>" />
<meta property="fb:admins" content="XXXXX"/>
<meta property="fb:app_id" content="XXXXXXXXXX">
<meta property="og:site_name" content="<?php bloginfo('name'); ?>" />
<meta property="og:description" content="<?php if ( is_singular() ) { echo strip_tags(get_the_excerpt()); } else { echo "comments about everything"; } ?>" />
<meta property="og:title" content="<?php if ( is_singular()) { echo esc_attr( get_the_title() ); } elseif (function_exists('is_tag') && is_tag()) {single_tag_title('Tag Archive for &quot;'); echo '&quot; - '; echo get_bloginfo('name');} else { echo get_bloginfo('name'); } ?>">
<meta property="og:type" content="<?php if ( is_singular() ) { echo "article"; } else { echo "website";} ?>">
if(!is_single()){
    if(is_home() || is_front_page()){ // not sure if you have set a static page as your front page
        echo '<meta property="og:url" content="'.bloginfo('url'); .'" />';
    }elseif(is_tag()){
        echo '<meta property="og:url" content="'.$_SERVER["HTTP_HOST"] . $_SERVER["REQUEST_URI"]; .'">';
        }
}    

<?php echo "\n<!-- End of OG Tags from DougTheme 2013 -->\n"; ?>
<?php }    

add_action('wp_head', 'wpc_fb_opengraph');