Am.  Jour.  Pharm.  \ 
June,  1883.  i 
Pyr'idine  and  QumoUne  Bases. 
329 
of  the  series,  being  regarded  as  a  methyl  derivative  of  pyridine,  three 
isomers  are  possible,  and  corresponding  to  each  there  should  be  a  pyridine- 
monocarbonic  acid.  Three  pieolines  are  known,  and  Weidel  and  Herzig^ 
obtained  the  third  pyridine  monocarbonic  acid  possible  by  heating  lutidi- 
nic  acid.  Nine  kitidines  are  predicted  by  theory,  six  dimethyl-  and  three 
€tiiyl  pyridines  Only  two  of  the  former  are  Ivnown.  On  the  other  hand, 
six  pyridine-dicarbonic  acids  have  been  isolated.  We  can  conceive  of  the 
formation  of  coUidines  by  replacing  the  hydrogen  of  pyridine  either  by 
three  metliyl  groups,  by  one  propyl  group,  one  isopropyl  group,  or  by  one 
methyl  and  one  ethyl  group.  There  are  tlius  possible  six  triniethyl  pyri- 
dines, three  propyl  pyridines,  three  isopropyl  pyridines,  and  ten  methyl 
€thyl  pyridines;  in  all,  twenty-two  coHidines.  A  number  of  these  are 
a.lready  known,  but  our  knowledge  of  their  properties,  physical  constants, 
and  especially  their  oxidation  products,  is  so  limited  that  at  present  it  is 
impossible  to  classify  them. 
The  homologues  of  pyridine  and  of  quinoline,  as  well  as  quinoline  itself, 
and  certain  natural  alkaloids,  such  as  quinine,  cinchonine,  nicotine,  etc., 
when  oxidized  yield  nitrogenous  acids,  which  may  be  regarded  as  carboxyl 
derivatives  of  pyridine.  Distilled  with  lime  they  give  pyridine  just  as 
benzoic,  phthalic  acids,  etc.,  under  the  same  conditions  give  benzene. 
Pyridine  itself  offers  a  much  greater  resistance  to  oxidizing  agents  than 
benzene;  chromic  acid,  and  even  boiling  fuming  nitric  acid,  have  no  effect 
upon  it.  Huber  first  obtained  nicotinic  acid  (pyridine  monocarbonic  acid) 
by  oxidizing  nicotine,  and  in  1871  Dewar  obtained  the  same  acid  by  the 
oxidation  of  a  picoline.  By  oxidizing  the  mixture  of  pieolines  contained 
in  bone  oil,  WeideP  obtained  two  isomeric  pyridine  monocarbonic  acids, 
which  he  calls  nicotinic  and  j)icolic  acids,  and  by  oxidizing  lutidine  Weidel 
and  Herzig^  succeeded  in  isolating  the  third  isomer  possible,  which  they 
<?all  isonicotinic  acid.  Wisehnegnidsky^  oxidized  the  aldehyde  collidine 
of  Baeyer,  and  obtained  a  methyl-pyridine-dicarbonic  acid;  while  Hooge- 
werf  and  van  Dorp''  have  obtained  pyridine  tricarbouic  acid  by  oxidizing 
quinine  and  cinchonine  with  potassium  permanganate.  A  second  acid  of 
this  composition  has  been  obtained  by  Bottinger*^  from  uvitonic  acid. 
The  pyridine  bases  have  the  power  of  uniting  directly  with  two,  four  or 
six  atoms  of  hydrogen.  Wischnegradsky'^  has  described  a  hexahydroluti- 
dine  which  has  the  properties  of  a  secondary  base.  The  isochlor-pyridine 
of  Ciamician  and  Dennstedt^  can  also  unite  with  six  atoms  of  hydrogen. 
Hofmann^  has  devised  a  general  method  for  building  up  the  hydropyri- 
dines.  By  distilling  a  mixture  of  a  pyridine  ammonium  iodide  with 
potassium  hydroxide,  oxygen  is  liberated,  potassium  iodide  formed,  and 
^  Monatshefte  lur  Chemie,  i,  41. 
2  Berichte  der  deutschen  chemischen  Gesellscliaft,  xii,  1989. 
^  Monat.sliefte  fill- Chemie,  i,  48.  j 
^  Berichte  der  deutschen  chemischen  Gesellschaft,  xii,  1506. 
*  Aniialen  der  Cliemie,  cciv,  84. 
«  Berichte  der  deutschen  chemischen  Gesellscliaft,  xiii,  2048,  and  xlv,  134. 
^  Bulletin  de  la  Societe  Chimique,  xxxiv,  310. 
«  Berichte  der  deutschen  chemischen  Gesellschaft,  xiv,  1153. 
s  Ibid,  xiv,  1497. 
