whupharm_xu - 14-9-2004 at 01:05
recently i get into difficulty in preparing CH3PCl2 in lab. the method is as follows:
CH3I+PCl3+AlCl3 ——CH3PCl3.AlCl3I
CH3PCl3.AlCl3I+Fe+KCl——CH3PCl2
it is a classic method (as described in a literature).i made the synthesis according to it,but the result is not promising.
in the first reaction, i get the complex CH3PCl3.AlCl3I, a yellow solid.in the second reaction,Fe powder is used as reducing agent, KCl is used as
decomplexing agent(combining with AlCl3 )
a problem is that this reaction is an absolutely solid-phase one.so when heating,the thermal transmit is not good,and the stir becomes difficult.
here i have to tell that CH3PCl2 b.p. 81-82, and easily decomposes at a little high temperature(for example 120 centigrade)
but,the fact is that when heated to about 180,the solid system has not melted well.
clearly,Fe and KCl has not reacted with the complex entirely, so the yield is not high.even if some CH3PCl2 is produced, and at the melting point of
the complex, most of CH3PCl2 decompose,the side-products are PCl3 and (CH3)2PCl.
now i have not got any the aim product
CH3PCl2, i am so depressed.
hope for some help!!!
JohnWW - 14-9-2004 at 01:46
What is the literature reference that you obtained this preparative method from? Are you sure that you are measuring temperatures correctly? - it does
not appear that you are.
BTW Volatile covalent compounds of trivalent phosphorus are VERY poisonous, like PH3 (and the likes of H2S and H2Se and AsH3), because they bond
tightly to the Fe in hemoglobin. Avoid breathing in any vapors from the reaction mixture.
John W.
Mephisto - 14-9-2004 at 05:49
Why you made this thread? You started a thread about this topic 1 ½ months ago.
If you are really from the Wuhan University, try to check out Nongyao, 41(5), 46-47,45; 2002. There is the reaction described which you need.
whupharm_xu - 14-9-2004 at 19:57
Nongyao is a chinese name for "农药",is it a chinese journal?
or tell me its full name
thank you!
Mephisto - 15-9-2004 at 02:04
It's a Chinese source indexed by CAS/CASREACT. There's no more about the source as "Nongyao, 41(5), 46-47,45; 2002". It's
probably about pesticides and their synthesis. I hope you will find more by doing a research in your university library.
iodine ???
whupharm_xu - 16-9-2004 at 23:25
CH3PCl3.AlCl3I+Fe+KCl——CH3PCl2 +KAlCl4+??
in this reaction, KCl is used as decomplexing agent which combines with AlCl3, Fe is reducing agent???
during the process,Ar is used as a protected gas. the fact remains that
much iodine has produced to stuff the bottle-neck, how does it happen
maybe I get the mixture incluidng I2and CH3PCl2