149 
: 
“The hccsuip formula of  pyccitrylidene duefoacelic acid is supported by the 
presults of the oxidation by aqueous-alkaline ‘permanganate solution. By action of six 
atoms of oxygen,.a solid degradation-product was obtained, 3-methyl- -2-butenyl pyruvic 
acid (CHs)2C : CH-CH,:CH,:-CO-COOH, m. ». 192° with strong evolution of CO... When 
heated in the dry state, 3-w-citrylidene acetoacetic acid yields £-pseudoionone, a feebly- 
smelling oil of. the b.p. 130° (23 mm.); insoluble in aqueous potassium hydrogen sulphite; 
nee tarane,, nh Ds as Zap & H.C-CO- CH CH, 
| cs CH. cH ve 
-Pseudoionone. 
3 In the cold, 2 citrylidens acetoacetic ester ae with HBr + glacial acetic acid 
a solid hydrobromide, m. p. 93 to 94°. 
When heated with zinc chloride, the (8-ester passes over, with evolution of COs. 
into the hydrocarbon Curia 8-ionene, an oil, of characteristic smell and the exceptionally 
‘low b.p. 63° (12mm.). The well-studied hydrocarbons ionene and irene show the 
-b.p. 106 to 107° (10 mm.) and 113 to 115° ( mm.) respectively. 
__ #-Citrylidene acetoacetic ester, in analogy with the «-isomeride, suffers, on treatment _ 
with, and re-abstraction of, hydrogen bromide (by means of sodium carbonate) a rearrange- 
ament and yields an isomeride, ,2-isocitrylidene acetoacetic ester ofa somewhat lower boiling 
point, with the Beak co er ae) vgs: ee 
a Ne XC ; 
ee CH CH. 
_ £-Isocitrylidene acetoacetic ester is a light yellow oil with a pleasant smell. Its 
_hydrobromide is identical with the one resulting from -citrylidene acetoacetic ester. 
The free -isocitrylidene acetoacetic acid melts at 153°; on oxidation with potassium 
permanganate in sodium carbonate solution small amounts of an acid melting at 160 to 
165° are formed. When esterified, by treatment of the silver salt with ethyl iodide, 
‘the acid is retransformed into the original ester. On heating above the m.p., 6-1so— 
‘citrylidene acetoacetic acid gives rise to @-isoionone, an oil of terpenic “smell, bp. 11a? 
(15 mm.); semicarbazone, m. p. 108°; p-bromophenylhydrazone, m. p:, 450. to, 192°. 
CH ¢ CH 
ane CH: CH,- CH, ae ee ee 
Hic” 2 NC Scr Aerts i 
_ B-Isoionone. - 
On condensing citral with two molecules of ethy! acetoacetate by means of organic 
bases, citrylidene bis-acetoacetic ester, a body belonging to the 1:5-diketones, is formed. 
This ester does not undergo the complicated isomerisations of the monoacetoacetate series 
dealt with above. For its preparation, two molecules of ethyl acetoacetate and one mol. 
© citral, with addition of piperidine, are allowed to stand for some time ina freezing mixture; 
.p. 649; oxime, m. p. ae Ke HsC,00C-CH —CO-CH; 
CH; CCH: CH» CH, ‘C: CH: oe 
CH, CH, 
-H;C,.00C-CH CO: CHs 
cierynidente bis-acetoacetic ester. 
