_ i6 5 - 



n Di8° 1,4802; mol. refr. found 49,89, calculated for C U H 18 /^ = 49 ) 84), 

 which yielded a solid tetrabromide (m. p. 124 to 125 ) and a readily 

 soluble nitrosochloride which could be converted into an oxime and 

 further into a ketone with a carvone-like odour. But these bodies 

 have not been examined further. From the above- described behaviour 

 it is clear that the hydrocarbon C u H 18 consists chiefly of the higher 

 homologue of dipentene: — 



CH CH 2 



// \ / CH 2 



CH..CH 2 .Cf >CH — C<f 



\ / \CH 3 



CH 3 CH 2 



The formation of the higher homologues did apparently not pro- 

 ceed as easily as that of methyl and ethyl nopinol. At any rate, 

 the yield of n-propyl nopinol was bad, as owing to secondary reactions 

 much nopinone had been converted into nopinol. 



With regard to analogous reactions of sabina ketone, see under 

 Terpinene, p. 142. 



In order to obtain a knowledge of the properties of the nopinene 

 (/?-pinene) which is present in turpentine oil but has not yet been 

 isolated, Wallach attempted the synthetic production of this body. 

 The crude material used was nopinone, which by the method indicated 

 by Wallach for the formation of methene hydrocarbons (which has 

 already repeatedly been described) should lead to nopinene (/?-pinene) : 



CH C H 2 CH _CH 2 



OC(H,C-a ^CH -> HX:C(HX-Cc )CH 



XH 3 / 2 • \ a \ 



\ / \ / 



C H 2 C H 2 C H 2 C H 2 



Nopinone Nopinene (/?-Pinene) 



Nopinone was converted with bromoacetic ester and zinc into the 

 corresponding hydroxy ester, and the latter by abstraction of water with 

 potassium bisulphate into the unsaturated ester. The acid (b. p. 190 

 to 2 1 o° at 13 mm. pressure) obtained by saponification of the latter, 

 yielded on distillation at ordinary pressure a terpene C 10 H 16 , of which 

 the bulk boiled at 158 (d 0,8630; Mi) + 15,93°; n r>20° 1,4699; mol. 

 refr. found 43>9 6 > calculated for C 10 H 16 /~43>53> for C 10 H 16 ^45,24). 

 The physical constants show that this is a bicyclic hydrocarbon with 

 one double bond. It possesses a pronounced turpentine odour, and 

 contains a methene -group, as may be assumed from the oxidation- 

 products. The terpene was oxidised under the conditions mentioned 

 for the formation of nopinic acid (see p. 161) when in a good yield 

 a sodium salt was obtained, which resembled the sodium nopinate 



