THE ULTRA-VIOLET PHOTO-OXIDATION OF N-HEPTALDEHYDE

84 Pages·5.523 MB·English

by  MCNESBY, JAMES ROBERT

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Xerox University Microfilms
300 North Zeeb Road
Ann Arbor, Michigan 48106
(A3907 1 3 ' M r i l s'
>C7 I.IcKosby, James Bobert, 1922-
1-952 Tho ultra-violet photo oxidation i
.{1(2)4. of n-heptaldehydo • I
7Cp* tables,dlagrs.
T/iesls {fh.D.) - N.Y.U., Graduate
School, 1952*
iiibliogrf.pny: p.7o-7d.
091501
i.U ltra-violet r^ys. 2 .aldehydes.
3.f x+dstion. I4. Dissert atl 011s, Aca-
nilc * li.Y.U. - 1952» I .T itle: Heptai—
dehydo.
^ Shelf List
Xerox University Microfilms, Ann Arbor, Michigan 48106
THIS DISSERTATION HAS BEEN MICROFILMED EXACTLY AS RECEIVED.
library OF
RFtV YfhK imiVKRnTrj
WTVFJKSITY HKiGH.-p
THE ULTRA-Vi UlET ITIOTU OXi^ATl OH OE R -HE.t'TALDEHYDE
by James R. Mcliesby
-3.0 0 cp i e mtre T !E9,5i>-'
F " \ *■ *\ B "i—
A dissertation in the department of chemistry submitted in
partial fu lfillm ent of the requirements for the degree of
Doctor of fhilosophy at few York U niversity.
Acknowledgement
The author wishes to express his sincere appreciation to
the entire faculty of the Chemistry Department and in particular
to Professors T. \7. Davis, bis research advisor, and H. A. Taylor
for suggestions which m aterially aided, the research. The work
and the author were financed by a Research Fellowship granted
by the United otates Army Chemical Corps. Horal support and
constant encouragement were provided by the author’s wife, "elen
L. Aclesby, to whom any degree of success attained in the work
is in large measure due.
TABLE OF CUi;TEATS
Page
Introduction 1
Experimental Section 8
1. Materials 8
2. Apparatus 12
3. Experimental Procedures 14
Data and Results 25
1. The Intensity Measurements 25
2. Preliminary Experiments with
Dimethylbenzofulvene 29
3. Preliminary Experiments with
n-Butyraldehyde 30
4. Experiments with n-Heptaldehyde 31
Discussion 56
Summary 74
L ist of References 76
Figures
1 . Cyclohexane Purification 11
2. System for Measuring Hate of Oxygen Absorption 15
3. The Reaction V essels 16
4. Bubbling Technique 17
5. Shaking Technique 17
6. Larap-Reaction Vessel Assembly 18
7. Build up of Light Intensity 26
8 . E ffect of Agitation 35
9. E ffect of A gitation 36
10. A Typical Photo Oxidation 38
TABLE OF COBTELT3
(continued)
Page
11. A Typical Photo Uxidation 39
12. The E ffect of Changing Light Intensity 40
13. Photo Oxidation in Cyclohexane Solution 41
14. U ltra-violet Absorption Spectrum of
n-Heptaldehyde 42
15. The Rapid Deceleration of the Rate of Photo
Oxidation of n-Heptaldehyde 43
16. Accelerating Dark Reaction 44
17. Rate as a Function of oxygen Pressure 45
18. The Order of the Reaction in Uxygen 46
19. Intensity E ffect in the Photo Oxidation
of n-Heptaldehyde 47
20. The order of the Reaction in Aldehyde 48
21. The Temperature C oefficient 49
Introduction
The oxidation of aldehydes has been the subject of consid­
erable investigation since Backstrom’s (l) demonstration that the
ultraviolet photoxidations of benzaldehyde and n-heptaldehyde
proceed with quantum yields of many thousands. Style and Summers
(2) have recently studied the gas phase photo oxidation of form­
aldehyde. They found that the reaction rate obeyed the follow ­
ing law: Kate Z 1 + kg/k3( ICj^) where I is the intensity of
absorbed lig h t and is the concentration of formaldehyde.
Quantum yield s of the order of 8-10 are reported. Bowen and
T ietz(3), in their study of the gas phase photo oxidation of
acetaldehyde, found quantum yield s of the order of 1,000 and
have shown that the rate of reaction is proportional to the
aldehyde concentration and to the square root of the lig h t in ­
ten sity, and is independent of oxygen pressure. For the liq uid
phase reaction, the rate is proportional to the aldehyde concen­
tration and to the square root of in ten sity, while the effect of
oxygen pressure was not studied. The ultraviolet photo oxidation
of paraldehyde proceeds very rapidly according to Remy Cantieni(4;
but a quantitative study is lacking. In 1939, Alexander and
Schumacher 15) reported a quantum yield of 3,000 for the chlorine
sensitized photo oxidation of chloral at seventy degrees Centi­
grade in the gas phase. The vapor phase photo oxidation of crot-
onaldehyde has been studied by Blacet and Volmanl6 ). The highest
pressure of oxygen that is reported in this work is 14 m illi­
meters. The authors state that above 14 m illim eters, the dark
reaction is prohibitively rapid. The quantum yield appears to
rise exponentially with oxygen pressure and at 14 m illim eters,
-2 -
i t ia about three for lig h t of wave length 2537 Angstrom un its.
The photo oxidation of liquid benzaldehyde has been studied ex­
tensively by Backstrom(l, 7, 12), by Backstrom and B eatty(8 ),
and by Haymond(9, 13, 14). Further, Almquist and Branch(lO)
studied the oxidation of benzaldehyde in the dark and found the
reaction to be f ir s t order in oxygen. Askey(ll) has studied the
vapor phase thermal oxidation of benzaldehyde at 200 degrees
Centigrade and found carbon dioxide in the products.
While the effect of inhibitors and sen sitizers and the in ­
fluence of surface were studied in an attempt to learn something
about the mechanism of liquid aldehyde photo oxidations, there
does not appear to be any work reported on the influence of ligh t
intensity or oxygen pressure on the reaction rate for a pure
liquid aldehyde. Raymond's(9) data on the effect of aldehyde
concentration in methyl cyclohexane upon the rate of the photo
oxidation of benzaldehyde suggest that the in itia l rate is second
order in aldehyde. His data are doubtful, however, since he does
not make clear whether or not the lig h t is completely absorbed
over the whole range of concentrations studied.
The lack of experimental data on the kinetics of the liquid
phase photo oxidation of aldehydes is partly the result of the fact
that such a reaction cannot be studied in its physico-chemical
aspects unless i t can be made to behave as a reaction taking place
in one homogeneous phase. It is a liquid phase reaction
that we are dealing with in studying the rate at which liquid
aldehyde absorbs oxygen, that is , a reaction between liquid
aldehyde and dissolved oxygen. Unless the oxygen can be driv­
en into solution faster than the dissolved oxygen reacts with
-3 -
the aldehyde, the rate of absorption of oxygen and the rate of
formation of products w ill be a function of the rate of diffusion
of the reaction products away from the aldehyde-oxygen interface
and of the rate of diffusion of dissolved oxygen. In the extreme
case of an unagitated quantity of illuminated liquid aldehyde
in contact with oxygen, the activated molecules of aldehyde formed
by the lig h t may react rapidly with the dissolved oxygen, thus
reducing the supply of dissolved oxygen to zero. Any further
activated molecules must then either wait u n til more oxygen can
reach them by diffusion from the oxygen-aldehyde in terface, that
is mutual diffusion, or they w ill be consumed by some mechanism
within the liquid phase. The latter alternative predominates
unless agitation is su fficien t to keep the liquid phase saturated
with oxygen. In other words, if the rate of oxygen absorption
is to be a true measure of the rate of the chemical reaction in
solution, the slow process must be the reaction and the fa st
process d iffu sion . Haymond(9) realized the great importance of
su fficien t agitation in the photo oxidation of benzaldehyde. He
found at f ir s t that he could not agitate the liquid rapidly enough
so that the rate of the photo oxidation was independent of a g ita t­
ion. He then reduced the volume of aldehyde by successive incre­
ments, and found that below a volume of three cc. of aldehyde,
the rate of oxygen absorption per cc. of aldehyde employed was
constant. In other words the observed rate is proportiona.1 to the
volume of aldehyde used. This method of assuring adequate a g ita t­
ion is open to question since the assumption is that the rate is
proportional to the volume of aldehyde used, when the agitation
is su fficien t to maintain the aldehyde saturated with oxygen.
-4-
Then, having altered the effective agitation by varying the v o l­
ume of aldehyde employed, Raymond concluded that the rate was
agitation independent when this condition had been met, v iz .,
that the observed reaction rate is proportional to the volume
used. Our work, however, seems to substantiate th is assumption.
Backstrom(7) attempted to study the effect of lig h t inten sity
on the benzaldehyde photo oxidation, but the a g itation used was
so inadequate that the reaction rate actually was lowered by
increased lig h t in ten sity. The lowered rate under increased
illum ination indicated that when the oxygen supply was inadequate
to sa tisfy the photo-activated radicals, an inh ibitor producing
reaction occurred, which caused the rate to f a l l . Backstrom then
attempted to study the effect of lig h t in ten sity on the strongly
in h ib ited reaction. Using benzyl alcohol as in h ib itor, he found
the rate to be proportional to the square root o f the lig h t in ­
ten sity ; when the inhibitor was diphenyl amine or hydroquinone,
0.9
the rate was proportional to 1 , and with anthracene as inhib­
ito r , to x0-65.
Bawn and Williamson(15) have studied the oxidation of acet-
aldehyde in solution in glacial acetic acid under the influence
of cobalt ions. They find the rate of oxygen up-take to be pro­
portional to the aldehyde concentration and to the cobalt ion
concentration and to b© independent of oxygen pressure between
550 and 950 mm. pressure. They also find that about 85 percent
of the total peroxide formed is peracetic acid and they claim
that an additional 15 percent is present in the form of an add­
itio n compound between the aldehyde and the peracetic acid. They
also report amounts of carbon dioxide and carbon monoxide corres­