www.Example.com works but not root (Example.com) - apache

Question

I am using Apache2 with UBUNTU14 LTS, all "standard" server.
The problem is simple, when using http://www.example.com it works fine, but when using http://example.com it doesn't, it goes to the wrong index.
Describing details
I have folders at ls /var/www/
example.com example2.example html
wiki.example.com wp.example2.example
Each with different and good index.htm working with http://www.example.com (goes to /var/www/example.com) or http://wiki.example.com, etc. But the index of http://example.com goes to /var/www/html/index.htm, not to /var/www/example.com (!).
At /etc/apache2/sites-available/example.com.conf we have,
<VirtualHost *:80>
ServerAdmin mymail#ggmail.com
ServerName example.com
ServerAlias www.example.com
DocumentRoot /var/www/example.com
ErrorLog ${APACHE_LOG_DIR}/error.log
CustomLog ${APACHE_LOG_DIR}/access.log combined
</VirtualHost>
<VirtualHost *:80>
ServerName wiki.example.com
DocumentRoot /var/www/wiki.example.com
</VirtualHost>
EDIT (notes)
We are using a workaround — and please ignore the "real world" examples in the comments, it is not valid as real testing —, an ugly piece of PHP code (not a solution) in the /var/www/html/index.php of the root (no subdomain), to redirect to www subdomain,
if ( preg_match( // if HTTP from other domain, redirects
'/(mydomain1|mydomain2|mydomain3)/',
strtolower($_SERVER['HTTP_HOST']),
$m
) ) switch($m[1]) {
case 'mydomain1':
header("Location: https://www.example.com"); die('');
case 'mydomain2':
header("Location: https://www.example2.example"); die('');
case '...':
header("Location: https://www...."); die('');
}
EDIT
As #covener comment suggest, apachectl -S, results in
VirtualHost configuration:
*:80 is a NameVirtualHost
default server localhost (/etc/apache2/sites-enabled/000-default.conf:1)
port 80 namevhost localhost (/etc/apache2/sites-enabled/000-default.conf:1)
port 80 namevhost atarica.com.br (/etc/apache2/sites-enabled/atarica.com.br.conf:1)
alias www.atarica.com.br
port 80 namevhost wiki.atarica.com.br (/etc/apache2/sites-enabled/atarica.com.br.conf:13)
port 80 namevhost atarica.com.br (/etc/apache2/sites-enabled/fabrincantes.com.conf:1)
alias www.fabrincantes.com
port 80 namevhost yellowtown.org (/etc/apache2/sites-enabled/yellowtown.org.conf:1)
alias www.yellowtown.org
port 80 namevhost wiki.yellowtown.org (/etc/apache2/sites-enabled/yellowtown.org.conf:35)
ServerRoot: "/etc/apache2"
Main DocumentRoot: "/var/www"
Main ErrorLog: "/var/log/apache2/error.log"
Mutex default: dir="/var/lock/apache2" mechanism=fcntl
Mutex mpm-accept: using_defaults
Mutex watchdog-callback: using_defaults
PidFile: "/var/run/apache2/apache2.pid"
Define: DUMP_VHOSTS
Define: DUMP_RUN_CFG
User: name="www-data" id=33 not_used
Group: name="www-data" id=33 not_used

Answer 1

Try this:
<VirtualHost *:80>
ServerName example.com
Redirect permanent / http://www.example.com/
</VirtualHost>
Then you just need to create another section with ServerName www.example.com for your real server configuration.
Also, wouldn't CNAME's records work has an alternative to this? (I'm not sure)

Answer 2

Sorry all, that was my "human error", as blind spot when reading file.conf scripts, and a general blindness here after my edit showing apachectl -S results, the error is there (! see fabrincantes.com lines), a wrong name "AAA" on the "BBB" configuration:
port 80 namevhost AAA (/etc/apache2/sites-enabled/BBB.conf:1)
alias BBB
so I fixed with simple name correction on my BBB.conf, that has an ServerName AAA instead "BBB",
<VirtualHost *:80>
...
ServerName BBB
...
</VirtualHost>

Answer 3

You would require to edit your /etc/hosts file so it points to correct links.
For example, configuration on my localhost would be
127.0.1.1 example.com www.example.com