My school had 4 periods a day (75 mins each) up until Year 11 and then 5 periods a day (60 mins each) in Year 12. 60 minutes is definitely a good compromise in my opinion. Any more than 5 periods a day would be a waste of time.
Bromohexane is hexane with a bromine on it, but nothing is named bromohexane. A hydrocarbon named 2,3-dibromopentane means that there are two bromines on the 5-carbon hydrocarbon structure at the 2nd and 3rd carbon.