Notes on scientific research. 145 



is difficultly obtainable in the pure state. In view of this circumstance and of the 

 optical constants found by them the authors regard the formula (III) of the ester 1 ), as 

 suggested by Steinle, as the correct one. 



From a citrylidene acetoacetic ester the authors prepared, via the «-isoester, a-iso- 

 ionone. In order to make the methods of preparation agree with the optical data, 

 Knoevenagel and Oelbermann assign to this ketone formula (IV) in lieu of formula (II) 

 hitherto accepted which they suggest for iso-^-ionone. 



When examining ^-citrylidene acetoacetic ester, the optical constants were not found 

 to agree with the formula propagated by Mechtersheimer 2 ) which constitutes a simple, 

 "disturbed" conjugated system. The optical data would agree best with formula (V), with 

 cumulated double bonds, the presence of which, however, has not been proved hitherto. 



CH 3 \ /CH 3 H 3 C X /CH 8 



C C 



1 

 C 



H 2 C X X CH-CH - C-O-CO-CrV H 2 Cf ^CH-CH 2 — CO— CH 3 



I 

 H 2 C^ x/CH CH3 H 2 C\ y^/CH 



c c 



I • I 



CH 3 CH 8 



(I) Pseudoionone acetate. (II) Isopseudoionone. 



H 3 Cv /CH 3 "\ c = CH-CH 2 -CH 2 -C == CH-CH = C-CO-CH 3 



CH H * C ' •' 



V CH 3 CO-OC 2 H 5 



C (III) ec-Citrylidene acetoacetic ester. 



HC^ X CH— CH 2 -CO-CH 3 

 H 2 Cx JcH 



H 8 C X 



C >C = CH— CH 2 — CH 2 — C = C '= CH— CH— CO— CH 8 



' H 3 C X I I 



CH 3 CH 3 CO-OC 2 H 5 



(IV) a-7*oionone. (V) /9-CitryIidene acetoacetic ester. 



From the /5-ester, a hydrocarbon was prepared according to Mechtersheimer by 

 means of zinc chloride, which was oxidised by a mixture of nitric and sulphuric acids. 

 The resulting body, a solid of the m. p. 154°, has not been examined further. 



The formulas for /?-y-ionone, /?-^ocitrylidene acetoacetic ester, and /?-isoionone 2 ) put 

 focward by Mechtersheimer agree approximately with the- values observed by the authors. 



On benzaldehyde, see p. 90 of this Report 



Concerning a specially devised flask for the estimation of phenylacetahhhyde. 

 cf. p. 114 of this Report. 



Salicylic aldehyde and acid are obtained, as per an American Patent 1380277, 

 May 31, 1921 of J.M.Weiss and C. R. Downs 3 ), by oxidising o-cresol in the vapour 

 phase with a gas containing oxygen in the presence of a metallic oxide as catalyst. 



») Cf. Report 1819, 148. — 2 ) Cf. Report 1919, 149. — 3 ) Journ. &oc, ohem. Ind. 40 (1921), A. 561, 



10 



