All drugs are different. As an example, Viagra with food diminishes effects by 50% or more while Cialis does not have the same issue. So yes, it matters.
As for timing, do the math:
If you took 100mg of an oral with a 9 hour half life at 8 am. By 5pm, you would have 50mg of effective drug in your blood. By 2am, 9 hours later, you would have 25mg of effective drug so forth and so on.
If you split that dose and took 50mg at 8am, by 5pm you would be left with 25mg, pop your other 50mg and now your at 75mg of effective drug. By 2am, 32.5mg.
Split your dose