Am.  Jour.  Pharm. 
Dec.  1892. 
Sesquiterpenes. 
621 
the  constitution  of  the  hydrocarbons,  C10Hl6,  is  in  a  fair  way  to  be 
extended,  the  hydrocarbons  C15H21  are  still  enveloped  in  obscurity. 
These  bodies  are  thick  liquids,  easily  resinified,  and  boiling  between 
2500  and  2800  C.  The  number'of  isomers  is  undoubtedly  great,  but 
hitherto  only  one  of  the  series  has  been  definitely  identified.1 
In  the  investigation  of  the  C15H24  compounds  the  same  methods 
have  to  be  adopted  as  in  the  study  of  the  terpenes.2 
Several  substances  are  described  as  having  the  formula  C15H260, 
which  may  be  regarded  as  hydrates  of  the  hydrocarbons  C15H2i;  for 
instance,  cubeb  camphor  and  patchouli  camphor.  It  is  known  that 
the  latter  is  convertible  by  dehydrating  agents  into  C15H24,  but  this 
product  has  not  been  further  investigated  and  no  attempt  has  been 
made  to  hydrate  a  C15H2i  body,  so  as  to  obtain  artificially  a  body 
corresponding  to  the  hydrate  occurring  naturally. 
In  operating  upon  patchouli  camphor  it  was  easily  ascertained 
that  under  the  same  conditions  that  turpineol  C10H18O  is  converted 
into  C10H16,  such  as  boiling  with  dilute  acids,  patchouli  camphor  may 
be  converted  into  C]5H24.  The  reproduction  of  the  crystalline 
hydrate  from  the  hydrocarbon  could  not  be  effected. 
To  obtain  further  knowledge  of  the  capacity  of  sesquiterpenes  to 
become  hydrated,  the  sesquiterpene  of  clove  oil  was  tried  and  found 
to  be  readily  convertible  into  a  crystalline  hydrate,  quite  different 
from  patchouli  camphor.  Caryophyllene,  the  sesquiterpene  of  clove 
oil  distils  over  between  2500  and  2600,  and  its  hydration  was  effected 
by  adding  25  grammes  to  a  mixture  of  1000  grammes  glacial  acetic 
acid,  20  grammes  concentrated  sulphuric  acid,  and  40  grammes 
water,  heating  the  whole  for  twenty-four  hours  on  a  water-bath. 
The  dark-colored  liquid  was  then  distilled  in  a  current  of  steam.  A 
thin  oil,  of  ethereal  odor,  was  thus  obtained,  which  separated  on  addi- 
tion of  water  to  the  first  part  of  the  distillate.  Subsequently,  a  less 
volatile  oil  was  obtained,  which  solidified  on  cooling.  After  separ- 
ating the  oily  portion  by  cooling  and  absorption,  this  crystalline 
substance  was  purified  by  redistillation  and  crystallization  from 
alcohol.  It  proved  on  analysis  to  be  the  hydrate  of  caryophyllene, 
C15H25.OH,  boiling  at  2870  to  2890,  and  melting  at  940  to  950.  It 
is  almost  insoluble  in  water,  slightly  soluble  in  hot  water,  readily 
1  Annalen,  238,  78  ;  252,  150. 
2  Berichte,  24,  1526. 
