10-11-03 10:54
No 464029
I've never read or heard about this, so I'll just try and ask it here. Does refluxing have any particular influence on chemical reactions, except constantly maintaining a certain temperature? E.g. could a reaction that normally is conducted in refluxing toluene (b.p. 110-112 °C) be done in xylene (b.p. 137 - 144 °C), being held as constantly as possible at a temperature of 110 °C or so?
(Moderator)
10-11-03 16:47
No 464083
Generally speaking, refluxing is used as a convenient means of controlling the temperature, since heating accelerates the rate of most chemical reactions by increasing the average kinetic energy of the molecules
These principle were first quantified by van't Hoff in 1884, d ln k/dT = Q/RT2 
The system you propose would bee inconvenient in practice, though of course possible 
One would normally reflux the xylene to increase the reaction rate, though naturally, this could bee counterproductive in certain cases 
Chemistry is our Covalent Bond
(Distinctive Doe)
10-12-03 15:26
No 464253
If I remember correctly the aproximate rule of thumb is that for every 10C increase in temperature the reaction rate doubles.
(Newbee)
10-14-03 05:15
No 464575
This was helpful. I guess I'll go the easy way first and use a higher reflux temperature, if that seems harmful, I'll try to constantly maintain a lower temperature (I might check into thermostates anyway, they can be useful for one or the other reaction).
(Chief Bee)
10-14-03 05:45
No 464583
When you reflux you automatically get great stirring - if you are heating xylene to 110°C you should compensate for that with good magnetic or overhead stirring.