328 
Pyridine  and  QuinoUne  Bases. 
f  Am  Jour.  Diarm. 
\      June,  1883. 
obtaining  pure  pyridine  is  to  distil  tlie  calcium  salt  of  nicotinic  acid  with 
lime.^  Of  the  three  picolines  theoretically  possible  Weidel  has  found  two 
in  bone  oil,  while  Baeyerfhas  made  a  third  by  the  distillation  of  acrolein- 
ammonia.  Lutidine  had  not  been  made  synthetically  until  very  recently. 
Hanlzsch^  describes  a  method  which  enabled  him  to  make  the  first  four 
members  of  this  series  of  bases,  By  heating  acetoacetic  ester  with  aldehyde- 
ammonia  in  the  i^roportion  of  two  molecules  of  the  former  to  one  of  the 
latter,  there  is  formed  a  crystalline  condensation  product  which  is  the  ester 
of  dihydro-collidine-dicarbonic  acid  (C2H500C)2C8Hii]N".H2.  By  the  oxi- 
dizing action  of  nitrous  acid  two  atoms  of  hydrogen  are  removed,  and  there 
remains  the  ester  of  collidine-dicarbonic  acid.  This  by  saponification 
yields  the  corresponding  acid,  which  when  distilled  with  lime  gives  colli- 
dine, 
C5(CH3)3(COOH)2N  -         =  C5(CH3)3H2N. 
Collidine-dicarbonic  acid.  Collidine. 
By  careful  oxidation  with  potassium  permanganate,  collidine  dicarbonic 
acid  yields  three  successive  oxidation  j^roducts,  each  of  which  in  turn  can 
be  converted  into  its  corresponding  base.  Thus  the  first  oxidation  product 
gives  lutidine, 
C5(CH3)2(COOH)3N  —  3CO2     C5(CH3)2H3N ; 
Lutidine-tricarboiiic  acid.  Lutidine. 
the  second,  picoline, 
C5'CH3)(COOH),N  —  4CO2  --=  C5(CH3)H,N  ; 
Picoline-tetracaibonic  Picoline. 
acid. 
and  the  third,  pyridine, 
C5(COOH)5N  —  5CO2  =  C5H5N. 
Pyiidine-penta-  Pyridine, 
carbonic  acid. 
Other  methods  for  the  preparation  of  collidine  are  known.  Baeyer  and  ^ 
Ador*  have  obtained  it  by  heating  an  alcoholic  solution  of  aldehyde- 
ammonia  to  120°.  Kramer,^  by  heating  ethylidene  chloride  with  alcoholic 
ammonia,  observed  its  formation  ;  while  more  recently  Wiirtz*^  obtained  it 
by  the  distillation  of  aldol-animonia.  The  higher  members  of  this  series, 
parvoline,  corridine,  rubidine,  and  viridine  have  not  yet  been  made  syn- 
thetically. 
The  hypothesis  of  Korner,  according  to  which  the  pyridine  molecule  is 
regarded  as  benzene,  in  which  one  of  the  six  CH  groups  is  replaced  by  an 
atom  of  nitrogen,  has  found  additional  support  daring  the  last  three  years.  , 
Accepting  this  hypothesis,  but  one  pyridine  is  theoretically  possible,  and 
indeed  it  has  been  found  that  from  whatever  source  obtained,  whether 
from  bone  oil,  from  coal  tar  or  from  nicotine,  cinchonine  or  quinoline, 
pyridine  always  has  the  same  boiling  point,  the  same  specific  gravity,  and 
the  same  phj^sical  and  chemical  properties.    Picoline,  the  second  member 
1  Laiblin,  Annalen  der  Chemie,  cxcvi,  159. 
2  Ibid,  civ,  283. 
3  Ibid,  ccxv,  1. 
<  Annalen  der  Chemie,  civ,  297. 
5  Berichte  der  deulschen  chemischen  Gesellschaft,  iii,  202. 
«  Comptes  Rendus,  Ixxxviii,  454. 
