THE REDUCTION OF CINNAMIC ALDEHYDE TO CINNAMYL ALCOHOL IN THE PRESENCE OF PLATINUM-OXIDE PLATINUM BLACK AND PROMOTERS.

Dec., 1925 REDUCTION OR CINNAMIC ALDEHYDE 3061
[Contribution from the Chemical Laboratory or the University op Illinois]
THE REDUCTION OF CINNAMIC ALDEHYDE TO CINNAMYL
ALCOHOL IN THE PRESENCE OF PLATINUM-OXIDE
PLATINUM BLACK AND PROMOTERS. XI
By W. F. Tuley1 with Roger Adams
Received August 18, 1925 Published December 12, 1925
Recent work from this Laboratory113 has shown that aldehydes can be
reduced to alcohols in the presence of pure platinum-oxide platinum
black and hydrogen only if the catalyst is repeatedly reactivated with
air, or better if some promoter such as ferrous chloride is present in the
reaction mixture. Most of the substances tested which acted as promoters
in the reduction of aldehydes acted as poisons to the catalyst in the
reduction of olefins;11 the speed of reduction of the olefins was decreased
and in the presence of traces of certain salts the reaction was stopped completely. It was of interest, therefore, to determine whether in compounds
containing both an olefin and an aldehyde group, the aldehyde might
be reduced with platinum-oxide platinum black in the presence of certain
salts to the corresponding alcohol without affecting the olefin group
at all. This paper describes the study of the reduction of cinnamic aldehyde in the presence of platinum-oxide platinum black under various
conditions, with the result that a very satisfactory method for the selective reduction2 of the aldehyde group, and consequently for the production of cinnamyl alcohol was found.
The catalytic reduction of cinnamic aldehyde has been investigated
by others. In every instance the ultimate product has been phenyl
propyl alcohol but in no instance was it possible to obtain any reasonable
amount of cinnamyl alcohol3 as a reaction product. Vavon4 studied
1 This communication is an abstract of a portion of a thesis submitted by W. F.
Tuley in partial fulfilment of the requirements for the degree of Doctor of Philosophy
in Chemistry at the University of Illinois.
The platinum used in this research was purchased with the aid of a grant from the
Bache fund of the National Academy of Sciences. For this aid the authors are greatly
indebted.
Previous articles in this field are, (a) Voorhees and Adams, This Journal, 44,
1397 (1922); (b) Carothers and Adams, ibid., 45, 1071 (1923); (c) Adams and Shriner,
ibid., 45, 2171 (1923), preparation of catalyst; (d) Kaufmann and Adams, ibid., 45,
3029 (1923); (e) Carothers and Adams, ibid., 46, 1675 (1924); (f) Shriner and Adams,
ibid., 46, 1684 (1924); (g) Carothers and Adams, ibid., 47, 1047 (1925); (h) Pierce and
Adams, ibid., 47, 1098 (1925); (i) Kern, Shriner and Adams, ibid., 47, 1147 (1925);
(j) Heckel and Adams, ibid., 47, 1712 (1925).
2 For some previous cases of selective reduction, see Ref. 1 d; 1 i; Richardson,
Knuth and Milligan, Ind. Eng. Chem., 17, 80 (1925); Hilditch and Moore, J. Soc. Chem.
Ind., 42, 15 (1923); Vavon, Compt. rend., 175, 277 (1922); Rosenmund, Ber., 51, 578,
585 (1918); Armstrong and Hilditch, J. Soc. Chem. Ind., 44, 701 (1925).
3 Armstrong and Hilditch, Chim. Ind., 12, 211 (1924).
4 Vavon, Compt. rend., 154, 359 (1912).
Downloaded via CALIFORNIA STATE UNIV BAKERSFIELD on October 28, 2021 at 05:40:59 (UTC).
See https://pubs.acs.org/sharingguidelines for options on how to legitimately share published articles.
3062 W. F. , WITH ROGER ADAMS Vol. 47
the reaction with platinum black and isolated only phenylpropyl alcohol.
Skita6 reduced cinnamic aldehyde using colloidal platinum and isolated
in succession after absorption of one molecular equivalent of hydrogen,
phenylpropionaldehyde; after two molecular equivalents, phenylpropyl
alcohol; and after five molecular equivalents, hexahydrophenylpropyl
alcohol. Traces of cinnamyl alcohol and phenylpropane were also found.
It is particularly noticeable that the olefin double bond is reduced first
to the practical exclusion of reduction of the aldehyde group.
When cinnamic aldehyde is reduced with pure platinum-oxide platinum
black in the presence of hydrogen (Table I) the reduction goes to only
Table I
Reduction with Pure Catalyst
Aide- 95% Cata- /————-Reaction time—-s ,-Product
hyde, alcohol, lyst, after after
g. cc. g. 1 mol. eq. 2nd mol. eq. 1 mol. eq. 2 mol. eq.
26.4 100 0.2 0.0378 mole in 70 min.
.0432 mole in 295 min.
52.8 200 .4 10 hrs. 46.8 g. not solid at
—5=
52.8 200 .4 9.5 hrs. 14 hrs.(10 reactivations ) 43 g. phenyl·
propyl alcohol
a very slight extent before it stops. This might be predicted from previous results with benzaldehyde. About 0.15 molecular proportion
of hydrogen is absorbed before the catalyst becomes entirely inactive.
Only by reactivation with air will the reduction proceed, and many reactivations are necessary before the reduction is complete with the absorption of two molecular equivalents of hydrogen and formation of
phenylpropyl alcohol. If the reaction mixture is worked up after the
absorption of one molecular equivalent of hydrogen it is found that there
exists a mixture of products; unchanged cinnamic aldehyde, phenylpropionaldehyde, cinnamyl alcohol and phenylpropyl alcohol. It was
possible to extract about 25% of such a mixture with sodium bisulfite
whereas the remaining 75% consisted chiefly of cinnamyl alcohol and a
little phenylpropyl alcohol.
A mixture of such products would be expected from THE REDUCTION OF CINNAMIC ALDEHYDE TO CINNAMYL ALCOHOL IN THE PRESENCE OF PLATINUM-OXIDE PLATINUM BLACK AND PROMOTERS.a consideration
of previous work on substituted olefins and aldehydes.lb,1‘ The olefin
linkage of a symmetrical disubstituted olefin such as cinnamic aldehyde would not be reduced very readily as compared with many other
types of olefins, and the presence of the aldehyde would especially affect the catalyst so as to cause the reaction to proceed very much more
slowly or to stop completely. The aldehyde group, on the other hand,
if the catalyst is frequently reactivated with air should be reduced readily.
It is not surprising, therefore, that a large proportion of cinnamyl alcohol
is formed. The separation of pure cinnamyl alcohol from the other prod5 Skita, Ber., 48, 1685 (1915).
Dec., 1925 reduction of cinnamic aldehyde 3063
ucts, however, is impossible by simple distillation and therefore the method
is not a feasible one for producing a· pure cinnamyl alcohol.
When 2 moles of cinnamic aldehyde are reduced with 0.20 g. of catalyst in 100 cc. of 95% alcohol in the presence of various amounts of
ferrous chloride it is possible to carry the reaction completely to phenylpropyl alcohol without any reactivations with air (Table II). An increase
Table II
Reduction of 26.4 G. of Cinnamic Aldehyde in 100 Cc. of 95% Alcohol with 0.2
G. of Catalyst and Ferrous Chloride
Product after
—Reaction time-< Product after 2 mol. eq.
Moles of For 1st For 2nd mol. eq., 1 mol. eq. Phenyl propyl
FeCl, mol. eq., min. hrs. wt., g. p V
o
p alcohol, g.
0.0005 168 20 16-18
.0005 180 6° 21.5
.0002 160 75% of 2nd mole in
26 hours
.0001 155 20 18-19
.00002 165 23 23-24
.00002 143 22 22-23
.00001 195 23 22-23
.000006 600 12 22
“ Two reactivations of the catalyst were necessary before the reduction was complete.
in the amount of ferrous chloride has very little effect upon the speed
of reduction. The ferrous chloride is obviously, therefore, a promoter
in the reduction of cinnamic aldehyde as it is with other aldehydes. If
such a reduction is stopped as soon as one molecular equivalent of hydrogen is absorbed it is found that only traces of aldehydes are present.
The product is cinnamyl alcohol, the purity depending to a certain extent
on the amount of ferrous salt present. Thus the use of 0.01 to 0.02 millimole gave the best results, with the production of a cinnamyl alcohol
which melted at 22-24°. Large amounts of ferrous salt up to 0.5 millimole allowed the absorption of one molecular equivalent of hydrogen
to take place in approximately the same time, but in every instance gave
a product melting somewhat lower, 14-19°. If the reaction was not
stopped after one molecular equivalent of hydrogen was absorbed, more
hydrogen was always absorbed and the absorption of the second molecular
equivalent was much slower than for the first.
The presence of zinc acetate in the catalytic reduction of benzaldehyde
led to interesting results; with extremely small amounts no noticeable
effect could be noted, a greater amount acted as an excellent promoter,
while still greater amounts poisoned the catalyst completely. The zinc
acetate was a poison in the reduction of olefins. The reduction of cinnamic aldehyde in the presence of 0.02 millimole of zinc acetate (Table III)
indicated that the zinc acetate in that concentration was a promoter, sinc