downward or simple distillation?

[ChemicalSolution]

Why do some papers (such as etBr synthesis from etOH/HBr) suggest downward distillation as opposed to simple distillation to remove the product as it is formed?

What are some instances where one type is prefered over another?

For downward distillation, where is the best place to provide ventilation?  Is this where one of those straight type vacuum adapters is used instead of the the angled one for a regular distillation?

xoxo
Julia

[Rhodium]

Could it be that a downward distillation Graham condenser is reccommended because of the high volatility of EtBr and things like that? I'd say that the place best suitable for ventilation is always as close to the reciever as possible.

[lugh]

Could it be that a downward distillation Graham condenser is reccommended because of the high volatility of EtBr and things like that? I'd say that the place best suitable for ventilation is always as close to the reciever as possible.

Downward distillation takes best advantage of gravity to restrain the vapors from escaping, thus it's recommended for very volatile compounds. For best results, run the vapor back up another condenser    
 
 

[ChemicalSolution]

For best results, run the vapor back up another condenser

Are you saying, for instance (downward distillation), attach the receiving flask to a Claisen adapter.  On one female end of the adapter, the condensed vapour drips from the distillation condenser directly into the receiving flask.  On the outer female end of the Claisen adapter, another (reflux) condenser is attached?

xoxo
Julia

[lugh]

If one didn't have a straight vacuum adapter, that would be another option, the narrowness of the restriction slows down the escape of vapors also. Plumbing systems can provide a good analogy for some of the behaviour of fluids.

[Vibrating_Lights]

a good ventilation is to run a hose from the vaccume adapter through a canister of charcole and then outside.
VL_