[kamiyu]

Hi guys

I think it is a quite common phenomenon that when you shake the stuff in a seperatory funnel, there will be some gas coming out (but there is no NaHCO3 or Na2CO3 used).

Can anyone come up with any explanation???

[TheUnassuming]

I think the pressure is due to the vapor pressure of the organic layer.   
When you shake up a lower boiling solvent in a contained vessel it will cause a rise in pressure as it attempts to equilibrate.   

[TheUnassuming]

Just tried DCM alone in a sep funnel, seems to cause a rise in pressure when you shake it up.

[kamiyu]

Thanks for your trial!

I quite often observe this gas formation when i am using DCM.

Shaking results in slight boiling

Just tried DCM alone in a sep funnel, seems to cause a rise in pressure when you shake it up.

[TheUnassuming]

... wait... when you shake the reaction in DCM it starts to bubble/boil?   
I've only ever seen that with Et2O when I rushed and didn't let the reaction cool down far enough before extracting.

[kamiyu]

Sorry, the word "boil" means sth like "more vigorous" vaporization.... not actually boiling

I would like to say, shaking may result in faster evaporization of DCM.

... wait... when you shake the reaction in DCM it starts to bubble/boil?   
I've only ever seen that with Et2O when I rushed and didn't let the reaction cool down far enough before extracting.

[TheUnassuming]

Ah, that makes more sense.  I was trying to envision an exothermic reaction that might take place upon partitioning and heat up your organic layer .
Increasing the evaporation is another way to think about it the rise in vapor pressure, just depends on how you best visualize it.