620 
Terpenes. 
Am.  Jour.  Pharm. 
Dec,  1887. 
Sylvestrene. 
Terpino- 
lene. 
Terpinene. 
Phellan- 
drene. 
CI0HI6 1 M-  p  I  
CxoH^HOijg^;;;;;;;;;;;;;;;;;;;-;;;";;;; 
CioHi6,2HC1.  "   
Ci0Hi6,2HBr.  "   
Ci0Hi6,2HI.  "   
CioHioBr4.  "   
€ioHi6N203.  "   
Color  with  acetic  anhydride  and 
cone.  H2SO4  
175—178° 
72° 
72° 
65—72° 
135° 
blue 
185—190° 
T 
116° 
red 
180° 
155° 
red 
about  170° 
94° 
red 
The  compounds  of  the  terpenes  with  two  mols.  HBr,  HI,  etc.,  may 
be  conveniently  prepared  on  the  small  scale  by  saturating  glacial  acetic 
acid  with  hydrogen  chloride,  and  adding  this  solution  to  the  terpene 
dissolved  in  acetic  acid.  When  the  product  is  poured  into  ice-cold 
water,  the  compound  separates  in  the  pure  state. 
The  bromides  are  prepared  by  adding  bromine  to  the  terpene  diluted 
with  ten  times  its  volume  of  glacial  acetic  acid.  They  are  purified 
by  recrystallization  from  warm  ethyl  acetate.  The  hydrochlorides  are 
easily  decomposed  by  boiling  with  glacial  acetic  acid  and  anhydrous 
sodium  acetate,  the  chief  product  being  the  original  terpene.  If  pi- 
nene  monohydrochloride  is  treated  in  this  manner  at  200°  for  four 
hours,  it  yields  camphene.  The  conversion  of  pinene  into  dipentene, 
terpinolene,  and  terpinene,  has  been  previously  described  (see  Amee. 
Joue.  Phae.,  1886,  p.  145).  Pure  pentene  and  all  its  derivatives  are 
optically  inactive.  The  dihydriodide,  C10H162HI,  is  deposited  from 
light  petroleum  in  two  distinct  forms,  namely,  in  rhombic  crystals 
[a :  b  :  =0*6644  :  1],  melting  at  77°,  and  in  monoclinic  crystals  [a:b  :c 
=  1-0269  :  1  :  0'92619  ;  0=  49°  54'],  melting  at  78-79°.  Pure 
dipentene  is  converted  into  terpinene  by  treatment  with  alcoholic  sul- 
phuric, or  hydrochloric  acid. 
Cineol,  cajeputol,  and  eucalyptol  are  identical.  This  substance  cry- 
stallizes when  it  is  cooled  in  a  freezing  mixture. 
Terpinolene  is  obtained  by  boiling  terpene  hydrate,  terpineol,  or 
cineol,  with  dilute  sulphuric  or  phosphoric  acid.  The  melting  point 
of  the  freshly  prepared  tetrabromide  is  116°,  but  old  specimens  melt 
at  about  112°.  At  the  moment  of  fusion,  a  slight  evolution  of  gas  is 
perceptible.    Solutions  of  the  tetrabromide  are  optically  inactive. 
By  the  action  of  hydrochloric,  hydrobromic,  or  hydriodic  acids  on 
fProbably  identical  with  the  corresponding  dipentene  compounds. 
