336 
Th alleio q uin  Reaction. 
Am.  Jour.  Pharm. 
May,  1921. 
hydroxycinchonine  hydroxychloride,  which  gives  the  thalleioquin  re- 
action on  treatment  with  an  oxidising  agent,  a  substance  that  com- 
bines with  chlorine  and  ammonia;  (3)  with  6  atoms  of  chlorine,  an 
unstable  base,  5-dichloro-6-ketocinchonine  hydroxychloride,  which 
liberates  2  atoms  of  iodine  from  potassium  iodide  for  the  1  active 
chlorine  present,  and  therefore  probably  contains  the  group  — 
CO.CCI2  —  in  the  quinoline  nucleus,  with  consequent  conversion 
into  the  group  —  C(OH)  :CC1 — .  This  base  gives  the  thalleioquin 
reaction  on  addition  of  ammonia  only;  the  green  product  on  drying 
leaves  a  residue  if  chloro-5.6-diketohydroxycinchonine,  the  group 
—  CO.CCI2  —  being  replaced,  in  presence  of  ammonia,  by  the  — 
CO. CO  —  group. 
As  far  as  is  known,  then,  the  action  of  chlorine  or  bromine  on 
quinine  in  dilute  aqueous  acidified  solution  is  similar,  and  the  prod- 
ucts, beyond  the  dihalogen  stage,  that  can  be  formed  during  or  can 
give  rise  to  the  thalleioquin  reaction,  are  numerous.  The  author 
attacked  the  problem  from  the  analytical  standpoint,  and  his  con- 
clusion, in  1909,  that  6  atoms  of  halogen  are  required  for  the  full 
reaction,  is  confirmed  by  the  later  results  of  Christensen ;  these  also 
explain  why,  in  the  results  of  the  bromine  absorption  in  aqueous 
solution,  apparently  not  more  than  4  atoms  as  a  maximum  are  ab- 
sorbed, while  actually  6  atoms  take  part  in  the  reaction,  the  2  atoms 
of  iodine  set  free  being  determined  as  unabsorbed  bromine.  It  fol- 
lows, then,  that  quinine  may  be  determined  from  its  bromine  absorp- 
tion for  five  minutes  in  the  manner  stated:  1  c.  c.  N/10  Br  —  0.0081 
g.  quinine. 
It  is  possible  and  probable  that  the  progressive  halogen  action 
runs  concurrently  to  some  extent ;  that  is  to  say,  part  of  the  halogen 
is  preferably  used  in  further  conversion  of  the  intei mediate  products 
than  in  full  conversion  of  quinine  into  intermediate  products ;  this 
would  explain  why  the  thalleioquin  reaction  is  obtained,  though  not 
to  the  full  extent,  by  the  action  of  much  less  than  6  atoms  of  bro- 
mine per  mol.  of  quinine.  Christensen's  statement  that  the  inter- 
mediate product,  5~chloro-6-hydroxycinchonine  hydroxychloride, 
gives  the  reaction  by  treatment  with  an  oxidising  agent,  a  substance 
that  combines  with  chlorine,  and  ammonia,  may  explain  the  mecha- 
nism of  the  delay  in  the  final  green  color,  production  by  Vogel's  re- 
action (1850),  and  also  by  Battandier's  reaction  (1904),  since  we 
