5  5o 
Oil  of  Polei. 
( Am.  Jour.  Pharm. 
t       Nov.,  1891. 
OIL  OF  POLEI.1 
By.  E.  Beckmann  and  M.  Pleissner. 
Spanish  oil  of  Polei,  from  Mentha  Pulegium,  is  a  light  yellow 
or  green,  rather  thick  liquid  with  an  odor  recalling  that  of  pepper- 
mint. On  fractionating  the  oil  (62  grams),  under  the  ordinary 
atmospheric  pressure,  considerable  decomposition  takes  place  j  a 
small  portion  (3  grams),  consisting  principally  of  water,  passes  over 
below  2120,  the  principal  portion  (50  grams)  between  21 2°  and 
2 1 6°,  and  a  small  quantity  of  a  dark  yellow  liquid  (4  grams) 
between  2160  and  2230,  leaving  a  brownish  residue  (5  grams). 
A  compound  of  the  composition  C10H16O,  named  by  the  author 
pulegone,  can  be  isolated  from  the  portion  boiling  at  212-216°  by 
repeated  fractional  distillation  under  reduced  pressure  (60  mm.);  it 
is  a  colorless  liquid,  of  sp.  gr.  0  9323  at  20°,  boils  at  130-1310  (60 
mm.),  and  has  an  odor  recalling,  but  distinct  from,  that  of  oil  of 
peppermint.  Its  specific  rotatory  power  is  [a]D  —  22-89,  Dut  this 
value  is  slightly  diminished  when  the  oil  is  treated  with  sulphuric 
acid  or  distilled  with  steam,  probably  owing  to  resinification. 
Pulegone  quickly  turns  yellow,  even  when  kept  in  closed  vessels, 
and  it  does  not  solidify  when  cooled  in  a  mixture  of  ice  and  salt ;  it 
is  gradually  resinified  by  hot  alcoholic  potash,  and  it  does  not  give 
an  ethereal  salt  with  benzoic  or  stearic  anhydride;  it  gives  some, 
but  not  all,  the  reactions  of  aldehydes,  and  with  phenylhydrazine  it 
yields  only  oily  or  resinous,  very  unstable  compounds.  Molecular 
weight  determinations  gave  results  in  accordance  with  those 
required  by  the  molecular  formula  C10H16O  ;  its  molecular  refractive 
power  was  found  to  be  MD  =  45-55,  whereas  the  value  calculated 
for  the  formula  C10H16O"  is  MD  ==  45-82. 
Pule  gone  oxime,  C10H19NO2,  can  be  obtained  by  treating  pulegone 
with  hydroxylamine  in  boiling  alcoholic  ethereal  solution  ;  it  crys- 
tallizes from  ether  in  long  needles,  melts  at  1 570  with  decomposi- 
tion, and  is  only  sparingly  soluble  in  cold  alcohol,  benzene  and 
light  petroleum;  its  specific  rotatory  power  is  ==  — 83-44. 
Molecular  weight  determinations  showed  that  the  compound  has 
the  molecular  formula  given  above.  Pulegoneoxime  is  more  readily 
soluble  in  dilute  acids  than  menthoneoxime,  and,  unlike  the  latter, 
it  is  not  acted  on  by  cold  sulphuric  acid  of  sp.  gr.  1-17  ;  it  dissolves 
1  Annalen,  262,  1-37  ;  Jour.  Chem.  Soc,  August,  1891,  p.  936. 
