Hi im planning on taking organic chem 2OA3 and 2OB3 during the summer at mac
it seemed as though there was always organic chem available at mac during the summer.
i just wanted to confirm if this is the case every year

It has been in the past.
There's never any guarantee that a given course will be offered in the summer, you won't ever know for sure until the courses are officially released, but I'd be very very surprised if the orgos weren't offered.

Both were offered last summer. Just remember that if a course was offered last summer, it might not be offered again this summer.

You can check to see if a course was offered last summer here:
http://registrar.mcmaster.ca /scheduling/coursett.html

Just select "Spring/Summer 2012" and then enter the course code.

Orgo has been offered every summer since at least 2005.

Edit: naturally I didn't take orgo every summer and can't personally verify that the courses actually ran but they were at least listed on the time table. For various reasons, courses may be cancelled (once a course I registered for was cancelled a week into classes and money refunded since the instructor had passed away and they could not quickly find a replacement)