— 156 — % 



keto acid, ^-ci/cZopentyl-^-keto-n-valeric acid (m. p. of the semicarbazone 

 181 to 183°). Reduction of cydopentylpentanone in alcoholic solution 

 with sodium gives rise to q/cZopentylpentanol CsrVCsHgOH, a liquid 

 with b. p. 235 to 236°: dno 0,9785, n D17 o 1,4884, m. p. of the phenylurethane 

 88 to 89°. If q/cfopentylpentanol is heated for about an hour to 150° 

 with twice its own quantity of zinc chloride the result is a terpene, cyclo- 

 pentylpentene (I), possessing the following constants: b. p. 196,5 to 198°. 

 (W- 0,9080, n D19l50 1,4938, mol. refr. calc. for Ci H 16 / = 43,53, found 43,59, 

 This terpene, which contains two pentacyclic systems in simple bond with 

 each other, is distinguished from the well-known bicyclic terpenes by its 

 considerably higher b. p. Its nitrosochloride has m. p. 113 to 114°. Di- 

 c«/cZopentene-pentanone, which is formed to the extent of from 12 to 13 p. c. 

 in the process of auto-condensation of c^/cfopentanone, when reduced by 

 Paal's method readily absorbs four hydrogen atoms and is converted into 

 saturated, colourless, diq/cfopentylpentanone (II): b, p. 165 to 170° (12 mm.), 

 di 9 o 0,9925. Oxidation of this ketone with chromic acid gives rise to a 

 keto acid, a-§-dicyclopenty\-§-kQto-n-va\Qvic acid. Reduction of diq/c/opentyl- 

 pentanone with sodium and alcohol yields dic^/cZopentylpentanol (III) (m. p. 

 68°; b. p. 210° at 100 mm.) from which, when heated with zinc chloride 

 to 150 to 200°, dicyclopQntylcyclopQntenQ (IV) is generated. This hydrocarbon 

 possesses the structure of a sesquiterpene. It cannot be volatilised under 

 ordinary pressure without decomposition: b. p. about 290°, 210° (100 mm.), 

 d 20 o 0,939, n D20O 1,5065, mol. refr. found 64,40, calc. for C i5 H 2 4/ = 64,45. 



O 



CyclopentylpentetiQ (I). Diq/cfopentylpentanone (II). 



OH 



Diq/cZopentylpentanol (III). Dicyclopentylcyclopentene (IV). 



Many years ago Wallach 1 ) showed that cyclic ketones are capable of 41 

 being condensed with acetone. He now reports 2 ), as the most important 

 result of his recent researches, that he has succeeded in showing that 

 when the q/cfohexanones are condensed with acetone, the oxygen-atom of 

 the cyclic ketone combines with the hydrogen of the acetone and is 

 eliminated in the form of water, giving rise to unsaturated extra-cyclic 

 ketones, which by reduction are . convertible into saturated extra-cyclic 



!) Berl. Berichte 29 (1896), 1597, 2955. 



2 ) Nachr. K. Ges. Wiss. Gottingen 1912. Meeting of 17 th February. 



