Am'No0vUr'i9Pi8arm' )        Preparation  of  Piperazine.  811 
resenting  loss  of  piperazine,  and  more  or  less  tar.  These  difficul- 
ties have  been  eliminated  to  a  large  extent  and  at  the  same  time  the 
hydrolysis  has  been  simplified  by  discarding  the  addition  and  sub- 
sequent neutralization  of  a  large  excess  of  hydrochloric  acid. 
The  following  procedure  has  proved  satisfactory,  and  can  be 
recommended,  although  it  should  be  understood  that  experiments  on 
a  larger  scale  will  doubtless  disclose  other  advantageous  modifica- 
tions : 
Experimental. 
958  Gm.  of  ethylene  bromide,  527  Gm.  of  aniline,  and  575  Gm. 
of  sodium  carbonate  (anhydrous)  were  thoroughly  mixed  and  heated 
for  5-6  hours  to  gentle  boiling  in  an  oil  bath  using  a  reflux  con- 
denser. Stirring  is  decidedly  beneficial  and  probably  essential  on  a 
large  scale,  as  the  reaction  product  tends  to  cake.  The  presence  of 
soda  is  necessary,  otherwise  ethylene  bromide  combines  with  aniline 
vigorously  at  about  95 0  to  give  diphenyl  ethylene  diamine  and  hydro- 
bromic  acid.  The  acid  so  freed  unites  with  aniline  to  form  the  salt 
and  liberates  sufficient  heat  to  cause  charring. 
The  warm  melt  was  extracted  with  hot  water  to  remove  sodium 
bromide  which  can  be  recovered  readily  and  used  as  the  source  of 
bromine  for  ethylene  bromide.  The  probability  that  ethylene 
chloride  will  be  available  soon  in  large  amounts  should  be  noted,  and 
that  it  can  be  condensed  with  aniline  similarly,  using  an  autoclave  to 
obtain  the  necessary  temperature.  The  crude  diphenyl  piperazine 
is  sufficiently  pure  for  making  its  dinitroso  derivative.  Yields  of 
from  90  to  95  per  cent,  are  usually  obtained. 
547  Gm.  of  diphenyl  piperazine,  dried  and  powdered,  was  sus- 
pended in  2200  Cc.  of  cold  cone,  hydrochloric  acid.  With  mechan- 
ical stirring  a  saturated  solution  containing  438  Gm.  of  sodium  nitrite 
was  slowly  added  through  a  tube  reaching  to  the  bottom  of  the  acid. 
In  this  way,  the  loss  of  nitrous  fumes  is  largely  prevented  and  the 
formation  of  tar  minimized.  Cooling  is  necessary  during  the  addi- 
tion of  nitrite.  The  resulting  product  was  filtered  off  with  suction 
and  washed  once  with  cold  water.  It  is  probably  the  hydrochloride 
of  dinitrosodiphenyl  piperazine,  but  no  effort  was  made  to  analyze 
the  material.  It  decomposes  readily  on  drying,  but  is  quite  stable  if 
kept  moist. 
The  moist  material  was  added  to  a  40  per  cent,  solution  contain- 
ing 1900  Gm.  of  sodium  bisulphite,  and  the  suspension  warmed  with 
