16  Constitution  of  the  Alkaloids.        {A jaiuaryfih9wm' 
morphine  and  codeine  minus  a  molecule  of  water  in  each  case. 
Chemists  now  undertook  to  decompose  alkaloids  and  obtain  decom- 
position products  from  them,  and  from  these  determine  what  are  the 
constituent  parts  that  make  up  the  molecule,  and,  as  a  final 
stage,  what  is  the  hydrocarbon  of  which  they  are  derivatives?  Thus 
in  1 87 1,  Kraut, in  distilling  pipsrine-trichloracetate  with  silver  oxide, 
noticed  that  pyridine  was  eliminated,  and  at  once  supposed  it  was  a 
derivative  of  pyridine.  Later,  Hofmann,  in  1879,  transformed  piper- 
idine  into  dibrom  oxy-pyridine  by  heating  it  to  2200  with  bromine 
and  water.  Next,  Kbnigs  succeeded  in  converting  piperidine  into 
pyridine  by  oxidizing  it  and  removing  six  hydrogen  atoms.  This 
made  it  appear  to  be  a  hexa-hydro-pyridine  derivative.  He  next 
tried  the  reverse  process,  and  by  reducing  pyridine  in  alcoholic  so- 
lution with  sodium  converted  it  directly  into  piperidine.  This 
proved  that  piperidine  is  hexahydro-pyridine,  and  we  know  its  consti- 
tution. Synthesis  now  came  to  the  aid  of  chemists  to  help  unravel 
the  constitution  of  these  complex  alkaloids,  and,  in  case  of  piper- 
ine,  it  was  Ladenburg  who,  in  1885,  treated  dicyan-trimethylene 
with  sodium  in  alcoholic  solution  and  obtained,  as  expected,  pentame- 
thylene  diamine.  On  rapidly  distilling  the  latter  it  is  decomposed 
into  free  ammonia  and  piperidine  identical  with  the  natural  product. 
What  first,  however,  put  confidence  in  this  work  of  determining  al- 
kaloidal  constitution  was  the  brilliant  work  of  Ladenburg  on  atro- 
pine, not  only  because  it  showed  how  beautifully  the  constitution  of 
these  substances  could  be  unravelled,  but  also  because  it  was  a  gen- 
erally used  substance  and  the  actual  identity,  both  chemically  and 
physiologically,  could  readily  be  determined.  If  atropine  could 
successfully  be  made  synthetically,  why  could  not  any  alkaloid  ? 
Atropine  was  isolated  in  1833  by  Geigerand  Hesse,  and  its  formula 
C17H23N03  was  established  by  analysis  by  Liebig.  It  is  laevogyre, 
bitter  and  powerfully  dilates  the  pupil.  Kraut  and  Lossen,  in  1863, 
showed  that  atropine  was  an  ester,  as  barium  hydrate  will  split  it  up 
at  6o°  into  tropine  and  tropic  acid :  . 
C17H23N03  +  H20  =  C8H15NO  +  C9H10Q3 
Atropine.  Tropine.         Tropic  Acid. 
If  the  reaction  is  prolonged  decomposition  proceeds  further,  and 
the  tropic  acid  is  converted  into  atropic  acid  C9H802  by  loss  of  H20, 
and  if  the  temperature  should  rise  to  1800  C.  the  tropine  will  also 
lose  a  molecule  of  water  and  be  converted  into  tropidine  C8H]3N. 
