108  Phytochemical  Research.  {AnVTou£-  Pharm- 
J  1      March,  1917 
Myrcene  is  very  susceptible  to  change,  becoming  readily  poly- 
merized by  distillation  under  ordinary  pressure  or  on  exposure  for 
some  time  to  the  air,  with  the  formation  of  a  viscid  product  which 
is  very  sparingly  soluble  in  alcohol.  The  isolation  of  myrcene  was 
not  only  of  considerable  scientific  interest,  but  a  consideration  of  its 
characters,  especially  its  tendency  to  polymerize,  also  served  to  ex- 
plain the  apparent  discrepancies  of  statement  respecting  the  solu- 
bility in  alcohol  of  oil  of  bay. 
The  more  recent  researches  in  another  direction,  to  which  I  have 
already  referred,  may  now  be  briefly  considered,  since  they  would 
seem  to  impart  added  interest  and  significance  to  the  observed  oc- 
currence in  nature  of  an  olefmic  terpene.  It  is  well  known  that  the 
hydrocarbon  isoprene,  C5HS,  or  CH2 :  C(CH3) .CH :  CH2,  when 
treated  with  suitable  reagents,  becomes  polymerized,  with  the  forma- 
tion of  a  product  having  the  general  characters  of  caoutchouc  or 
rubber,  and  the  various  processes  for  the  production  of  synthetic 
rubber  have  been,  in  fact,  chiefly  based  upon  the  utilization  of  this 
hydrocarbon.  It  has,  however,  recently  been  asserted19  that  all  the 
polymerides  of  isoprene  thusfar  obtained  differ  from  natural  Para 
caoutchouc,  inasmuch  as  the  decomposition  of  their  diozonides  with 
water  yields  acetonylacetone  and  succinic  acid  in  addition  to  lsevu- 
linic  aldehyde  and  lsevulinic  acid.  No  succinic  acid  or  acetonyl- 
acetone could  be  detected  in  the  products  of  hydrolysis  of  the 
diozonides  from  natural  caoutchouc.  The  correctness  of  these  ob- 
servations is  apparently  confirmed  by  the  results  of  some  further, 
quite  independent  investigations,  which,  together  with  the  deductions 
from  them,  are  of  particular  interest.  It  has  been  found,  for 
example,  by  Russian  chemists20  that  when  isoprene  is  cautiously 
heated  at  a  temperature  of  80  to  900  C.  it  yields  an  open  chain 
hydrocarbon  of  the  composition  C10H16,  which  contains  three  ethyl- 
enic  linkings,  and  resembles  the  myrcene  obtained  from  oil  of  bay. 
This  new  hydrocarbon  has  been  designated  by  its  discoverers  as 
/?-myrcene,  and  its  most  probable  constitution  is  considered  by  them 
to  be: 
CH2 :  CH.C(CH3)  :  CH.CH2.CH2.C(CH3)  :  CH2. 
It  is  a  colorless,  mobile  liquid,  boiling  at  63 0  C.  at  20  mm.  pressure, 
19  Steimmig,  Ber.  d.  deutsch.  chem.  Ges.,  1914,  47,  pp.  350-354. 
20  Ostromyslenski  and  Koschelev,  Jour.  Russ.  Phys.-Chcm.  Soc,  1915,  47, 
pp.  1928-1931. 
