Re a in ~ 
aia 
94 REPORT OF SCHIMMEL & Co. OCTOBER 1914/ APRIL 1915. =a 
: U Seay 
between the spontaneous reaction in the dark (polymerization) and the photochemical 
dark . 
' reaction (depolymerization): nCgsH sO aT (CsHsO)n. In order to study this poly- 
ight s . 
merization process more closely, the ate determined the index of refraction, 
which shows higher values as the polymerization proceeds. On heating freshly pre- 
pared phenylacetaldehyde under pressure for some time, finally an odourless, opaque, 
viscid mass results, which does not show Caro’s reaction and is therefore most 
likely identical with the pentameric product described above. On further heating, it . 
depolymerizes into monomeric phenylacetaldehyde. ; 
Phenylacetaldehyde likewise polymerizes in daylight, without the addition of any 
catalysts. Freshly distilled phenylacetaldehyde was preserved during a fortnight, at 
room temperature and in the dark, in an ordinary glass vessel and daily exposed to 
diffuse daylight for from 5 to 10 minutes, in order to measure the refraction. The 
substance remained liquid and colourless up to the 12th day, the index of refraction 
increasing steadily. On the 14th day, crystals of triphenylparaldehyde had formed. This 
likewise resulted after a long exposure to diffuse, long-waved daylight. Consequently 
polymerization of phenylacetaldehyde in the absence of catalysts leads to two different 
bodies, the quantities of which depend upon the intensity and the length of the light 
waves. 
Stobbe and Lippold were able to confirm that moist phenylacetaldehyde is more 
stable than the dry substance, an observation which had been made in praa. In the 
dark as well as when exposed to the light, moist aldehyde polymerizes more slowly 
than the dry one. Water therefore acts as a negative catalyst. 
Benzylidene crotonaldehyde. Benzylidene crotonaldehyde (cinnamylidene acetalde- 
hyde), as obtained in the manufacture of cinnamaldehyde, has been investigated by 
G. Engelberg’). He prepared it by condensing cinnamaldehyde and acetaldehyde and 
likewise examined a preparation supplied by our firm. The pure, recently distilled 
aldehyde is a pale yellow, refractive liquid, which soon becomes brown, when exposed: 
to the air. If kept under water, it remains unaltered for a fairly long time. Its odour 
reminds one somewhat of cinnamaldehyde, and its taste is extremely burning; b. p. 176 
to 178° (12 mm.). The aldehyde exists too in a beautifully crystallized modification of 
a rather unstable nature, which can be obtained by distillation in vacuo and treating 
the solid deposit in a centrifugal machine. Sol. p. 35°; m. p. 38,59; digo 1,19. 
The sodium bisulphite compound cannot very well be used for separating ben- 
zylidene crotonaldehyde. It is difficult to purify it, and it decomposes easily. The 
phenylhydrazone forms beautiful, light yellow crystals melting at 177°, the semicar- 
bazone melts at 229°. With hydrazine sulphate and sodium. acetate, benzylidene 
crotonaldehyde forms an azine melting at 207°. The oxidation of benzylidene croton- | 
aldehyde with ammoniacal silver solution leads to cinnamenylacrylic acid (m. p. 165°). | 
Benzylidene crotonaldehyde cyanohydrine (m.p.97°) was not saponifiable to the expected | 
cinnamylidene-a-hydroxypropionic acid, but when being boiled with dilute hydrochloric 
acid it affords the transposition product of said acid, 7.e. the isomeric benzallaevulic 
acid (m. p. 123°). By condensation of benzylidene crotonaldehyde with hippuric acid, — 
a mixture of azlactones of benzylidene crotonaldehyde is formed, from which an 
azlactone melting at 203° and another melting at 162° could be isolated; this latter 
1) Uber Benzylidencrotonaldehyd und einige seiner Kondensationsprodukte. (On benzylidene crotonaldehyde 
and some of its condensation products.) Inaug.-Dissert., Berlin 1914. 
