proxypassreverse cookie domain

[vtapas]

I have 7-8 websites
running on Apache2

<VirtualHost *:80>

ServerAdmin webmaster@localhost
ServerName mydomain.com
ProxyRequests off
<Proxy *>
Order deny,allow
Allow from all
</Proxy>

ProxyPreserveHost On

ProxyPass /something1 192.168.1.5/something1
ProxyPassReverse /something1 192.168.1.5/something1

ProxyPass /something2 192.168.1.5/something2/www/
ProxyPassReverse /something2 192.168.1.5/something2/www/

ProxyPass /something3 192.168.1.5/something3/
ProxyPassReverse /something3 192.168.1.5/something3/

ProxyPass /something4 192.168.1.5/something4/
ProxyPassReverse /something4 192.168.1.5/something4/

ProxyPass /something5 192.168.1.5/something5
ProxyPassReverse /something5 192.168.1.5/something5

ProxyPass /something6 192.168.1.5:8080/something6
ProxyPassReverse /something6 192.168.1.5:8080/something6

ProxyPass /something7 192.168.1.5:6060/portal
ProxyPassReverse /something7 192.168.1.5:6060/something7

ProxyPass /atutor 192.168.1.5atutor
ProxyPassReverse /atutor 192.168.1.5atutor
ProxyPassReverseCookieDomain internal.domain.com external.domain.com
ProxyPassReverseCookiePath / /atutor







ProxyPass / 192.168.1.5/
ProxyPassReverse / 192.168.1.5/

ErrorLog /var/log/apache2/mydomain_error.log

# Possible values include: debug, info, notice, warn, error, crit,
# alert, emerg.
LogLevel debug

CustomLog /var/log/apache2/mydomain_access.log combined

CustomLog /var/log/apache2/mydomain-resp_log resp
LogFormat "%D %{X-Forwarded-For}i %t" resp

</VirtualHost>

If some one has to login to http://mydomain.com/atutor then his session is not getting maintained can some one point what is the mistake in above configuration?