— i3i — 



carvone is shaken with 40 per cent, sulphuric acid. On the contrary, 

 by addition of water there is formed 8 -hydroxy tetrahydrocarvone: 

 /CO CH 2X 7 CH 3 



ch 3 .c< >ch.c(oh)< 



\ch 2 -ch/ x ch 3 



a body which Knoevenagel and Samel 1 ) had already obtained 

 by another method. Its oxime melts at 120 to 12 1°, the semicarbazone, 

 recrystallised from methyl alcohol, at 157 to 15 8°. When 8 -hydroxy tetra- 

 hydrocarvone is boiled, carvenone is formed. On reduction of 8-hydroxy- 

 tetrahydrocarvone the a-compound of 2,8-dioxyterpane (m. p. 112 to 

 1 1 3 ) is formed, and this fact confirms the constitution of the former. 



In a third communication Rupe describes, jointly with Dorschky 2 ), 

 the two semicarbazones of carvone. The first (m. p. 141 to 142 ) 

 obtained also by Knoevenagel and Samel 3 ) is only formed if carvone, 

 alcohol, and potassium acetate are added to a concentrated aqueous 

 solution of semicarbazide hydrochloride, and an increase of tem- 

 perature is avoided. Without this precaution, and if sodium bicarbo- 

 nate is used instead of potassium acetate, the second semicarbazone 

 (m. p. 162 to 163 ) of v. Baeyer is formed. The lower melting 

 one is more labile, and already passes over into the other form 

 when simply left standing. The constants of the two bodies are 

 as follows: carvone semicarbazone of the m. p. 141 to 142 : [«]p20° 

 -j- 11,30° (in pyridine); carvone semicarbazone of the m. p. 162°: 

 [ a JD20° + 11 >5°° ( in Py ridm e). 



In connection with the work of Rupe and Liechtenhan quoted 

 above, A. Klages 4 ) states that he also, independent of the above- 

 mentioned authors, in conjunction with F. Sommer has succeeded in 

 producing in a good yield, from carvone and bromomethyl magnesium, the 

 hydrocarbon C n H 16 , and also the 2 - methylcarveol which Rupe and 

 Liechtenhan had been looking for. As the hydrocarbon could be con- 

 verted into 2 -methyl cymene, Klages gives it the formula of a 2-methyl- 

 ^2, 6, 8(9)- mentnatr iene, and not the formula of a methene hydrocarbon 

 drawn up by Rupe and Liechtenhan. The conversion succeeds best 

 by boiling the methyl menthatriene with a mixture of 2 per cent, 

 glacial acetic acid and hydrochloric acid. 2 -Methylcarveol (2-methyl- 

 J 6j8(9r menthadienol), d^- 0,9471; n D20,4° M9 11 ; a moA° +37^7°; 

 Md20,4° -f-3 6 > o8 °; b. p. iii° (14 mm. pressure). 2 -Methyl- J 2| 6,8(9)- 

 menthatriene: d^- 0,8724; n D21}1 o 1,5000; a D2 i° +60,30°; Md21° 

 -{-69,2 1°; b. p. 82 to 83° (15 mm. pressure). 2-Methyl-p-cymene: 



x ) Berl. Berichte 39 (1906), 677; Report April 1906, 122. 



*) Berl. Berichte 39 (1906), 21 12. 



3 ) Ibidem 39 (1906), 681. 



4 ) Berl. Berichte 39 (1906), 2306. 



